PETROFACIES AND PALEOTECTONIC EVOLUTION OF GONDWANAN AND 
POST-GONDWANAN SEQUENCES OF NEPAL 
 
Except where reference is made to the work of others, the work described in this thesis is 
my own or was done in collaboration with my advisory committee. 
This thesis does notinclude proprietary 
or classified information. 
 
 
 
 
 
_____________________________________ 
Raju Prasad Sitaula 
 
 
 
Certificate of Approval: 
 
 
 
 
_____________________     _____________________ 
Charles E. Savrda      Ashraf Uddin, Chair 
Professor       Associate Professor 
Geology and Geography     Geology and Geography 
 
 
 
 
_____________________     _____________________ 
Willis E. Hames      George T. Flowers 
Profesor       Dean 
Geology and Geography     Graduate School  
 
  
 
 
 
 
PETROFACIES AND PALEOTECTONIC EVOLUTION OFGONDWANAN AND 
POST-GONDWANAN SEQUENCES OF NEPAL 
 
Raju Prasad Sitaula 
 
A Thesis 
Submitted to 
the Graduate Faculty of 
Auburn University 
in Partial Fulfillment of the 
Requirement for the 
Degree of 
Master of Science 
Auburn, Alabama 
 
 
Auburn, Alabama 
December 18, 2009 
iii 
 
 
 
 
PETROFACIES AND PALEOTECTONIC EVOLUTION OF GONDWANAN AND 
POST-GONDWANAN SEQUENCES OF NEPAL 
 
Raju Prasad Sitaula 
 
Permission is granted to Auburn University to make copies of this thesis at its discretion, 
upon the request of individuals or institutions and at their expense.  
The author reserves all publication rights. 
 
 
 
 
_____________________________ 
Raju Prasad Sitaula 
 
___________________________ 
Date of Graduation  
iv 
 
 
 
 
 
 
 
VITA 
 
 
 
 
 
Raju Prasad Sitaula, son of Mr. Murari Prasad Sitaula and Mrs. Renuka Devi 
Sharma Sitaula, was born in 1979 in Bhadrutar, Nuwakot. He passed his school Leaving 
Certificate Examination in 1996 from Adarsha Yog Hari Madhyamik Vidhyalaya. He 
passed the Proficiency Certificate Level Examination in 1998 from Amrit Science 
College. He received his Bachelor of Science and Master of Science degrees in Geology 
in 2002 and 2005, respectively, from Tri-Chandra Multiple Campus and Tribhuvan 
University in Nepal. He entered the graduate school at Auburn University to pursue his 
second Masters degree from the Department of Geology and Geography in Fall 2007. 
v 
 
 
 
THESIS ABSTRACT 
PETROFACIES AND PALEOTECTONIC EVOLUTION OF GONDWANAN AND 
POST-GONDWANAN SEQUENCES OF NEPAL 
Raju Prasad Sitaula 
Master of Science, December 18, 2009 
(Bachelor of Science, Trichandra College, Nepal, 2004) 
(Master of Science, Tribhuvan University, Nepal, 2005) 
 
206 Typed Pages 
Directed by Ashraf Uddin 
The Gondwanan sequences are widely distributed in several intracratonic basins 
of peninsular India and also as discontinuous patches along the Himalayan orogenic belt. 
The Tansen Group (2400 m) in western Nepal is thicker and more complete than the 
Katari (380 m) and the Barahachettra (350 m) groups located in eastern Nepal.  
In the Tansen Group, modal compositions of sandstone change from arkosic 
(Permo-Carboniferous unit) to quartz arenitic and then to litharenitic (Eocene-Early 
Miocene). Similar modal compositions are also present only in alleged Permo-
Carboniferous units Katari and Barahachettra groups of eastern Nepal. The 
quartzofeldspathic sandstones of the Permo-Carboniferous Sisne (western Nepal) and 
Saptakoshi (eastern Nepal) formations show high Eu values. The Quartzite unit of the 
Saptakoshi Formation seems similar to the Amile Formation of western Nepal as both 
contain higher percentages of mature quartz and stable heavy minerals, and show similar 
vi 
 
REE patterns. High contents of lithic fragments with relatively rare feldspars indicate that 
the Tamrang sandstones were deposited in the juvenile foreland basin between India and 
Tibet like the Eocene Bhainskati Formation of western Nepal.  
Garnet chemistry suggests sediment supply from variously graded metamorphic 
rocks.  Tourmaline chemistry indicates sediments derivation from both lithium-high and 
lithium-low igneous rocks. Chrome-spinels with low TiO
2
 contents in the Taltung 
Formation show evidence of provenance from alkaline basalts. 
Cooling ages of detrital muscovites from the Permo-Carboniferous units of all 
three study sections show some older ages (300 Ma to 1700 Ma) and few younger (17 Ma 
to 25 Ma) ages. The older ages could be related to the magmatism in the Indian craton 
(e.g., Malani Rhyolite, Erinpura Granite, Chotanagpur Gneissic Terrain). Ages ~ 40 Ma 
muscovites from the Bhainskati Formation suggest a Himalayan orogenic source. 
Relatively younger ages, however, could indicate about the possible argon loss from the 
muscovite or misinterpretation of the stratigraphy.  
This study suggests that the stratigraphy of the Gondwana sequences in eastern 
Nepal needs to be re-evaluated. The existing quartzite unit of supposedly Permo-
Carboniferous Saptakoshi Formation (eastern Nepal) should belong to Late Cretaceous, 
equivalent to the Amile Formation of western Nepal. The Tamrang Formation (eastern 
Nepal), which is currently considered as Permo-Carboniferous to Cretaceous, could be an 
equivalent unit of the Eocene Bhainskati Formation of western Nepal.
vii 
 
 
 
 
ACKNOWLEDGEMENTS 
I would like to express my thanks and gratitude to my dear teacher Dr. Ashraf 
Uddin for bringing me to Auburn University and giving me the chance to get a Master?s 
degree in Geology. Dr. Uddin helped me not only as the principal advisor but also as a 
real guardian to get the best outcome of this research. 
I would like to express my sincere thanks to Dr. Charles Savrda, who helped with 
significant editing in this thesis. It would have been difficult to get this research work 
done without Dr. Savrda. I also would like to thank Dr. Willis Hames for help with the 
geochronology part of this research. 
I also acknowledge Mr. Chris Fleisher of University of Georgia for help during 
microprobe analysis. I thank Dr. Bishal Nath Upreti and Dr. Megh Raj Dhital for 
continuously guiding me through my research, supporting my fieldwork, and reviewing 
my thesis work. I want to thank my colleagues Pawan Budhathoki, Ashok Sigdel, and 
Biraj Gautam for their immense help in my fieldwork. I also want to pay my sincere 
thanks to Mr. Suryalal Shrestha who provided lodging support at Masyam, Palpa, during 
my fieldwork at the Tansen section. I am truly grateful to my colleagues at Auburn 
University, Subhadip Mandal and Shahadat Hossain, for their significant support 
throughout the development of thesis work, for literature review, lab work, data analysis 
viii 
 
and computer work. I am thankful for Subhadip not only for his support but also for the 
support I got from him while sharing an apartment.  
I am very grateful to Eva Lilly and Sheila Arington for their kind support 
throughout my study with all administrative work. John Simms always helped to solve 
the computer hardware problems I got during my work in the department. I also like to 
thank Dr. Zeki Billor for his moral support and proper guidance for muscovite separation.  
I also want to pay my sincere thanks to my seniors Prakash Dhakal and 
Mohammad Wahidur Rahman for their guidance. Prakash was the one who helped me to 
adjust with educational system and social life in United States.  I am also grateful to 
Bibek Upreti for his support in my thesis work as well as in my daily life. It was Bibek 
who broke most of my sandstones samples which were very hard. 
This research was funded by the U.S National Science Foundation (NSF-EAR- 
0310306), Geological Society of America, and the Department of Geology and 
Geography of Auburn University.  
I want to thank my parents who gave me the opportunity to see this wonderful 
world and supported me in every step of my life.  I would like to thank my brother and 
sisters for their love and support.  
ix 
 
 
Style manual or journal used 
Geological Society of America Bulletin 
 
Computer software used 
Adobe Acrobat 6 Professional 
Adobe Illustrator 8.0 
Adobe Photoshop CS 2 
Macromedia FreeHand 11.0 
Golden Software Grapher 3.0 
Golden Software Surfer 8.0 
Microsoft Excel 2007 
Microsoft Word 2007 
Microsoft Office Picture Manager 2007 
 
x 
 
 
 
 
 
 
TABLE OF CONTENTS 
 
 Page
LIST OF FIGURES xii
LIST OF TABLES xx
CHAPTER 1: INTRODUCTION??????????????????....... 
 
1
1.1 Introduction??????????????????????????.. 1
1.2 Location of the study area?????????????????..???.. 4
1.3 Previous Works????????????????????????? 5
1.4 Objectives???????????????????????????. 
 
7
CHAPTER 2: GONDWANAN SEQUENCES OF NEPAL HIMALAYA AND 
PENINSULAR INDIA???????????????????????... 
 
8
2.1 General Geological Setting of Nepal Himalaya????????????... 8
2.2 Gondwana Stratigraphy of Nepal??????????????????. 10
2.3 Gondwanan Sequences in other parts of Nepal????????????? 24
2.4 Distribution of Gondwanan Basins in Peninsular India?????????... 26
2.5 Gondwanan Stratigraphy of other parts of extra-Peninsular India and other 
parts of Gondwanaland???????????????????????... 
 
31
CHAPTER 3: EVOLUTION OF GONDWANAN BASINS????????? 
 
36
3.1 Continental Breakup of Gondwanaland???????????????... 36
3.2 Evolution of the Passive Margin at the Northern Boundary of India????... 38
3.3 Evolution of Facies and Climatic control during the Evolution of Gondwanan 
Sequences????????????????????????????... 
 
40
CHAPTER 4: SANDSTONE PETROGRAPHY?????????????... 44
4.1 Introduction??????????????????????????.. 44
4.2 Methods???????????????????????????? 45
4.3 Petrography??????????????????????????... 47
4.4 Sandstone Modes????????????????????????.. 60
4.5 Petrofacies Evolution ??????????????????????... 
 
62
xi 
 
CHAPTER 5: HEAVY MINERAL ANALYSIS?????????????... 68
5.1 Introduction?????????????????????.?????. 68
5.2 Methods???????????????????????????? 71
5.3 Results????????????????????????????.. 74
5.4 Provenance??????????????????????????... 
 
82
CHAPTER 6: MICROPOBE ANALYSIS????????????????. 
 
86
6.1 Introduction??????????????????????????.. 86
6.2 Mineral Chemistry???????????????????????.... 86
6.3 Sample Preparation???????????????????????.. 88
6.4 The Electron Micropobe?????????????????????... 89
6.5 Results????????????????????????????.. 92
6.6 Discussion???????????????????????????. 
 
102
CHAPTER 7: WHOLE ROCK CHEMISTRY???????????.???. 
 
107
7.1 Introduction??????????????????????????.. 107
7.2 Methods???????????????????????????? 108
7.3 Results????????????????????????????.. 
 
110
CHAPTER 8: 
40
Ar/
39
Ar DETRITAL MUSCOVITE DATING??????.?... 130
8.1 Introduction??????????????????????????.. 130
8.2 Methodology??????????????????????????. 134
8.3 
40
Ar/
39
Ar Results????????????????????????.. 135
8.4 Provenance Interpretation?????????????????????. 145
 
CHAPTER 9: DISCUSSION AND CONCLUSION????????????. 147
9.1 Synthesis???????????????????????????... 147
9.2 Sandstone Petrography and Stratigraphy???????????????.. 147
9.3 Heavy Mineral Study??????????????????????? 152
9.4 Micropobe Analysis???????????????????????.. 152
9.5 Geochemical Analysis??????????????????????.. 153
9.6 
40
Ar/
39
Ar Muscovite Geochronology????????????????... 154
9.7 Paleotectonic Setting??????????????????????? 155
9.8 Conclusions??????????????????????????.. 159
 
xii 
 
REFERENCES??????????????????????????... 161
APPENDICES??????????????????????????? 176
 
  
xiii 
 
 
 
 
LIST OF FIGURES 
 Page
Figure 1.1 Configuration of continental masses in Gondwanaland (after Gray et 
al., in press)??????????????????????????... 
2
Figure 1.2 Location map of study sites in Nepal. Map also shows the Damodar 
Basin of Peninsular India?????????????????????.. 
4
Figure 2.1 Geological map of Nepal showing locations of Gondwanan sequences 
investigated in this study (modified from Amatya and Jnawali, 
1994)??????????????????????????????.   9
Figure 2.2 Stratigraphic column of the Tansen Group, eastern Nepal (after Sakai, 
1983), showing position of samples used in the current study????????. 
12
Figure 2.3 Geological map (A) of Tansen area (after Sakai, 1983) and geological 
cross section (B) of Tansen area???????????????????.. 13
Figure 2.4 Roadside outcrop of the Sisne Sandstone near Charchare area???.. 14
Figure 2.5 Steeply dipping Amile Quartzite along Bhainskati Khola near the 
Charchare area, western Nepal????????????????????. 16
Figure 2.6 Geological map of the Barahachettra area (after Dhital, 1992 and 
2006) and sample collection locations?????????????????. 20
Figure 2.7 Stratigraphic Column of the Barahachettra (Dhital, 1992) and Katari 
groups (Dhital 2006), eastern Nepal?????????????????? 
21
 
xiv 
 
Figure 2.8 Geological map of the Katari area (Dhital, unpublished) and sample-
collection locations????????????????????????... 22
Figure 2.9 Outcrop of Kokaha Diamictite along Kokaha Khola, eastern Nepal?.. 23
Figure 2.10 Outcrop of sandstone along Maruwa Khola in Katari area, eastern 
Nepal??????????????????????????????. 23
Figure 2.11 (A) Geological map of peninsular India (after Najman, 2005) and (B) 
distribution of Gondwanan basins in peninsular India (after Dutta, 2002)???? 27
Figure 2.12 Stratigraphic column of Gondwanan sequences in the Damodar 
Basin (after Veveers and Tiwari, 1995)????????????????... 29
Figure 2.13 Distribution of Gondwanan basins on the Indian subcontinent (Frakes, 
1975)??????????????????????????????.. 32
Figure 2.14 Main tectonic subdivision and relation of Indian Precambrian shield 
(after Khan, 1994)?????????????????????????.. 33
Figure 2.15 Distribution of Gondwanan basins in Gondwanaland in Early Permian 
(Veveers and Tiwari, 1995)?????????????????????... 35
Figure 3.1 Generalized reconstructions of (A) Early Cretaceous and (B) Tertiary 
Gondwanaland (from Segev, 2002)??????????????????... 38
Figure 3.2 Schematic reconstruction of micro continent barrier supposed to have 
existed between the Lesser Himalayan and the Higher Himalayan terrains???..
40
Figure 3.3 Paleogeography of Gondwanaland (www.paleoportal.com, 2009)??.. 41
Figure 3.4 Marine incursion in Gondwanaland during the Permian (Valdiya, 
1998)??????????????????????????????.. 43
Figure 4.1 Representative photomicrographs of Gondwanan sandstones, western 
Nepal. (A) Sisne Formation. (B )Taltung Formation?????????...?? 
54
  
xv 
 
Figure 4.2 Representative photomicrographs of Gondwanan sandstones, western 
Nepal. (A) Amile Formation. (B) Bhainskati Formation??????????. 
  
 55 
Figure 4.3 Representative photomicrographs of Gondwanan sandstones, (A) 
Dumri Formation, western Nepal. (B) Katari Group, eastern Nepal?????? 56
Figure 4.4 Representative photomicrographs of the Gondwanan sandstones, (A) 
Saptakoshi Formation, eastern Nepal, sample 23-5. (B) Saptakoshi Formation, 
eastern Nepal, sample 22-7?????????????????????... 57
Figure 4.5 (A) Representative photomicrograph of the Tamrang sandstone, 
eastern Nepal (B) Aulis Basalt, Western Nepal?...???????????.... 58
Figure 4.6 Variation of modal mineralogical composition of the Gondwanan 
sandstones of Nepal. ????????????????????...??... 61
Figure 4.7 QtFL plot of Gondwanan sandstones of Nepal showing mean and 
standard deviation polygons?????????????????????. 65
Figure 4.8 QmFLt plot of Gondwanan sandstone of Nepal showing mean and 
standard deviation polygons?????????????????????. 66
Figure 4.9 QmPK plot of the Gondwanan sandstones of Nepal showing mean and 
standard deviation polygons ????????????????????? 
66
Figure 4.10 LsLvLm plot of the Gondwanan sandstones of Nepal showing mean 
and standard deviation polygons. ??????????????????? 67
Figure 5.1 Representative photomicrograph of tourmalines in Amile sandstone 
(sample 15-6) of the Tansen Group, western Nepal????????????. 74
Figure 5.2 Representative photomicrograph of heavy mineral assemblage in the 
Taltung sandstone (sample K-1) of the Tansen Group, western Nepal????? 76
Figure 5.3 Representative photomicrograph of heavy mineral assemblage in the 
Sisne sandstone (sample 16-3) of the Tansen Group, western Nepal?????.. 78
xvi 
 
Figure 5.4 Representative photomicrograph of heavy mineral assemblage in the 
Permo-Carboniferous sandstone (sample 26-8) of the Katari Group, eastern 
Nepal??????????????????????????????. 78
Figure 5.5 Representative photomicrograph of heavy mineral assemblage in the 
Permo-Carboniferous sandstone (sample 26-8) of the Katari Group, eastern 
Nepal??????????????????????????????. 81
Figure 5.6 Representative photomicrograph of heavy mineral assemblage in the 
Permo-Carboniferous sandstone (sample 23-4) of the Barahachettra Group, 
eastern Nepal??????????????????????????.... 81
Figure 5.7 Distribution of heavy minerals among different units and sections of 
Gondwanan sandstones in Nepal???????????????????.. 83
Figure 5.8 Distribution of highly stable heavy minerals (ZTR) among different 
units and sections of Gondwanan sandstones in Nepal??????????? 84
Figure 5.9 Distribution of garnets among different units and sections of 
Gondwanan sandstones in Nepal???????????????????.. 84
Figure 5.10 Variation in distribution of garnets and ZTR among different units 
and sections of Gondwanan sandstones in Nepal?????????????. 85
Figure 5.11 Possible source rock units for the Gondwanan sandstones of Nepal 
from cratonic India????????????????????????... 85
Figure 6.1 Chemical composition of garnets of Gondwanan sequences of Nepal 
(Tansen Group, western Nepal; Barahachettra and Katari groups in eastern 
Nepal) plotted on (Sp+Gro)-Py-Alm?????????????????? 94
Figure 6.2 Chemical composition of garnets of Gondwanan sequences of Nepal 
(Tansen Group, western Nepal; Barahachettra and Katari groups in eastern 
Nepal) plotted on (Py+Alm)-Gro-Sp????????????????? 94
 
xvii 
 
Figure 6.3 Chemical composition of garnets of Gondwanan sequences of Nepal 
(Tansen Group, western Nepal; Barahachettra and Katari groups in eastern 
Nepal) plotted on (Alm+Sp)-Py-Alm????????????????? 95
Figure 6.4 Chemical composition of garnets of Gondwanan sequences of Nepal 
(Tansen Group, western Nepal; Barahachettra and Katari groups in eastern 
Nepal) plotted on Alm-Py-Sp????????????????????... 
95
Figure 6.5 Grossular contents  of garnets from Gondwanan sequences of Nepal 
(Tansen Group, western Nepal; Barahachettra and Katari groups in eastern 
Nepal) plotted on Alm-Py-Sp????????????????????... 96
Figure 6.6 Al-Fe (tot)-Mg plot (in molecular proportion) for tourmalines from 
Gondwanan sequences of Nepal (Tansen Group, western Nepal; Barahachettra 
and Katari groups in eastern Nepal)??????????????????. 98
Figure 6.7  Ca-Fe(tot)-Mg plot (in molecular proportion) for tourmalines from 
Gondwanan sequences of Nepal (Tansen Group, western Nepal; Barahachettra 
and Katari groups in eastern Nepal)??????????????????. 99
Figure 6.8 Ternary plot of major trivalent cations in chrome-spinels of the 
Taltung Formation of the Tansen Group (Gondwanan sequences) of the Nepal 
Himalaya with three major provenance fields  (adapted after Nixon et. al, 1990)... 99
Figure 6.9 Plot of Mg/(Mg+Fe
2+
) vs Cr/(Cr+Al) for chrome-spinels of the 
Taltung Formation of the Tansen Group (Gondwanan sequences) of the Nepal 
Himalaya (adapted after Nixon et. al, 1990)??????????????? 100
Figure 6.10 Plot of Mg/(Mg+Fe
2+
) vs the ratio of trivalent cations                  
Fe
3+
/( Fe
3+
+Cr+Al) for chrome-spinels of the Taltung Formation of the Tansen 
Group (Gondwanan sequences) of the Nepal Himalaya??????????.. 101
Figure 6.11 Petrographic grid for the KFMASH system contoured with isopleths 
of X
Alm
 in garnet (after Spear and Cheney, 1989) showing isopleth values for 
garnets of Gondwanan sequences of Nepal???????????????.. 103
xviii 
 
Figure 6.12 Plot of TiO
2
 vs Cr# of Gondwanan sequences of Nepal (Tansen 
Group, western Nepal; Barahachettra and Katari groups in eastern Nepal) relative 
to spinels from various potential source rocks??????????????. 105
Figure 6.13 Schematic diagram showing spinel composition from different 
tectonic settings, including those of sea-floor and continental crust origins 
(modified from Cookenboo et al., 1997)????????????????.. 106
Figure 7.1 Chemical classification of Gondwanan sandstones of Nepal, 
classification fields are taken from Herron (1988)????????????... 113
Figure 7.2 Distribution pattern of major element oxides in Gondwanan sandstone 
of Nepal. Data are normalized to Post Archean Australian Shale (PAAS) (Taylor 
and McLennan, 1995)???????????????????????... 116
Figure 7.3 Distribution pattern of major element oxides in Gondwanan sandstone 
of Nepal????????????????????????????? 117
Figure 7.4 CIA values for the Gondwanan sandstones of Nepal???????. 119
Figure 7.5 CIA plot of Gondwanan sandstones of Nepal (modified from Nesbit 
and Young, 1984, 1989; and Soreghan and Soreghan, 2007)???????... 120
Figure 7.6 Distribution patterns of trace elements in Gondwanan sandstone of 
Nepal. Data are normalized to Post Archean Australian Shale (PAAS) (Taylor 
and McLennan, 1995)???????????????????????... 125
Figure 7.7 Distribution patterns of rare earth elements (REE) in Gondwanan 
sandstone of Nepal. Data are normalized to Post Archean Australian Shale 
(PAAS) (Taylor and McLennan, 1995)????????????????? 126
Figure 7.8 Plot of TiO
2
 vs Zr content of the Gondwanan sandstones of Nepal. 
Fields for source rocks are drawn from Hayashi et al. (1997)????????. 127
Figure 7.9 Tectonic discrimination diagram for Gondwanan sandstones of Nepal  128
 
xix 
 
Figure 7.10 Plot of elemental percentage of La-Th-Sc of Gondwanan sandstones 
of Nepal Fields of tectonic setting are drawn from Bhatia and Crook (1986)??. 129
Figure 8.1 Some stable and radioactive isotopes related to 
40
Ar/
39
Ar dating 
method?????????????????????????????.. 131
Figure 8.2 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the 
Eocene Bhainskati Formation (sample 15-8)??????????????... 137
Figure 8.3 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the 
Permo-Carboniferous Sisne Formation (sample 16-3)???????????. 138
Figure 8.4 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the 
Permo-Carboniferous Saptakoshi Formation (sample 22-8)????????? 139
Figure 8.5 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the 
Permo-Carboniferous Katari Group (sample 26-8)????????????.. 140
Figure 8.8 Possible source rock with the age given by the detrital muscovite 
analyzed????????????????????????????? 146
Figure 9.1 Correlation of stratigraphy of Gondwanan sequences in western part 
of Nepal and proposed stratigraphy of eastern Nepal 151
Figure 9.2 Chondrite normalized REE pattern of Bengal Trap Basalt (from Baksi, 
1995)??????????????????????????????. 154
Figure 9.3 
40
Ar/
39
Ar cooling ages of single grain muscovite from the Gondwanan 
sandstone of Nepal???????????????????????...? 156
Figure 9.4 Paleotectonic setting of India from Permo-Carboniferous to Miocene 
during deposition of Gondwanan and post-Gondwanan sequences (modified after 
Sakai, 1989; Veevers and Tiwari, 1995; DeCelles et al., 1998)???????... 158
xx 
 
 
 
 
LIST OF TABLES 
 Page
Table 2.1 Generalized correlations of Gondwanan sequences of Nepal 
Himalaya????????????????????????????... 25
Table 4.1 Recalculated modal parameters of sand and sandstone??????? 46
Table 4.2 Normalized modal compositions of Gondwanan sandstones in Nepal? 59
Table 5.1 Relative stability of heavy minerals for different sedimentary 
processes????????????????????????????... 69
Table 5.2 Four fractions of different magnetic susceptibility (Hess, 1966)???. 72
Table 5.3 Heavy mineral data in Gondwanan sandstones from western Nepal 
(Tansen Group)??????????????????????????. 79
Table 5.4 Heavy mineral distribution in Gondwanan sandstones from eastern 
Nepal (Barahachettra and Katari groups)????????????????. 
80
Table 6.1 Electron microprobe standards used for this study????????.. 91
Table 7.1 Results of whole-rock chemical analysis of Gondwanan sandstones 
from Nepal???????????????????????????? 110
Table 7.2 Ratios of some major oxides of Gondwanan sandstones from Nepal?.. 114
Table 7.3 Ratios of some trace elements in Gondwanan sandstones of Nepal?? 122
Table 8.2 Isotopes produced during the irradiation process of muscovite???... 132
Table 9.1 Proposed Stratigraphy of Gondwanan and post- Gondwanan sequences 
in the Barahachettra area (eastern Nepal) and its correlation with Gondwanan 
sequences in other parts of Nepal???????????????????. 
150
 
 
 
1 
 
 
 
CHAPTER 1: INTRODUCTION 
1.1 INTRODUCTION 
Studies of petrofacies evolution are based on the assumption that the composition 
of detrital sediments records the composition of the source rocks from which those 
sediments were derived (Dickinson and Suczek, 1979). This theoretical relationship 
enables interpretation of paleogeography, paleoclimate, ancient plate tectonic settings 
(Graham et al., 1976; Dickinson and Suczek, 1979), and rock-uplift and exhumation 
histories (Graham et al., 1976) from the sedimentary record. Sometimes sedimentary 
rocks may provide the only source of this information particularly in cases of deeply 
denuded source terranes. The validity of this assumption has been demonstrated for 
numerous samples detrital sediments and sedimentary rocks (Dickinson, 1970; Dickinson 
and Suczek, 1979). However, interpretation of provenance from sediment compositional 
data also requires consideration of other controlling factors such as transport distance, 
time, energy, and climate (Suttner, 1974; Johnsson, 1993). 
Sandstone compositional studies are very important in tracing sediment 
provenance (Dickinson and Suczek, 1979). Sandstone compositional analyses, in which 
proportions of detrital framework grains within a sand (stone) sample are plotted on 
various ternary plots (QtFL, QmFLt, etc.), can distinguish various tectonic settings of 
source areas (Ingersoll et al., 1995). Composition of detrital sediments is controlled by 
 
2 
 
various factors, including source rocks, modes of transportation, depositional 
environments, climate, and diagenesis (Suttner, 1974). Provenance studies that focus on 
key attributes of detrital mineralogy provide important constraints on basin evolution and 
unroofing history of orogenic belts.  
The term ?Gondwanaland? was coined by Eduard Suess, referring to India as the 
land of ?Gond?, which was the name of a local Indian tribe. However, Gondwanaland is 
now defined as southern supercontinent that existed from 550 Ma to 167 Ma (Fig. 1.1).  
 
Figure 1.1 Configuration of continental masses in Gondwanaland (after Gray et al., in 
press) 
Sedimentary sequences deposited from early Carboniferous to Late Jurassic in 
peninsular India (Gondwanaland) are known as Gondwanan sequences (Wadia, 1919). 
Most of these sequences were deposited in continental depositional environment with few 
marine invasions. The name is also applied to the sequences deposited in other parts of 
 
3 
 
Gondwanaland during that period, including there now in Australia, Africa, South 
America and Antarctica. 
The Gondwanan system in the Indian subcontinent is not confined to peninsular 
India. Outliers of Gondwanan sequences have been found in northern India across the 
Indo-Gangetic plain in the western Himalayas (Punjab Salt Range, Afghanistan, 
Kashmir) and the eastern Himalayas (Nepal, Sikkim, Bhutan, Assam, etc.). These are 
known as extra-peninsular Gondwanan sequences. Gondwanan strata of peninsular India 
are thick and relatively undisturbed, whereas the extra-peninsular occurrences are 
incomplete and have been folded, compressed, and, in many cases, metamorphosed.  
The provenance history of the Gondwanan sequences in the Nepal Himalaya 
(Lesser Himalaya) has not been studied as thoroughly as the Gondwanan sequences of 
peninsular India. Although parts of this sequence have been studied (Bashyal, 1980, 
Sakai, 1983; Dhital, 1992; DeCelles et al., 2004; Najman et al., 2005) at different 
localities along the Nepal Himalaya, a complete and comparative study has not been 
done. The Tansen Group in western Nepal consists of relatively complete and thick 
Gondwanan and post-Gondwanan sequences documenting sedimentation for an extended 
period ranging from late Carboniferous to early Miocene (DeCelles et al., 2004). 
However, the sequences in the eastern part (Katari and Barahchettra groups) are thinner 
and incomplete and stratigraphy has received little attention. As the Gondwanan 
sequences of the eastern part of Nepal are close to the Main Central and Main Boundary 
thrust (MCT and MBT) zones, they are intensely deformed by numerous imbricate faults 
(Dhital, unpublished). A thorough study comparing and contrasting Gondwanan 
 
4 
 
sequences from the Nepal Himalaya and India has not been done. Sakai (1983) made an 
effort to correlate the Gondwanan sequences of the Tansen Group of Nepal with Indian 
units. However, this correlation was based solely on lithology.  
1.2 LOCATION OF THE STUDY AREA 
The present study is focused on Gondwanan sequences preserved in three sections 
within the Nepal Himalaya (Fig. 1.2).  
 
Figure 1.2 Location map of study sites in Nepal. Map also shows the Damodar Basin of 
Peninsular India. 
 
5 
 
These selected sections are distributed from western part of Nepal to eastern part. 
The Tansen Group is approximately 400 km west of Kathmandu valley in the Palpa 
District and is easily accessible with motor vehicles. The Barahachettra and Katari groups 
are exposed approximately 650 km and 500 km, respectively, to the east of Kathmandu 
valley and are also easily accessible.  
Damodar basin, type locality of peninsular Indian Gondwanan sequences, is 
approximately 100 km southeast of New Delhi and only 300 km south of the 
Barahachettra Group in eastern Nepal. 
1.3 PREVIOUS WORK 
Medlicott (1864) documented a tillitic horizon,--the Blaini Formation-- in the 
Lesser Himalaya of the Simla area (India). Pilgrim and West (1928) carried out further 
detailed lithostratigraphic studies of this and correlated it with the Lower Gondwanan 
tillitic sequences of peninsular India. However, when Early Cambrian and late 
Precambrian fossils were discovered from the Krol and Tal formations above the Blaini 
Formation (Azmi and Pancholi, 1983), these tillitic beds were interpreted as a Proterozoic 
sequences. Auden (1935) was the first to record Gondwanan sequences in eastern Nepal 
based on mapping along the Lesser Himalaya. 
 In contrast with the tillitic beds in the western Himalaya, most of tillitic beds in 
the eastern Himalaya are considered to be part of the Lower Gondwanan system based on 
occurrence of plant fossils. However, Gansser (1983) introduced the Diuri Formation, a 
 
6 
 
boulder bed sequence lacking coal from the Bhutan Lesser Himalaya and correlated it 
with the late Precambrian tilloids. 
 Sakai (1983) developed a detailed stratigraphy of the Tansen Group. He identified 
five stratigraphic units in the group including the Sisne, Taltung, Amile, and Bhainskati 
formations. Earlier, the distribution of this group was thought to be confined to the 
Tansen-Sallyan-Jajarkot area of western Nepal. However, later works show that it is 
distributed over a much wider area (Upreti, 1999) and may be present beneath the recent 
Gangetic sediments of the Terai plain overlain by the Siwalik sediments (Friedenreich et 
al., 1994). Bashyal (1980) divided Gondwanan sequences in eastern Nepal into 5 units 
and grouped them together as the Barahachettra Formation. Dhital and Kizaki (1987) 
recognized another diamictite horizon in the Dang-Sallyan area within low-grade 
metamorphic rocks constituting a thrust sheet covering the sedimentary rocks of the 
Lesser Himalaya. Dhital (1992) worked on the diamictitic unit within Gondwanan 
sequences at three different locations in Nepal and mapped the Gondwanan sequences in 
the Barahachettra area.  
 DeCelles et al. (1998) studied the fluvial history of the Dumri Formation and, 
based on detrital zircon dates, assigned an early Miocene age. Zircon and Nd-isotopic 
dates generated by Decelles et al. (2004) indicate an Archean to Early Proterozoic Indian 
cratonic provenance for the Amile Formation. DeCelles et al. (2004) determined the 
provenance of the Eocene Bhainskati Formation to be Tethyan and Lesser Himalayan 
rocks. The increased proportion of late Proterozoic zircons in fluvial litharenites of the 
lower Miocene Dumri Formation reflects a Greater Himalayan provenance (DeCelles et 
 
7 
 
al., 2004). The time lag between Eocene deposition in the western and eastern parts of 
Nepal was determined to be 2 m.y.  (Najman et al., 2005) suggesting that early 
exhumation of the Himalayas was diachronous.  
1.4 OBJECTIVES 
This study focuses on evaluating the petrofacies evolution and paleotectonic 
settings of Gondwanan sequences of Nepal, in order to reconstruct the paleogeographic 
scenario of Gondwanaland, the late Paleozoic supercontinent of the southern hemisphere. 
Several approaches were taken to carry out this study. 
Petrographic studies of representative Gondwanan sandstone samples from three 
different sections of Nepal were performed to picture characteristic modes of occurrence 
and environments of deposition. Traditional heavy mineral studies and mineral chemistry 
of representative heavy minerals of Gondwanan sandstones collected from the three study 
sections were completed to evaluate the provenance and weathering history of the 
sediments. Bulk whole-rock chemistry of major, trace, and rare-earth elements of selected 
Gondwanan samples were performed to decipher their probable source rocks, 
paleogeographic positions, and weathering history. Laser 
40
Ar/
39
Ar geochronology of 
detrital muscovite grains from allegedly similar stratigraphic levels of Gondwanan 
sequences at three localities was used to uncover temporal relationships and probable 
tectonic histories of source terranes. Ultimately, this research sought to evaluate the long-
disputed along-strike stratigraphy of Gondwanan sequences of Nepal.  
 
8 
 
 
CHAPTER 2: GONDWANAN SEQUENCES OF NEPAL HIMALAYA 
2.1 GENERAL GEOLOGICAL SETTING OF NEPAL HIMALAYA 
Nepal occupies the central segment of the 2400-km-long Himalayan arc. Similar 
to other parts of the Himalayas, from south to north, Nepal can be subdivided into the 
following five major tectonic zones: (1) the Gangetic Plain, consisting of recent alluvial 
deposits of Ganga river system; (2) the Siwaliks or sub-Himalayas are typically Miocene 
deposits, deposited in the foreland depression developed after collision of the Indian plate 
with the Tibetian block; (3) the Lesser Himalayas consist of a thick succession of 
Precambrian to early Paleozoic low-grade and high-grade metamorphic rocks; (4) the 
Higher Himalayas consist of high-grade metamorphic gneiss, schists, marble and 
quartzite;  and (5) the Tibetan or Tethys Himalayas are thick successions of fossiliferous 
rocks deposited during Paleozoic and Mesozoic eras (Fig. 2.1).  
These tectonic zones are separated from each other by thrust and fault boundaries. 
The thrust system in the Nepal Himalaya includes the Main Frontal Thrust (MFT) 
between Siwaliks and Gangetic Plain, the Main Boundary Thrust (MBT) between the 
Lesser Himalaya and the Siwaliks, the Main Central Thrust (MCT) between the Higher 
Himalaya and the Lesser Himalaya, and the South Tibetian Detachment System (STDS), 
which is a gravity driven normal fault. 
 
9 
 
Figure 2.1 Geological map of Nepal show
ing locations of Gondwanan sequenc
es investigated in this study  
(after Amatya and Jnawali, 1994) 
 
10 
 
2.2 GONDWANAN STRATRIGRAPHY OF NEPAL 
The Lesser Himalayas contain three units: (1) The lowermost Precambrian to 
early Paleozoic low-grade metamorphic unit, (2) a late Paleozoic to early Cenozoic 
Gondwanan sequence, and (3) a late Precambrian high-grade metamorphic unit. The 
Gondwanan rocks occur in patches in the Lesser Himalayas. The lowermost unit is 
considered as the equivalent of the Vindhyan Group of peninsular India, which is 
unconformably underlain by Gondwanan sequences. The unconformity between these 
two groups is known as the Great Lesser Himalayan Unconformity (Upreti, 1999) or Pan-
African Unconformity (Valdiya, 1997) and is contemporary with Late Pan-African 
diastrophism. The late Precambrian high-grade metamorphic unit is actually an 
allocthonus unit thrusted over other Lesser Himalayan rocks and likely has a root zone 
within the Higher Himalaya. 
2.2.1 TANSEN GROUP 
The Tansen Group (type locality of Gondwanan sequences in Nepal) is a largely 
continental deposit, with some periodic marine incursions. The lithological succession 
and fossil content of Gondwanan sequences in the Tansen area have been very well 
studied. The Tansen Group consists of the Sisne Formation (Lower Gondwana), the 
Taltung and Amile formations (Upper Gondwana), and the Bhainskati and Dumri 
formations (post-Gondwana) (Figs. 2.2, 2.3A, B).  
Sisne Formation: The Sisne Formation unconformably overlies the Kerabari 
Dolomite of the Kaligandaki Supergroup. This disconformity is the same as the Pan-
 
11 
 
African disconformity. However, the base of the Sisne Formation cannot be defined in 
Tansen area due to its fault relation with the Kerabari Dolomite. The reported maximum 
thickness of this formation is 1020 m (Sakai, 1983). The Sisne Formation mostly consists 
of diamictite and mudstone with some beds of sandstone and conglomerate. Diamictite 
with both clayey matrix and sandy matrix are present in the area. The majority of the 
clasts are granites, gneissic rocks, limestone, sandstone, and dolomite ranging in size 
from sand to boulder. Though there is no direct evidence of a glacial origin for the  
diamictite (e.g., striations), the deposit is considered as glacial based on poor sediment 
sorting, and presence of dropstone in interbedded clay layers.  
Sandstone beds are more prominent in the middle part of Sisne section, which is 
about 80 m thick at the type section (Sakai, 1983). Beds are massive in the middle part 
but gradually show climbing ripples and parallel lamination in the upper part. Sandstone 
beds are highly fractured as a result of various tectonic stresses (Fig. 2.4). The uppermost 
part of the Sisne Formation consists of bioturbated mudstone. Some shale floats 
resembling the Ritung Bioturbated Member of the upper part of the Sisne Formation 
contain bryozoan remains ( Fenestella, Polypora and Acanthocladia), which is consistent 
with Carboniferous Fenestella shales in the Lower Gondwana of Salt Range (Sakai, 
1983).  
Taltung Formation: The Taltung Formation unconformably overlies the Sisne 
Formation; angular boulders of the Sisne diamictite and shale occur in the basal 
conglomerate of the Taltung Formation (Figs. 2.2, 2.3A, B). The basal member of the 
 
12 
 
Taltung Formation, the Charchare Conglomerate, is ~13 m thick at the type locality area 
(Sakai, 1983).  
 
 
Figure 2.2 Stratigraphic column of the Tansen Group, eastern Nepal (after Sakai, 1983), 
showing position of samples used in the current study. 
 
13 
 
 
Figure 2.3 Geological map (A) of Tansen area (after Sakai, 1983) and geological cross 
section (B) of Tansen area. 
 
14 
 
The conglomerate beds fine upward and are capped by sandstone beds. Pebbles of 
conglomerate are composed mostly of quartzite and volcanic rocks. Locally, the pebbles 
are imbricated. Imbrications suggest that the flow direction during the deposition of 
conglomerate was from SE to NW. Associated with the lower part of the Taltung 
Formation and Charchare Conglomerate is the Aulis Basalt, which is present in the 
southern part of Tansen area (Sakai, 1983). The basalt is porphyritic with plagioclase 
phenocrysts and dark-green to gray. 
 
Figure 2.4 Roadside outcrop of the Sisne Sandstone near Charchare area. 
 
The lower member of the Taltung Formation consists of several upward fining 
sequences, each of which consists of conglomerate, sandstone, and silty shale. Plant 
 
15 
 
fossils referable to Upper Gondwana are found in siltstone beds (Sakai, 1983). This 
member is interpreted as meandering fluvial deposit.   
Rhythmic sequences of sand and shale characterize the upper member of the 
Taltung Formation. The thickness of each rhythm ranges from 8 ? 20 m. The light green 
sandstone beds are mostly massive but some are cross bedded and contain scour-and-fill 
structures. Shales are characterized by hematite speckles and calcareous concretions. The 
lower part of the Taltung Formation contains the fossil plant genera Ptillophyllum, 
Pterophyllum, Cladophrebis and Elatocladus, which indicates a Jurassic-Cretaceous age 
(Sakai, 1983). 
Amile Formation: The total thickness of the Amile Formation is 230 m at the 
type locality. The basal unit of the formation consists of conglomeratic quartz arenite 
followed by white quartz arenite (Fig. 2.4) with interbedded shale.  
The middle member of the Amile Formation is characterized by the presence of 
fossiliferous argillaceous limestones, siltstones, and hematitic quartz arenite. Limestone 
beds yield several types of marine fossils including bivalves, gastropods, echinoids, and 
corals (Sakai, 1983).  
 
16 
 
 
Figure 2.5 Steeply dipping Amile Quartzite along Bhainskati Khola near the Charchare 
area, western Nepal.  
 
The upper Member of the formation is characterized by an increase in mud 
content in quartzose beds and the presence of calcareous muddy sandstones and 
carbonaceous shales. The uppermost part of the formation consists of bioturbated 
carbonaceous muddy sandstone containing coalified wood fragments. The Amile 
Formation is considered as Cretaceous to Paleocene in age based on its stratigraphic 
position and presence of scleractinian corals, which are also present in the Jurassic-
Cretaceous Tal Formation of the Kumaon Himalaya (Sakai, 1983) However, that part of 
the Tal Formation is no longer considered as the Tal Formation (Valdiya, 1997).  
 
17 
 
Bhainskati Formation: The Bhainskati Formation is not considered as 
Gondwanan deposits as it was deposited after the break up of Gondwanaland. However, 
it was deposited in the same basin where Gondwanan sequences were deposited. The 
contact between the Bhainskati Formation and the underlying Gondwanan sediments is 
unconformable. The total thickness of the formation at the type locality is about 160 m. 
The Bhainskati Formation consists of largely black shale, interbedded with calcareous, 
fossiliferous, and greenish-reddish shale. The hematite beds are present at top part.   
The fossiliferous beds of the Bhainskati Formation contain abundant bivalves, 
gastropods, and larger foraminifera (Sakai, 1983). Black shale beds contain pyritized 
wood fragments. The presence of Nummulites sp in the Bhainskati Formation indicates an 
Eocene age for this formation and suggests correlation with the Subathu Formation of the 
Kumaon Himalaya.  
Dumri Formation: The Dumri Formation disconformably overlies the Bhainskati 
Formation (Figs. 2.2 and 2.3). The formation consists of a thick succession of medium-
grained, bluish-gray quartzose sandstones interbedded with red and green shales. The 
proportion of shale decreases towards the upper part of the formation. Sandstones are 
quartzose wackes with little carbonaceous material. There are also several 
intraformational shale-pebble conglomerates and conglomeratic sandstones. The age of 
the Dumri Formation is not known. However, based on relationships with the underlying 
Bhainskati Formation and correlation with the Murree Group of Pakistan and the Dagshai 
Formation of Simla Himalaya, it is assigned an Early Miocene age. 
 
18 
 
2.2.2 BARAHACHETTRA AND KATARI GROUPS 
Barahachettra Group: Bashyal (1980) identified Gondwanan sequences in the 
eastern part of Nepal and referred to that that tectono-stratigraphic package as the 
Barahachettra Formation. He divided the whole formation into five members and defined 
the Main Boundary Thrust (MBT) as the southern boundary of the formation. The latter 
was based on the consideration that the dolomite unit just north of the MBT is the 
youngest unit of the package. Dhital (1992), however, did not include the Dolomite Unit 
in that formation. He revised the stratigraphy and divided the sequences into the 
Saptakoshi Formation, the Kokaha Diamictite and the Tamrang Formation. He assigned 
the rank of ?Group? to the Barahachettra Formation of Bashyal (1979, 1980) (Figs. 2.6 
and 2.7). 
Quartzite unit of the Saptakoshi Formation unconformably overlies the dolomite 
beds of the Precambrian Lukuwa Formation. Notably, quartzites are absent on top of 
Precambrian basement in peninsular and in other extra-peninsular Gondwanan basins 
(Bashyal, 1979, 1980). The formation consists of medium to thick bedded, gray and dark 
gray, carbonaceous quartzite, carbonaceous shale, and conglomerate with lenses of coal. 
Bashyal (1980) reported the occurrence of plant species Shizonera gondwanensis at 
Takure Khola, which belongs to the Damuda flora of Permian age. 
The Kokaha Diamictite consists of diamictite beds with clasts of quartzite, 
dolomite, schist, granite, shale and sandstone. The formation sharply overlies the 
Saptakoshi Formation. Some interbedded sandstones are also present in the formation 
 
19 
 
(Fig. 2.9). The Kokaha diamictite is overlain by calcareous sandstones of the Tamrang 
Formation. These sandstones are composed of quartz, calcite, and plagioclase in an 
argillo-calcareous matrix (Bashyal, 1980) 
Katari Group: A small patch of Gondwanan sequence rocks is observed in the 
Katari area, eastern Nepal. Along the Maruwa Khola section, Gondwanan sequences are 
observed resting unconformably over stromatolitic dolomite (Figs. 2.7 and 2.8). In the 
basal part, thin beds of diamictite with dolomite clasts embedded in a dark gray matrix 
are overlain by a trachy-basalt (Dhital, unpublished). The latter rock consists of alkali 
feldspar and potassium-rich laths of sanidine. The volcanic unit is overlain by 
carbonaceous quartz arenite (Fig. 2.10) containing abundant coalified wood. The quartz 
arenites are followed by 1-m-thick interval of volcanic tuff and thick-bedded 
conglomerate. Greenish to bluish gray calcareous sandstones and dark gray shales are 
present in the upper section. 
 
 
 
 
 
 
 
 
20 
 
 
 
 
Figure 2.6 Geological map of the Ba
rahachettra area (after D
h
ital, 
1992 and 2006) and sample collection 
locations. 
 
21 
 
  
Figure 2.7 S
t
ratigraphic Column of the Barahachet
tra (Dhital, 1992) and 
Katari groups (Dhital 
2006), eastern Nepal.  
 
22 
 
Figure 2.8 Geological map of the Katari area (Dhital, 
unpublished
) and sa
mple
-collec
t
ion loca
tion
s
. 
 
 
23 
 
 
Figure 2.9 Outcrop of Kokaha Diamictite along Kokaha Khola, eastern Nepal. 
 
Figure 2.10 Outcrop of sandstone along Maruwa Khola in Katari area, eastern Nepal. 
 
24 
 
2.3 GONDWANAN SEQUENCES IN OTHER PARTS OF NEPAL 
Sharma et al. (1984) worked on the Daban Group of Jajarkot-Piuthan-Sallyan area 
of western Nepal, which is equivalent to Gondwanan sequences. The lower unit 
(Kochhap Formation) of the Daban Group is equivalent to the Sisne Group, whereas the 
upper unit (Goyaltham Formation) is equivalent to the Taltung Formation.  
Dhital and Kizaki (1987) worked on the Gondwanan section of the Dang area of 
western Nepal. They described the Sallyan Formation as consisting of phyllitic 
conglomerate and diamictite and the Phalabang Formation as consisting of phyllitic 
slates. These formations are considered to be Lower Gondwanan sequences. The Sattim 
Formation, characterized by alternating beds of quartzose sandstone and shale, is 
considered to be Upper Gondwana. The overlying Durbing Formation is considered to be 
a post-Gondwanan sequence. 
In Surkhet area (Western Nepal), Shrestha et al. (1987) worked on the Surkhet 
Group and divided it into three formations: Melpani, Swat, and Suntar. However, only 
the Melpani Formation is considered to be part of an Upper Gondwanan sequence. The 
Swat and Suntar formations are considered to be post-Gondwanan sequences. 
The ages and stratigraphic positions of some of the Gondwanan sequences of 
Nepal are doubtful due to the absence of fossils and tectonic complexities. However, 
correlation is been done between these sequences primarily based on lithology (Table 
2.1). 
 
 
25 
 
Barahachettra 
Group 
(Bashyal, 
1980) 
    
Barahache
ttr
a 
Group 
Katar
i
 
Group 
(Dhital, 
2006) 
    
Katari  Group 
Tansen 
Group (Sakai, 
1983 
Dumri 
Formaiton Bhainskati Formation 
Amile 
Formation 
Taltung 
Formation 
Sisne 
Formation 
Sharda 
Group 
(Dhital and 
Kizaki, 
1987) 
Durbing 
Formation 
Sattim 
Formation Phalabang Formation 
Sallyan 
Formation 
Sallyan-
Jajarkot 
Group 
(Shrestha, 
1987) 
Dumri 
Formaiton Bhainskati Formation 
Amile 
Formation 
Goyaltham 
Formation 
Kochhap 
Formation 
Surkhet 
Group 
(Kayastha, 
1989) 
Suntar 
Formation 
Swat 
Formation 
Melpan
i 
Formation 
  
 
Post 
Gondwana
 
Upper 
Gondwana
 
Lower 
Gondwana
 
Age 
Mid. Mioen
e
 
Eocene 
Late Cret-
Paleocene 
L. Jurassic-
Early 
Cretaceous
 
Permo-
Carboniferous 
Table 2.1 Generalized correlation of Gondw
anan sequences of Nepal Himalaya 
 
26 
 
2.3 DISTRIBUTION OF GONDWANAN BASINS IN PENINSULAR INDIA 
The Carboniferous-Permian Gondwanan system occurs in a number of isolated 
basins of peninsular India. Three large tracts have been identified (Wadia, 1919): (1) a 
large linear tract in Bengal along the valley of the Damodar River, with sizeable 
exposures in the Rajmahal Hills; (2) an extensive outcrop in Madhya Pradesh, which 
follows the Mahanadi Valley; and (3) a series of more or less connected troughs forming 
an elongated band along the Godavari River (Fig. 2.11). 
The major Gondwanan basins in peninsular India are the Pranita Godavari Basin 
(PGB), Mahanadi Basin (MB), Damodar Basin (DB), Son Basin (SB), Satpura Basin 
(SPB), and Rajmahal Basin (RB). All these basins are aligned with three linear tracts of 
India (Fig. 2.11). 
The evolution of these basins is related to mountain building and other crustal 
movements. Earlier crustal movements include the rejuvenation of the Aravalli and the 
Eastern Ghat ranges, which caused the subsidence of large blocks between vertical or 
slightly inclined normal faults (Wadia, 1919). However, normal faulting in extensional 
lineaments between the cratonic blocks of India is also considered as the mechanism of 
Gondwanan basin development in India (Dutta, 2002).  Most of the Gondwanan basins are 
half-graben basins bounded by a fault on one side. However, this mechanism does not 
apply to all Gondwanan basins. 
 
27 
 
 
    
Figure 2.11 (A) Geological map of peninsular India (after Najman, 2005) and (B) 
distribution of Gondwanan basins in peninsular India (after Dutta, 2002) 
A 
B 
 
28 
 
 The Gondwanan system of India is divided into three classic divisions-- the 
Lower, Middle and Upper--corresponding in a general way to the Permian, Triassic, and 
Jurassic of Europe, respectively (Wadia, 1919). These units have been further divided 
into different formations. Lithological associations of the Gondwanan sequences that are 
distinct are designated as facies. Veevers (1995) has provided a composite startigraphic 
column for the Damodar Basin (DB) (Fig. 2.12)  
Talchir Formation: The Talchir Formation refers to of the lowermost beds of 
Gondwanan sequences that were first recognized in the Talchir district of Orissa, 
southeast India. This series is quite homogenous and uniform in composition over 
different basins and thus is considered as a valuable stratigraphic horizon. Boulder beds 
characteristically contain glaciated, striated, and faceted blocks embedded in a fine 
matrix, and, thus, suggest glacial action during the deposition. The formation is 
approximately 300 m thick in the Damodar basin and is considered to have been derived 
from a granitic source (Dutta, 2002) 
Damuda Group: The Damuda Group is further divided into three formations: the 
Raniganj, the Barren Measures, and Barkar formations.  
Barakar Formation: The Barakar Formation rests conformably upon the Talchir 
Formation and consists mostly of coarse-grained, white, massive sandstones and shales 
with coal seams. The Barakar Formation contains a large quantity of coal in thick seams. 
Sandstones of the Barakar Formation are more mature compared to the Talchir 
Formation; sandstones are subarkosic, occasionally grading to quartz arenite (Dutta, 
2002).  
 
29 
 
 
Figure 2.12 Stratigraphic column of Gondwanan sequences in the Damodar Basin (after 
Veveers and Tiwari, 1995).  
 
30 
 
Barren Measures: The Barren Measures is a thick sequence of carbonaceous 
shales with concretions of impure iron carbonates and oxides. This unit varies in 
thickness and composition among basins (Wadia, 1919). Towards the eastern part (in the 
DB), shale is more predominant, while in the west sandstone is more common, 
particularly in the PGB (Dutta, 2002).  
 Raniganj Formation: The Raniganj Formation consists of coal, carbonaceous 
shale, siltstone, and sandstone. Coal seams of the Raniganj Formation are thinner than 
those of the Barakar Fomation; sandstones, mostly arkosic and sub-arkosic, are finer than 
the Barakar sandstones (Dutta, 2002). The thickness of this formation ranges from 700 m 
to 900 m. 
Panchet Formation: The Panchet Formation lies unconformably on the Raniganj 
Formation, but in some places it directly overlies the Barakar Formation. The formation 
contains alternations of red clay and coarse sandstone. However, greenish shale and 
sandstone are abundant in the lower part of the formation, near the boundary with the 
underlying Raniganj Formation (Dutta, 2002).  
Mahadev Formation (Supra Panchet): The Mahadev Formation is well 
developed in Madhya Pradesh where a section of approximately 1,300 m is exposed near 
Nagpur. This formation contains of variegated, massive, coarse- to medium-grained 
sandstones with ferruginous and micaceous clay. Sandstones are super-mature quartz 
arenites with very little or no feldspar (Dutta, 2002). In the Damodar Basin, thick-bedded, 
massive sandstones and shale beds of the Mahadev Formation are exposed. The thickness 
of this formation is about 800 m at SB, but in some basins it just appears as a thin cover. 
 
31 
 
2.4 GONDWANAN STRATIGRAPHY OF OTHER PARTS OF EXTRA-
PENINSULAR INDIA AND PARTS OF GONDWANALANDS 
The Gondwanan sequences on the Indian subcontinent are not confined to 
peninsular India. Outliers of Gondwanan units have been found in northern India across 
the Indo-Gangetic plain in the western Himalayas (Punjab Salt Range, Hazara, 
Afghanistan, Kashmir) and the eastern Himalayas (Nepal, Sikkim, Bhutan, Assam, etc.). 
These units developed along the northern boundary of India during the Permo-
Carboniferous (Fig. 2.13) and are known as extra-peninsular Gondwanan sequences. 
Gondwanan sequences of peninsular India are usually relatively undisturbed. The extra-
peninsular occurrences have been folded, compressed, and, in many cases, 
metamorphosed. Basic problems related with Gondwanan sequences in extra-peninsular 
India along the Himalayan range include the identification and age evaluation of the 
sequences.  
In Kumaon Himalaya, the Blaini Formation of the Krol Belt has been correlated 
with the Sisne Formation of Nepal (Sakai, 1983; Bashyal, 1979). However, later works 
disputed the late Paleozoic position of the Blaini Formation. Nummulite-bearing shales of 
the Subathu Formation of the Garhwal Himalaya are, however, easily correlated with the 
post-Gondwanan Bhainskati Formation of the Nepal Himalaya. Only Eocene and Upper 
Cretaceous units are present in Jammu and Simla area of the western Himalaya.   In 
contrast, only Permian units are found in Bhutan and Arunachal areas of the eastern 
Himalaya. 
 
32 
 
Permian Gondwanan units have been reported from the Khalaspur Basin. Here, 
these are overlain by Miocene and younger deposits (Hossain et al., 2002). Gondwanan 
sequences have been divided into six facies including coal lithofacies. However, unlike in 
Nepal and India, marine successions have not been reported from this Bangladesh 
Gondwanan basin in Bangladesh.  
 
Figure 2.13 Distribution of Gondwanan basins on the Indian subcontinent (Frakes, 1975)  
 
33 
 
Fluvial conglomerates have been reported from this basin (Hossain et al., 2002). 
However, Gondwanan sequences of this basin belongs to peninsular Indian Gondwanan  
sequences based on paleo-tectonic reconstructions (Khan, 1994). 
 
Figure 2.14 Main tectonic subdivision and relation of Indian Precambrian shield (after 
Khan, 1994).  
 
 
34 
 
Based on gravity data, the eastward extension of Gondwanan basins extends up to 
the Yilgarn craton of Western Australia (Fig. 2.14; Khan et al., 1994). This east-west 
stretched basin is the northernmost Gondwanan sub-basin that was separated from 
southern Gondwanan sub-basin by a northeast-southwest intra-cratonic high connecting 
the Shillong Massif and the Chhotanagpur gneissic terrane. The southern Gondwanan 
sub-basin was extended from Eastern Ghat palaeo-shelf to the western periphery of the 
Shillong plateau through Ghatal- Behrampur. 
Gondwanan basins were distributed on all continental blocks of Gondwanaland 
including India, Australia, Antarctica, Africa, and South America. However, the 
distributions of basins and facies were controlled by paleolatitude and topographic highs 
(Fig. 2.15). Gondwanan sequences of peninsular India are usually correlated with the 
Collie Basin of Australia and Karoo Basin of South Africa (Veevers, 2006)).  
The Collie Basin lies within the Yilgarn craton and contains Permian coal-bearing 
sequences (Veveers, 2006). The oldest unit of Collie Basin is the Stockton Formation, 
which consists of sandstone, shale, and diamictite confirming a glaciogenic origin of 
sediments. Three coal measures with varying thickness (Ewington, Premier, and Muja 
Coal measures) overly the Stockton Formation (Veveers, 2006). These coal measures are 
underlain by sandstones of the Cretaceous Nakina Formation.  
The Karoo Basin of South Africa consists of several connected or isolated basins 
that developed between the Carboniferous and Jurassic. The Karoo system in the south, 
also known main Karoo system, includes the signature of a subduction environment. To 
the west, the system reflects deposition associated with an extensional environment 
 
35 
 
(Catuneanu et al., 2005). The lowermost part of the Dwyka Formation consists of glacial 
till. The overlying Volksrust Formation consists mostly of shale with sandstone. The 
Estcourt, Belmont, Otterburn, Mol Teno, and Elliot formations contain varying amount of 
sandstone and shale. The Estcourt Formation also contains several coal horizons. The 
total thickness of the Karoo system at the Main Karoo Basin (South Africa) is 1100 m. 
 
Figure 2.15 Distribution of Gondwanan basins in Gondwanaland in Early Permian 
(Veveers and Tiwari, 1995). 
 
36 
 
 
 
CHAPTER 3: EVOLUTION OF GONDWANAN BASINS 
3.1 CONTINENTAL BREAK UP OF GONDWANALAND  
The sedimentation cycle in the Purana Basin of peninsular India and its 
equivalents, in the Lesser Himalaya was ended by early Cambrian time 
contemporaneously with Pan-African mountain-building (Valdiya, 1997). However, due 
to localized uplift, narrow fluvial depositional system developed in the Zanskar and 
Hazara areas.  
The break up of the Gondwanaland has been related with continental flood 
volcanism that occurred since early Mesozoic (Segev, 2002). Several models have been 
proposed to explain the mechanisms for the break up, but none of these are free from 
controversy. However, the popular model involves lower mantle upwelling. The 
Carboniferous Variscan (Hercynian) orogen has been related with the collision of several 
Gondwanan plates and Laurasia during the final assembly of Pangaean supercontinent 
and to post-convergent extension by crustal thinning, lowering of crustal viscosity, 
formation of numerous sedimentary basins and widespread alkaline magmatism between 
320- 240 ma (Segev, 2002). The load of accumulated sediments in these rifted basin 
caused normal faulting that resulted in the famous half-graben Gondwanan basins. 
The Gondwana supercontinent was bounded on its southern side until Early 
Jurassic by an active subduction zone responsible for the fold belts of South Africa, 
 
37 
 
South America, and southwest Antarctica. During the Jurassic, the Karoo area was 
uplifted and subsequent Karoo plume activity resulted in proto oceanic rifting between 
East Gondwana (India, Antarctica, and Australia) and West Gondwana (Africa and South 
America) (Segev, 2002).  
Extensional movement between East Antarctica, India, and the western Australian 
margin was reactivated during the Early Cretaceous. The break up between India and 
Western Australia along the Cuvier and Gascyone Abyssal Plains started between 132-
130 Ma (Segev, 2002). During that period, a variety of igneous rocks were emplaced in 
the northeast Indian graben along with seaward dipping flows forming the Rajmahal, 
Bengal and Sylhet traps (Fig. 3.1 A). After break up and initial drifting, the space 
between India and Antarctica was filled by Kerguelen plateau basalts. During the Upper 
Cretaceous, the rifting between Madagascar and Seychelles-India occurred, along with 
basaltic volcanism in Madagascar and Seychelles, and gabbroic intrusions in India.  
The breakup between Seychelles and India was followed by rifting along the Goa, 
Narmada-Son, which resulted in the extrusion of the Deccan Trap basalts between 70-61 
Ma (Segev, 2002) (Fig. 3.1B). 
 
38 
 
 
 
 
Figure 3.1 Generalized reconstructions of (A) Early Cretaceous and (B) Tertiary 
Gondwanaland (from Segev, 2002)   
3.2 EVOLUTION OF PASSIVE MARGIN ALONG THE NORTHERN 
BOUNDARY OF PENINSULAR INDIA 
The character of the northern margin of peninsular India prior to collision with 
Tibet remains controversial. What was the total length of India subducted beneath Tibet? 
In the various models and mechanism proposed, the length has been estimated to be as 
little as a few kilometers and as high as 2800 km. The latter estimate involves the concept 
of a ?Greater India?. India was a part of Gondwanaland from the Precambrian to Jurassic, 
A B
 
39 
 
before it became isolated from Africa, Australia, and Antarctica. India remained a passive 
margin during its northeast-directed movement from the Cretaceous to the Eocene when 
it collided with Asia (Brookfield, 1993).  
The Tibetian block was separated from India during the Permian, which resulted 
in subsidence of the High Himalaya and deposition of a very thick sedimentary 
succession on oceanic crust in the North Himalaya (Brookfield, 1993). Some still believe 
that a proto-Himalayan range and Himalayan micro-continent existed between the Lesser 
Himalaya and Tethys Himalayan zones between the Cambrian and late Paleozoic. Such a 
high would have an important role as a sedimentary and faunal barrier between the basins 
of both zones (Sakai, 1989) (Fig. 3.2). However, this hypothesis cannot be proved with 
existing stratigraphic, sedimentological, and paleomagnetic field data. Rather, spatial and 
environmental differentiation between the Lesser Himalayan and the Tethys Himalayan 
basins with separation of about 5,000 km is proposed as the probable cause of different 
sedimentary facies development in these two domains (Jain and Kunwar, 1970).  
Generally, the classification of ?extra-peninsular Gondwanan sequence? is given 
only to the sequences developed in the Lesser Himalayan terrains that have more or less 
similar depositional environment and source rocks as peninsular Indian Gondwanan 
sequences.  
 
40 
 
 
Figure 3.2 Schematic reconstruction of micro continent barrier supposed to have existed 
between the Lesser Himalayan and the Higher Himalayan terrains.  
3.3 EVOLUTION OF FACIES AND CLIMATIC CONTROL DURING 
DEPOSITION OF GONDWANAN SEQUENCES  
Variation of paleoclimate was an important factor controlling sedimentation in 
Gondwanan basins. The separations of eastern Gondwanaland from western 
Gondwanaland, then separation of India from Australia and later from Madagascar were 
accompanied by the northward movement of India. Hence, the distributions of lithologies 
on these basins are related with paleolatitudes (Fig. 3.3) of the basins and ongoing 
tectonic activity. 
The composition of sand and clay minerals in shale, and the presence of coal in 
these different facies was controlled by climatic conditions during deposition (Dutta, 
2002). 
 
41 
 
 
Figure 3.3 Paleogeography of Gondwanaland (www.paleoportal.com, 2009). 
 
 
42 
 
 Dutta (2002) inferred that initial embryonic basins started to receive glacial 
deposits, when the Gondwanan basins were situated along southern high latitudes. 
Afterwards, glacial outwash plains and glacial lakes gave rise to a meandering fluvial 
system with well-defined channels and broad flood plains. The latter were filled with 
coal, carbonaceous shale, gray shale and siltstone (Dutta, 2002) during the Permian when 
the climate was humid. After sometime, climate became less humid and deposition of 
coal was reduced; sand, carbonaceous shale, and gray shale-siltstone became more 
abundant. However, coal-forming environments returned during the Late Permian, but 
were not as extensive as earlier (Dutta, 2002). Although this facies formed mainly in 
meandering fluvial systems, some marine signatures have been identified by some 
workers, reflecting, periodic incursion of the sea (Valdiya, 1997) (Fig 3.4). During the 
Triassic, coal-bearing facies were replaced by red-bed sequences (Dutta, 2002). 
Alternating sequences of bright colored red shale and feldspar-rich sandstones beds 
comprise the major thickness during this period. However, Triassic deposits are not 
present in extra-peninsular Gondwanan sequences. 
Subsequently, a major tectonic event caused the entire source area throughout 
India to uplift due to rifting. This tectonic uplift was coupled with a change of climate 
from arid to warm humid conditions. Climatic change resulted in deposition of super-
mature sediments, while tectonic uplift caused river systems to change from meandering 
to braided (Dutta, 2002). The overall change caused deposition of coarse-grained 
conglomerates, pebbly sandstones, and sandstones. These sediments covered the entire 
landscape and overlapped on to older sediments and basement rocks (Dutta, 2002).  
 
43 
 
Extra-peninsular Gondwanan sequences were being deposited in meandering-
braided fluvial systems but also reflect periodic marine incursion. Few extra-peninsular 
Gondwanan successions consist of volcanic clasts and volcanic flows that show the proof 
of syn- or pre-depositional volcanic activities (Fig 21 B). During deposition of the Amile 
Formation, which is dominated by sandstones, the environment was shallow marine. The 
Eocene Bhanskati Formation not only shows the change in depositional environment 
from marine to continental but also a change in provenance from cratonic India to the 
Himalayan orogenic belt. Deposition of Gondwanan sequences in eastern and western 
parts of Nepal was not synchronous; sequences are older towards the west (Bashyal, 
1980). 
 
Figure 3.4 Marine incursion in Gondwanaland during the Permian (Valdiya, 1998). 
 
44 
 
 
CHAPTER 4: SANDSTONE PETROGRAPHY 
4.1 INTRODUCTION 
 Sandstone petrography is a classical method of provenance study. Sandstone 
petrology is based on the assumption that sandstones from similar tectonic settings will 
have similar composition. The ratios of major clastic components (e.g., quartz, feldspar, 
and lithic fragments) from known tectonic settings have been plotted by several workers 
to discrminate various provenance fields (Dickinson and Suczek, 1979; Ingersoll and 
Suczek, 1979; Dickinson, 1985). Besides rock types in source areas, sediments are also 
influenced by climate, relief, transporting agent, weathering and diagenesis. Hence, 
sandstone composition can help to reconstruct paleogeography, paleotectonics, and 
paleoclimate (Suttner, 1977; Ingersoll et al., 1984; Johnson, 1993).  
 Provenance studies based on mineralogical abundance are based on the 
assumption that detrital composition has not been altered significantly by sedimentary 
processes including, transportation, weathering, and diagenesis. However, tectonic 
discrimination based on mineralogical analysis will not be that effective to trace 
provenance if there is mixing detritus derived from different source areas (Velbel, 1985). 
Multiple basin analytical techniques, including mineral chemistry, bulk-rock chemistry, 
detrital thermochornology, and traditional modal analysis, are generally required to 
identify the influence of multiple provenances or source terranes (Morton and 
Hallsworth, 1999).  
 
45 
 
4.2 METHODS 
A total of twenty-three sandstone samples were collected from three different 
Gondwanan sequences of Nepal; the Tansen (western Nepal), Katari (eastern Nepal), and 
Barahachettra (eastern Nepal) groups. After preparation in the rock cutting lab of 
Department of Geology and Geography at Auburn University, samples were sent to 
Spectrum Laboratories in Vancouver, WA for preparation of petrographic thin sections. 
Half of each thin section was stained to assist in the identification of various feldspar 
grains. Mineralogical compositions of the samples were determined by compositional 
modal analysis following the Gazzi-Dickinson point-count convention which minimizes 
the control of grain size on sand composition (Dickinson, 1970; Ingersoll et al., 1984). A 
minimum of 300 framework grains were counted from each sample. Different end-
members were recalculated from the point-count data to plot different ternary diagrams 
for the discrimination of tectonic setting (Dickinson, 1970; Dorsey, 1988; Uddin and 
Lundberg, 1998). The following compositional parameters (Table 4.1) were calculated: 
Qt = total quartz; Qm = monocrystalline quartzose grains; Qp = polycrystalline quartz 
grains, including chert grains; F = total feldspar grains; P = plagioclase feldspar grains; K 
= potassium feldspar grains; L = lithic fragments; Lt = total lithic fragments; Ls = 
sedimentary lithic fragments; Lv = volcanic lithic fragments; Lm =metamorphic lithic 
fragments.  
Polycrystalline quartz is included at the Qt end member for QtFL plot to keep 
plutonic polycrystalline quartz grains distinct from the metaquartzite fragments. All 
quartzose grains are plotted at Qt end member for QtFL plots. This is intended to provide 
 
46 
 
emphasis to the stability of grains during various processes of sedimentary cycles 
including weathering, transport, etc. In contrast, chert and polycrystalline quartz are 
included in the Lt end-member on QmFLt plots. Details of the normalized modal 
compositional calculations are given in Table 4.2 . 
Table 4.1 Recalculated modal parameters of sand and sandstone.  
 
Primary parameters (after Graham et al., 1976; Dickinson and Suczek, 
1979; Dorsey, 1988; Uddin and Lundberg, 1998)  
 
Qt = Qm + Qp, where  
                  Qt = total quartzose grains  
                  Qm = monocrystalline quartz (> 0.625 mm)  
                  Qp = polycrystalline quartz (or chalcedony)  
Feldspar Grains (F = P + K), where  
                  F = total feldspar grains  
                  P = plagioclase feldspar grains  
                  K = potassium feldspar grains  
Unstable Lithic Fragments (Lt = Ls + Lv +Lm), where 
                  Lt = total unstable lithic fragments  
                  Lv = volcanic/metavolcanic lithic fragments  
                  Ls = sedimentary/metasedimentary lithic fragments 
                  Lm
1
= very low- to low grade metamorphic lithic fragments 
                  Lm
2
= low-to intermediate grade metamorphic lithic fragments 
 
 
47 
 
 
4.2 PETROGRAPHY 
 The Gondwanan and post-Gondwanan sequences of the Lesser Himalaya in Nepal 
are mostly continental and shallow marine deposits. The Gondwanan sequence was 
deposited on an eroded surface of Precambrian basement of the Lesser Himalaya. Like in 
all other peninsular and extra-peninsular Gondwanan sequences, Gondwanan stratigraphy 
of Nepal begins with a diamictite bed except for the Barahachettra Group.  
4.2.1 TANSEN GROUP 
4.2.1.1 Sisne Formation 
 The Sisne Formation is composed of a thick pile of diamictite and rthymite beds. 
However, there are few sandstone beds between the diamictites. Pale-green, medium-
grained Sisne sandstones are highly fractured and consist of numerous quartz veins. Four 
sandstone samples were collected from the Sisne Formation: 16-3, 16-4, 16-5, and 16-6.  
 Sandstones of the Sisne Formation are composed mostly of quartz and feldspar. 
The average modal composition of the Sisne sandstone is Qt
56
F
42
L
2
. Quartz grains are 
rounded to angular.  Plagioclase, K- feldspar, and perthite are abundant and variably 
altered to clay minerals. A few low-medium grade metamorphic rock fragments are 
observed in the samples. Mica flakes are also abundant. The Sisne sandstone also 
contains common garnets (Fig. 4.1A), some of which are very well preserved. 
 The Sisne sandstones contain approximately 20% matrix, which consists of 
organic-rich and calcareous clay. Clay matrix resulted from alteration of feldspars. The 
 
48 
 
distribution of the matrix is not uniform in the formation. Sutured framework grain 
contacts are observed where matrix contents are low.  
4.2.1.2 Taltung Formation  
 The Taltung Formation, which has been divided into two members, consists of 
cyclic deposits of conglomerate, sandstone, and shale in the lower member and rhythmic 
beds of sandstone and shale in the upper member (Sakai, 1983). The Aulis Basalt is also 
included in the Taltung Formation. In the absence of good outcrop during fieldwork for 
this study, only one sample (K-1) of sandstone from the lower member was collected 
from this formation. 
 The Taltung Formation sandstone sample consists mostly of quartz, feldspars, and 
volcanic fragments. The modal composition of the Taltung Formation is Qt
32
F
36
L
32
. 
Monocrystalline quartz grains are subrounded to angular. A few grains of polycrystalline 
quartz are also present. Feldspar grains are highly altered and replaced by calcite. 
Volcanic fragments contain euhedral plagioclase crystals (Fig. 4.1B). Numerous irregular 
grains of organic material are also present in the sample. Rare metamorphic rock 
fragments variably altered to sericite are present in the thin section.  The framework 
grains have been cemented and locally replaced by sparry calcite. 
The Aulis Basalt is associated with lower member of the Taltung Formation in the 
Aulis area of Tansen. Sample 15-2 collected from that area shows the interstitial 
groundmass of lath-shaped plagioclase microlites (Fig. 4-5B).  
 
 
49 
 
4.2.1.3 Amile Formation 
 The Amile Formation consists of alternating layers of shale and quartzose 
sandstone. The middle part of the Amile Formation consists of calcareous beds, which 
according to Sakai (1983), yield several types of marine fossils. Five samples 16-12, 16-
8, 16-9, 15-5 and 15-6 were collected from quartzose sandstone beds of the Amile 
Formation. The modal composition of the Amile Formation is Qt
100
F
0
L
0
. Quartz grains 
are mostly monocrystalline.  
The matrix content of the samples is very low. Some of the samples with very low 
matrix contents exhibit concavo-convex contacts between quartz grains (4.2 A), although 
interstitial space is locally filled with clay minerals. Samples from the lower part of the 
formation are cemented by hematite. Samples from the upper part of the formation 
contain common carbonaceous materials. Some heavy minerals like zircon, tourmalines 
are observed in all samples.  
4.2.1.3 Bhainskati Formation 
 The Bhainskati Formation is dominated by black shale in the lower part with red 
purple shales and hematite bands in the upper part. Few sandstones beds are present 
within the upper part. One sample, 15-8 was collected from the Bhainskati Formation. 
The Bhainskati sandstone is dark gray. The modal composition of the sandstone is 
Qt
63
F
13
L
24
. Quartz grains are very angular to angular. Feldspar grains are highly altered 
to clay minerals. Lithic fragments include high-grade metamorphic, low-grade 
metamorphic and sedimentary lithic grains. 
 
50 
 
 The sample is characterized by fair amount of clay minerals. However, concavo-
convex sutures between grains are also present locally (Fig. 4.2 B). Alteration of 
feldspars grains to sericite was observed which is more prominent along grain 
boundaries. 
  4.2.1.3 Dumri Formation 
 The Dumri Formation, the top most unit of the Tansen Group, is a thick series of 
medium-grained, bluish gray quartzose sandstones interbedded with red and green shales. 
As the objective of this work was initially focused on the Gondwanan sequences only one 
sample (sample 16-1) was collected from the Dumri Formation from the Makhlo Dumri 
area.  
 The Dumri sandstone (sample 16-1) is pale green. The modal composition of the 
sample is Qt
73
F
5
L
22
. The sample consists of immature and various sized quartz grains. 
Most of the polycrystalline quartz grains are angular and irregular, whereas most of the 
monocrystalline grains are moderately- to well-rounded. The percentage of feldspar is 
very low. The few feldspar grains observed are plagioclase grains that show various 
degrees of alteration. Lithic fragments include low- to medium-grade metamorphic, chert, 
and volcanic clasts (Fig. 4.3 A). 
 Clay matrix makes up more than 25% of the total composition of this sample. The 
framework grains contacts vary from floating to sutured.  Most of the framework grains 
show alteration along the grain boundaries.   
 
 
51 
 
4.2.2 KATARI GROUP 
The entire Katari Group is considered to be a Permo-Carboniferous unit. It 
consists of diamictites, volcanic rocks, and quartzites. In the Katari Group, three types of 
quartzites are found in outcrops; white, carbonaceous, and calcareous. White quartzites 
are dominant in the lower part of the section, while carbonaceous and calcareous 
quartzites are dominant in the upper part. White quartzites are highly fractured, 
weathered and altered. As such, fresh sample collection was not possible from this unit. 
Two samples, 26-6 and 26-8, of carbonaceous-calcareous quartzites were collected from 
the Maruwa Khola section. 
The average composition of the Katari Group sandstones is Qt
100
F
0
L
0
,
 
Samples 
contain ~ 65% monocrystalline grains. The sample consists of various sized quartz 
grains. Some of the grains are deformed following particular direction of deformation 
indicating post depositional deformation into polycrystalline quartz. However, some of 
them are not significantly distorted and preserve their rounded shapes (Fig. 4.3 B). Some 
of the quartz grains are altered along boundaries and fractures. 
Matrix materials consist of mica and calcite in roughly equal abundance (~15%). 
Calcite is also present as the cement.  
 
52 
 
4.2.2 BARAHACHETTRA GROUP 
 The Barahachettra Group consists of diamictites, quartzites, calcareous 
sandstones, and volcanic tuffs. All these units were previously considered to have been 
deposited during the same geological age (Permo-Carboniferous). However, Dhital 
(1992) has proposed that the Group includes two temporally distinct formations; the 
Permo-Carboniferous Saptakoshi Formation and the Cretaceous Tamrang Formation. 
4.2.2.1 Saptakoshi Formation 
 The Saptakoshi Formation consists of quartzites, diamictites, and volcanic 
materials. Four samples were collected from the Saptakoshi Formation; samples 22-7 
(volcanic tuff) and 22-9 were collected along the Kokaha Khola, and samples 23-5 and 
23-7 were taken along the Saptakoshi River. Sample 23-5 collected from sandstone 
interbed between diamictites, differs significantly from samples 23-7 and 22-9 which are 
mostly quartzites.  
 Sample 23-5 has the modal composition of Qt
60
F
37
L
2
, with abundant various sized 
quartz clasts. Quartz grains are rounded to angular in shape. Plagioclase and potassium 
feldspars are abundant and are variably altered to clay minerals (4.4 A). A few chert 
grains were observed in the sample. Micas are also common. This sandstone is similar in 
composition to the Sisne sandstone of the Tansen Group of the western Nepal. Not only 
are feldspar contents high, but sample also contains common garnets as seen in the Sisne 
Formation.  
 
53 
 
 Samples 22-9 and 22-7 have an average modal composition of Qt
100
F
00
L
00
. Sixty 
five percentage of the quartz is monocrystalline. The quartz grains are deformed along 
particular direction indicating post depositional deformation (4.4 B). Matrix present in 
the samples is composed of micritic calcite and mica.  
4.2.2.1 Tamrang Formation 
 The Tamrang Formation consists mostly of calcareous sandstones. Seven samples 
were collected from the Tamrang Formation along the Saptakoshi River (23-2, 23-3, 23-
4) and along the Kokaha Khola (22-4, 22-5, 22-6). The modal composition of the 
Tamrang Sandstone is Qt
61
F
29
L
19
. Tamrang sandstone consists of various sized and 
immature quartz grains. Feldspars are slightly smaller than quartz and are highly altered. 
The samples consist of various types of lithic fragments, including metamorphic (various 
grades) and sedimentary (chert and dolomite).  
 The matrix observed present in the samples are of two types; calcite and mica. 
The percentage of mica is higher in samples 22-4, 22-5, 23-2, and 23-3. However, in the 
samples 22-6 and 23-4, the proportion of micritic calcite matrix is higher. The framework 
grain contacts vary from concavo-convex to floating (4.5 A). 
 
54 
 
 
(A) 
 
(B) 
Figure 4.1 Representative photomicrographs of Gondwanan sandstones, western Nepal. 
(A) Sisne Formation; (B)Taltung Formation (Qp = polycrystalline quartz, Qm = 
monocrystalline quartz, Plag = plagioclase, K-spar = potassium feldspar, Grt= garnet, 
Lm
1
= low-grade metamorphic lithics, Lm
2
= low- to intermediate-grade metamorphic 
lithics, Ls = sedimentary lithic fragments, Lv = volcanic fragments, Cal = Calcite). 
 
55 
 
 
(A) 
 
(B) 
Figure 4.2 Representative photomicrographs of Gondwanan sandstones, western Nepal. 
(A) Amile Formation; (B) Bhainskati Formation (Qp = polycrystalline quartz, Qm = 
monocrystalline quartz, Plag = plagioclase, K-spar = potassium feldspar, Ls = 
sedimentary lithic fragments, Lm
2
 = high-grade metamorphic fragments, Lm
1
= low-grade 
metamorphic fragments). 
 
56 
 
 
(A) 
 
(B) 
Figure 4.3 Representative photomicrographs of Gondwanan sandstones, (A) Dumri 
Formation, western Nepal. (B) Katari Group, eastern Nepal (Qp = polycrystalline quartz, 
Qm = monocrystalline quartz, Plag = plagioclase, K-spar = potassium feldspar, Ls = 
sedimentary lithic fragments, Lm
2
 = low- to intermediate-grade metamorphic fragments, 
Lm
1
= very low- to low-grade metamorphic fragments).
 
57 
 
 
(A) 
 
(B) 
Figure 4.4 Representative photomicrographs of the Gondwanan sandstones, (A) 
Saptakoshi Formation, eastern Nepal, sample 23-5; (B) Saptakoshi Formation, eastern 
Nepal, sample 22-7 (Qp = polycrystalline quartz, Qm = monocrystalline quartz, Plag = 
plagioclase, K-spar = potassium feldspar, Ls = sedimentary lithic fragments, Lm
2
 = low- 
to intermediate-grade metamorphic fragments, Lm
1
= very low- to low-grade 
metamorphic fragments).
 
58 
 
 
(A) 
 
(B) 
Figure 4.5 (A) Representative photomicrograph of the Tamrang sandstone, eastern Nepal 
(Qp = polycrystalline quartz, Qm = monocrystalline quartz, Plag = plagioclase, K-spar = 
potassium feldspar, Ms = muscovites, Lm
2
 = low- to intermediate grade metamorphic 
fragments, Lm
1
= very low- to low-grade metamorphic fragments); (B) Photomicrograph 
of Aulis Basalt (Tansen, western Nepal) with abundant plagioclase laths.  
 
59 
 
Table 4.2 Normalized modal compositions of Gondwanan sandstones in Nepal 
  Qt F L Qm F Lt Qm P K Ls Lv Lm 
Rock Unit/Sample No.                   
Dumri Fm             
16-1 73 5 22 65 5 30 92 6 2 27 0 73 
Bhainskati Formation                       
15-8 63 13 24 38 13 49 74 21 5 15 7 78 
Amile Quartzite                          
16-12 100 0 0 76 0 24 100 0 0 0 0 0 
16-8 100 0 0 58 0 42 100 0 0 0 0 0 
16-9 100 0 0 70 0 30 100 0 0 0 0 0 
15-5 100 0 0 40 0 60 100 0 0 0 0 0 
15-6 100 0 0 48 0 52 100 0 0 0 0 0 
Mean  100 0 0  58  0 42  100 0 0 0 0 0 
Standard Deviation 0 0 0  15  0  15 0 0 0 0 0 0 
Taltung Fm                          
K-1 32 36 32 15 26 59 15 37 48 43 40 17 
Sisne Fm                          
16-3 57 43 0 27 43 30 39 30 31 0 0 0 
16-4 52 45 3 33 45 22 42 27 31 0 0 100 
16-5 56 41 3 30 41 29 42 27 31 0 0 100 
16-6 60 40 0 27 40 33 40 28 22 0 0 0 
Mean  56 42 2 29 42 29 41 28 29 0 0 50 
Standard Deviation 3 2 2 3 2 5 2 1 5 0 0 58 
Katari Group                         
26-6 100 0 0 68 0 32 100 0 0 0 0 0 
26-8 100 0 0 62 0 38 100 0 0 0 0 0 
Mean  100 0 0 65 0 35 100 0 0 0 0 0 
Standard Deviation 0 0 0 4 0 4 0 0 0 0 0 0 
Tamrang Formation                    
22-4 57 16 27 27 16 57 63 9 28 0 0 100 
22-5 58 20 22 27 20 53 57 17 26 13 0 87 
22-6 66 18 18 31 18 51 53 10 37 0 0 100 
23-2 63 27 8 29 27 42 51 5 46 0 0 100 
23-4 59 19 22 33 19 48 64 13 23 0 0 100 
22-10 60 19 21 22 19 59 46 15 39 14 0 86 
22-6 66 18 18 31 18 51 53 10 37 0 0 100 
Mean  61 20 19 29 20 52 55 11 34 4 0 96 
Standard Deviation 4 4 6 4 4 6 6 4 8 7 0 7 
Saptakoshi Formation                      
23-5 60 37 3 22 37 41 37 32 31 0 0 3 
Saptakoshi Formation (Quartzite)                    
23-7 100 0 0 63 0 37 100 0 0 0 0 0 
22-9 100 0 0 67 0 33 100 0 0 0 0 0 
Mean  100 0 0 65 0 35 100 0 0 0 0 0 
Standard Deviation 0 0 0 2.8 0 2.8 0 0 0 0 0 0 
 
60 
 
4.2 SANDSTONE MODES 
A vertical profile is constructed to show the distribution of major framework 
grains used for modal analysis (Fig. 4.6). The Tansen Group (western Nepal) shows that 
the percentage of feldspar is relatively higher in the Permo-Carboniferous Sisne 
Formation than the younger units. The percentage of lithic fragments is higher in the 
Jurassic-Cretaceous Taltung Formation, Eocene Bhainskati Formation and early Miocene 
Dumri Formation. In the Cretaceous-Paleocene Amile Formation Quartz percentages are 
higher than other units.  
The percentage of quartz in the Permo-Carboniferous Katari Group is higher than 
the Tansen Group of western Nepal. Further east, in the Barahachettra area, the quartz 
dominated during the initial phases of Permo-Carboniferous deposition. However, lithic 
fragments became more significant in the upper sections. The percentage of lithic 
fragments increases in the Tamrang Formation than in the underlying Barahachettra 
Formation. 
 
 
 
61 
 
 
Figure 4.6 Variation of modal miner
alogical composition of the Gondw
anan sandstones of Nepal.  
 
62 
 
4.2 PETROFACIES EVOLUTION 
Tectonic discrimination plots of Gondwanan sandstone from the three different 
sections of Nepal were prepared on the basis of modal compositional analyses of 
sandstone framework grains. Tectonic discrimination plots of Gondwanan sandstones 
from three different sections of Nepal were prepared based on modal compositional 
analysis of sandstone framework grains. The QtFL plot (Fig. 4.7) shows that the Sisne 
Formation sandstones are intermediate between ?basement uplift? and ?transitional 
continental? deposits. All diamictites of the Permo-Carboniferous in peninsular India 
were deposited in half-graben basins along major lineaments (Veevers and Tiwari, 1995). 
The high percentage of feldspars and low amount of lithic fragments (Qt
56
F
42
L
2
) reflect 
that tectonic setting. Moreover, another controlling factor during the Permo-
Carboniferous was climate; the area was situated at high southern latitude which inhibited 
intensive weathering. As the central part of the India was blocked by the Satpura-
Bundhelkhand-Aravali mountain series (Naqvi, 2005), the northern part of peninsular 
India, which could have changed gradually from continental to shallow marine 
environments, was receiving sediments from the orogenic belts. However, in the QmFLt 
diagram, the Sisne Formation plots in the ?dissected arc? due to concentration of 
monocrystalline quartz (Fig. 4.8). Plagioclase contents are almost equal to potassic 
feldspars (Fig. 4.9). Most point-count data plots at the Lm end of Ls-Lm-Lv triangular 
diagram (Fig. 4.10). 
The Taltung Formation, with a modal composition of Qt
32
F
36
L
32
,
 
plots in 
?dissected arc? field (Fig. 4.7). The Taltung Formation consists mostly of continental 
 
63 
 
deposits and contains common volcanic fragments associated with the rifting of Australia 
from India and associated volcanic eruption (Sakai, 1989). The Taltung sandstones are 
dominated by volcanic and sedimentary fragments. They contain very few metamorphic 
lithic fragments. On the QmFLt plot, these sandstones fall in ?transitional arc? field.  
During deposition of the Amile Formation (Late Cretaceous to Paleocene), the sea 
level was falling globally (Vail, 1977) probably resulting in land barriers for sediment 
transport from source areas to the basins. Moreover, at that time India was characterized 
by humid and tropical climate in which intensive chemical weathering may have 
produced mature sands. The Amile Formation with modal composition of Qt
100
F
0
L
0
 is a 
?craton interior? deposit (Fig. 4.7). However, presence of polycrystalline quartz pulls the 
Amile Formation down to the ?Quartzose recycled? provenance field at the QmFLt plot 
(Fig. 4.8). 
The Bhainskati Formation has higher lithic fragments than the underlying Amile 
Formation. The QtFL modal composition of the formation is Qt
63
F
13
L
24
. Bhainskati 
deposition took place during the Eocene when India began colliding with Tibet (Sakai, 
1983). DeCelles et al. (1998) suggested a back bulge setting for deposition of the 
Bhainskati Formation. The source rock for the sediment could be the Indian craton and 
also the Higher Himalaya and Tibetan Tethys sediments. The Bhainskati Formation has 
very low feldspar contents and plots in the ?recycled orogenic? provenance field in the 
QtFL diagram (Fig. 4.7). But it falls in ?transitional recycled? field on the QmFLt plot 
(Fig. 4.8).  
 
64 
 
The Dumri Formation, which has even higher lithic fragment contents than the 
Bhainskati Formation falls, in the ?recycled orogenic? provenance field on the QtFL plot 
and in ?the quartzose recycled? field on the QmFLt plot (Fig. 4.8). The modal 
composition of the Dumri Sandstone is Qt
73
F
5
L
22
. As the Indian continent already had 
collided with Tibet before deposition of the Dumri Formation, the source terranes shifted 
from cratonic India to the Himalayan orogenic belt. The Higher Himalaya could have 
provided high-grade metamorphic fragments, while the Lesser Himalaya could be the 
source areas for the low-grade metamorphic and sedimentary grains. 
The modal composition of the Permo-Carboniferous unit of the Katari Group is 
Qt
100
F
0
L
0
, which fall in the ?cratonic interior? provenance field on the QtFL plot (Fig. 
4.8) and ?quartzose recycled? field in the QmFLt plot (Fig. 4.9). However, it is unlikely 
to get major change in climatic conditions during same geological time interval between 
the depositional basins of the Tansen Group and the Katari groups, as both were part of 
the northern passive margin of the Indian peninsula aligned almost in the same latitude.  
Further east, the Barahachettra section shows more problems to validate the 
present stratigraphy based on paleogeographic position of the Indian peninsula and 
stratigraphy of other contemporaneous Gondwanan units deposited in similar tectono-
climatic domain (Tansen Group). The change in composition from Qt
60
F
37
L
2
 for 
sandstone of the Saptakoshi Formation to Qt
100
F
00
L
00 
of Saptakoshi quartzite and 
Qt
61
F
29
L
19
 of the Tamrang Formation is unlikely to have occurred within Permo-
Carboniferous when Gondwanaland was situated in southern high latitudes. The QtFl plot 
of the Tamrang Formation indicates a similarity to the Eocene Bhainskati Formation (Fig. 
 
65 
 
4.8). The Saptakoshi quartz arenite shows affinity to the late Cretaceous-early Paleocene 
Amile Formation and the Saptakoshi arkosic sandstone shows alikeness to the Permo-
Carboniferous Sisne sandstone. 
 
 
Figure 4.7 QtFL plot of Gondwanan sandstones of Nepal showing mean and standard 
deviation polygons (provenance fields are taken from Dickinson, 1985). 
 
66 
 
 
Figure 4.8 QmFLt plot of Gondwanan sandstone of Nepal showing mean and standard 
deviation polygons (provenance fields are taken from Dickinson, 1985). 
 
Figure 4.9 QmPK plot of the Gondwanan sandstones of Nepal showing mean and 
standard deviation polygons.  
 
67 
 
 
Figure 4.10 LsLvLm plot of the Gondwanan sandstones of Nepal showing mean and 
standard deviation polygons.  
 
68 
 
 
CHAPTER 5: HEAVY MINERAL ANALYSIS 
5.1 INTRODUCTION 
Detrital heavy minerals are powerful indicators of provenance. Analysis of heavy 
minerals from sediments can provide important information on provenance and help to 
discriminate distinct source rocks even within same tectonic unit (Morton, 1985; Najman 
and Garzanti, 2000; Garzanti et al., 2007). As wide ranges of heavy minerals are 
available in sandstones and the effects of sedimentation processes on heavy minerals 
have been comprehensively evaluated, high resolution provenance study is feasible with 
the analysis of heavy mineral assemblages (Uddin and Lundberg, 1998b; Morton and 
Hallsworth, 1999). Heavy minerals, which have a specific gravity of 2.9 or more, are 
usually present in sandstones in proportions of less than 1% (Tucker, 1988). More than 
30 translucent heavy minerals are suggested as indicator of characteristics source terranes 
(Morton, 1985; Mange and Maurer, 1992).  
Heavy mineral assemblages reflect the petrology of the source area, particularly in 
the case of proximal synorogenic sediments that have been transported relatively for short 
distances. However, various sedimentary processes operating from the source rock area 
to depositional basin can remarkably overprint the original assemblages of heavy 
minerals. These processes include weathering of the source rock, alluvial storage, 
mechanical breakdown and hydraulic processing during transport, and diagenesis during 
burial (Morton and Hallsworth, 1994; 1999). The stability of some key heavy minerals 
for major sedimentary processes is given in Table 5.1.  Morton and Hallsworth (1999) 
 
69 
 
proposed that the effects of overprinting of these sedimentary processes can be overcome 
by relative abundances of minerals with similar hydraulic and diagenetic behaviors.   
 
Table 5.1 Relative stability of heavy minerals for different sedimentary processes 
Stability in weathering  
profiles (source rocks) 
(Grimm, 1973; Bateman & 
Catt, 1985; Dryden & 
Dryden, 1946) # 
Mechanical  
stability during 
transport 
(Freise, 1931) # 
Burial persistence 
North Sea  
(Morton. 1984, 
1986)  
Chemical 
weathering 
(Pettijohn, 
1941) 
Zircon, Rutile 
 
Tourmaline, Andalusite, 
Kyanite, Staurolite 
 
Epidote* 
 
Garnet 
 
Calcic Amphibole** 
Clinopyroxene 
Orthopyroxene 
 
Apatite 
 
 
Tourmaline 
Corundum 
Chrome-spinel 
Spinel 
Rutile 
Staurolite 
Augite 
 
Topaz 
Garnet 
Epidote 
Apatite 
Zircon 
 
Kyanite 
Olivine 
Andalusite 
Diopside 
Monazite 
Apatite, 
Monazite, Spinel, 
TiO
2
 
minerals, 
Tourmaline, 
Zircon 
 
Chloritoid 
Garnet 
Staurolete 
Kyanite 
Titanite 
Epidote 
 
Calcic 
Amphibole 
Andalusite, 
Silimanite 
Pyroxene 
Olivine 
TiO
2 
minerals 
 
Zircon 
Tourmaline 
Sillimanite 
Andalusite 
Kyanite 
Staurolite 
Topaz 
Titanite 
Monazite 
Garnet 
Epidote 
Calcic 
amphibole 
Orthopyroxene 
Clinopyroxene 
Olivine 
Apatite 
[Stability of mineral increases towards the top part of the table; *Epidote has lower 
ranking than garnet and **Calcic Amphibole has lower ranking than clino- and ortho-
pyroxene for eolian cover deposits in Bateman and Catt (1985)?s work; # doesn?t include 
the opaque minerals] 
 
Heavy mineral analysis has been used for in several provenance studies of 
peninsular India and also the adjoining Himalayan domain. The study of heavy mineral 
suites in the Barakar sandstone (Gondwanan sequence) of the Moher sub-basin in 
 
70 
 
peninsular India was done by Aslam et al. (1991). The method has been applied to paleo-
tectonic and provenance studies of Himalayan foreland sequences (Chaudhri, 1972; Sinha 
and Sastri, 1973; Cerveny et al., 1989, Uddin and Lundberg, 1998a; Najman and 
Garzanti, 2000; Uddin et al., 2007) and on deep-sea cores from the Bengal fan 
(Yokoyama et al., 1990; Amano and Taira, 1992). These studies have been proved 
powerful in evaulating the nature of source rocks, in reconstructing the course of 
ancestral fluvial systems, and in establishing associations of source rocks to the unroofing 
of the Himalayas and Indo-Burman Ranges. 
Further advances in heavy mineral analysis has led to the method of varietal 
studies that concentrates on relative abundances of minerals that are stable during 
diagenesis and have similar hydraulic behavior (Morton and Hallsworth, 1994). The 
hydraulic parameter is controlled by grain size, density, and shape. Morton and 
Hallsworth (1994) formulated several mineral ratios, pairs and indexes of heavy minerals 
comprising similar hydraulic behavior (e.g. index ATi with mineral pair apatite and 
tourmaline, GZi with mineral pair Garnet and Zircon, CZi with mineral pair chrome 
spinel and zircon). However, these methods are only applicable to the sedimentary rocks 
containing abundant heavy minerals. 
In the absence of a full range of heavy minerals, study can be accomplished by 
determining the relative abundance of all important heavy mineral species preserved in 
each stratigraphic unit, recognizing dominant members of mineral groups, identifying the 
first key minerals indicative of certain levels of metamorphism, evaluating associations or 
 
71 
 
paragenesis of specific heavy minerals, and establishing index minerals from 
stratigraphic levels in selected sections (Rahman, 2008). 
5.2 METHODS 
Due to similar hydraulic behaviors, heavy minerals remain in certain grain-size 
fractions.  Samples were disintegrated by drying in an oven and then sieving to extract 0-
4 phi the size fractions.  The samples were then treated with high-density liquids to 
separate the heavy minerals. As there is sharp difference in the density of heavy minerals 
with regular framework minerals, the heavy fraction gets settled first due to gravity. The 
liquid used for heavy mineral separation in this study was tetrabromoethane (C
2
B
2
Br
4
, 
density 2.89-2.96 gm/cc). The samples were weighed and added to the heavy liquid in a 
separating funnel. The mixture was stirred three times to ensure that the grains were 
thoroughly wetted and not coagulated. As time passed, the heavy minerals settled down 
to the bottom of the funnel and the lighter fractions appeared floating above the heavy 
liquid at the top of the separating funnel. After 24 hours, the stopcock was opened slowly 
and the liquid bearing the heavy mineral fraction in the bottom part of the separating was 
allowed to flow slowly through a filter paper. The separated heavy fractions were washed 
carefully with acetone and dried in the open air and oven for 2 hours. The lighter fraction 
of the samples were also cleaned with acetone, dried, and stored. The heavy mineral 
fractions of samples were weighed and processed for magnetic separation. Magnetic 
separation of heavy minerals was carried out using a Frantz magnetometer at the 
Department of Geology and Geography at Auburn University. Four fractions of different 
magnetic susceptibility (Hess, 1966) were separated, including Group-1: Strongly 
 
72 
 
Magnetic (SM); Group-2: Moderately Magnetic (MM); Group-3: Weakly Magnetic 
(WM); and Group-4: Poorly Magnetic (PM). The separation of four groups of mineral 
was done by applying different slide slope angle and current values in the magnetic 
separator (Table 5.2).  
Table 5.2 Four fractions of different magnetic susceptibility (Hess, 1966) 
Side slope 15
o
 Side slope 5
o
 
Strongly 
magnetic 
Moderately magnetic 
Weakly 
magnetic 
Poorly magnetic 
Hand 
magnet 
0.4 Amps 0.8 Amps 1.2 Amps 1.2 Amps 
Magnetite 
Pyrrhotite 
 
Fe-oxides 
Illmenite 
Garnet 
Olivine 
Chromite 
Chloritoid 
Hornblende 
Hypersthene 
Augite 
Actinolite 
Staurolite 
Epidote 
Biotite 
Chlorite 
Tourmaline 
(dark) 
Diopside 
Tremolite 
Enstatite 
Spinel 
Staurolite 
(light) 
Muscovite 
Zoisite 
Clinozoisite 
Tourmaline 
(light) 
Sphene 
Leucozxene 
Apatite 
Andalusite 
Monazonite 
Xenotine 
 
Zircon 
Rutile 
Anatase 
Brookite 
Pyrite 
Corundum 
Topaz 
Fluorite 
Kyanite 
Silimanite 
Anhydrite 
Beryl 
Group 1 Group 2A Group 2B Group 3 Group 4 
 
Group-1 consists of strongly magnetic minerals including magnetite, pyrrhotite 
and Fe-oxides. However, this group was not separated using a hand magnet. Rather, it 
was separated along with Group 2A minerals including illmenite, garnet, olivine, 
chromite and chloritoid using a 15
o
 side slope and a 0.4-Amp current. 
 Group 2B minerals include of hornblende, hypersthene, augite, actinolite, 
staurolite, epidote, biotite, chlorite, and tourmaline. These were separated from weakly to 
poorly magnetic minerals using a 0.8-Amp current and a 15? side slope. Group 3 
 
73 
 
minerals, including diopside, tremolite, enstatite, spinel, staurolite (light), muscovite, 
zoisite, clinozoisite, and tourmaline (light), were separated from Group 4 using a 1.2-
Amp current and a 15? side slope. The rest of the heavy minerals were classified as Group 
4 (poorly magnetic) which was not separated further due to presence in small amount.  
This group includes slightly magnetic minerals, such as sphene, leucoxene, apatite, 
andalusite, monazite, and xenotine, and other non-magnetic minerals like zircon, rutile, 
pyrite, corundum, fluorite, kyanite, sillimanite and beryl. However, separation of heavy 
minerals belonging to all four groups was not achieved for each sample due to the 
absence or rarity of minerals from certain groups.  
Separated heavy minerals were sent to Spectrum Laboratories in Vancouver, WA 
to prepare polished thin sections. Fourteen polished thin sections were prepared from 
fourteen samples. Each of the magnetically separated heavy mineral fractions were 
segregated in different areas (holes) of each thin section. Identification of minerals was 
carried out using a petrographic microscope and a modified Fleet method (Fleet, 1926). 
Numbers of grains from each holes were counted and then added together to calculate the 
percentage of different species of heavy minerals.  
 
 
74 
 
5.3 RESULTS 
 Heavy mineral assemblages of Gondwanan sandstones of Nepal are not very 
diverse. Only four to five minerals specimens dominate in all samples (Tables 5.3 and 
5.4).  
 Heavy mineral suites in the Permo-Carboniferous Sisne sandstones (samples 16-3 
and 16-5) differ markedly those of younger units (the Taltung and Amile formations of 
the Tansen Group). Highly stable minerals (ZTR) are present in very small numbers, and 
moderately stable garnets are abundant (Table 5.3) (Fig. 5.3). The abundance of opaque 
minerals is less than in overlying other units. A possible explanation for this major 
difference in heavy mineral assemblage is due to change of provenance in younger units. 
The garnets are irregular in shape and highly fractured (Fig. 5.3). Some of the grains also 
show corroded surfaces. These surface features suggest a burial dissolution for the Sisne 
heavy minerals letting only garnets to survive among all heavies contributed by source 
rocks. 
The heavy mineral assemblage of Cretaceous-Jurassic Taltung sandstone (sample 
K-1) mostly consists of zircon, chrome-spinel, rutile, tourmaline, garnet, and dolomite as 
well as common opaque minerals (Table 5.3). Tourmaline grains are highly fractured and 
also show the effects of corrosion (Fig. 5.2). Chrome-spinel grains are in variable sizes 
and shapes. Garnets are rare and are irregular in shape. Abundant opaque grains present 
in this sample could have contributed from source rocks or formed as authigenic iron-
oxide coating is the basin. 
 
75 
 
The Paleocene-Cretaceous Amile Formation of the Tansen Group in western 
Nepal is dominated by tourmaline, zircon and rutile, as well as opaque grains. Three 
samples from the Amile Formation were subjected to heavy mineral analysis (samples 
15-6, 16-8, and 16-9) (Table 5.3).   
  
Figure 5.1 Representative photomicrograph of tourmalines in Amile sandstone (sample 
15-6) of the Tansen Group, western Nepal.  
 
Tourmaline grains are easy to identify with their strong pleochroism and low 
relief. Tourmalines from the Amile Formation are highly fractured (both primary and 
secondary fractures are present). The shape and size of the grains are variable (Fig. 5.1). 
Some of the grains are corroded.  The zircon crystals are rounded and a little smaller than 
the tourmalines. The rutile grains are deep red and rounded. The presence of numerous 
 
76 
 
opaque minerals could have contributed from authigenic coating of iron oxides on 
mineral grains as well as a contribution from source rocks.  
 
Figure 5.2 Representative photomicrograph of heavy mineral assemblage in the Taltung 
sandstone (sample K-1) of the Tansen Group, western Nepal (Cr- Chromium, Rt-Rutile, 
Tr-Tourmaline). 
 
 The Permo-Carboniferous Katari Group in eastern Nepal also shows variations in 
heavy mineral assemblage. Besides common heavy minerals present in other Gondwanan 
samples, this unit also contains biotite and chlorite/chloritoid (Table 5.4). The garnet 
grains are more irregular in shape than the zircons which are mostly rounded. As 
expected based on hydraulic equivalence, biotite and chlorite grains are larger than other 
types of heavy minerals (Morton and Hallsworth, 1999). However, the mica grains are 
deformed and folded (Figs. 5.4 and 5.5). This likely is related to some kind of 
 
77 
 
deformation in the source rocks rather than in the depositional basin as petrographic 
analyses of the thin section of this sample does not reflect post depositional deformation. 
 The Saptakoshi and Tamrang formations of the Barahachettra Group, another 
Permo-Carboniferous unit in eastern Nepal, show quite different heavy mineral 
assemblages. However, these assemblages are correlatable with assemblages of some 
units of the Tansen Group, albeit of different age. 
The Tamrang sandstones (samples 22-6, 22-10, 23-4) from eastern Nepal are 
primarily dominated by highly stable minerals like zircon, tourmaline and rutile (Table 
5.4) (Fig. 5.6) as well as opaque grains. However, the Tamrang Formation also contains 
common micas and a large number of unidentified heavy minerals. 
The Saptakoshi sandstone (sample 23-5) contains few highly stable heavy 
minerals (i.e. zircon, rutile and tourmaline) but large numbers of less stable garnets 
(Table 5.4). This dominant assemblage of garnets in the Saptakoshi sandstone is similar 
to that of the Sisne sandstone of western Nepal. However, the sizes of garnets are smaller 
than that in the Sisne Formation. The Saptakoshi sandstones contain fewer opaque grains 
than the Sisne Formation.  
 
78 
 
  
Figure 5.3 Representative photomicrograph of heavy mineral assemblage in the Sisne 
sandstone (sample 16-3) of the Tansen Group, western Nepal, showing abundance of 
garnets. 
  
Figure 5.4 Representative photomicrograph of heavy mineral assemblage in the Permo-
Carboniferous sandstone (sample 26-8) of the Katari Group, eastern Nepal. (Bt?Biotite; 
Chl- Chlorite; Gt?Garnet). 
 
79 
 
Table 5.3 Heavy mineral data in Gondwanan sandstones from western Nepal (Tansen 
Group).  
 
Sample No 16-9   16-8   15-6   
Rock Unit Amile Formation  Amile Formation  Amile Formation  
Age (Paleo-Cretaceous)  (Paleo-Cretaceous)  (Paleo-Cretaceous)  
Heavy  
Minerals 
No of  
Grains 
Percentage No of  
Grains 
Percentage No of  
Grains 
Percentage 
Zircon 22.00 6.73 11.00 5.02 7.00 4.05 
Rutile 10.00 3.06 8.00 3.65 2.00 1.16 
Tourmaline 97.00 29.66 55.00 25.11 53.00 30.64 
Chrome-Spinel 0.00 0.00 0.00 0.00 0.00 0.00 
Dolomite 0.00 0.00 0.00 0.00 0.00 0.00 
Garnet 0.00 0.00 0.00 0.00 0.00 0.00 
Biotite 0.00 0.00 0.00 0.00 0.00 0.00 
Chlorite/Chloritoid 0.00 0.00 0.00 0.00 0.00 0.00 
Opaque 186.00 56.88 136.00 62.10 103.00 59.54 
Others 12.00 3.67 9.00 4.11 8.00 4.62 
Total 327.00 100.00 219.00 100.00 173.00 100.00 
ZTR    39.45   33.79   35.84 
Sample No 16-3   16-5   K-1   
Rock Unit Sisne Formation  Sisne Formation  Taltung Formation  
Age (Permo-
Carboniferous)  
(Permo-
Carboniferous)  
(Cretaceous-
Jurassic)  
Heavy  
Minerals 
No of  
Grains 
Percentage No of 
 Grains 
Percentage No of  
Grains 
Percentage 
Zircon 7.00 2.06 42.00 6.91 24.00 8.25 
Rutile 5.00 1.47 16.00 2.63 32.00 11.00 
Tourmaline 6.00 1.76 4.00 0.66 9.00 3.09 
Chrome-Spinel   0.00   0.00 35.00 12.03 
Dolomite   0.00   0.00 65.00 22.34 
Garnet 280.00 82.35 480.00 78.95 17.00 5.84 
Biotite   0.00   0.00   0.00 
Chlorite/Chloritoid   0.00   0.00   0.00 
Opaque 30.00 8.82 54.00 8.88 102.00 35.05 
Others 12.00 3.53 12.00 1.97 7.00 2.41 
Total 340.00 100.00 608.00 100.00 291.00 100.00 
ZTR    5.29   10.20   22.34 
 
 
80 
 
Table 5.4 Heavy mineral distribution in Gondwanan sandstones from eastern Nepal  
(Barahachettra and Katari groups).  
 
Sample No 26-8   23-5   22-6   
Rock Unit Katari Group Saptakoshi 
Formation 
Tamrang Formation 
Age (Permo-
Carboniferous)  
(Permo-
Carboniferous) 
(Permo-
Carboniferous)  
Heavy Minerals No of  
Grains 
Percentage No of  
Grains 
Percentage No of  
Grains 
Percentage 
Zircon 12.00 4.63 5.00 2.38 33.00 7.91 
Rutile 12.00 4.63 2.00 0.95 43.00 10.31 
Tourmaline 15.00 5.79 3.00 1.43 90.00 21.58 
Chrome-Spinel   0.00   0.00   0.00 
Dolomite   0.00   0.00   0.00 
Garnet 123.00 47.49 182.00 86.67   0.00 
Biotite 9.00 3.47   0.00   0.00 
Chlorite/Chloritoid 17.00 6.56   0.00 55.00 13.19 
Opaque 56.00 21.62 13.00 6.19 174.00 41.73 
Others 15.00 5.79 5.00 2.38 22.00 5.28 
Total 259.00 100.00 210.00 100.00 417.00 100.00 
ZTR    15.06   4.76   39.81 
       
Sample No 22-10   23-4     
Rock Unit Tamrang 
Formation  
Tamrang 
Formation  
  
Age (Permo-
Carboniferous)  
(Permo-
Carboniferous)  
  
Heavy Minerals No of  
Grains 
Percentage No of  
Grains 
Percentage   
Zircon 25.00 7.00 18.00 9.63   
Rutile 18.00 5.04 15.00 8.02 
Tourmaline 99.00 27.73 34.00 18.18   
Chrome-Spinel   0.00 2.00 1.07 
Dolomite   0.00   0.00   
Garnet   0.00   0.00 
Biotite   0.00   0.00   
Chlorite/Chloritoid 22.00 6.16 28.00 14.97 
Opaque 180.00 50.42 72.00 38.50   
Others 13.00 3.64 18.00 9.63 
Total 357.00 100.00 187.00 100.00   
ZTR    39.78   35.83 
 
 
 
81 
 
  
Figure 5.5 Representative photomicrograph of heavy mineral assemblage in the Permo-
Carboniferous sandstone (sample 26-8) of the Katari Group, eastern Nepal (Bt-Biotite; 
Rt-Rutile; Zr-Zircon). 
 
Figure 5.6 Representative photomicrograph of heavy mineral assemblage in the Permo-
Carboniferous sandstone (sample 23-4) of the Barahachettra Group, eastern Nepal (Tr-
Tourmaline). 
 
82 
 
5.3 PROVENANCE 
The weight percentage of heavy minerals of the Gondwanan sandstones in eastern 
Nepal is less than that of western Nepal (Fig. 5.7). The presence of numerous faults in the 
eastern part could have played a significant role by allowing acid water to leach the 
heavy minerals (Morton and Hallsworth, 1999). Among individual units, the Taltung 
Formation (Cretaceous-Jurassic) of the Tansen Group contains the highest amount of 
heavy minerals, which may reflect sediment contribution from nearby lava flows (Sakai, 
1983). The overall signature of heavy minerals in Gondwanan sequences of Nepal is the 
dominant contribution of garnet in Permo-Carboniferous units in western and eastern 
Nepal (Fig. 5.8). Assemblages dominated by highly stable minerals ( zircon, rutile and 
tourmaline) characterize the Cretaceous-Paleocene Amile Formation of western Nepal 
(Tansen Group) and purported Permo-Carboniferous unit (Bashyal, 1979) of western 
Nepal (Fig. 5.9).  
Presence of abundant chrome-spinel in the Jurassic-Cretaceous Taltung Formation 
of the western Nepal indicates a volcanic source. The puported Permo-Carboniferous 
Katari Group does not show similarities in heavy mineral contents with the Permo-
Carboniferous units of Tansen and Barahachettra groups.  
The garnet and tourmaline contents of Gondwanan units of Nepal show strong 
negative correlation (Fig. 5.10), which suggests a change in source rocks rather than 
some other control.  Moreover, during the Permo-Carboniferous, India together with 
other masses of Gondwanaland, was situated in high southern latitudes (Veever and 
Tiwari, 1995). However, during Jurassic to Cretaceous deposition, India was already 
 
83 
 
positioned in an equatorial area, which resulted in intense weathering of source rocks and 
destruction of unstable heavy minerals. The possible provenance of garnet contributing 
sediments for the Gondwanans sequences of Nepal could be the Chotnagpur Gneissic 
terrain of peninsular India (Fig. 5.11).  However, the Aravali-Delhi Supergroup and the 
Bundelkhand Gneiss could have also contributed garnets depending on the paleodirection 
of northerly flowing rivers from central India (e.g. Chambal, Betawa, and Son Rivers). 
The highly stable heavy minerals in Jurassic to Cretaceous units could have been 
supplied from Proterozoic sedimentary sequences of the Vindhyan Group. 
 
Figure 5.7 Distribution of heavy minerals among different units and sections of 
Gondwanan sandstones in Nepal. 
 
84 
 
 
Figure 5.8 Distribution of highly stable heavy minerals (ZTR) among different units and 
sections of Gondwanan sandstones in Nepal. 
 
Figure 5.9 Distribution of garnets among different units and sections of Gondwanan 
sandstones in Nepal. 
 
85 
 
 
Figure 5.10 Variation in distribution of garnets and ZTR among different units and 
sections of Gondwanan sandstones in Nepal. 
 
Figure 5.11 Possible source rock units for the Gondwanan sandstones of Nepal from 
cratonic India. 
 
86 
 
 
 
CHAPTER 6: MICROPROBE ANALYSIS 
6.1  INTRODUCTION 
 Heavy mineral studies have been used as one of the most powerful tools in 
provenance analysis in the past and are gaining more recognition recently. Sandstones are 
easy to collect in the field and to process and analyze in the lab and hence are the 
materials utilized for heavy mineral analysis. 
Mineral chemistry of some heavy minerals are very good indicators on 
discriminating source rock types. Chrome-spinel chemistry is useful in differentiating 
various types of mafic igneous rocks. The supply of sediment from different-grade 
metamrophic rocks can be tracked down with the help of garnet chemistry. Tourmaline 
chemistry is valuable in distinguishing types of plutonic source rocks. 
 Mineral chemistry analysis on some selected heavy minerals has been carried out 
with an objective to fingerprint provenance of Gondwanan sequences distributed in 
several patches along the Nepal Himalaya.  
6.2 MINERAL CHEMISTRY 
 Three mineral groups were chosen for microprobe analysis: garnet, tourmaline, 
and chrome-spinel. Several workers have used these minerals to determine provenance of 
sediments (e.g., Kumar, 2004; Zahid; 2005; Rahman, 2008). The compositional variation 
of these mineral can be linked to different source rocks (Henry and Guidotti, 1985; 
 
87 
 
Morton, 1985; Henry and Dutrow, 1990; Morton and Taylor, 1991; Nanayama, 1997, 
Zhu et. al, 2004).  
 Garnet [X
3
Y
2
(Si0
4
)
3
], found commonly in metamorphic rocks and also in some 
igneous rocks, has proven to be a good indicator of pressure and temperature conditions 
during the formation of the source rock. The X-site is occupied by Fe
2+
, Mg
2+
, Ca
2+
 , and 
Mn
2+
. As the metamorphic grade of the source rock will increases, the ratio of (Fe
2+
 + 
Mg
2+
)/(Ca
2+
 + Mn
2+
) also increases (Sturt, 1962; Nandi, 1967). With an increase in 
metamorphic grade, pelitic schists will show an increase in Mg concentration with 
respect to Fe
2+ 
 
(Spear, 1993). The Y-site is occupied by trivalent cations like Fe
3+
, Cr
3+
 
except Al
3+ 
 . The cations occupancy of this site can also be related to the type of source 
rock.  
 Compositional analysis of chrome-spinel has also been used by several workers 
for sediments provenance analysis. Chrome-spinel is a good indicator of provenance, 
particularly for discriminating  different types of mafic and ultramafic rocks (Irvine, 
1973, 1977; Dick and Bullen, 1984; Nixon et al., 1990). Chrome-spinel [AB
2
O
4
], found 
mostly in mafic igneous rocks, gives a good indication of source rocks based on 
variations of elements in cation sites. There are 4 oxygen ions and 3 cations in the unit 
cell (Brady and Perkins, 2009). The A-site is occupied by Fe
2+
, Mg
2+
, Ca
2+
 , Mn
2+ 
 and 
the B-site is occupied by Al
3+
, Cr
3+
, Ti
4+
, Si
4+
. Different end members can be calculated 
based on the occupancy of these two sites. In most cases, there will be presence of solid 
solutions rather than true end members (Deer et al., 1992). 
 
88 
 
 Tourmaline generally has very complex compositional structure. The general 
structural formula of tourmaline is XY
3
Z
6
(BO
3
)Si
6
O
18
(OH)
4
. The X-site is usually 
occupied by Na
+
, Ca
2+
, the Y-site is by Mn
2+
, Fe
2+
, Al
3+
, Li
2+
, Mg
2+
, and the Z-site by 
Al
3+
, Cr
3+
, Mn
2+
or  Mg
2+ 
(Deer et. al, 1992). This mineralogical structure provides the  
opportunity for a wide range of cation substitutions during crystallization of tourmalines. 
Plots of tourmaline composition, Al-Fe(tot)-Mg and Ca-Fe(tot)-Mg, have been used for 
provenance analysis by many authors (e.g., Henry and Guidotti, 1985; Henry and 
Dutrow, 1990). 
6.3  SAMPLE PREPARATION 
 Heavy minerals were separated from disintegrated samples using a heavy liquid. 
The separation process is described in the heavy mineral chapter (Chapter 5). Thin 
sections used for normal microscopic study of heavy mineral were also used for the 
microprobe analysis. The polished thin sections were carbon-coated to ensure proper 
conduction of the electron beam on the surface of the thin sections. Along with the 
desired samples, one standard sample was also coated to the same thickness. The carbon 
coating was carried out by carbon evaporation under vaccum, and the thickness of the 
carbon coat was monitered with the reference of its color on polished brass block. As the 
thickness of coat increases on the brass, its color will change from orange (150 ?) to 
indigo red (200 ?), then to blue (250 ?) and then to bluish green ( 300 ?).  
 
89 
 
6.4  THE ELECTRON MICROPROBE 
An electron microprobe (EMP) is an analytical tool used for nondestructive  
micron-scale quantitative chemical analysis of small volumes of solid materials. It is also 
referred  to as an electron probe microanalyser (EPMA) or electron micro probe analyser 
(EMPA).The working method of EMP is similar to the scanning electron microscope 
(SEM). The method utilizes characteristic x-rays excited by the bombardment on the 
surface of sample with an electron beam. When the electron beam hits on the surface of 
the sample it creates two different kinds of response. Some of the electrons of the 
incident beam will be scattered backward elastically multiple times carrying the energy 
between 0 and Eo (the incident beam energy). These back-scattered electrons carry 
information about the chemical composition of the sample. As the electron beam hits the 
sample, electron beam will loses its energy which will be received by the electrons in the 
shell of atoms of the sample. These electrons of the sample will be excited and jump from 
one shell to another shell throwing certain amount of energy. That energy transforms to 
x-rays that are very characteristic of the compositon of the sample. Secondary electrons 
from the sample are also mobilized by the beam through inelastic scattering. These have 
energies in the range of 0-50 eV (most probable energy 3-5 of eV). Different detector 
setups are required to detect these different types of electron signal. 
The basic purposes of EPM are: (1) to get a complete quantitative chemical 
analysis of a small sample through x-ray emission spectral analysis without destroying 
the samples; and (2) to get high-resolution scanning electron and concentration maps 
(scanning x-ray). Among the scanning electron images, backscattered electron (BSE) will 
 
90 
 
show compositional contrast, while secondary electron (SE) will enhance surface and 
topographic features. 
 For this research, a JEOL JXA 8600 Superprobe was utilized at the  Department 
of Geology, University of Georgia. The probe is automated by a Geller Micro analytical 
laboratory dQANT with the an accelerating voltage of 15 KV and a beam current of 15 
nanno amps. Both natural and synthetic standards were used to calibrate the data. 
Standard Intensity Calibration:  
Before starting the actual microprobe analysis of samples, the standard x-ray 
intensities of the elements to be measured were obtained on appropriately chosen 
standards. These standards were also verified for the reproduction by analyzing 
secondary standards that were run as unknowns. The analytical environment (e.g., 
accelerating voltage, beam current, etc.) was remained fixed throughout the lab session.  
The list of the standards used during this analysis is  given in Table 6.1. Most of 
the standards came from C.M. Taylor Corporation. The USNM standards came from the 
National Museum of Natural History, a branch of the Smithsonian Institution. Standards 
from University of Oregon Microprobe Laboratory and an almandine standard obtained 
from the Harvard Mineral Museum were also used. Calbration for each analysis session 
was checked using the Kakanui Hornblende (USNM) and Pyrope # 39 (C.M. Taylor) 
standards. 
 
91 
 
Table 6.1 Electron microprobe standards used for this study 
Electron Microprobe Standards 
Element Standard Source Comment 
Cr Chromite#5 C M Taylor Corp  
Mn Spessartine#4b C M Taylor Corp  
TiO
2
 Rutile C M Taylor Corp  
Ca Sphene#1A C M Taylor Corp  
Fe Hematite#2 C M Taylor Corp Used for oxide (spinel) 
analysis 
Fe Syn. Fayalite Ol-
11 
Univ. of Oregon Used for silicate analyses 
Ni Ni metal C M Taylor Corp  
Si Diopside 5A C M Taylor Corp Si standard for all phases 
except garnet 
Mg Olivine #1 C M Taylor Corp  
Al Syn. Spinel C M Taylor Corp  
K Orthoclase 
MAD-10 
C M Taylor Corp  
Na Ameila Albite USNM This is ubiquitous Na 
Standard 
Si Almandine Harvard Mineral Museum 
oxygen standard # 112140 
Si standard for garnet 
analyses 
F Syn. Fluoro-
Phlogopite 
University of Oregon M-6  
Cl Scapolite USNM R 6600-1  
 
 
92 
 
6.5 RESULTS 
 A total of 45 grains were analyzed under the supervision of Mr. Chris Fleisher. 
These included garnets, tourmalines, and chrome-spinels.  
6.5.1 Garnet 
 Garnet grains are abundant in the Sisne Formation of the Tansen Group and also 
in the Barahachettra and Katari groups. However, garnets are rare to absent in younger 
units (Taltung and Amile formations ) of the Tansen Group. Calculated endmembers and 
their variations of  20 garnet grains are plotted in figures 6.1 through 6.6. The end-
member calculation was done for four endmembers-- almandine, pyrope, grossular and 
spessartine-- among which almandine is the dominant end-member. The average and 
maximum content of almandine in garnet grains is 65.49% and  81.88%, respectively. 
The average pyrope content is 14.44% with a maximum of 35.80%. Higher pyrope 
contents are found in the Taltung Formation of the Tansen Group. The average grossular 
content is 13.70% with a maximum of 32.83%. The average spessartine content is 6.35%. 
However, this average usually reflects high spessartine contents in just a few grains. 
 The (Sp+Gro)-Py-Alm plot (Fig. 6.1) shows that most of the garnets have high 
almandine content. Almost all of the grains from the Katari Group have very low pyrope 
content. Similary, the  (Py+Alm)-Gro-Sp plot (Fig. 6.2) shows that most of the grains 
have high Py+Alm, particularly garnets from the Taltung Formation. Garnet grains from 
the Barahachettra Group show low spessartine contents of except one grain. The 
(Alm+Sp)-Py-Gro plot (Fig. 6.3) shows that all the garnets from the Katari Group fall in 
 
93 
 
field I with almandine and grossular and pyrope < 10%. Most of the garnets from the 
Barahachettra Group fall in field III with both pyrope and grossular >10%. The garnets 
from the Taltung Formation falls in field II with grossular <10%.  The plot of Sp-Alm-Py 
(Fig. 6.4) shows that most of the garnet grains from all rock units fall in the amphobolite 
facies. Only one grain of the Sisne Formation falls in granulite facies. However, the 
grains from the Taltung Formation fall in the overlapping field between granulite facies 
and amphioblite facies. 
 The plot of grossular content (mol %) with the number of grains from each rock 
unit (Fig. 6.5) also shows that  most of the grains fall in low- to medium-grade 
metamorphic pressure regimes. The only one grain from the Sisne Formation falls in 
eclogite facies. Garnet from the Taltung Formation reflects a low-grade metamorphic 
regime. 
 
94 
 
 
Figure 6.1 Chemical composition of garnets of Gondwanan sequences of Nepal (Tansen 
Group, western Nepal; Barahachettra and Katari groups in eastern Nepal) plotted on 
(Sp+Gro)-Py-Alm (adapted after Nanayama, 1997). 
 
 
Figure 6.2 Chemical composition of garnets of Gondwanan sequences of Nepal (Tansen 
Group, western Nepal; Barahachettra and Katari groups in eastern Nepal) plotted on 
(Py+Alm)-Gro-Sp (adapted after Nanayama, 1997). 
 
95 
 
 
Figure 6.3 Chemical composition of garnets of Gondwanan sequences of Nepal (Tansen 
Group, western Nepal; Barahachettra and Katari groups in eastern Nepal) plotted on 
(Alm+Sp)-Py-Gro (adapter afted Nanayama, 1997). 
 
 
Figure 6.4 Chemical composition of garnets of Gondwanan sequences of Nepal (Tansen 
Group, western Nepal; Barahachettra and Katari groups in eastern Nepal) plotted on 
Alm-Py-Sp (adapted after Nanayama, 1997). 
 
96 
 
 
Figure 6.5 Grossular contents  of garnets from Gondwanan sequences of Nepal (Tansen 
Group, western Nepal; Barahachettra and Katari groups in eastern Nepal) plotted on 
Alm-Py-Sp (adapted after Nanayama, 1997). 
 
6.5.2 Tourmaline 
 Tourmaline has very complex structure and is commonly considered in terms of 
end-members. There is a complete solid solution between two end-member series: schorl-
elbaite and schorl-dravite. However, there is a large miscibility gap between elbaite and 
dravite. Hence, tourmalines are usually described by their positions in the schorl-elbaite 
series or in the schorl-dravite series. Two different plot have been prepared using Al-
Al
50
Fe
50(tot)
 -Al
50
Mg
50  
( Fig. 6.6) and Ca-Fe(tot)-Mg (Fig. 6.7). These plots Al-
Al
50
Fe
50(tot)
 -Al
50
Mg
50  
show that all tourmaline grains from three different sections of 
Nepal (the Tansen, Barahachettra and Katari groups) fall between Li-poor granitiods and 
pegmatites and aluminous meta-pelites and meta-psammites.  
 
97 
 
 On the Ca-Fe(tot)-Mg plot (Fig. 6.7), tourmalines from the Katari Group fall in 
three different fields: Li-rich granitoids pegmatites, Li-poor granitoids pegmatites, and 
Ca-poor metapelites, metapsammites. Samples from Barahachettra and Tansen groups  
have fallen only between the Li-poor granitoids pegmatites and Ca-poor metapelites, 
metapsammite fields. As the compositon of grains are fallen in different rock group 
types, there should be different sources of rocks for these units. 
6.5.3 Chrome-spinel 
Chrome-spinel was only found in the Taltung Formation of the Tansen Group. 
Five grains of chrome-spinel from this unit were analyzed. The average elemental 
percentage of chormium in these grains is 24.17%, with the maximum of 33.02%.  
Various plots have been prepared from the compositional data of these chrome-
spinel grains to judge the source rock of the sediment. A ternary plot of Al
3+
-Cr
3+
-Fe
3+ 
 
suggests Alpine-type peridotite source rock (Fig 6.8). Alpine-type peridotites have 
compositions of > 95% harzburgite and originate as depleted residues of partial melting. 
The lower concentration of Fe
3+
 also supports this scenario.  
The possibility that chrome-spinels from the Taltung Formation were derived 
from Alpine-type peridotite is also supported by a  plot of Cr/(Cr+Al) with 
Mg/(Mg+Fe
2+
) (Fig. 6.9). The low value of Cr# makes the grains fall in the Alpine-type 
peridotite field.  
The plot of Mg/(Mg+Fe
3+
) versus Fe
3+
/(Fe
3+
+Al+Cr) (Fig. 6.10) also shows the 
Alpine-type peridotite as the possible source rock. However, the plots also overlap with 
 
98 
 
the field of stratiform complexes. Hence, derivation of these sediments from stratiform 
complex source terranes is also possible.   
 
Figure 6.6 Al-Fe (tot)-Mg plot (in molecular proportion) for tourmalines from 
Gondwanan sequences of Nepal (Tansen Group, western Nepal; Barahachettra and Katari 
groups in eastern Nepal) plotted on Al-Al
50
Fe
(tot)50
-Al
50
Mg
50
 (adapted after Henry and 
Guidotti, 1985). 
 
99 
 
 
Figure 6.7  Ca-Fe(tot)-Mg plot (in molecular proportion) for tourmalines from 
Gondwanan sequences of Nepal (Tansen Group, western Nepal; Barahachettra and Katari 
groups in eastern Nepal) plotted on Ca-Fe
(tot)
-Mg, (adapted after Henry and Guidotti, 
1985). 
 
Figure 6.8 Ternary plot of major trivalent cations in chrome-spinels of the Taltung 
Formation of the Tansen Group (Gondwanan sequences) of the Nepal Himalaya with 
three major provenance fields  (adapted after Nixon et al., 1990).  
 
100 
 
 
Figure 6.9 Plot of Mg/(Mg+Fe
2+
) vs Cr/(Cr+Al) for chrome-spinels of the Taltung 
Formation of the Tansen Group (Gondwanan sequences) of the Nepal Himalaya (adapted 
after Nixon et al., 1990). 
 
101 
 
 
Figure 6.10 Plot of Mg/(Mg+Fe
2+
) vs the ratio of trivalent cations Fe
3+
/( Fe
3+
+Cr+Al) for 
chrome-spinels of the Taltung Formation of the Tansen Group (Gondwanan sequences) 
of the Nepal Himalaya (adapted after Irvine, 1974). Note that all grains fall in the overlap 
between Alpine and stratifrom peridotite fields. 
 
 
102 
 
6.6  DISCUSSION 
6.6.1 Garnets 
Garnet composition of samples from different Gondwanan sequences in Nepal 
suggest different source terranes. The Katari Group, with low pyrope contents, belongs to 
the amphibolite regime, while the Taltung Formation, with low grossular and spessartine 
contents reflects low metamorphic grade (Figs 6.4 and 6.11). Most of the grains from the 
Barahachettra Group contain both grossular and pyrope (Fig. 6.3) but have low 
spessartine content. The most probable source of garnet could be the Bihar Mica Belt, the 
Ranchi Supracrustal Belt and the Munger Belt of Chotanagapur Gneissic Terrain. 
However, different igneous bodies, including the Malani Granite of the Delhi Supergroup 
and the Vindhyan System of peninsular India also could have supplied garnets to the 
Gondwanan basins of Nepal  (Sakai, 1983). 
 
6.6.2 Tourmaline 
Microprobe data for tourmaline supports that the source rock for these 
tourmalines are Li-poor granitoids and aluminous meta-psammities and meta-pelites (Fig. 
6.6). However, the plot of Ca, Fe(tot) and Mg, suggests different types of source rocks 
(Fig 6.7). The Amile Formation, which is basically rich in quartz arenite, shows a 
granitoid provenance, whereas other formations show a mixed provenance of granitioids 
and meta-psammites and meta-pelites. Hence, different granitic bodies of the Indian 
craton as well as pelites, from Vindhyan could have contributed tourmaline.   
 
103 
 
 
Figure 6.11 Petrographic grid for the KFMASH system contoured with isopleths of X
Alm
 
in garnet (after Spear and Cheney, 1989). The isopleths are constructed assuming that 
garnet formed in equilibrium with biotite in a rock of pelitic bulk composition. The blue 
region shows the range of isopleth values for garnets from Gondwanan sequences of 
Nepal while solid color lines show the average of isopleth value for different rock units.  
 
 
104 
 
6.6.3 Chrome-spinel 
The TiO
2
% versus Cr# in chrome spinels shows that these grains were derived 
from mid-oceanic, island arc  and alkaline basaltic sources (Fig. 6.11). However, as TiO
2
 
contents of these chrome-spinel grains are very low which is charecteristic of alkaline 
basalts, these chrome-spinel grains could have been contributed by the alkaline Aulis 
Basalt considered to be equivalent to the Rajmahal Traps (Sakai, 1983; Segev, 2002). 
The Cr# value for the peridotites and basalts of mid-ocean ridges is less than 0.06 
with Mg# between 0.55 -0. 85 (Dick and Bullen, 1984). This tectonic setting has been 
classified as Type I. Another type of tectonic setting that is also regarded as Type I 
setting is depleted marginal seafloor basalts which show slightly lower value for Mg# and 
narrower range of Cr# than mid-oceanic ridge basalts (MORB). The Cr# and Mg# of the 
Taltung Formation indicate mid oceanic ridge type basalts or peridotite as the source of 
chrome-spinels. The Cr# and Mg# for island arc basalts (Types III setting) are 0.6-0.9, 
and 0.4-0.69, respectively (Cookenboo et al., 1997). Ophiolites, which have compositions 
transitional between Type I and Type III are regarded as Type II settings (Dick and 
Bullen, 1984).  
     The high aluminium and high chromium contents of the Taltung Formation also 
suggest a mid-oceanic type of source rock. 
 
105 
 
.  
Figure 6.12 Plot of TiO
2
 vs Cr# of Gondwanan sequences of Nepal (Tansen Group, 
western Nepal; Barahachettra and Katari groups in eastern Nepal) relative to spinels from 
various potential source rocks. MORB=Mid-oceanic ridge basalt (after Nanayama, 1992). 
 
 
106 
 
 
 
 
 
   
   
   
Figure 6.13 Schematic diagram show
ing spinel composition from 
different tectonic settings, 
including those of sea-floor and continenta
l crust origins (modif
ied from Cookenboo et al., 
1997).
 
 
107 
 
 
 
CHPATER 7: WHOLE ROCK CHEMISTY  
7.1 INTRODUCTION 
The whole rock chemistry of a sedimentary rock can provide an improved 
understanding of provenance of sediments and contemporaneous and subsequent 
sedimentary and weathering processes that impacted the sediments or the rock. 
Composition of sedimentary rock is primarily controlled by the composition of the source 
rocks and to some extent also by weathering and diagenetic processes (Dickinson, 1985; 
McLennan et al., 1993,).  
It is necessary to understand the weathering process and climatic conditions 
during deposition of sedimentary rocks before making final interpretations on the source 
rock. The chemistry of sedimentary rocks is significantly influenced by weathering of the 
source rock and also post depositional diagenetic processes after the deposition of 
sediments (Nesbitt and Young, 1992). The ?Chemical Index of Alteration? (CIA) and 
ternary plot of Al
2
O
3
-(CaO+Na
2
O)-K
2
O are valuable tools to evaluate the degree of 
weathering and diagenetic processes. All chemical constituents present in a source rock 
do not behave in same way under a given weathering regime. When source rocks are 
exposed to weathering, they become depleted in oxides that are not resistant to 
weathering. Other more resistant oxides remain almost in the same amount that they were 
in parent rock. The proportions of some of the major oxides, such as SiO
2
, Al
2
O
3
 and 
K
2
O, have been found to be constant from source rock to the basin (Bhatia, 1983; Roser 
 
108 
 
and Korsch, 1988). Some trace elements (Zr, Th, Sc, Nb, Ga) and rare earth elements 
(REE) are generally remain constant from source rocks to the sediment because of their 
low solubility in water during weathering (McLennan et al. 1985; Bhatia and Crook, 
1986). Relative concentration of resistant major oxides and trace elements present in 
sedimentary rocks are valuable indicators of source rocks.   
One major limitation of using whole-rock chemistry alone is the inability to detect 
the mixing of different kinds of source rocks.  Hence, chemical analyses should be 
supported by other methods of provenance study (e.g., traditional petrography, heavy 
mineral analysis, detrital geochronology, etc.). Representative sandstone samples have 
been subjected to whole-rock geochemical study to aid in the interpretation of 
paleotectonics and sediment provenance of Gondwanan sequences from Nepal.    
7.2 METHODS 
Nine representative sandstone samples were selected for the whole-rock 
geochemical analysis. The selected samples representing the Gondwanan sequence 
(Tansen Group) in the western part of Nepal include sample 16-1 from the Dumri 
Formation, sample 15-8 from the Bhainskati Formation, sample 15-5 from the Amile 
Formation, sample K-1 from the Taltung Formation, and sample 16-6 from the Sisne 
Formation. Samples from the eastern part of Nepal include samples 26-3 and 26-8 from 
the Katari Group, and sample 23-5 from the Tamrang Formation, and sample 22-9 from 
the Saptakoshi Formation of the Barahachhetra Group.  
 
109 
 
Selected samples were crushed in the rock-preparation lab of the Department of 
Geology and Geography, Auburn University. The size of the samples was further reduced 
with a mortar and pestle to the 200 mesh. Subsamples of ~10 gm from each sample were 
sent to ACME Laboratories Limited.  Each sample was analyzed for 58 parameters 
including major oxides, minor elements, trace elements (rare earth and refractory 
elements), and precious and base metals. Major oxides, minor, rare earth and refractory 
elements were determined by ?Inductively Coupled Plasma? (ICP) mass spectrometry 
following lithium metaborate/tetraborate fusion and nitric acid digestion of 0.2-gm sub-
samples.  Precious and base metals were analyzed by ICP mass spectrometer after 
digesting separate 0.5-gm splits in Aqua Regia. Loss of ignition was calculated by 
weighing the difference after ignition at 1000
o
C.  
 
 
110 
 
7.3 RESULTS 
The results of geochemical analysis of 9 samples for 58 parameters including major 
oxides, minor elements, and trace elements are given in Table 7.1. 
Table 7.1 Results of whole-rock chemical analysis of Gondwanan sandstones from Nepal  
      S. No                 
  Unit MDL 16-1 15-8 15-5 K-1 16-6 23-5 22-9 26-3 26-8 
SiO
2
 % 0.01 70.09 85.01 89.79 35.4 70.19 70.98 76.99 95.8 85.19 
Al
2
O
3
 % 0.01 8.09 5.64 4.38 14.48 10.37 8.52 5.03 2.14 5.61 
Fe
2
O
3
 % 0.04 20.97 2.58 4.72 13.66 13.16 16.81 18.3 0.32 2.32 
MgO % 0.01 0.57 0.79 0.05 3.22 0.88 0.99 0.28 0.05 0.93 
CaO % 0.01 0.1 1.47 0.04 12.56 0.84 0.55 0.07 0.09 1.17 
Na
2
O % 0.01 1.42 0.04 0.11 1.06 2.11 1.63 0.04 0.02 0.07 
K
2
O % 0.01 1.53 1.36 0.08 2.1 2.82 2.07 0.73 0.03 1.21 
TiO
2
 % 0.01 0.69 0.47 0.35 2.38 0.33 0.21 0.51 0.08 0.41 
P
2
O
5
 % 0.01 0.06 0.07 <0.01 0.77 0.08 0.07 0.03 0.01 0.07 
MnO % 0.01 0.13 0.04 0.02 0.44 0.1 0.09 0.07 <0.01 0.04 
Cr
2
O
3
 % 0.002 0.008 0.003 0.006 0.118 0.007 0.007 0.01 0.002 0.004 
Ni PPM 20 57 <20 <20 282 30 29 42 <20 <20 
Sc PPM 1 6 5 4 27 8 4 5 1 5 
LOI % -5.1 -3.9 2.4 0.4 13.3 -1.1 -2.1 -2.2 1.4 2.8 
Ba PPM 1 363 179 25 1352 604 357 148 358 247 
Be PPM 1 1 <1 <1 2 1 <1 1 <1 <1 
Co PPM 0.2 12 4.5 3 50.5 9.2 8.6 10.1 1.3 6.5 
Cs PPM 0.1 2.8 2.1 0.2 3.7 1.8 3.2 1.3 <0.1 1.8 
Ga PPM 0.5 10.8 6.6 6.7 16.3 12.1 10.1 8.5 3.2 7.7 
Hf PPM 0.1 11.4 9.3 3.5 8 7.2 5.7 6.9 0.7 7.2 
Rb PPM 0.1 69 55.4 3.3 74.8 96.9 76.9 36.7 1 45.1 
Sn PPM 1 6 3 2 4 4 4 5 <1 2 
Sr PPM 0.5 47.3 51.8 23.6 568 122.8 85.4 38.2 11.9 20.4 
Ta PPM 0.1 1.2 0.9 0.4 8 0.6 0.4 0.9 0.2 0.8 
Th PPM 0.2 18.9 13.2 3.7 27.4 6.5 4.5 10 2.1 12 
U PPM 0.1 3.2 2.2 1.6 5.1 1.2 1 2 0.8 2.4 
V PPM 8 35 28 43 217 43 26 30 14 28 
W PPM 0.5 2 1.5 <0.5 3.7 0.7 0.8 2.3 <0.5 1.5 
Contd. (MDL = Minimum Detection Limit) 
 
111 
 
Table 7.1 Results of whole-rock chemical analysis of Gondwanan sandstones from Nepal 
Contd. 
      S. No                 
  Unit MDL 16-1 15-8 15-5 K-1 16-6 23-5 22-9 26-3 26-8 
Zr PPM 0.1 375.7 318.8 114.4 333.5 246.6 201.9 266 25.5 270.8 
Y PPM 0.1 36.6 25.2 6 28.7 19.1 13.7 14.8 3.1 20.3 
La PPM 0.1 48.8 40 20.4 142.4 22.3 14 33.6 7.3 30.7 
Pr PPM 0.02 12.25 9.61 3.68 26.33 5.2 3.53 8.4 1.98 7.54 
Nd PPM 0.3 46.2 35.8 11.4 90.2 19.4 13.6 30.1 7.3 27.1 
Sm PPM 0.05 8.45 6.26 1.78 12.09 3.24 2.48 4.85 1.29 5.17 
Eu PPM 0.02 1.4 1.03 0.3 3.18 0.82 0.7 0.86 0.28 0.89 
Gd PPM 0.05 7 5.19 1.32 9.02 2.94 2.32 3.59 1.01 4.38 
Tb PPM 0.01 1.08 0.76 0.19 1.12 0.52 0.39 0.49 0.17 0.66 
Dy PPM 0.05 6.27 4.38 1.12 5.76 3.15 2.33 2.6 0.71 3.84 
Ho PPM 0.02 1.21 0.86 0.2 1 0.67 0.46 0.51 0.14 0.72 
Er PPM 0.03 3.38 2.5 0.63 2.72 1.99 1.43 1.52 0.32 2.21 
Tm PPM 0.01 0.47 0.34 0.08 0.35 0.29 0.21 0.22 0.08 0.34 
Yb PPM 0.05 3.33 2.58 0.61 2.3 2.02 1.38 1.41 0.32 2.18 
Lu PPM 0.01 0.48 0.37 0.09 0.34 0.31 0.22 0.23 0.07 0.34 
Mo PPM 0.1 9.2 0.4 2.8 1.4 5.3 7.2 7.2 0.1 0.2 
Cu PPM 0.1 160.6 56.6 64.1 42.1 84.9 121.7 114.9 7 6.1 
Pb PPM 0.1 18.8 11.5 5.5 14.2 11.8 15 12.2 2.4 9.5 
Zn PPM 1 41 30 42 94 31 19 46 8 24 
Ni PPM 0.1 50.9 9.3 14.6 245.5 31.2 36.2 44.7 1.8 10.1 
As PPM 0.5 4 1.4 1.5 7.3 5 4.5 18.8 0.7 5 
Cd PPM 0.1 0.2 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 0.1 
Sb PPM 0.1 0.9 0.2 0.3 0.3 0.6 0.9 1.2 0.1 0.2 
Bi PPM 0.1 0.3 0.1 <0.1 0.1 0.1 <0.1 0.3 <0.1 0.1 
Ag PPM 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 
Au PPB 0.5 0.8 0.7 1 1.8 0.7 1 0.9 1.3 0.7 
Hg PPM 0.01 <0.01 <0.01 <0.01 0.03 <0.01 <0.01 0.03 <0.01 0.02 
Tl PPM 0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 
Se PPM 0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 <0.5 
(MDL = Minimum Detection Limit) 
 
 
112 
 
7.3.1 Major Elements 
Major elements, which are generally measured in the form of oxides, are not 
generally considered as good source rock indicators. Some of the major oxides leach out 
during the weathering process. Additionally, diagenetic processes also contaminate and 
alter detrital grains. However, some of elements are immobile and remain in the sediment 
almost in the same amount as in the source rocks. Ratios of major oxides have been used 
as an indicator of provenance (Bock et al., 1998; Gotze, 1998, Rahman and Suzuki, 
2007). Different discrimination functions have been developed by adding or subtracting 
the amount of major oxides that will be depleted or enriched in sediments during 
weathering to fabricate the proportions of major oxides similar to the parent rocks 
(Bhatia, 1983; Roser and Korsch, 1988). The effect of weathering and diagenetic 
processes on the concentration of major elements in sedimentary rocks has been clearly 
depicted in the chemical classification of the Gondwanan sandstones (Fig. 7.1). 
The Amile sandstones, with its abundant well-rounded quartz grains are supposed 
to fall in the field of quartz arenite of figure 7.1. However, Al
2
O
3
 contents of the Amile 
sandstone are a little too high and the K
2
O contents are somewhat too low to put this unit 
in the quartz arenite field. High iron oxide contents due to weathering, or presence of 
mica and other iron minerals made samples from the Dumri and Sisne formations, sample 
23-5 from the Saptakoshi Formation, and sample 26-3 from the Katari Group to fall in the 
Fe-sandstone field.  
 
 
113 
 
 
Figure 7.1 Chemical classification of Gondwanan sandstones of Nepal, classification 
fields are taken from Herron (1988). 
Some major oxide ratios have been used to evaluate tectonic setting of source 
rocks. The Taltung sandstones (sample K-1) have SiO
2
/Al
2
O
3
 ?5 (Table 7.2), which is 
typical for active margins. The remainder of the other samples, except for 26-3 from the 
Katari Group, has ratios between 5.2-28.2, which are typical for modern passive-margin 
settings (McLennan et al., 1990; Roser and Korsch, 1998). Sample 26-3 from the Katari 
Group has an anomalously high ratio of 44.  
K
2
O/Na
2
O ratios for all samples, except those from the Amile sandstones, are 
higher than 1 which is expected for passive margin setting (McLennan et al., 1990). The 
lower values of Al
2
O
3
/TiO
2 
in the Taltung sandstone reflect a mafic source rock signature 
(Sugitani et. al., 1996), while values for other samples indicate derivation from felsic 
terranes.  
 
114 
 
Table 7.2 Ratios of some major oxides of Gondwanan sandstones from Nepal. 
 Rock Unit Sample 
No SiO
2
/Al
2
O
3
 K
2
O/Na
2
O Al
2
O
3
/TiO
2
 
Dumri Formation 
16-1 8.66 1.08 11.72 
Bhainskati Formation 
15-8 15.07 34.00 12.00 
Amile Quartzite 
15-5 20.50 0.73 12.51 
Taltung Formation 
K-1 2.44 1.98 6.08 
Western 
Nepal 
Sisne Formation 
16-6 6.77 1.34 31.42 
Samptakoshi 
Formation 23-5 8.33 1.27 40.57 
Saptakoshi Formation 
22-9 15.31 18.25 9.86 
Katari Group 
26-3 44.77 1.50 26.75 
Eastern 
Nepal 
Katari Group 
26-8 15.19 17.29 13.68 
 
Distribution of major elements in rock is usually related to the mineralogy of the 
rock. The distribution pattern of eight major element oxides in the Gondwanan 
sandstones of Nepal after normalizing the weight percentage of oxides with the values for 
Post-Archean Australian shales (PAAS) (Taylor and McLennan, 1985), is plotted in 
Figure 7.2. SiO
2
 values in sandstone are expected to be little higher than for shale. 
Sample K-1 from the Taltung Formation, fall below the SiO
2 
values of PAAS (62.4%). 
This sample contains higher amounts of Al
2
O
3
, Fe
2
O
3
, and CaO. CaO content could have 
elevated due to the presence of calcite cements in the rock. The SiO
2
 and Al
2
O
3
 contents 
of the Bhainskati and Amile formations from the Tansen, the Saptakoshi Formation from 
the Barahachettra, and Katari group are typical of cratonic sandstones (SiO
2
 ?90%, 
Al
2
O
3
<5%), (Condie, 1993). With a slightly high aluminum content and a slightly low 
silica content, sample 23-5 from the Saptakoshi Formation, and samples from the Sisne 
and the Dumri sandstones fall between the graywacke and cratonic sandstones fields 
(Condie, 1993). With very low SiO
2
 content and high Al
2
O
3
 content, the Taltung 
 
115 
 
sandstone falls in the oceanic island arc tectonic field (Bhatia, 1983).  Usually, 
sandstones are more depleted in K
2
O, Fe
2
O, and TiO
2 
than shales. The excessive iron 
oxide in the Dumri, Sisne, and Saptakoshi formations is related to daigenesis. However, 
the Taltung Formation not only contains high amount s of iron oxide, but also contains a 
range of Al
2
O
3
, Fe
2
O
3
 and TiO
2
 values that are consistent with derivation from oceanic 
island arc settings. Na
2
O content is higher in the Sisne sandstones in comparison to other 
units. 
The Harker Variation diagram (Fig. 7.3) shows no correlation between SiO
2
 and 
other oxides except for Al
2
O
3
. A negative correlation between SiO
2
 with Al
2
O
3
 is due to 
sequestration of most of silica in quartz (Osman, 1996). The percentages of  particular 
oxides in different samples do not change in accordance with SiO
2
 percentage, indicating 
various source terranes for different Gondwanan sequences. Moreover, the Taltung 
sandstones show major shifts in composition from other analyzed samples, suggesting a 
significant difference in source rocks.  
 
116 
 
Figure 7.2 Distribution pattern of major el
ement oxides in Gondwanan sandstone of
 Nepal. Data are normalized to Post 
Archean Australian Shale (PAAS) (Taylor and McLennan, 1995).
 
 
117 
 
 
Figure 7.3 Distribution patterns of major element oxides in Gondwanan sandstone of 
Nepal.  
 
 
118 
 
7.3.2 Source Area Weathering and Diagenesis  
The composition of sedimentary rocks can vary significantly based on the 
influence of the weathering through the whole sedimentary process starting with initial 
disintegration of the source rock to deposition in basin followed by diagenesis. The effect 
of weathering processes on sedimentary rocks can be measured quantitatively in terms of 
the molecular percentage of four major oxides (Nesbitt and Young, 1982). These 
percentages allow the determination of the chemical index of alteration (CIA), which is 
calculated as  
CIA = 100 X Al
2
O
3
/ (Al
2
O
3
+CaO*+K
2
O+Na
2
O),  
where CaO* is the amount of CaO in silicate minerals only. If CaO weight percent for an 
analysis appears greater than Na
2
O weight percent then CaO* is fixed by taking value 
equal to Na
2
O. A CIA value of 50 is considered for the fresh rocks whereas 100 is the 
value for extremely weathered rock which includes weathering of both the source rock 
and sedimentary deposit. In comparison to mudstones, sandstones generally show lower 
values for CIA (McLennan et al., 1990). CIA plots of the Gondwanan sandstones of 
Nepal show significant variations in CIA values (Fig. 7.4). Generally, the Amile 
Formation of the Tansen Group, the Saptakoshi Formation of Barahachettra Group, and 
the Katari Group (sample 26-3) show high values of CIA, which is consistent with their 
quartzose compositions. The ternary plot of Al
2
O
3
-(CaO+Na
2
O) + K
2
O (Fig. 7.5) shows 
that most of the Gondwanan sandstone samples are following usual weathering trends. 
The sample from the Amile Formation and sample 26-3 from the Katari Group fall very 
close to Al
2
O
3 
corner, affirming the highest degree of weathering. The slight offset of the 
 
119 
 
Taltung Formation samples towards CaO-Na
2
O can be attributed to contribution by of 
volcanic rock fragments. 
 
Figure 7.4 CIA values for the Gondwanan sandstones of Nepal. The reference values are 
given from average shale (AS), North America Quaternary loess (NAQL), Colorado 
Plateau crustal model (CPCM), and upper continental crust (UCC) (after Soreghan and 
Soreghan, 2007) where green bars represent the CIA value and yellow bars represent the 
ranges of maximum CIA values.  
 
 
 
120 
 
 
 
Figure 7.5 CIA plot of Gondwanan sandstones of Nepal (modified from Nesbit and 
Young, 1984, 1989; and Soreghan and Soreghan, 2007). The average composition of 
upper continental crust (UCC) is taken from Taylor and McLennan (1985) 
 
7.4.4 Trace Elements 
Trace element concentrations in sediments result from the competing influence of 
provenance, weathering, diagenesis, sediment sorting, and the aqueous geochemistry of 
the individual elements (Rollinson, 1993). The highest concentration of trace elements is 
found in clay-rich sediments rather than sand-sized sediments. However, several studies 
have been carried out on trace elements present in sand-sized sediments (Willan, 2003; 
Osae et al., 2006; Rahman and Suzuki, 2007).  
 
121 
 
Trace elements usually enter silicate structures replacing the major elements 
during fractional crystallization (Krauskopf and Bird, 1995).  Large ion lithophile 
elements (LILE) like Rb, Cs, Ba, and Sr, usually replace K due to similarities in their 
ionic radii and are concentrated in rock in the late stages of crystallization. Transition 
trace elements (TTE), like Ni, Cr, Mn, V, and Ti, substitute for Fe and Mg during early 
stages of crystallization.  High field strength elements (HFSE) including, Zr, Nb, Hf and 
Y, are partitioned into melts during crystallization and anatexis. Hence, they usually enter 
into felsic rocks rather than mafic rocks. Generally, compatible elements (TTE) are 
enriched in mafic rocks while incompatible elements (LILE, HFSE) are enriched in felsic 
rocks. Moreover, trace elements and rare earth elements (REE) remain essentially 
constant in abundance during weathering because of their low solubility in aqueous 
solutions at surface conditions (Taylor and McLennan, 1985).  
The ratios of some trace elements in sedimentary samples have proven useful in 
tracing sediment provenance.  
 
122 
 
Table 7.3 Ratios of some trace elements in Gondwanan sandstones of Nepal. Reference 
values are taken from (a) Cullers et al. (1988) for ranges in sediments from felsic and 
mafic sources, and (b) McLennan (1981) for upper continental crust 
Sample No Eu/Eu* La/Sc Th/Sc La/Co Th/Co Cr/Th 
Western Nepal 
16-1 (Dumri Fm) 0.56 8.13 3.15 4.07 1.58 2.90
15-8 (Bhainskati Fm) 0.55 8.00 2.64 8.89 2.93 1.56
15-5 (Amile Fm) 0.60 5.10 0.93 6.80 1.23 11.10
K-1 (Taltung Fm) 0.93 5.27 1.01 2.82 0.54 29.48
16-6 (Sisne Fm) 0.81 2.79 0.81 2.42 0.71 7.37
Eastern Nepal 
23-5 (Saptakoshi Fm) 0.89 3.50 1.13 1.63 0.52 10.65
22-9 (Saptakoshi Fm) 0.63 6.72 2.00 3.33 0.99 6.84
26-3 (Katari Gp) 0.75 7.30 2.10 5.62 1.62 6.52
26-8 (Katari Gp) 0.57 6.14 2.40 4.72 1.85 2.28
Ranges in sediments 
from felsic sources (a) 
0.40-
0.94
2.50-
16.3
0.84-
20.5
1.80-
13.8
0.04-
3.25 
4.00-
15.00
Ranges in sediments 
from mafic sources (a) 
0.71-
0.95
0.43-
0.86
0.05-
0.22
0.14-
0.38
0.04-
1.40 25-100
Upper Continental 
Crust (b) 0.63 2.21 0.79 1.76 0.63 0.76
 
Most of the trace element ratios of trace elements support that all Gondwanan 
sandstones are supplied from mixed sources of felsic and mafic igneous rocks (Table 
7.3). The Eu/Eu* ratio shows possible mafic source rock for the Taltung sandstone. La/Sc 
values for all samples support the supply from felsic igneous rocks. Th and Sc being 
incompatible and compatible respectively are used widely in provenance studies. The 
calculated ratio supports a mafic igneous source only for the Sisne Formation. La/Co 
ratios show that all the Gondwanan sandstones received sediment from felsic igneous 
sources, while Th/Co ratio indicates the possibility of mafic igneous source for the 
 
123 
 
Taltung and Sisne formations. Cr/Th ratio strongly supports a mafic source for the 
Taltung sandstone. The calculated Zr/Nb value of 1.95 indicates possible derivation from 
alkali-olivine basalt (Rollinson, 1993).     
The distribution pattern (Fig. 7.6) of trace elements of the Gondwanan sandstones 
shows enrichment of some elements and depletion of others. The high value of Sr in the 
samples form the Taltung Formation correlates with Eu distribution (Fig. 7.7), which is 
probably due to high concentration of plagioclase. Also high Zr and Hf can be related 
with zircon content of this sample. Another major departure in the distribution pattern of 
trace elements is the high contents of Sr in many of samples. This also supports an 
alkaline source rock where Sr can replace K. The copper content of the Taltung sandstone 
is notably lower than other samples. 
The distribution pattern of rare earth elements (REE), (Fig. 7.7) shows that 
sample K-1 from the Taltung Formation has high LREE (Light REE, La-Sm) than HREE 
(Heavy REE, Gd-Y). However, Eu value is significantly high in this sample. Generally, 
initial partial melting of mantle generates magma enriched in LREE (incompatible) and 
depleted in HREE (relatively compatible) (Rollinson, 1993). However, Eu is usually 
incorporated in Ca-plagioclase. Very high value of Eu and also LREE in any particular 
type of source rock is unusual and suggests for the mixing of source rocks or enrichment 
of plagioclase by sedimentary sorting (Nance and Taylor, 1977). In comparison to 
Archean basalts, post-Archean basalts are enriched in LREE (Condie, 1993). Hence, the 
REE pattern of the Taltung Formation can be explained by a post-Archean basalt source 
rock and sedimentary enrichment of plagioclase. Sample 26-3 from the Katari Formation 
 
124 
 
and the sample from the Amile Formation show relatively lower values of REE than 
PAAS which is expected for quartz-rich sandstones (McLennan, 1989). The Amile 
Formation is comparatively enriched LREE. Several samples, including samples from the 
Dumri, Bhainskati, Sisne, Saptakoshi formations and sample 26-8 from the Katari Group, 
show patterns similar to PAAS, although a few of them have slightly little lower values. 
This is typical for a provenance consisting of recycled sedimentary debris and/or older 
plutionic/metamorphic material with a relatively small volcanic component (Potter, 1978)  
 
125 
 
 
Figure 7.6 Distribution patterns of
 trace elements in Gondwanan sandstone of
 Nepal. Data are normalized to P
o
st 
Archean Australian Shale (PAAS) (Taylor and McLennan, 1995).
 
 
126 
 
 
Figure 7.7 Distribution patterns of
 rare earth elements (REE) in Gondwanan 
sandstone of Nepal. Data are normalized 
to Post Archean Australian Shale (P
AAS) (Taylor and McL
e
nnan, 1995).
 
 
127 
 
The relationships among some major oxides and trace elements also have been used to 
trace source-rock types and tectonic setting. The immobile oxide TiO
2
 and immobile 
trace element Zr have been used to infer the type of igneous source rock (Hayashi et al. 
1997). The TiO
2
-Zr plot (Fig. 7.8) shows that, except for the sample from the Taltung 
Formation, all units are derived from felsic igneous source rocks. Data for the Taltung 
Formation suggests derivation from an intermediate source rock.  
 
Figure 7.8 Plot of TiO
2
 vs Zr content of the Gondwanan sandstones of Nepal. Fields for 
source rocks are drawn from Hayashi et al. (1997). 
 
 
128 
 
7.4.5 Tectonic Setting and Source Rocks 
The K
2
O/Na
2
O-SiO
2
 discrimination diagram of Roser and Korsh (1986) is plotted 
in figure 7.9. The plot suggests that Dumri sandstone of the Tansen Group fall in active 
margin setting. The sample K-1 of the Taltung Formation falls in the volcanic arc setting 
(Fig. 7.9). All other samples including Eocene Bhainskati sandstone fall in passive 
margin setting.  
  
Figure 7.9 Tectonic discrimination diagram for Gondwanan sandstones of Nepal. 
Tectonic fields are from Roser and Korsh (1986). Tectonic setting: ARC = Volcanic Arc; 
ACM = Active Continental Margin; PM = Passive Margin. 
 
 
129 
 
The trace element plot of La-Th-Sc (Fig. 7-10, adopted from Bhatia and Crook, 
1986) also shows that most of the samples fall in the passive and active continental 
margin fields. However, the Taltung Formation samples fall in the continental island arc 
field, and the Sisne Formation samples unexpectedly falls into continental island arc 
field.  
 
Figure 7.10 Plot of elemental percentage of La-Th-Sc of Gondwanan sandstones of 
Nepal. Fields of tectonic setting are drawn from Bhatia and Crook (1986).  
 
130 
 
 
 
CHAPTER 8 
40
Ar/
39
Ar DETRITAL MUSCOVITE DATING 
8.1 INTRODUCTION 
  Argon is a naturally occurring noble gas occupying 0.94% of the total 
atmospheric volume of the earth. The main isotopes of argon found in the earth are 
40
Ar 
(99.6%), 
36
Ar (0.34%), and 
38
Ar (0.06%). Naturally occurring 
40
K, with a half-life of 
1.25 ? 10
9
 years, decays to stable 
40
Ar (11.2%) by electron capture and positron emission, 
and also to stable 
40
Ca (88.8%) via beta decay (Scherer, 2007). As 
40
K in rock decays into 
40
Ar through the time, the ratio of 
40
Ar to its other isotopes will increase. The 
40
Ar/
36
Ar in 
the atmospheric air is 295.5, which is taken as reference to compare with 
40
Ar/
36
Ar in 
rock (McDougall and Harrison, 1999). 
38
Ar forms by the radioactive decay of 
38
Cl, 
37
Ar 
formed from 
40
Ca, and 
36
Ar forms by the radioactive decay of 
40
Ca (Dickin, 1995) (Fig. 
8.1). 
The 
40
K/
40
Ar method of dating is based on the decay of 
40
K to 
40
Ar with a half life 
of 1.25 Ga (McDougall and Harrison, 1999). This method was first applied by Wanke 
and Konig (1959). The 
40
K/
40
Ar dating method and the 
40
Ar/
39
Ar method differ. In 
40
K/
40
Ar method, K is determined by independent analysis, while in the 
40
Ar/
39
Ar dating 
method, 
40
Ar and 
39
Ar, produced by neutron irradiation of sample, are measured 
 
131 
 
simultaneously. The abundance of 
39
Ar in the irradiated sample is a measure of the K 
content of that sample. The nuclear reaction that takes place during the irradiation is  
 
 
where n denotes neutron capture and p proton emission (Faure, 1986).  
In addition to 
39
Ar several other beneficial and undesirable isotopes are produced 
during irradiation in nuclear reactors. The effects of these interference reactions are 
corrected by using laboratory salt and glasses (Scherer, 2007). Table 8.1 shows the 
isotopes produced during the irradiation process. 
 
Figure 8.1 Some stable and radioactive isotopes related to 
40
Ar/
39
Ar dating method. The 
isotopes in yellow box are unstable isotopes. The blue arrow shows the natural decay 
reaction of 
40
K?
40
Ar. The red arrow shows the 
39
K (n,p)
39
Ar
K
 reaction during 
irradiation.  
 
   
39 
19 
K (n, p) 
39 
18 
Ar 
 
132 
 
Table 8.1 Isotopes produced during the irradiation process of muscovite. 
Argon Produced Calcium Potassium Argon  Chlorine 
36
Ar 
40
Ca    
37
Ar 
40
Ca 
39
K 
36
Ar  
38
Ar 
42
Ca 
39
K 
40
K 
40
Ar 
37
Cl 
39
Ar 
42
Ca 
43
Ca 
39
K 
40
K 
38
Ar 
40
Ar 
 
40
Ar 
43
Ca 
44
Ca 
40
K 
41
K 
  
 
The age equation for 
40
Ar/
39
Ar dating (e.g., McDougall and Harrison, 1999) is as 
follows:  
t = (1/?)ln(
40
Ar*/
39
Ar
K
(J)+1),  
where ? is the decay constant for 
40
K?
40
Ar, which is 5.543 X 10
-10
/year. 
40
Ar* is the 
40
Ar formed due to radioactive decay in the phase of interest. 
39
Ar
K
 is the 
39
Ar formed 
artificially by bombardment with fast, high-energy neutrons in a nuclear reactor during 
the irradiation process (Merrihue and Turner, 1966; McDougall and Harrison, 1999) and 
is used as a proxy for measurement of the parent potassium. The parameter J reflects the 
neutron flux (fluence) in the reactor and is determined from a standard sample (monitor) 
with a known age that is irradiated at the same time as the sample of interest (Scherer, 
2007). 
The 
40
Ar/
39
Ar method is equally applicable for igneous, metamorphic, and 
sedimentary systems. However, for intrusive igneous rocks, the 
40
Ar/
39
Ar method does 
Beneficial reactions  Insignificant 
reactions 
 Undesirable reactions  
 
133 
 
not provide the date of intrusion; rather, it will provide the age when the K-bearing 
mineral cooled through its closing temperature. The closing temperature varies among 
minerals. For example, it is approximately 300
o
C for biotite, 400
o
C for muscovite and 
550
o
C for hornblende. An igneous rock containing all three of these minerals will have 
three different ages for three separate cooling temperatures and will not give the true age 
of intrusion. However, it is helpful to know the thermal history of the rock. In the case of 
metamorphic rocks, minerals crystallized through their cooling temperatures during any 
metamorphic event will record the age of that metamorphic event. The 
40
Ar/
39
Ar dating 
method has been widely used also in the field of sedimentary research, with muscovite 
being the primary mineral for the analysis. When muscovite grains are transported from a 
source rock unit to a sedimentary basin, the 
40
Ar/
39
Ar dates of these grains can provide a 
measure of the time of cooling of its source through the closure temperature interval 
(typically 300-400?C; Hames and Bowring, 1994), with the consideration that no 
additional 
40
Ar is added or lost during the transportation and deposition (Hodges et al. 
2005).  
Detrital minerals usually will show a range of ages related to different sediment 
source terranes. The stronger relative probability of a particular age suggests greater 
contribution of detritus from the source rock having that age. The age of the sediment 
source rock and the depositional age of the sample represent the maximum time gap that 
is required for sediment transport.  To the extent that rapid transport is related to high 
relief in the source region, this phenomenon may indicate that a well-developed 
 
134 
 
Himalayan orogenic ?front? existed, and uplifted and unroofing ages may come closer to 
the depositional age of the clastic wedge (Hodges et al., 2005). 
The northern passive margin of India has evolved through different tectonic 
settings through geological time and has contributed sediment to its northern margin in 
the Tethys Sea. After the collision with the Tibetian block, the depositional environments 
changed from marine to continental accompanied by a change in drainage patterns. 
Previous workers have used 
40
Ar/
39
Ar method for age-dating sediments accumulated in 
the Tethys Sea and attempted to identify their provenance (e.g., Gizbert et al., 2008). 
8.2 METHODOLOGY 
Muscovite crystals from four sandstone samples from three different Gondwanan 
sections of Nepal were selected for analysis. Two samples, sample 15-8 from the 
Bhainskati Formation and sample 16-3 from the Sisne Formation of the Tansen Group, 
were selected from western Nepal. The other two samples, sample 22-8 from the 
Tamrang Formation of the Barahachettra Group and sample 26-8 from the Katari Group, 
are from eastern Nepal.  
Samples were prepared in the Himalayan Research Laboratory at Auburn 
University. Sandstone samples were crushed and sieved to extract grains in 0-4 phi size 
range. Afterwards, samples were processed for heavy mineral separation using a heavy 
liquid (tetrabromoethane). Lighter fractions of the samples were collected after washing 
carefully with acetone. From each sample, approximately 100 muscovite grains were 
separated using binocular microscope and packed into an irradiation disc. The samples 
 
135 
 
were sent to the McMaster University Research Reactor in Hamilton, Ontario, Canada for 
irradiation produce to 
39
Ar from 
39
K.   
The Gondwanan sandstones of Nepal were analyzed at the Auburn Noble Isotope 
Mass Analysis Laboratory (ANIMAL) at Auburn University. ANIMAL is equipped with 
a low-volume, high-sensitivity, 10-cm radius sector mass spectrometer and automated 
sample extraction system (based on CO
2 
laser) for analysis of single crystals (Uddin et 
al., 2007). Analyses are typically made using a filament current of 2.240 Amp, and 
potentials for the source and multiplier of 2000 V and ?1300 V, respectively. The high 
sensitivity and low blank of the instrument permits measurement of 10
-14
 mole samples to 
within 0.2% precision. The GA-1550 biotite (9.879 Ma; Renne et al., 1998) was used as a 
flux monitor for this study.  
Twenty-five irradiated muscovite grains from each sample were placed in a 
copper holding disc and analyzed by fusing single muscovite crystals with a CO
2
 laser. 
Data were reduced using Isoplot 3 (Ludwig, 2003). All samples were corrected for 
atmospheric argon contamination and inferring nuclear reactions. Mass fractionation was 
evaluated by measuring multiple air aliquots daily and procedural blanks were measured 
after every sample analyses.   
8.3 
40
Ar/
39
Ar RESULTS 
The distribution of age populations provided by the 
40
Ar/
39
Ar method for each 
sample is plotted in relative probability plots (Figs. 8.2 through 8.5). The data used for 
these plots are given in Appendix E. All samples show polymodal distributions of 
 
136 
 
muscovite age. However, some samples show fewer modes than others. Sample 15-8 
from the Eocene Bhainskati Formation of the Tansen Group shows several modes in age 
distribution. Significant age distributions are found approximately at 50 Ma, 140 Ma, 300 
Ma, 800 Ma and 900 Ma (Fig. 8.2). These multiple age distributions and wide range of 
age indicate contribution of muscovites from multiple source terranes. Sample 16-3 from 
the Permo-Carboniferous Sisne Formation of the Tansen Group also shows multiple age 
distributions with signification age distributions at 30 Ma, 135 Ma, 300 Ma, 500 Ma, 800 
Ma, 1300 Ma and 1700 Ma (Fig. 8.3). Unlike other samples, sample 26-8 from the Katari 
Group shows only three modes in age distributions: 18 Ma, 24 Ma, and 290 Ma (Fig. 
8.4). Sample 22-8 from the Permo-Carboniferous Saptakoshi Formation of the 
Barahachettra shows a wide range of age distribution modes at 20 Ma, 32 Ma, 220 Ma, 
290 Ma, 580 Ma, 790 Ma, 900 Ma, 1050 Ma and 1180 Ma (Fig. 8.5) 
The results for the sample from the Eocene Bhainskati Formation are consistent 
with the stratigraphic age assignment to this unit. The Cenozoic ages of other samples in 
this study, however, are dramatically younger than the Permo-Carboniferous stratigraphic 
ages assigned to them. The ages of ca. 18-30 Ma determined for them, in contrast, are 
suggestive of Himalayan orogenesis.  
 
137 
 
 
 
Figure 8.2 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the Eocene 
Bhainskati Formation (sample 15-8) (A) all data (B) ages less than 150 Ma of the Tansen 
Group, western Nepal.  
A
B
 
138 
 
 
 
Figure 8.3 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the Permo-
Carboniferous Sisne Formation (sample 16-3) (A) all data (B) ages less than 200 Ma, of 
the Tansen Group, western Nepal. 
A
B
 
139 
 
 
 
Figure 8.4 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the Permo-
Carboniferous Saptakoshi Formation (sample 22-8) (A) all data (B) ages less than 200 
Ma of the Tansen Group, eastern Nepal. 
A
B
 
140 
 
 
 
Figure 8.5 Probability plot for 
40
Ar/
39
Ar of single muscovite crystals from the Permo-
Carboniferous Katari Group (sample 26-8) (A) all data (B) ages less than 50 Ma, eastern 
Nepal. 
B
A
 
141 
 
The fact that some detrital muscovite ages from the Sisne and Saptakoshi 
formations as determined in this study appear younger than expected o the basis of 
stratigraphic age assignment could be explained in several ways. Possible causes of the 
age discrepancy are raised and discussed below: 
1. Laboratory error in the measurement, including incorrect J-value, or mass 
spectrometer parameters (ratio measurement, etc.). 
Laboratory analytical errors listed in the appendices (Appendix ?F) represent the 
precision of argon isotopic measurements for the individual muscovite crystals, and 
generally result in an uncertainty of about 1% in the single-crystal ages. The J-values 
were constrained by placing monitor minerals in close proximity to the samples of this 
study and are reproducible to within 0.5%. Combining all sources of laboratory and 
monitor mineral uncertainty a resulting accuracy for the ages determined would be within 
2% (or, about 200,000 years for the Miocene ages determined in this study). Thus, it is 
certain that laboratory errors cannot be responsible for producing the Miocene ages in 
samples of this study. 
2. Sample misidentification, and mislabeling, or contamination in the field or in 
the laboratory. 
Samples 15-8, 16-3, and 22-8 contain muscovite with ages of calculated 500-1700 
Ma that are compatible with Gondwanan source terranes in the Indian craton, and ages 
less than ~ 17 Ma are not found in these samples or in sample 26-8. In contrast, 
muscovite samples collected and processed for laboratory analysis in the same general 
 
142 
 
time frame as samples of the present study are from the Bengal Basin (with typical 
muscovite ages of 14-20 Ma, and a large proportion of micas that are 15-16 Ma) and the 
Appalachians (with ages of 300-450 Ma). Considerable care was taken in handling 
samples, both in the field and laboratory, and sample contamination is very unlikely to be 
a cause of the ages that are younger than stratigraphic assignment. Furthermore, the 
modes of 19-22 Ma (see samples 26-8, 22-8, and 16-3), and the pre-500 Ma ages, are not 
compatible with other laboratory samples. Therefore, there is no basis to infer sample 
mishandling or laboratory contamination could be responsible for the Miocene ages 
determined for these presumably pre-Cretaceous stratigraphic units. 
3. Incorrect assessment of geology including (3a) stratigraphy and (3b) tectonics 
of the study area. 
3a. Wide-ranging and polymodal age distributions for the Bhainskati Formation 
(sample 15-8) of the Tansen Group was expected. Post-Gondwanan fossils like 
Nummulites beaumonti d?ARCHAIC and HEIME, and Assilina papillata NUTTLE are 
reported from the Eocene Bhainskati Formation (Sakai, 1983). The Bhainskati Formation 
is considered as the record of sediment source switching from Indian craton to the 
Himalayan orogenic belt (Najman, 2003).  
The depositional age of the Sisne Formation has been suggested to be Permo-
Carboniferous based on discovery of Fenestella, Polypora and Acanthocladia from the 
Tansen area (Sakai, 1983). Sakai (1983) has suggested that this formation was supplied 
sediment from cratonic India. However, muscovite dating of sample 16-3 from the Sisne 
Formation unexpectedly yields few much younger age of 30 Ma and other expected older 
 
143 
 
ages correlatable to Indian source rocks. Notably, the Sisne Formation is overlain by the 
Taltung Formation. The latter unit contains basalt flows considered to be equivalent of 
Rajmahal Traps (Sakai, 1983). The age of the Rajmahal Traps is considered to be 118 Ma 
(Kent et al., 2002). Thus, the Permo-Carboniferous ages inferred for regional Gondwanan 
sequences in the Tansen area seem well supported.  
The age distribution of sample 22-8 from the Saptakoshi Formation of the 
Barahachettra Group poses a similar problem. The Gondwanan plant fossils, Schizoneura 
gondwanesis FEISTM of Permian age, have been reported from the black slate of the 
Barahachettra Group (Bashyal, 1980). However, occurrence of plant fossils in that area 
has not been reported afterwards. The quartzite unit of the Saptakoshi Formation, which 
also includes fossiliferous slate, has been kept below the diamictic beds and above 
Precambrian basement rock (Bashyal, 1980, Dhital 1992). Everywhere else, diamictite 
beds are reported above Precambrian basement in the Gondwanan sequences. Moreover, 
the contact between the quartzite beds and Precambrian basement rocks is not an 
unconformity but a normal fault. So, all these controversies make the stratigraphy of the 
Barahachettra difficult to understand. The younger muscovite ages for sample 22-8 (~17 
Ma) would be compatible with the Miocene Dumri Formation. However, the latter is a 
litharenite and is lithologically very different than the Barahachettra quartzite unit. 
Sample 26-8 of Katari Group poses similar problem. Muscovite grains from this sample 
are not giving significant older age modes representing source rocks from the India 
except one 290 Ma. The major age modes occur at 18 and 24 Ma (Fig. 8.5).  
 
144 
 
3b. The major tectonic structure of the Himalayan orogenic belt is Main Central 
Thrust (MCT) (Fig. 2.1) which was activated during 25~20 Ma and reactivated during 
~10 Ma (Le Fort, 1996). Another major thrust is Main Boundary Thrust (MBT) which 
became activated ~3 Ma and move the Lesser Himalayan rocks above the Siwaliks. 
However, there are several small scale thrusts between MCT and MBT and the area of 
this study, particularly in the eastern part. MCT itself is an issue of major debate in 
Himalayan geology. Several believe that the MCT is a zone rather than single plane. The 
Barahachettra and Katari groups include several small scale thrusts and some of the 
samples in the present study show post-depositional deformational features.  
4. Thermal resetting of muscovite grains 
 A closure temperature of 350-400 ?C has been commonly suggested for 
muscovite (e.g., Hames and Bowring, 1994; McDougall and Harrison, 1999). In 
metamorphic rocks, early-formed muscovite has been shown to be resistant to argon loss 
during overprinting metamorphism (to temperatures of at least 425?C; Hames and 
Cheney, 1997). There are also many examples of detrital muscovite that was not 
completely reset during low grade metamorphism of slates (Dallmeyer and Takasu, 
1992). The muscovite grains analyzed during this study shows their detrital 
characteristics with well rounded shape and average diameter of grains ~0.3 - 0.5 mm 
(see representative photographs in Appendix ? G). So there is no possibility to get young 
ages by analyzing the diagenetically formed sericitic muscovite in low temperature due to 
activities of the Main Central Thrust (MCT).  Quartz textures in the sandstones of this 
study, including sample 26-8, include undulose extinction, sutured grain boundaries, and 
 
145 
 
polycrystalline grains. Such intercrystalline strain textures and disequilibrium grain 
boundaries would presumably anneal if sandstone were heated to ~ 300 ?C or higher for a 
geologically significant length of time. MCT, which could be the only possible 
deformational agent, was suggested to be active around 24 Ma (Le Fort, 1996) that may 
not provide sufficient heat and time period of high temperature for resetting of muscovite. 
In metamorphic rocks younger ages of muscovite has been recorded from the overgrown 
muscovite due to polymetamorphism rather than the lattice diffusion due to temperature 
increase (Hames and Cheney, 1997). But none of these Gondwanan samples show any 
attribute of metamorphism. The loss of argon along deformed edges and cracks of 
muscovite has been also reported. However, the relationship of detrital muscovite 
behavior to that of metamorphic muscovite is unclear. The older, Precambrian ages 
determined in this are compatible with Gondwanan sources and do not seem ?reset? by 
younger events. Thus, on the basis of preserved detrital mineral texture (e.g., quartz 
undulose extinction) and previous studies of muscovite, it is not easy to explain younger 
ages by thermal resetting. 
8.4 PROVENANCE INTERPRETATION 
The older muscovite age mode for the Gondwanan sandstone samples can be 
correlated with the ages of possible source rocks in Pennisular India, primarily the 
Aravalli-Delhi Supergroup, the Malani Igneous Suite, the Bundelkhand Massif, and the 
Chotnagpur Gneissic Terrain (Fig. 8.8). In addition to these igneous and metamorphic 
units; the Vindhyan Supergroup, equivalent to the Lesser Himalaya, also may have been 
a major contributor of sediments for the Gondwanan sequences of Nepal (Sakai, 1983). 
 
146 
 
Chaudhary et al. (1984) have identified five broad periods of acid magmatism in the 
Delhi Supergroup, including 1700-1500 Ma which gave rise to Erinpura Granite, and 
870-750 Ma, which related with the Malani Igneous Suites. These ages were obtained 
from Rb-Sr geochronology. Another possible source of older muscovites could be the 
Pilbara craton of Western Australia, where alkaline intrusive rocks have been dated at 
1,724 Ma using 
40
Ar/
39
Ar analyses (Matchan, 2008).  
 
Figure 8.8 Possible source rock with the age given by the detrital muscovite analyzed.  
 
147 
 
 
 
CHAPTER 9: DISCUSSION 
9.1 SYNTHESIS 
 Permo-Carboniferous Gondwanan sequences of the Nepal Himalaya are mostly 
continental deposits developed along a passive-margin setting. However, sequences also 
include some marine beds and have been influenced by at least one event of rifting. The 
setting gradually changed to a foreland basin when the Indian plate collided with the 
Tibetan plate. Post-Gondwanan sequences preserve the history of this collision. The 
research carried on the petrography; heavy minerals, whole-rock geochemistry, mineral 
chemistry, and detrital muscovite dating of sandstones has generated two important types 
of information regarding the provenance and the correlation of the Gondwanan sequences 
in different sections of Nepal Himalaya.  
9.2 SANDSTONE PETROGRAPHY AND STRATIGRAPHY 
 The Tansen Group, the type section of the Gondwanan sequence and post-
Gondwanan sequences, shows very sharp compositional variation between different time-
stratigraphic units. The Permo-Carboniferous Sisne Formation contains abundant 
feldspars in sandstones that are interbedded with daimictitic beds (Sakai, 1983). Another 
important character of the Sisne sandstones is common garnets. Clasts of the diamicite 
are believed to have come from the Malani Granite and other associated rock units, 
including the Vindhyan Group (Sakai, 1983). The depositional environment can be 
 
148 
 
inferred to be glacial with intervals of glacio-fluvial deposits. The Chotanagpur Gneissic 
terrain of peninsular India could have been the main source for providing garnets. The 
300 Ma alkaline syenite intrusive rocks in the Chotanagapur Terrain (Mahadevan, 2000) 
may have been a source for the feldspars in the Sisne Formation (Fig. 4.1A). 
 A major shift is observed in the depositional environment of Jurassic- Cretaceous 
Taltung Formation. The fluvial depositional basin was not only receiving detritus from 
the southern highland in India but also accumulating volcanic rock fragments from the 
rift volcanics, which are believed to be contemporary with the Rajmahal Basalt (Sakai, 
1983). Diagenetic replacement of quartz and feldspars by calcite is very strong in the 
Taltung Formation (Fig. 4.1B). The Late Cretaceous-Paleocene Amile Formation is 
shallow-marine deposit that is dominated by mature quartz (Figure 4.2 A). Besides quartz 
arenite, the sequence contains shale and limestone, which likely reflect sea-level changes 
rather than shifts in source terranes.  
 The Eocene Bhainskati Formation contains abundant lithic fragments (Fig. 4.2B). 
The Bhainskati Formation has been suggested to receive sediments from both the 
Himalayan orogenic belts and as well as the Indian craton (DeCelles, 1998). The lower 
Miocene Dumri Formation is considered to be a foreland deposit. It is distinguished from 
other units based on low abundance of feldspar contents (DeCelles, 1998). 
 The Permo-Carboniferous Gondwanan sequence of the Katari area in the eastern 
Nepal has not been studied well (Dhital, 2006). Petrographic study of the carbonaceous 
quartzite from the Katari area shows mature quartz grains cemented by calcite. The 
quartzites are deformed but the degree of deformation is variable. From perspective of 
 
149 
 
petrology only, the quartzite beds of the Katari section can be correlated with the Amile 
Formation of western Nepal. 
 Dhital (1992) revised the stratigraphy of the Barahachettra area of eastern Nepal. 
The Saptakoshi Formation of the Barahachettra Group consists of diamictite, quarzites, 
and volcanic materials. Quartzites are carbonaceous and interbedded with gray shale. 
Petrographic studies of quartzites show that these are pure quartz arenites with mature 
quartz grains. However, the quartz grains are deformed in many instances. The 
petrography of these quartzites as well as the alternation with the gray shale strongly 
suggests correlation with the Amile Formation of the Tansen Group (western Nepal). The 
sandstone beds, interbedded in diamictites, contain abundant plagioclase and garnet (Fig. 
4.4 A), which suggests that the Saptakoshi Formation may be correlated with the Sisne 
sandstones.  
 The Tamrang sandstone contains of angular to subrounded grains of quartz, 
feldspar, and metamorphic rock fragments. Abundant mica is present. The matrix consists 
of calcite and clay. This formation was earlier proposed to be Cretaceous-Paleocene by 
Dhital (1992). However, based on high percentages of metamorphic fragments; it could 
be correlated with the Bhainskati Formation of western Nepal.  
The occurrence of quartzite beds below the diamictite in the Saptakoshi 
Formation which is below the diamictite makes the finding of the Gondwanan fossils in 
these beds suspicious. Elsewhere, in peninsular India and in extra-peninsular basins, 
Gondwanan sequences always begin with a diamictite directly above the Precambrian 
basement which is not consistent in the Barahachettra Group (Sakai, 1983; Dhital, 1992, 
 
150 
 
Veevers, 1995, Dhital, 2006). The fossils reported from the Barahachettra Group have 
been never reported in that area by other workers after their first discovery by Bashyal 
(1980, 1981).  The unconformity considered contact between the quartzites of the 
Saptakoshi Formation and the underlying Precambrian basement is actually a normal 
fault.   
 Based on a recent communication with Dr. Meghraj Dhital, a leading expert in 
Gondwana sequences of Nepal, a new stratigraphic framework for eastern Nepal is 
proposed (Table 9.1) (Fig. 1). 
Table 9.1 Proposed Stratigraphy of Gondwanan and post- Gondwanan sequences in the 
Barahachettra area (eastern Nepal) and its correlation with Gondwanan sequences in 
other parts of Nepal. 
Age Tansen Group Katari Group 
Barahachettra 
Group 
Early Miocene Dumri Formation Yellow Sandstone - 
Eocene 
Bhainskati 
Formation 
disconformity Tamrang Formation 
Paleocen-L. 
Cretaceous 
Amile Formation 
Carbonaceous 
Quartzite 
Saptakoshi Formation 
Cretaceous-
Jurassic 
Taltung 
Formation 
Volcanics Volcanic Tuffs 
Permo-
Carboniferous 
Sisne Formation Diamictite Kokaha Diamictite 
 
 
151 
 
 
Figure 9.1 Correlation of stratigraphy 
of Gondwanan sequences in wester
n part of Nepal and proposed 
stratigraphy of eastern N
e
pal 
 
152 
 
9.3 HEAVY MINERAL STUDY  
  Heavy minerals in Gondwanan sandstones are dominated by two assemblages; 
garnet rich and ZTR (zircon, tourmaline, and rutile) rich. The Sisne and Kokaha 
(Saptakoshi Formation of Dhital, 1992) sandstones contain abundant garnet grains, which 
not only require garnet-rich source rocks as well as preservation of those grains. 
Subordinate amounts of ZTR are also present in the samples where garnet dominates. In 
contrast, the samples that are rich in ZTR contain few garnets, reflecting their relatively 
low preservation potential. The Amile Formation does not contain unstable minerals. The 
Taltung Formation consists of high number of garnets as well as ZTR. The Tamrang 
Formation of the Barahachettra contains abundant micas. The probable provenance for 
the garnets could be the Bihar Mica Belt and the Munger Belt of the Chotanagpur 
Gneissic terrain of eastern peninsular India. The recycled Vindhyan systems, the Aravalli 
Belt and the Bundhelkhand Granite could be potential sources of the ZTR grains. 
9.4   MICROPROBE ANALYSIS 
Garnets 
Garnets are found mostly in the Sisne and Taltung formations in the western part 
of Nepal, and the Saptakoshi Formation and Katari Group in the eastern part of Nepal. 
The garnets are mostly almandine rich. Pyrope is significantly high in garnet from the 
Taltung Formation. Grossular content is high for some samples from the Saptakoshi 
Formation. As most of the garnet grains are rich in almandine, these grains were derived 
 
153 
 
from a low-grade metamorphic source rocks. The high pyrope contents in the Taltung 
Formation may reflect high grade metamorphic source rock.  
Tourmaline  
On the Ca-Fe(tot)-Mg plot, the Katari Group tourmaline show high variations 
reflecting three different source rock types: Li-rich granitoid pegmatites, Li-poor 
granitoid pegmatites, and Ca-poor metapelites, metapsammites. Tourmaline from  the 
Barahachettra (the Tamrang Formation) and Tansen group fall in within the Li-poor 
granitoid pegmatites and Ca-poor metapelites, and metapsammite fields.  
Chrome Spinel 
Chrome spinels are not very common in the Gondwanan sequence of the Nepal 
Himalaya. Chrome-spinel was found only in the Taltung sandstones. These chrome 
spinels contain high aluminum and high chromium, suggesting a source from an Alpine-
type peridotite. Low percentages of TiO
2
 contents suggest that alkaline basalts were the 
source of volcanic clasts.  
9.5 GEOCHEMICAL ANALYSIS 
The Taltung Formation differs geochemically from other samples, which could be 
due to sediment supply from the volcanic source rocks. Various ratios of major oxides 
and trace elements like Al
2
O
3
/TiO
2
, TiO
2
/Zr also show that Taltung Formation is derived 
from igneous sources. The Harker plot does not show any evolutionary trends. Hence, the 
rock units supplying sediments to the Gondwanan basins likely were not genetically 
related. 
 
154 
 
Discrimination analysis of the tectonic setting diagrams (Figs. 7. 9 and 7.10) show 
that the Taltung Formation belongs to arc or rift zones, the Dumri and the Bhainskati 
formations deposited in active continental margins, and  other formations deposited 
passive margin setting. Basaltic materials commonly have lower HREE, but if the basalt 
is alkaline, HREE can be significantly high and contain high Eu value. The REE pattern 
of the Taltung Formation is similar to the Bengal Trap alkali basalts (Fig. 9.2) (Baksi, 
1995). 
 
Figure 9.2 Chondrite normalized REE pattern of Bengal Trap Basalt (from Baksi, 1995). 
9.6 
40
Ar/
39
Ar MUSCOVITE GEOCHRONOLOGY 
The 
40
Ar/
39
Ar muscovite dating of the Gondwanan sandstones carried for this 
study has provided two types of ages. The older ages (>40 Ma) provide cooling ages of 
muscovite crystals from igneous intrusions or metamorphic events that took place in the 
Indian craton. Hence, this gives the approximate ages of source rocks. In contrast, 
 
155 
 
younger ages (<24 Ma) given by muscovites could have one of the reasons including 
misunderstanding of stratigraphy or loss of argon from the detrital muscovites.  Several 
older ages of detrital muscovite grains from the Gondwanan sandstone samples may be 
related with the cooling ages of the Malani igneous suites (870-750 Ma), the Erinpura 
granite (1700 ? 1500 Ma), the Munger orogeny (400 ? 320 Ma) and or alkali syenite 
intrusions ( 300 Ma) in the Chotanagpur Terrain (Fig. 9.3).  
 The 40 Ma age found from muscovite grains in the Eocene Bhainskati Formation 
(sample 15-8) indicates the source rocks from the Himalayan orogenic belt and other 
older ages going up to 900 Ma indicates source rocks from Indian craton as well. 40 Ma 
could refers to the cooling ages may also be related to the Gangdese batholith (Copeland 
et al., 1995).  
9.7 PALEOTECTONIC SETTING 
 During the Permo-Carboniferous, West Gondwanaland had already separated 
from East Gonwananland. India together with East Gonwanaland was in the southern 
hemisphere around 60
o
 S (Fig. 9.4A). Due to initial stretching along a major lineament, 
the half graben basins were created in peninsular India. At the same time, towards the 
northern margin of India, glacial diamictite and glacio-fluvial deposits were being 
deposited.  
 
156 
 
 
 
Figure 9.3 
40
Ar/
39
Ar cooling ages of single grai
n muscovite from the Gondwanan sa
ndstone of Nepal. The thick 
horizontal bars represent published ge
ochronological data for potential so
urce rocks in peninsular India and 
Himalay
a
s.  
 
 
157 
 
  
 During the Cretaceous, Gondwanaland was positioned around 30
o
S latitude and 
deposition was in fluvial environments. As Australia rifted from India toward east, 
several hot spots formed in India (Fig. 9.4 B), including the well-known Rajmahal Trap. 
Further west, more volcanic activities were taking place, including the eruption of the 
Aulis Trap, which contributed volcanic clasts to the Taltung Formation. 
 Due to global fall of sea level during the Late Cretaceous-Paleocene, sediments 
eroding from the central region of India had to cover a longer distance. Moreover, as the 
Indian continent was already in a temperate zone at that time, weathering was extreme 
resulting in deposition of the Amile Formation (Fig. 9.4 C). 
 The collision between India and Tibet occurred by the Eocene. However, there 
was still a shallow sea at the backbulge of the foreland basin (DeCelles, 1998). Sediment 
derived from the Himalayan belt as well as from the Indian craton towards the south were 
deposited in these shallow sea (Fig. 9.4 D).  
 The India-Tibet collision was complete by the early Miocene, resulting in the 
complete retreat of the sea. A thick pile of sediment resulting from the rapid unroofing of 
the Himalayan belt was deposited in the forebulge of the foreland (Fig. 9.4 E).   
 
158 
 
 
Figure 9.4 Paleotectonic setting of India from Permo-Carboniferous to Miocene during 
deposition of Gondwanan and post-Gondwanan sequences (modified after Sakai, 1989; 
Veevers and Tiwari, 1995; DeCelles et al., 1998) (1= Delhi-Aravalli Supergroup, 2= 
Bundelkhand Granite, 3= Chotanagapur Gneissic Terrain). 
 
 
159 
 
9.8 CONCLUSIONS 
Based on the results of Analysis done for this research following conclusions can been 
drawn: 
1. Gondwanan and post-Gondwanan sequences were deposited along the northern 
passive margin of India from Late Carboniferous to Early Miocene. 
2. In the Barahachettra area, quartzites of the Saptakoshi Formation are not Permo-
Carboniferous in age. These quartzites are equivalent to the Paleocene-late 
Cretaceous Amile Formation of western Nepal. The contact between quartzites of 
the Saptakoshi Formation and underlying Precambrian basement is a fault, not an 
unconformity. 
3. The carbonaceous quartzite beds of the Katari area also do not belong to the 
Permo-Carboniferous age. Rather, based on sandstone petrography, whole-rock 
geochemistry, heavy mineral analysis and mineral chemistry of this unit suggest 
that they are equivalent to the Amile Formation of western Nepal. 
4. The Tamrang Formation, which contains high percentage of the lithic fragments, 
could be equivalent to the Eocene Bhainskati Formation of western Nepal. 
5. The older detrital muscovite ages are sensibly correlated to the source rocks in the 
Aravali-Delhi Supergroup, Bundelkhand Granite, and Chotanagpur Gneissic 
Terrain.  Source rocks from the Himalayan orogenic belts have been inferred for 
the ~40 Ma ages from the Eocene Bhainskati Formation. However, the younger 
muscovites ages (< 30 Ma) are difficult to explain given our present 
 
160 
 
understanding and the argon-retention characteristics of muscovite along with the 
regional stratigraphic and tectonic constraints for the study area. 
6. Further sampling from the study area is suggested to address the problem related 
with younger ages. Dating of basalt flow units from all three units may give a 
better control on stratigraphy. The fossil study on the Cretaceous-Paleocene units 
will be also helpful to clarify the stratigraphy. 
 
161 
 
REFERENCES 
Amatya, K.M., and Jnawali, B.M., 1994, Geological map of Nepal: Department of Mines 
and Geology, Nepal, Scale 1:1000000, 1 sheet 
Acharya, S.K., 2000, Coal and lignite resources of India: an overview: Geological 
Society of India, Banglore, 50 p. 
Amano, K., and Taira, A., 1992, Two-phase uplift of Higher Himalayas since 17 Ma: 
Geology, v. 20, p. 391-394. 
Auden, J. B., 1935, Traverses in the Himalaya, Record of Geological Survey of India, v. 
69, p. 123?169. 
Aslam, M., Arora, M., and Tewari, R.C., 1991, Heavy mineral suite in the Barakar 
sandstone of Moher sub-basin, Singrauli coalfield, central India: Journal of the 
Geological Society of India, v. 29, p. 66-75. 
Baksi, A.K., 1995, Petrogenesis and timing of volcanism in the Rajmahal flood basalt 
province, north eastern India: Chemical Geology, v. 121, p 73-90 
Azmi, R.J., and Pancholi, V.P., 1983, Early Cambrian (Tommotian) conodonts and other 
shelly microfauna from the Upper Krol of Mussoorie Syncline, Garhwal Lesser 
Himalaya, with remarks on the Precambrian-Cambrian boundary: Himalayan 
Geology, v. 11, p. 360-372. 
Bateman, R.M., and Catt, J.A., 1985, Modification of heavy mineral assemblages in 
English coversands by acid pedochemical weathering: Catena, v. 12, p. 1-21. 
Bashyal, R.P., 1980, Phosphatic rocks of Barakhsetra Formation: 3rd International field 
workshop and seminar, Khubsugul, Ulan-bator, p. 1-9. 
Bashyal, R.P., 1979, The Gondwana type of formation with phosphatic rocks in 
southeastern Nepal: Report Published by Department of Mines and Geology, p. 4-
18. 
 
162 
 
Bhatia, M., 1983, Plate tectonics and geochemical composition of sandstones: Journal of 
Geology, v. 91, p. 611-627. 
Bhatia, M. R., and Crook, K. A. W., 1986, Trace element chracteristics of graywacke and 
tectonic setting discrimination of sedimentary basins: Contributions to 
Mineralogy and Petrology, v. 92, p. 181-193. 
Bock, Barbara, McLennan, S.M., and Hanson, G.N., 1998, Geochemistry and provenance 
of the Middle Ordovician Austin Glen Member (Normanskill Formation) and the 
Taconian Orogeny in New England: Sedimentology, v. 45, p. 635-655. 
Brookfield, M.E., 1993, The Himalayan passive margin from Precambrian to Cretaceous 
times: Sedimentary Geology, v. 84, p. 1-35. 
Catuneanu, O., Wopfner, H., Eriksson, P.G., Carincross, B., Rubidge, B.S., Smith, 
R.M.H., and Hancox, P.J., The Karoo basins of south-central Africa: Journal of 
African Earth Sciences, v. 43, p. 211-253. 
Clark, M.K., and Bilham, R., 2009, Miocene rise of Shilong Plateau and the beginning of 
the end for the Eastern Himalaya: Earth and Planetary Science Letters, v. 269, p. 
337-351. 
Cookenboo, H.O., Bustin, R.M., and Wilks, K.R., 1997, Detrital chromian spinel 
compositions used to reconstruct the tectonic setting of provenance: Implications 
for orogeny in the Canadian Cordillera: Journal of Sedimentary Research, v. 67, p 
116-123. 
Condie, K. C., 1993, Chemical composition and evolution of the upper continental crust: 
Contrasting results from surface samples and shale: Chemical Geology, v. 104, p. 
1-37. 
Cerveny, P.F., 1986, Uplift and Erosion of the Himalaya over the past 18 Million years: 
Evidence from Fission Track Dating of Detrital Zircons and Heavy Mineral 
Analysis, unpublished MS thesis, Dartmouth College, 198 p. 
 
163 
 
Cerveny, P.F., Johnson, N.M., Tahirkheli, R.A.K., and Bonis, N.R., 1989, Tectonic and 
geomorphic implications of Siwalik Group heavy minerals, Tectonics of western 
Himalayas: Geological Society of America Special Paper, v. 232, p. 129-136. 
Chaudhary, A.K., Gopalan, K., and Sastry, C.A., 1984, Present status of the 
geochronology of the Precambrian rocks of Rajasthan: Tectonophysics, v. 105, 
pp. 131-140. 
Chaudhri, R.S., 1972, Heavy minerals from Siwalik formations of the northwestern 
Himalayas: Sedimentary Geology, v. 8, p. 77-82. 
Copeland, P., Harrison, T.M., Yun, P., Kidd, W.S.F., Roden, M., and Yuquan, Z., 1995, 
Thermal evolution of the Gangdese batholith, southern Tibet: A history of 
episodic unroofing: Tectonics, v.14, p.223-236. 
Cullers, R.L., Basu, A., and Suttner, L.J., 1988, Geochemical signature of provenance in 
sand-size material in soils and stream sediments near the Tobacco Root Batholith, 
Montana, U.S.A: Chemical Geology, v. 70, p. 335-348. 
Dallmeyer, R.D., and A. Takasu., 1992, 
40
Ar/
39
Ar ages of detrital muscovite and whole-
rock slate/phyllite, Narragansett Basin, RI-MA, USA: implications for 
rejuvenation during very low-grade metamorphism: Contributions to Minearlogy 
and Petrology, v. 110, p. 515-527. 
Decelles, P.G., Gehrels, G.E., Quade, J., and Ojha, T., 1998, Eocene-early Miocene 
foreland basin development and the history of Himalayan thrusting, western and 
central Nepal: Tectonics, v.17, p. 741-765. 
Decelles, P.G., Gehrels, G.E., Najman, Y., Martin, A.J., Carter, A., Garzanti., E., 2004, 
Detrital geochronology and geochemistry of Cretaceous-Early Miocene strata of 
Nepal: implications for timing and diachroneity of initial Himalayan orogenesis: 
Earth and Planetary Science Letters, v. 277, p. 313-330. 
Deer, W.A., Howie, R.A., and Zussman, J., 1992, An introduction to the rock-forming 
minerals: Longman Scientific Technical, Harlow, United Kingdom, 696 p. 
 
164 
 
Dhital, M.R., and Kizaki, K., 1987, Lithology and Stratigraphy of The Northern Dang, 
Lesser Himalaya: Bulletin of College Sciences, University of Ryukus, v. 45, p. 
183-244. 
Dhital, M. R., 1992, Lithostratigraphic comparison of three diamictite successions of 
Nepal Lesser Himalaya: Journal of Nepal Geological Society, v. 8, p. 43?54. 
Dhital, M.R., unpublished, The study of Gondwana type of rock in eastern Nepal Lesser 
Himalaya, (report submitted to Nepal Academy of Science and Technology), 38 
p. 
Dickin, A.P., 1995, Radiogenic Isotope Geology: New York, Cambridge Press, 452 p. 
Dickinson, W.R., 1970, Interpreting detrital modes of greywacke and arkose: Journal of 
Sedimentary Petrology, v. 40, p. 695-707. 
Dickinson, W.R., and Suczek, C., 1979, Plate Tectonics and Sandstone compositions: 
American Association of Petroleum Geologists Bulletin, v. 63, p. 2164-2182. 
Dickinson, W.R., 1985, Interpreting provenance relations from detrital modes of 
sandstones, in Zuffa, G.G., ed., Reading Provenance from Arenites: Dordecht, 
The Netherlands, Riedel,  p. 333-361. 
Dick, H.J.B., and Bullen, T., 1984, Chromian spinel as a petrogenetic indicator in abyssal 
and alpine-type peridotites and spatially associated lavas: Contributions to 
Mineralogy and Petrology, v. 86, p. 54-76. 
Dorsey, R. J., 1988, Provenance evolution and unroofing history of a modern arc-
continent collision: Evidence from petrography of Plio-Pleistocene sandstones, 
eastern Taiwan: Journal of Sedimentary Petrology, v. 58, p. 208-218. 
Dryden, A.L., and Dryden, C., 1946, Comparative rates of weathering of some common 
heavy minerals: Journal of Sedimentary Petrology, v. 16, p 91-96.  
Dutta, P., 2002, Gondwana lithostratigraphy of Peninsular India: Gondwana Research 
(Gondwana Newsletter Sec), v. 5, p. 540-553. 
 
165 
 
Dutta, P.K., and Ghosh, S.K., 1993, The century old problem of the Pali?Parsora ?Tiki 
stratigraphy and its bearing on the Gondwana classification of Peninsular India. 
Journal Geological Society of India, v. 42, p. 17?31. 
Faure, G., 1986, Principles of Isotope Geology, second edition: New York, John Wiley 
  and Sons, 589 p. 
Fleet, W.F., 1926, Petrological notes on the Old Red Sandstones of the West Midlands:  
Geological Magazine, v. 63, p. 505-516. 
Frakes, L.A., Kemp, E.M., and Crowell, J.C., 1975, Late Paleozoic Glaciation: Part VI, 
Asia, Geological Society of America Bulletin, v. 86, p. 454-464 
Freise, F.W., 1931, Untersuchung von Mineralen auf Ab-nutzbarkeit bei Verfrachtung im 
Wasser: Tschermaks Mineralogy of Petrology, v. 41, p. 1-7 
Friedenreich, O.R., Slind, O.L.,  Pradhan, U. M.S.  and Shrestha, R.B., 1994, Petroleum 
Geology of Nepal; Canadian Journal of Exploration Geophysics, v. 30, p. 103-
114. 
Gansser, A., 1983, The morphogenic phase of mountain building, in Hsu, K.J., eds., 
Mountain building processes: Academic Press, London, p. 221-28. 
Garzanti, E., Vezzoli, G., Ando, S., Lave, J., Attal, M., France-Lanord, C., and DeCelles, 
P., 2007, Quantifying sand provenance and erosion (Marsyandi River, Nepal 
Himalaya): Earth and Planetary Science Letters, v. 258, p. 500-515. 
Gizbert,, C.S., Burchfiel, B.C., Li, Z., and Chen, Z., Early Tertiary Gonjo basin, eastern 
Tibet: Sedimentary and structural record of the early history of India-Asia 
collision: Geosphere, v. 4, p. 713-735 
Graham, S.A., Ingersoll, R.V., and Dickinson, W.R., 1976, Common provenance for 
lithic grains in Carboniferous sandstones from Ouachita Mountains and Black 
Warrior Basin: Journal of  Sedimentary Petrology, v. 46, p. 620-632. 
 
166 
 
Gray, D.R., Foster, D.A., Meert, J.G., Goscombe, B.D., Armstrong, R.,Truow, R.A.J., 
and Passchier, C.W., (in press), A Damaran perspective on the assembly of 
southwestern Gondwana: Geological Society of London, special publication, 
Grimm, W.D., 1973, Stepwise heavy mineral weathering in the resiudal quartz gravel, 
Bavarian Molasse (Germany): Contribution to Sedimentology, v. 1, p 103-125 
Gotze, J., 1998, Geochemistry and provenance of the Altendorf feldspathic sandstone in 
the Middle Bunter of the Thuringian basin (Germany): Chemical Geology, v. 150, 
p. 43-61. 
Hames, W.E., and Bowring, S.A., 1994, An empirical evaluation of the argon diffusion 
geometry in muscovite: Earth and Planetary Science Letters, v. 124, p. 161-167 
Hames, W.E., and Cheney, J.T., 1997, On the loss of 40Ar* from muscovite during 
polymetamorphism*: Geochimica et Cosmochemica Acta, v. 61, p. 3863-3872 
Hayashi, K. I., H.Fujisawa, Holland, H. D., and H.Ohmoto, 1997b, Geochemistry of 1.9 
Ga sedimentary rocks from northeastern Labrador, Canada: Geochimica et 
Cosmochimica Acta, v. 61, p. 4115?4137. 
Henry, D.J., and Dutrow, B.L., 1992, Tourmaline as a low grade clastic metasedimentary 
rock: an example of the petrogenetic potential of tourmaline: Contributions to 
Mineralogy and Petrology, v. 112, p. 203-218. 
Henry, D.J., and Guidotti, C.V., 1985, Tourmaline as a petrogenetic indicator mineral: an 
example from the staurolite grade metapelites of NW Maine: American 
Mineralogists, v. 70, p. 1-15. 
Hess, H.H., 1966, Notes on operation of Frantz isodynamic magnetic separator, Princeton 
University: User manual guide, 6 p. 
Hodges, K.V., Rhul, K.W., Wobus, C.W., and Pringle, M.S., 2005, 
40
Ar/
39
Ar 
thermochronology of the detrital minerals, in Thermochronology, Reviews in 
Mineralogy and Geochemistry, Reiners, P.W., and Ehlers, T.A., eds., 
  Mineralogical Society of America, Washington, D.C., v. 58, p. 235-257. 
 
167 
 
Hossain, H.M.Z., Islam, M.S.U., Ahmed, S.S., and Hossain, I., 2002, Analysis of 
sedimentary facies and depositional environemnts of the Permian Gondwana 
sequence in borehole GDH-45, Khalaspir Basin, Bangladesh: Geosciences 
Journal, v. 6, n. 3, p. 227-236 
Hubbard, M., and Harrison, T.M., 
40
Ar/
39
Ar Age Constraints on the Deformation and 
metamorphism in the Main Central Thurst zone:  Tectonics, v. 8, p 865-880 
Ingersoll, R.V., Bullard, T.F., Ford, R.L., Grimm, J.P., Pickle, J.D., and Sares, S.W., 
1984, The effect of grain size on detrital modes: A test of the Gazzi-Dickinson 
point-counting method: Journal of Sedimentary Petrology, v. 54, p. 103-116. 
Ingersoll, R.V., and Suczek, C.A., 1979, Petrology and provenance of Neogene sand 
from Nicobar and Bengal Fans, DSDP sites 211 and 218: Journal of Sedimentary 
Research, v. 49, p. 1217-1228. 
Ingersoll, R.V., Graham, S.A., and Dickinson, W.R., 1995, Remnant ocean basins, in 
Busby, C.J., and Ingersoll, R.V., eds., Tectonics of sedimentary basins: Blackwell 
Science, Cambridge, p. 363-391. 
Irvine, T.N., 1974, Petrology of the Duke Island ultramafic complex, southern Alaska: 
Geological Society of America Bulletin, v. 138, p. 240.  
Irvine, T.N., 1977, Origin of chromite layers in the Muskox Intrusion and other stratiform 
intrusions; a new interpretation: Geology, v. 5, p. 273-277. 
Jain, S.P., and Kanwar, R.C., 1970, Himalayan ridge in the light of the theory of 
continental drift: Nature, v. 227, p. 829 
Johnsson, M.J., 1993, The system controlling the composition of clastic sediments, in 
Johnsson, M.J. and Basu, A., eds., Processes controlling the composition of 
clastic sediments: Geological Society of America Special Paper 284, p. 1-19. 
Kayastha, N.B., 1992, Stratigraphy of the lower Tertiary rocks of Nepal Himalaya: 
Journal of Nepal Geological Society, v. 8, p. 21-30 
 
168 
 
Kent, R.W, Pringle, M.S., Muller, R.D., Saunders, S.D. , Ghose, N.C., 
40
Ar/
39
Ar 
Geochronology of the Rajmahal Basalts, India, and their Relationship to the 
Kerguelen Plateau: Journal of Petrology, v. 43, p. 1141-1153 
Khan, A.A., Sattar, G.S., Rahman, T., 1994, Tectogenesis of the Gondwana rifted basins 
of Bangladesh in the so-called Garo-Rajmahal gap and their pre-drift regional 
tectonic correlation: Ninth International Gondwana Symposium, p 647-655. 
Krauskopf, K. B., and D. K. Bird, 1995, Introduction to geochemistry: McGraw-Hill, 
New York, 647 p 
Kumar, P., 2004, Provenance history of Cenozoic sediments near Digboi-Margherita 
area, eastern syntaxis of the Himalayas, Assam, northeast India [M.S. Thesis]: 
Auburn University, Auburn, Alabama, 131 p. 
Kumar, R., 1998, Fundamental of historical geology and stratigraphy of India, New Age 
International Publishers, p. 176-188 
Le Fort, P., 1996, Evolution of the Himalaya, in Yin, A., and Harrison, M., eds., The 
tectonic evolution of Asia: New York, Cambridge University Press, World and 
Regional Geology Series, p. 95-109. 
Ludwig, K.R., 2003, User?s manual for Isoplot, v. 3.0, a geochronological toolkit for  
Microsoft Excel: Berkeley Geochronological Center, Special Publication no. 4. 
Mahadevan, T.M., 2002, Geology of Bihar and Jharkhand: Geological Society of India, 
Bangalore, 563 p. 
Mange, M. A., and Maurer, H. F. W., 1992, Heavy minerals in color.: London, Chapman 
& Hall, London, 147 p. 
Matchan, E., 2008, The age, geochemisty and petrogenesis of an unusual alkaline 
intrusion in the western Pilbara craton, Western Australia: 9th International 
Kimberlinte Conference Extended Abstract  
McDougall, I., and Harrison, M.T., 1999, Geochronology and thermochronology by the 
40
Ar/
39
Ar method: New York, Oxford University Press, 269 p. 
 
169 
 
McLennan, S.M., Taylor, S.R., McCulloch, M.T., Maynard, J.B., 1990, Geochemical and 
Nd-Sr isotopic composition of deep-sea turbidites: Crustal evolution and plate 
tectonic associations, Geochemica et Cosmochemica Acta, v. 54. p. 2015-2050. 
McLennan, S. M., Hemming, S., McDaniel, D. K., and Hanson, G. N., 1993, 
Geochemical approaches to sedimentation, provenance and tectonics. in Johnson, 
M. J., Basu, A., eds, processes controlling the composition of the clastic 
sedimemts: Geological Society of America., Boulder, Colorado, Special Paper, v. 
284, p. 21-40. 
Medlicott, H. B., 1864, On the geological structure and relations of the southern portion 
of the Himalayan ranges between the rivers Ganges and the Ravee: Memoire of 
Geological Survey of India, v. 3, p. 1?212. 
Merrihue, C., and Turner, G., 1966, Potassium-argon dating by activation with fast 
neutrons: Journal of Geophysical Research, v. 71, p. 2852-2856. 
Morton, A.C., 1984, Stability of detrital heavy minerals in Tertiary sandstones of the 
North Sea Basin: Clay Mineralogy, v. 19, p 287-308. 
Morton, A.C., 1985, Heavy minerals in provenance studies, in Zuffa, G.G., eds., 
Provenance of Arenites: Boston, D. Reidel Publishing Company, p. 249-277. 
Morton, A.C., 1986, Dissolution of apatite in North Sea Jurassic sandstone: implications 
for the gengeration of secondary porosity: Clay Mineralogy, v. 21, p 711-733. 
Morton, A. C., and Hallsworth, C., 1994, Identifying provenance-specific features of 
detrital heavy mineral assemblages in sandstones: Sedimentary Geology, v. 90, p. 
241-256. 
Morton, A.C., and Hallsworth, C.R., 1999, Processes controlling the composition of  
heavy mineral assemblages in sandstones: Sedimentary Geology, v. 124, p. 3-30.. 
Morton, A.C., and Taylor, P.N., 1991, Geochemical and isotopic constraints on the nature 
and age of basement rocks from Rockall Bank, NE Atlantic: Journal of the 
Geological Society, London, v. 148, p. 630-634. 
 
170 
 
Najman, Y., and Garzanti, E., 2000, Reconstructing early Himalayan tectonic evolution 
and paleogeography from Tertiary foreland basin sedimentary rocks, northern 
India: Geological Society of America Bulletin, v. 112, p. 435-449. 
Najman, Y., Carter, A., Oliver, G., Garzanti, E., 2005, Provenance of Eocene foreland 
basin sediments, Nepal: Constraints to the timing and diachroneity of early 
Himalayan orogenesis: Geology, v. 33, p. 309-312. 
Najman, Y., 2005, The detrital record of orogenesis: A review of approaches and 
techniques used in the Himalayan sedimentary basins: Earth Science Reviews, v. 
74, p. 1-72. 
Nanayama, F., 1997, An electron microprobe study of the Amazon Fan: Proceedings of  
the Ocean Drilling Program, Scientific Results, v. 155, p. 147-168. 
Nance, W.B., and Taylor, S.R., 1977, Rare earth element patterns and crustal evolution-II 
Archean sedimentary rocks from Kalgoorlie, Australia: Geochemicia et 
Cosmochimica Acta, v. 41. p 225-231. 
Nandi, K., 1967, Garnets as indices of progressive regional metamorphism: 
Mineralogical Magazine, v. 36, p. 89-93. 
Naqvi, S.M., 2005, Geology and Evolution of the Indian Plate: Capital Publishing 
Company, 450 p. 
Nesbitt, H.W., and Young, G.M., 1984, Prediction of some weathering trends of plutonic 
and volcanic rocks based on thermodynamic and kinetic considerations: 
Geochimcia Cosmochimcia Acta, v. 48, p.1523?1548. 
Nixon, G.T., Cabri, L.J., and Laflamme, J.H.G., 1990, Platinum-group-element 
mineralization in lode and placer deposits associated with the Tulameen 
alaskantype complex, British Columbia: The Canadian Mineralogist, v. 28, p. 
503-535. 
Osae, S., Asiedu, D.K., Yakubo, B.B., Koeberl, C., and Dampare, S.B., 2005, Provenance 
and tectonic setting of Late Proterozoic Buem sandstones of southeastern Ghana: 
 
171 
 
Evidence from geochemistry and detrital modes: Journal of African Earth 
Sciences, v. 44, p. 85-96. 
Pettijohn, F.J., 1941, Persistence of heavy minerals and geologic age: Journal of Geology, 
v. 49, p 610-625. 
Pilgrim, G.E., West, W.D., 1928, The structure and correlation of the Simla rocks: 
Memoire of the Geological Survey of India 53, 140 p. 
Potter, P.E., 1978, Petrology and Chemistry of Modern Big River Sands: Journal of 
Geology, v. 86, p. 423-449. 
Le Fort, P., 1996, Evolution of Himalaya, in Yin, A., and Harrison, M., eds., Tectonic 
Evolution of Asia: World and regional geology series, Cambridge University 
Press, p. 95-107. 
Rahman, M. J. J., and Suzuki, S., 2007, Geochemistry of sandstones from the Miocene 
Surma Group, Bengal Basin, Bangladesh: Implications for Provenance, tectonic 
setting and weathering: Geochemical Journal, v. 41, p. 415-428 
Rahman, M.W., 2008, Sedimentation and tectonic evolution of Cenozoic sequence from 
Bengal and Assam foreland basin, Eastern Himalayas [Unpublished M.S. Thesis]: 
Auburn, Auburn University, 180 p. 
Renne, P.R., Swisher, C.C., Deino, A.L., Karner, D.B., Owens, T.L., and DePaolo, D.J., 
1998, Intercalibration of standards, absolute ages, and uncertainties in 
40
Ar/
39
Ar dating: 
Chemical Geology, v. 145, p. 117-152. 
Rollinson, 1993, Using geochemical data: evaluation, presentation, interpretation: 
Longman Scientific and Technical and J. Wiley & Sons, 352 p. 
Roser, B. P., and Korsch, R. J., 1988, Provenance signatures of sandstone-mudstone 
suites determined using discriminant function analysis of major-element data 
Chemical Geology, v. 67, p. 119-139. 
 
172 
 
Sakai, H., 1983, Geology of the Tansen Group of the Lesser Himalaya in Nepal: Memoirs 
of the Faculty Science, Kyushu University, Series D, v. XXV (1), p. 27-74. 
Sakai, H., 1989, Rifting of the Gondwanaland and uplifting of the Himalayas recorded in 
Mesozoic and Tertiary fluvial in the Nepal Himalayas in Taira, A. and Masuda, 
F., eds., Sedimentary Faceis in the Active Plate Margin, p. 723-732. 
Sakai, H., 1999, Inverted metamorphism in the Pre-Siwalik foreland basin sediments 
beneath the crystalline nappe, western Nepal Himalaya: Journal of Asian Earth 
Sciences, v. 17, p. 727-739. 
Scherer, A., 2007, 
40
Ar/
39
Ar dating and errors, www.geoberg.de, (June, 2009) 
Segev, A., 2002, Flood basalts, continental breakup and the dispersal of Gondwana: 
evidence for periodic migration of upwelling mantle flows (plumes): EGU 
Stephen Mueller Special Publication Series, v. 2, p. 171-191. 
Selley, R.C., 1998, Elements of Petroleum Geology: 2nd edition, Academic Press, 
London, 470 p. 
Sharma, T., Kansakar, D.R., Kizaki, K., 1984, Geology and tectonics of the region 
between Kali Gandaki and Bheri rivers in central west Nepal: Bulletin of the 
College of Science University of the Ryukyus, v. 38, p. 57-102. 
Shrestha, S.B., Shrestha, J.N., Sharma, S.R., 1987, Geological map of mid-western Nepal 
(scale: 1250,000): Department of Mines and Geology, Kathmandu. 
Singh, S.P., 1998, Precambrian stratrigraphy of Bihar-An overview in The Indian 
Precambrian. Paliwal, B.S., eds., Scientific Publication of India, p. 376-408 
Sinha, R.N., and Sastri, V.V., 1973, Correlation of the Tertiary geosynclinal sediments of 
the Surma Valley, Assam, and Tripura state (India): Sedimentary Geology, v. 10, 
p. 107-134. 
Spear, F.S. and Cheney, J.T., 1989, A petrogenetic grid for pelitic schists in the system 
SiO2 - Al2O3 - FeO - MgO - K2O - H2O: Contributions to Mineralogy and 
Petrology, v. 101, p. 149-164. 
 
173 
 
Soreghan, M. J., and Soreghan, G. S. L., 2007, Whole-rock geochmistry of upper 
Paleozoic loessite, western Pangaea: Implication for paleo-atmospheric 
circulation: Earth and Planetary Science Letters, v. 255, p. 117-132. 
Strut, B.A., 1962, The composition of garnets from pelitic schists in relation to the grade 
of regional metamorphism: Journal of Petrology, v. 3, p. 181-191. 
Sugitani, K., Yamashita, F., Nagako, T., Yamamota, K., Minami, M., Mimura, K., and 
Suzuki, K., 2006, Geochemistry and sedimentary petrology of Archean clastic 
sedimentary rocks at Mt. Goldsworthy, Pilbara Craton, Western Australia: 
Evidence for the early evolution of continental crust and hydrothermal alteration: 
Precambrian Research, v. 147, p. 124-147 
Suttner, L.J., 1974, Sedimentary petrologic provinces: An evaluation, in Ross, C.A., eds., 
Paleogeographic Provinces and Provincialtiy, Society of Economic 
Paleontologists and Mineralogists, special publication, v. 21, p. 75-84. 
Taylor, S. R., and McLennan, S. M., 1985, The continental crust: Its composition and 
evolution: Oxford, Blackwell Scientific Publication, 312 p. 
Tucker, M., 1988, Techniques in Sedimentology: Blackwell Scientific Publications, 
London, 395 p. 
Uddin, A., Hames, W.E., Rahman, M.W., and Zahid, K.M., 2007, Rapid middle Miocene 
denudation of the eastern Himalayas: Laser 
40
Ar /
39
Ar age constraints on Miocene 
sequences from the Bengal basin: Geological Society of America, Abstracts with 
Programs, v. 39, p. 592. 
Uddin, A., and N., Lundberg, 1998, Cenozoic history of the Himalayan-Bengal system: 
Sand composition in the Bengal basin, Bangladesh: Geological Society of 
America Bulletin, v. 110, p. 497-511. 
Upreti, B.N., 1999, An overview of the stratigraphy and tectonics of the Nepal Himalaya: 
Journal of Asian Earth Sciences, v. 17, p. 577-606. 
 
174 
 
Vail, P.R., Mitchum, R.M. and Thompson, S., 1977, Seismic stratigraphy and global 
changes of sea-level, Part 4: Global cycles of relative changes of sea-level: 
American Association of Petroleum Geologists Memoir, v. 26, p. 83-97. 
Valdiya, K.S., 1997, Himalaya, the Northern Frontier of East Gondwanaland: Gondwana 
Research, v. 1, no, 1, p. 3-9. 
Veevers, J.J., and Tiwari, R.C., 1995, Gondwana Master Basin of peninsular India 
between Tethys and the interior of the Gondwanaland province of Pangea: 
Memoir of Geological Society of America, v. 187, 71 p.  
Veevers, J.J., 2006, Updated Gondwana (Permian-Cretaceous) earth history of Australia: 
Gondwana Research, v. 9, p. 231-260. 
Velbel, M.A., 1985, Mineralogically mature sandstone in accretional prisms: Journal of 
Sedimentary Petrology, v. 55, p. 685-690. 
Wadia, D.N., 1919, Geology of India, 3rd edition, Macmillan and Co Ltd., London, 536 
p. 
Wanke, H., and Konig, H., 1959, Eine neue Methode zur Kalium-Argon-
Altersbestimmung und ihre Anwendung auf Steinmeteorite: Z. Naturforschung, v. 
14a, p. 860 ? 866. 
Willan, R.C.R., 2003, Provenance of Triassiac-Cretaceous sandstones in the Antartic 
peninsula: implications for terrance models during Gondwana breakup: Journal of 
Sedimentary Research, v. 73, p. 1062-1077 
Yokoyama, K., Taira, A., and Saito, Y., 1990, Mineralogy of silts from the Bengal Fan: 
Proceedings of Ocean Drilling Programs, Scientific Results, v. 116, p. 59-73. 
Zahid, K.M., 2005, Provenance and basin tectonics of Oligocene-Miocene sequences of 
the Bengal Basin, Bangladesh [M.S. Thesis]: Auburn University, Auburn, 
Alabama, 142 p. 
Zhu, B., Delano, J.W., and Kidd, S.F.W., 2005, Magmatic compositions and source 
terranes estimated from melt inclusions in detrital Cr-rich spinels: An example 
 
175 
 
from mid-Cretaceous sandstones in the eastern Tethys Himalaya: Earth and 
Planetary Science Letters, v. 233, p. 295-309. 
 
 
 
176
 
APPENDIX A:  Micropobe Analysis Data of Tourmaline from the Gonwanan sequences  
of the Nepal Himalaya (Tansen, western Nepal) 
Sample?No.??
15?6??
trm?1??
15?6??
trm?2??
15?6?
?trm?3??
16?5??
trm?1??
16?8??
trm?1??
16?8??
trm?2??
16?8?
?trm?3??
16?8??
trm?4??
16?8?
?trm?5??
16?9?
?trm?1??
16?9?
?trm?2?? Standard1?
SiO
2
? 35.98? 35.76? 35.97? 34.51? 34.69? 35.31? 35.25? 34.94? 35.05? 35.19? 34.22? 39.73?
TiO
2
? 0.58? 0.54? 0.84? 0.36? 0.69? 0.27? 0.68? 0.77? 0.83? 0.65? 0.89? 4.90?
Al
2
O
3
? 34.42? 34.73? 33.74? 34.89? 29.61? 33.69? 33.95? 33.67? 34.27? 33.61? 32.94? 14.64?
MgO? 3.06? 2.60? 5.28? 1.19? 2.07? 2.41? 3.36? 3.24? 2.40? 1.28? 1.03? 12.90?
FeO? 11.81? 10.73? 7.90? 13.40? 16.27? 12.07? 10.97? 11.03? 11.82? 14.86? 15.74? 10.99?
CaO? 0.56? 0.25? 0.51? 0.18? 0.67? 0.33? 0.59? 0.31? 0.35? 0.16? 0.49? 10.63?
MnO? 0.10? 0.30? 0.00? 0.09? 0.13? 0.07? 0.04? 0.04? 0.11? 0.12? 0.04? 0.04?
K
2
0? 0.06? 0.03? 0.03? 0.08? 0.05? 0.04? 0.04? 0.06? 0.01? 0.01? 0.06? 2.32?
Na
2
O? 1.51? 1.59? 1.64? 1.65? 1.91? 1.54? 1.73? 1.83? 1.92? 2.05? 2.10? 2.30?
Cr
2
O
3
? 0.04? 0.01? 0.00? 0.06? 0.01? 0.00? 0.00? 0.00? 0.09? 0.00? 0.01? 0.00?
Total? 86.94? 86.53? 85.92? 86.85? 86.11? 85.75? 86.74? 85.92? 86.92? 88.12? 88.08? 98.55?
End?Member?Calcualtion? ???????????
Ca? 3.97? 2.01? 3.61? 1.45? 4.11? 2.52? 4.28? 2.34? 2.69? 1.17? 3.42? ??
Mg? 30.34? 29.57? 52.41? 13.48? 17.71? 25.60? 33.80? 33.56? 25.88? 13.19? 10.06??
Fe?(tot)? 65.69? 68.42? 43.99? 85.08? 78.18? 71.89? 61.91? 64.10? 71.43? 85.64? 86.52??
Total? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00??
? ?? ?? ? ?? ? ????
Al? 45.91? 46.36? 45.83? 46.34? 44.66? 46.03? 45.93? 45.93? 46.15? 45.85? 45.68??
Al50Fe(tot)50? 28.55? 28.26? 26.72? 29.49? 31.04? 28.87? 28.23? 28.31? 28.72? 30.12? 30.58??
Al50Mg50? 25.54? 25.38? 27.45? 24.17? 24.30? 25.10? 25.84? 25.76? 25.12? 24.03? 23.74??
Total? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00??
 
 
 
 
177
 
APPENDIX B:  Micropobe Analysis Data of Tourmaline from the Gonwanan sequences  
of the Nepal Himalaya (Katari and Brahachettra groups, eastern Nepal) 
Sample?No.??
22?10?
?trm?1??
22?10??
trm?2??
22?10??
trm?3??
23?4?
?trm?1??
23?4??
trm?2??
23?4??
trm?3??
23?4??
trm?4??
23?4?
?trm?5??
26?8??
trm?1??
26?8?
?trm?2??
26?8??
trm?3?? Standard?
SiO
2
? 34.90? 36.12? 34.98? 35.98? 35.21? 35.98? 35.25? 34.73? 36.20? 34.13? 35.82? 39.73?
TiO
2
? 0.92? 0.11? 0.74? 0.65? 0.82? 0.51? 0.31? 0.10? 0.19? 0.28? 0.16? 4.90?
Al
2
O
3
? 35.01? 34.56? 34.84? 33.45? 31.88? 31.12? 34.22? 34.03? 36.23? 32.86? 35.67? 14.64?
MgO? 4.58? 0.99? 3.12? 4.12? 6.45? 5.46? 2.12? 0.70? 2.57? 0.12? 2.47? 12.90?
FeO? 8.95? 13.32? 11.30? 9.60? 8.17? 10.25? 11.87? 14.26? 11.05? 16.69? 11.28? 10.99?
CaO? 0.61? 0.03? 0.53? 0.13? 0.60? 0.69? 0.22? 0.19? 0.15? 0.14? 0.08? 10.63?
MnO? 0.05? 0.00? 0.07? 0.02? 0.07? 0.05? 0.16? 0.10? 0.00? 0.15? 0.16? 0.04?
K
2
0? 0.04? 0.00? 0.01? 0.04? 0.00? 0.04? 0.02? 0.03? 0.02? 0.09? 0.02? 2.32?
Na
2
O? 1.74? 1.27? 1.61? 1.93? 2.21? 1.98? 1.61? 1.63? 1.35? 1.92? 1.34? 2.30?
Cr
2
O
3
? 0.00? 0.00? 0.02? 0.05? 0.01? 0.06? 0.00? 0.00? 0.00? 0.10? 0.02? 0.00?
Total? 86.81? 86.41? 87.22? 85.97? 85.44? 86.16? 85.78? 85.76? 87.77? 86.65? 87.03? 98.55?
End?Member?Calcualtion? ? ? ?? ???? ??
Ca? 4.36? 0.26? 3.86? 0.95? 3.74? 4.23? 1.75? 1.50? 1.21? 1.08? 0.61??
Mg? 45.62? 11.68? 31.71? 42.93? 56.28? 46.65? 23.75? 7.95? 28.94? 1.28? 27.87??
Fe?(tot)? 50.02? 88.06? 64.43? 56.12? 39.99? 49.12? 74.49? 90.55? 69.85? 97.64? 71.52??
Total? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00??
? ? ?? ? ?? ???? ??
Al? 46.01? 46.41? 46.05? 45.88? 45.07? 44.89? 46.25? 46.26? 46.45? 45.82? 46.38??
Al50Fe(tot)50? 27.18? 29.55? 28.32? 27.61? 26.63? 27.69? 28.81? 30.01? 28.25? 31.17? 28.40??
Al50Mg50? 26.81? 24.04? 25.63? 26.51? 28.30? 27.42? 24.94? 23.73? 25.31? 23.02? 25.22??
Total? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00??
 
 
 
178
 
 
APPENDIX C:  Micropobe Analysis Data of Garnet from the Gonwanan sequences  
of the Nepal Himalaya (Tansen, western Nepal) 
Sample?No.??
K?1??
Gt1?
K?1??
Gt2??
16?3??
Gt1??
16?3??
Gt2??
16?3?
?Gt3??
16?5??
Gt1??
16?5?
?Gt2??
16?5??
Gt3??
16?5??
Gt4?? Standard
SiO
2
? 36.45? 37.13? 37.77? 36.85? 36.89? 36.01? 36.57? 36.28? 38.61? 38.58
TiO
2
? 0.28? 0.24? 0.01? 0.02? 0.00? 0.04? 0.00? 0.02? 0.00? 0.1168
Al
2
O
3
? 21.56? 21.84? 21.93? 20.75? 21.89? 21.04? 21.39? 20.98? 22.87? 22.73
MgO? 6.45? 6.73? 7.27? 1.54? 7.31? 1.01? 2.37? 1.06? 9.72? 10.4
FeO? 31.90? 30.61? 31.64? 32.70? 31.78? 28.31? 37.12? 32.96? 22.07? 21.08
CaO? 1.33? 1.01? 1.19? 5.54? 2.25? 1.58? 1.66? 6.83? 6.24? 7.45
MnO? 1.14? 1.02? 0.95? 2.75? 0.33? 11.78? 1.84? 1.44? 0.99? 0.6193
Cr
2
O
3
? 0.02? 0.05? 0.00? 0.03? 0.08? 0.10? 0.00? 0.01? 0.00? 0
Total? 99.14? 98.63? 100.77? 100.19? 100.53? 99.88? 100.96? 99.57? 100.51? 100.97
End?Members? ? ? ? ?? ? ???
?
Pyrope? 24.85? 26.70? 27.52? 6.04? 27.13? 4.10? 9.31? 4.18? 35.80?
?
Almandine? 68.95? 68.13? 67.18? 72.15? 66.17? 64.23? 81.89? 73.16? 45.60?
?
Grossular? 3.69? 2.88? 3.25? 15.66? 6.00? 4.60? 4.68? 19.42? 16.52?
?
Spessartine?? 2.50? 2.29? 2.05? 6.14? 0.70? 27.07? 4.12? 3.23? 2.07?
?
Total? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00?
?
 
 
 
 
179
 
APPENDIX D:  Micropobe Analysis Data of Garnet from the Gonwanan sequences  
of the Nepal Himalaya (Katari and Brahachettra groups, eastern Nepal) 
Sample?No.??
23?5??
Gt2??
23?5?
?Gt3??
23?5??
Gt4??
23?5?
?Gt5??
23?5?
?Gt6??
26?8?
?Gt1??
26?8??
Gt2??
26?8?
?Gt3??
26?8?
Gt4??
26?8?
?Gt5??
23?5??
Gt1??
SiO
2
? 37.79? 34.84? 36.44? 35.55? 36.75? 37.15? 35.76? 36.37? 36.57? 35.93? 37.48?
TiO
2
? 0.04? 0.11? 0.00? 0.12? 0.07? 0.04? 0.07? 0.08? 0.04? 0.08? 0.05?
Al
2
O
3
? 20.95? 22.14? 21.79? 21.25? 21.87? 21.87? 21.62? 21.20? 21.56? 21.01? 21.76?
MgO? 3.76? 4.20? 3.88? 3.31? 6.57? 1.97? 0.98? 1.18? 1.81? 0.93? 2.94?
FeO? 26.75? 24.05? 27.00? 29.10? 32.03? 27.06? 28.77? 32.96? 35.84? 30.83? 24.87?
CaO? 6.83? 2.50? 8.76? 7.30? 1.64? 8.91? 8.61? 6.59? 5.03? 2.13? 11.94?
MnO? 0.84? 10.21? 1.18? 1.36? 0.93? 4.18? 3.88? 1.27? 0.12? 9.18? 1.16?
Cr
2
O
3
? 0.00? 0.09? 0.11? 0.00? 0.03? 0.05? 0.00? 0.02? 0.03? 0.16? 0.00?
Total? 96.96? 98.14? 99.15? 97.99? 99.90? 101.23? 99.69? 99.68? 101.00? 100.24? 100.22?
End?Members? ? ? ????? ??? ?
Pyrope? 15.57? 16.61? 14.93? 12.90? 25.03? 7.59? 3.84? 4.71? 7.09? 3.71? 11.26?
Almandine? 62.13? 53.35? 58.28? 63.64? 68.46? 58.55? 63.26? 73.57? 78.53? 69.28? 53.38?
Grossular? 20.32? 7.10? 24.22? 20.45? 4.48? 24.70? 24.26? 18.85? 14.12? 6.12? 32.83?
Spessartine?? 1.98? 22.94? 2.57? 3.00? 2.02? 9.16? 8.64? 2.88? 0.27? 20.89? 2.53?
Total? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00? 100.00?
 
 
 
 
180
 
APPENDIX E:  Micropobe Analysis Data of Chrome-spinel from the Gonwanan sequences  
of the Nepal Himalaya (Tansen Group, western Nepal) 
Sample?No.??
K?1?
CrSp1?
K?1?
CrSp2?
K?1??
CrSp3?
K?1?
?CrSp4?
K?1?
?CrSp5? Standard?
SiO
2
? 0.11 0.20 0.15 0.15 0.14 0.00
TiO
2
? 0.80 0.21 0.29 0.89 0.68 0.11
Al
2
O
3
? 36.95 40.10 42.72 35.55 41.89 23.65
MgO? 17.76 18.74 17.66 18.01 17.31 16.08
FeO? 15.99 13.57 16.29 17.04 16.78 12.65
CaO? 0.03 0.01 0.03 0.04 0.04 0.01
MnO? 0.16 0.21 0.16 0.18 0.23 0.17
Cr
2
O
3
? 28.15 24.39 21.09 27.74 23.08 46.47
NiO? 0.21 0.20 0.20 0.14 0.02 0.14
Total? 100.16 97.63 98.59 99.73 100.17 99.28
End?Member?Calculation? ?? ? ?
Al3+? 64.32 69.12 72.99 63.09 71.27 ?
Cr3+? 32.87 28.20 24.17 33.03 26.34 ?
Fe3+? 2.80 2.68 2.83 3.88 2.39 ?
Total? 100.00 100.00 100.00 100.00 100.00 ?
??????
Fe3+/Fe3++Cr+Al? 0.03 0.03 0.03 0.04 0.02 ?
Mg#(Mg/Mg+Fe2+)? 0.70 0.75 0.69 0.70 0.68 ?
Cr#(Cr/Cr+Al)? 0.34 0.29 0.25 0.34 0.27 ?
TiO2?(wt%)? 0.80 0.21 0.29 0.89 0.68 ?
 
 
 
 
181
 
APPENDIX F: 
40
Ar/
39
Ar GEOCHRONOLOGY 
 
        Sample Name: Raju Situala            
     Date Run: 4/3/09              
     
Irradiation 
Packages: AU-12, 13               
     
Date of 
Irradiation: 1/30/2009              
     Monitor Age 9.879E+07              
        Air 
40
Ar/
36
Ar: 293.0 + 1.5            
Single crystal, total fusion analyses of muscovite crystals, obtained with automated laser extraction in the ANIMAL facility.   
Data are in Moles; samples generally run with a sensitivity of 5.1x10-15 moles/volt        
Data are corrected for interfering nuclear reactions and blanks.           
Errors are the standard deviation in precision, obtained by regression or averaging of measurements (8 cycles).   
 
 
 
182
 
APPENDIX F (1): 
40
Ar/
39
Ar Age data of detrital muscovite from the Katari Group (eastern Nepal, sample 26-8; Permo-
Carboniferous) 
n 40Ar(*+atm) 39ArK 38Ar(atm+Cl) 37ArCa 36Ar(atm) %Rad R 
  
Age (Ma) 
  
%-
sd 
11 2.9983E-15 + 1.2E-17 2.898E-15 + 6.31E-18 5.5E-18 + 1.11E-19 2.6E-18 + 6.5E-19 6.2E-19 + 1.4E-19 93.9% 0.9717 24.7 + 0.4 2% 
12 1.3742E-15 + 1E-17 1.553E-15 + 5.61E-18 2.8E-18 + 7.97E-20 -1.9E-19 + 8.3E-19 4.3E-19 + 1.4E-19 90.7% 0.8026 20.4 + 0.7 3% 
13 3.2175E-15 + 1.4E-17 4.056E-15 + 1.36E-17 7.5E-18 + 1.44E-19 3.3E-18 + 6.8E-19 5.1E-19 + 1.3E-19 95.3% 0.7563 19.2 + 0.3 1% 
14 1.3373E-15 + 1E-17 1.119E-15 + 4.32E-18 1.8E-18 + 4.75E-20 -5.9E-19 + 5.1E-19 1.6E-18 + 1.2E-19 65.0% 0.7773 19.8 + 0.9 4% 
15 8.9989E-16 + 1E-17 7.975E-16 + 3.28E-18 1.4E-18 + 5.33E-20 3.8E-18 + 1.3E-18 8.4E-19 + 1.5E-19 72.3% 0.8158 20.7 + 1.5 7% 
16 2.0129E-15 + 9.4E-18 2.088E-15 + 9.31E-18 4.4E-18 + 8.7E-20 9.3E-19 + 9.5E-19 5.5E-19 + 1.1E-19 91.9% 0.8859 22.5 + 0.4 2% 
17 1.486E-14 + 1.6E-17 1.212E-15 + 3.88E-18 2.2E-18 + 3.42E-20 9.3E-19 + 3.3E-19 1.9E-19 + 3.8E-20 99.6% 12.2172 290.6 + 1.0 0% 
18 2.2236E-15 + 9.6E-18 2.836E-15 + 5.82E-18 6.6E-18 + 1.6E-19 2.5E-18 + 5.5E-19 8.5E-19 + 1.1E-19 88.6% 0.6949 17.7 + 0.3 2% 
19 3.5085E-15 + 6.3E-18 4.670E-15 + 1.38E-17 7.4E-18 + 1.43E-19 3.9E-18 + 9.8E-19 5.8E-19 + 1.1E-19 95.1% 0.7148 18.2 + 0.2 1% 
20 1.4732E-15 + 8.3E-18 1.524E-15 + 6.91E-18 3.2E-18 + 5.37E-20 4.4E-18 + 1.1E-18 1.1E-18 + 1.2E-19 77.3% 0.7474 19.0 + 0.6 3% 
21 7.3014E-16 + 3.9E-18 8.25E-16 + 2.74E-18 1.4E-18 + 4.55E-20 2.1E-18 + 4.9E-19 2.6E-19 + 4.8E-20 89.5% 0.7923 20.3 + 0.5 2% 
23 8.0824E-16 + 3.4E-18 1.057E-15 + 4.96E-18 4.1E-18 + 2.46E-19 2.1E-18 + 7.5E-19 1.1E-19 + 4.5E-20 95.8% 0.7322 18.8 + 0.3 2% 
24 6.9889E-16 + 1.5E-18 9.637E-16 + 2.87E-18 1.7E-18 + 4.24E-20 -6E-19 + 4.6E-19 -3.6E-20 + -5E-20 101.5% 0.7362 18.9 + 0.4 2% 
25 4.4652E-16 + 4.7E-18 5.955E-16 + 2.74E-18 1.6E-19 + 2.01E-20 -1.7E-18 + 9.1E-19 6.7E-20 + 5.2E-20 95.6% 0.7167 18.4 + 0.7 4% 
26 3.3196E-16 + 2E-18 4.194E-16 + 1.64E-18 1E-18 + 4.71E-20 -8.9E-19 + 4.3E-19 -2.3E-20 + -4E-20 102.1% 0.8081 20.7 + 0.8 4% 
27 3.511E-16 + 5.1E-18 4.472E-16 + 4.68E-18 8.5E-20 + 8.42E-21 -8.5E-19 + 6.4E-19 -1.4E-19 + -8E-20 112.0% 0.8796 22.6 + 1.4 6% 
28 1.1392E-15 + 2.3E-18 1.042E-15 + 2.9E-18 2.6E-18 + 5.12E-20 2.9E-19 + 4.9E-19 1.2E-18 + 6.1E-20 68.3% 0.7464 19.2 + 0.5 2% 
30 5.2395E-16 + 4.7E-18 5.584E-16 + 5.32E-18 8.9E-19 + 3.76E-20 -1.3E-18 + 4.1E-19 2.2E-21 + 4.4E-20 99.9% 0.9372 24.0 + 0.7 3% 
31 9.4041E-16 + 3.2E-18 1.214E-15 + 4.06E-18 2.1E-18 + 4.22E-20 1.4E-18 + 4E-19 3.1E-19 + 4E-20 90.3% 0.6996 18.0 + 0.3 1% 
32 3.032E-16 + 2.6E-18 4.023E-16 + 1.92E-18 1.2E-18 + 3.66E-20 9.8E-19 + 3.7E-19 5.6E-20 + 4E-20 94.5% 0.7124 18.3 + 0.8 4% 
33 7.7194E-16 + 3.5E-18 9.039E-16 + 4.72E-18 1.6E-18 + 5.77E-20 4.9E-19 + 4.8E-19 5.7E-20 + 3.7E-20 97.8% 0.8353 21.4 + 0.3 2% 
34 8.4182E-16 + 1.7E-17 8.385E-16 + 2.01E-17 1.1E-18 + 3.25E-20 9E-19 + 3.3E-19 6.1E-20 + 5.8E-20 97.9% 0.9826 25.2 + 1.0 4% 
35 3.0781E-16 + 2.2E-18 3.288E-16 + 1.05E-18 7.5E-19 + 3.26E-20 9E-20 + 3.4E-19 3.1E-19 + 4.4E-20 70.1% 0.6564 16.9 + 1.0 6% 
 
 
 
 
183
 
APPENDIX F (2): 
40
Ar/
39
Ar Age data of the detrital muscovite form the Barahachettra Group (eastern Nepal, sample 
22-8, Permo-Carboniferous) 
51 2.7939E-13 + 4.5E-16 6.005E-15 + 2.31E-17 1.7E-17 + 1.08E-19 4.3E-17 + 1.8E-18 5.9E-18 + 2.1E-19 99.4% 46.2327 908.9 + 3.8 0.4% 
52 5.2428E-14 + 5.7E-17 5.616E-15 + 2E-17 1.3E-17 + 1.55E-19 7.2E-18 + 7.5E-19 2.1E-18 + 1.4E-19 98.8% 9.2251 221.6 + 0.9 0.4% 
53 3.754E-16 + 2.3E-18 3.412E-16 + 2.5E-18 9E-19 + 2.44E-20 4.5E-19 + 2.3E-19 3E-19 + 3.5E-20 76.4% 0.8405 21.6 + 0.8 3.8% 
54 3.1709E-14 + 7E-17 7.991E-16 + 5.18E-18 2.1E-18 + 7.69E-20 1.3E-18 + 4.4E-19 5.5E-19 + 9.4E-20 99.5% 39.4806 801.5 + 5.6 0.7% 
55 1.5678E-15 + 4.9E-18 1.067E-15 + 7.9E-18 4.1E-18 + 2.28E-19 -6.3E-19 + 4.9E-19 8E-19 + 1E-19 84.9% 1.2483 31.6 + 0.8 2.4% 
56 6.8798E-14 + 3.8E-17 1.278E-15 + 4.38E-18 4E-18 + 1.16E-19 3.7E-18 + 3.1E-19 2.8E-19 + 3.6E-20 99.9% 53.7632 1029.3 + 3.6 0.3% 
57 5.8735E-15 + 9.1E-18 1.537E-15 + 2.99E-18 3.3E-18 + 6.26E-20 1.1E-18 + 6.9E-19 3.6E-19 + 8.5E-20 98.2% 3.7512 93.4 + 0.5 0.5% 
58 3.665E-15 + 7.1E-18 2.881E-16 + 1.89E-18 5.5E-19 + 1.76E-20 1.7E-19 + 2.8E-19 1.8E-19 + 2.5E-20 98.6% 12.5422 297.7 + 2.1 0.7% 
59 1.3314E-14 + 1.2E-17 1.082E-15 + 6.18E-18 3.6E-18 + 1.04E-19 2.2E-18 + 2.8E-19 4.6E-19 + 3.7E-20 99.0% 12.1800 289.8 + 1.7 0.6% 
60 1.0247E-14 + 2.3E-17 2.818E-16 + 1.96E-18 5.6E-19 + 1.79E-20 3.3E-19 + 3E-19 1.6E-19 + 2.9E-20 99.5% 36.1982 752.9 + 5.6 0.7% 
61 1.1048E-14 + 1.1E-17 2.61E-16 + 2.08E-18 3.8E-19 + 2.9E-20 1.1E-19 + 3.7E-19 4.8E-19 + 4.6E-20 98.7% 41.7783 845.4 + 7.0 0.8% 
62 4.6771E-14 + 3.7E-17 1.243E-15 + 4.19E-18 3.9E-18 + 7.99E-20 4.8E-18 + 6.5E-19 5.5E-19 + 6E-20 99.7% 37.4848 774.6 + 2.7 0.3% 
63 2.6937E-14 + 2E-17 5.833E-16 + 4.55E-18 2.1E-18 + 6.93E-20 4E-18 + 6.2E-19 8.1E-19 + 5.5E-20 99.1% 45.7698 908.7 + 7.2 0.8% 
64 6.4939E-14 + 3E-16 1.28E-15 + 1.71E-17 4.1E-18 + 8.55E-20 5.7E-18 + 7.7E-19 9.7E-19 + 2.3E-19 99.6% 50.5106 981.2 + 14.0 1.4% 
65 7.4333E-14 + 2.8E-16 1.691E-15 + 9.79E-18 3.8E-18 + 6.34E-20 1.1E-17 + 5.8E-19 4E-19 + 5.5E-20 99.8% 43.8922 879.2 + 6.1 0.7% 
66 3.1208E-14 + 6.2E-17 7.521E-16 + 1.83E-18 2.4E-18 + 4.59E-20 4.4E-18 + 4.9E-19 4E-19 + 5.6E-20 99.6% 41.3403 838.3 + 2.7 0.3% 
67 5.2662E-16 + 3.4E-18 1.372E-17 + 4.17E-19 -1E-19 + 
-5.54E-
19 3.7E-20 + 3.3E-19 -6.8E-21 + -5E-20 100.4% 38.5234 792.0 + 31.9 4.0% 
68 3.1468E-14 + 3.6E-17 4.789E-16 + 1.56E-18 2.3E-18 + 6.9E-20 7.5E-18 + 6.3E-19 1.1E-18 + 6.6E-20 99.0% 65.0374 1186.7 + 4.2 0.4% 
69 3.1042E-16 + 3.4E-18 2.436E-16 + 2.3E-18 9.1E-19 + 3.84E-20 2.9E-18 + 2.5E-19 4.6E-19 + 2.9E-20 56.2% 0.7161 18.4 + 1.0 5.6% 
70 4.2647E-14 + 2.4E-17 8.639E-16 + 4.81E-18 4E-18 + 1.49E-19 8.3E-18 + 8.5E-19 9.4E-19 + 7.4E-20 99.3% 49.0422 959.0 + 5.4 0.6% 
71 4.6713E-14 + 3.9E-17 1.079E-15 + 4.5E-18 3.3E-18 + 8.94E-20 5.2E-18 + 6.3E-19 2.6E-18 + 7.2E-20 98.4% 42.5710 858.1 + 3.7 0.4% 
72 6.3681E-14 + 3.8E-17 1.658E-15 + 6.92E-18 4.2E-18 + 6.25E-20 5.7E-18 + 5E-19 2.4E-19 + 5.2E-20 99.9% 38.3750 789.5 + 3.3 0.4% 
73 3.5047E-14 + 4.6E-17 9.924E-16 + 7.34E-18 3.2E-18 + 9.59E-20 5.1E-18 + 4.5E-19 3.5E-19 + 1.3E-19 99.7% 35.2096 736.0 + 5.6 0.8% 
74 1.2338E-14 + 4.8E-17 4.602E-16 + 4.38E-18 1.9E-18 + 1.19E-19 4.7E-18 + 5.2E-19 5.5E-19 + 1.3E-19 98.7% 26.4552 579.1 + 6.3 1.1% 
 
 
 
184
 
APPENDIX F (3): 
40
Ar/
39
Ar Age data of detrital muscovite from the Tansen Group (western Nepal, sample 16-3, 
Permo-Carboniferous) 
76 4.8053E-15 + 6.1E-18 3.444E-16 + 4.13E-18 -1E-20 + -1.34E-21 4.7E-18 + 6.6E-19 5.7E-20 + 8.4E-20 99.7% 13.9051 327.3 + 4.3 1.3% 
77 4.0994E-16 + 4E-18 4.896E-16 + 2.85E-18 6.9E-19 + 5.08E-20 7.3E-19 + 6.7E-19 1.2E-19 + 8E-20 91.4% 0.7657 19.7 + 1.3 6.4% 
78 2.9399E-15 + 1.3E-17 5.36E-16 + 3.58E-18 1.3E-18 + 7.62E-20 9.5E-19 + 6E-19 1E-19 + 7.8E-20 99.0% 5.4279 134.9 + 1.5 1.1% 
79 9.1023E-15 + 1.7E-17 2.587E-16 + 2.21E-18 9.8E-19 + 9.8E-20 2.2E-20 + 7.3E-19 -6.8E-20 + -8E-20 100.2% 35.2580 736.8 + 6.7 0.9% 
80 6.7013E-16 + 3.7E-18 8.825E-16 + 4.01E-18 2.2E-18 + 1.08E-19 2.7E-18 + 7.1E-19 1.3E-19 + 8.8E-20 94.3% 0.7164 18.4 + 0.8 4.2% 
81 5.109E-16 + 3.9E-18 3.765E-16 + 2.51E-18 3.8E-19 + 2.56E-20 -1E-19 + 6.3E-19 -1.7E-20 + -9E-20 101.0% 1.3702 35.0 + 1.8 5.1% 
82 3.447E-15 + 9E-18 1.689E-16 + 1.4E-18 -2E-20 + -3.88E-21 1.2E-18 + 5.6E-19 3.5E-20 + 9.1E-20 99.7% 20.3522 461.0 + 5.4 1.2% 
83 2.0933E-14 + 2.9E-17 9.185E-16 + 5.41E-18 1.9E-18 + 6.89E-20 1.9E-18 + 5.4E-19 4.7E-19 + 1E-19 99.3% 22.6374 506.2 + 3.2 0.6% 
84 3.5185E-14 + 3.5E-17 3.145E-16 + 1.38E-18 3.9E-19 + 4.16E-20 1.2E-18 + 5.4E-19 5.1E-19 + 1E-19 99.6% 111.3972 1719.5 + 7.9 0.5% 
85 9.8256E-17 + 8.2E-19 9.895E-17 + 5.46E-19 1.6E-19 + 2.09E-20 -2.3E-19 + 2.3E-19 5.6E-21 + 3.4E-20 98.3% 0.9762 25.0 + 2.6 10.4% 
86 8.9053E-14 + 9.3E-17 1.164E-15 + 4.69E-18 4.6E-18 + 1.46E-19 1.3E-17 + 6.4E-19 2.5E-18 + 8.1E-20 99.2% 75.8617 1325.9 + 5.6 0.4% 
87 1.3632E-15 + 4.4E-18 1.481E-15 + 2.1E-18 3.3E-18 + 3.75E-20 -7.3E-19 + 6.3E-19 3.1E-19 + 4.5E-20 93.3% 0.8590 22.0 + 0.2 1.1% 
88 9.2332E-16 + 3.1E-18 8.69E-16 + 3.19E-18 1.9E-18 + 2.91E-20 -2E-19 + 4.4E-19 4.6E-19 + 4.4E-20 85.2% 0.9056 23.2 + 0.4 1.7% 
89 2.5189E-14 + 2.1E-17 5.947E-16 + 1.04E-18 1E-18 + 3.28E-20 -5.6E-19 + 4.5E-19 1.4E-19 + 4.5E-20 99.8% 42.2863 853.5 + 1.7 0.2% 
90 7.8196E-16 + 5E-18 5.74E-16 + 3.74E-18 1.2E-18 + 2.59E-20 5.3E-18 + 6.6E-19 3.4E-19 + 4.8E-20 87.1% 1.1866 30.4 + 0.7 2.4% 
91 9.9713E-14 + 8E-17 9.254E-16 + 3.05E-18 3.2E-18 + 7.42E-20 6E-18 + 5.2E-19 4.5E-19 + 5.7E-20 99.9% 107.6054 1681.3 + 5.7 0.3% 
92 1.0431E-14 + 6.6E-18 7.741E-16 + 2.04E-18 1.5E-18 + 4E-20 2.1E-17 + 4.5E-19 4.2E-19 + 5E-20 98.8% 13.3165 314.6 + 1.0 0.3% 
93 2.6471E-16 + 6E-18 2.674E-16 + 1.34E-18 6.4E-19 + 3.04E-20 -1.4E-19 + 3.2E-19 5.4E-21 + 7.4E-20 99.4% 0.9840 25.2 + 2.2 8.6% 
94 1.7893E-14 + 3E-17 1.275E-15 + 4.88E-18 2.5E-18 + 4.7E-20 1.8E-17 + 3.5E-19 7E-19 + 4.9E-20 98.8% 13.8769 326.7 + 1.4 0.4% 
95 2.4941E-14 + 2.2E-17 2.248E-16 + 8.26E-19 1.5E-18 + 1.27E-19 5.8E-19 + 2.6E-19 5.5E-19 + 3.9E-20 99.4% 110.2149 1707.7 + 6.5 0.4% 
96 8.8812E-14 + 5.3E-17 8.599E-16 + 3.76E-18 2.4E-18 + 5.91E-20 5.5E-18 + 4.8E-19 1.2E-18 + 7.2E-20 99.6% 102.8641 1632.5 + 7.3 0.4% 
97 1.1838E-15 + 2.8E-18 9.55E-16 + 2.34E-18 1.9E-18 + 3.18E-20 6.2E-19 + 5.3E-19 1.1E-18 + 6.2E-20 73.4% 0.9093 23.3 + 0.5 2.1% 
98 4.7833E-15 + 1.1E-17 3.343E-16 + 1.69E-18 9.9E-19 + 3.07E-20 3.7E-18 + 3.7E-19 4.8E-19 + 4.2E-20 97.0% 13.8845 326.9 + 2.1 0.6% 
99 7.0591E-15 + 8.9E-18 6.278E-16 + 2.6E-18 1.5E-18 + 3.15E-20 2E-17 + 6.2E-19 6.5E-19 + 4.6E-20 97.3% 10.9373 262.3 + 1.3 0.5% 
100 8.4636E-14 + 4.8E-17 2.131E-15 + 7.73E-18 5.9E-18 + 8.14E-20 6.1E-18 + 5.7E-19 1.6E-18 + 7.5E-20 99.4% 39.4861 807.9 + 3.0 0.4% 
 
 
 
185
 
APPENDIX F (4): 
40
Ar/
39
Ar Age data of detrital muscovite from the Tansen Group (western Nepal, sample 15-8, 
Eocene)` 
1 6.7706E-15 + 7.9E-18 6.16E-17 + 4.48E-19 6.3E-19 + 7.37E-20 8E-19 + 3.8E-19 7.7E-20 + 4.2E-20 100% 109.5987 492.7 + 3.8 0.76% 
2 6.3919E-15 + 1.2E-17 1.02E-16 + 3.96E-19 6E-19 + 4.93E-20 -4.8E-19 + 5E-19 2.4E-19 + 4.5E-20 99% 62.1894 295.8 + 1.4 0.49% 
3 2.89E-15 + 3.2E-18 2.75E-17 + 3.8E-19 3.4E-19 + 7.52E-20 -1.6E-18 + 3.5E-19 -5.2E-20 + -4E-20 101% 105.4777 476.4 + 6.8 1.42% 
4 3.5787E-15 + 4.3E-18 3.15E-17 + 2.52E-19 3.9E-19 + 8.79E-20 -1.1E-18 + 3.2E-19 -7.2E-20 + -4E-20 101% 114.3535 511.3 + 4.4 0.86% 
5 2.4316E-14 + 3.7E-17 1.27E-16 + 4.55E-19 1.3E-18 + 8.37E-20 3.7E-18 + 5.5E-19 1.8E-19 + 5E-20 100% 191.0953 787.7 + 3.1 0.40% 
6 9.3613E-15 + 1.9E-17 4.00E-17 + 5.99E-19 4.5E-19 + 3.27E-20 4.8E-19 + 6.5E-19 -4.9E-20 + -5E-20 100% 234.2799 926.5 + 14.0 1.52% 
7 9.2501E-15 + 9.4E-18 8.60E-17 + 8E-19 4.2E-19 + 2.43E-20 -4.7E-20 + 3.5E-19 1E-19 + 4.2E-20 100% 107.2100 483.2 + 4.6 0.95% 
8 4.9712E-15 + 9.2E-18 2.25E-17 + 2.54E-19 3.1E-19 + 4.49E-20 6.5E-19 + 5.7E-19 1.3E-19 + 3.6E-20 99% 219.5829 880.4 + 10.3 1.17% 
9 1.4737E-14 + 1.3E-17 6.62E-17 + 4.07E-19 5E-19 + 2.64E-20 9.3E-19 + 5.4E-19 1.7E-19 + 4.3E-20 100% 221.8770 887.7 + 5.6 0.63% 
10 5.9933E-15 + 9E-18 4.31E-17 + 4.18E-19 6E-19 + 4.67E-20 9.7E-19 + 4.7E-19 8.8E-19 + 4.1E-20 96% 133.1298 582.9 + 6.1 1.05% 
11 1.5281E-14 + 1.8E-17 6.71E-17 + 7.86E-19 3.2E-19 + 2.54E-20 -2.9E-19 + 4.6E-19 1.4E-19 + 4.3E-20 100% 227.1964 904.4 + 10.7 1.18% 
12 8.4694E-15 + 1E-17 6.58E-17 + 5.37E-19 3.7E-19 + 3.19E-20 -9.8E-19 + 4E-19 9.6E-20 + 4.1E-20 100% 128.3320 564.9 + 4.7 0.84% 
13 1.9595E-15 + 2.3E-18 2.50E-17 + 3.21E-19 2.3E-19 + 3.48E-20 -5.6E-19 + 3.9E-19 7.9E-20 + 4.1E-20 99% 77.5755 362.1 + 5.3 1.45% 
14 9.5745E-15 + 9.6E-18 8.65E-17 + 5.43E-19 2.2E-19 + 1.75E-20 1.7E-19 + 4.4E-19 6.9E-20 + 4.1E-20 100% 110.4149 495.9 + 3.2 0.65% 
15 2.3154E-15 + 2.2E-18 2.12E-17 + 1.68E-19 1.6E-19 + 3.06E-20 -6.6E-19 + 5.4E-19 4.6E-20 + 3.8E-20 99% 108.5661 488.6 + 4.6 0.94% 
16 3.7531E-15 + 6E-18 3.39E-17 + 3.12E-19 3.9E-19 + 9.76E-20 -4.3E-19 + 5.6E-19 2.4E-19 + 6.8E-20 98% 108.5554 488.5 + 5.4 1.10% 
17 1.1116E-14 + 6.7E-18 5.15E-17 + 2.82E-19 2.3E-19 + 2.6E-20 -6.6E-19 + 3.4E-19 6E-20 + 4.1E-20 100% 215.5280 867.5 + 4.9 0.56% 
18 2.8996E-16 + 3E-18 3.10E-17 + 2.97E-19 5.7E-20 + 1.03E-20 8.6E-19 + 4.7E-19 3.8E-20 + 4.1E-20 96% 8.9806 45.8 + 2.1 4.64% 
19 1.7357E-15 + 3.5E-18 1.76E-17 + 2.29E-19 2E-19 + 3.92E-20 9E-19 + 3.9E-19 5.4E-19 + 3.8E-20 91% 89.6522 412.4 + 6.7 1.62% 
20 3.6205E-15 + 6.5E-18 3.22E-17 + 3.51E-19 1.9E-19 + 3.32E-20 1.1E-19 + 5E-19 1.8E-20 + 3.6E-20 100% 112.1908 502.8 + 5.8 1.15% 
21 1.0792E-15 + 4E-18 1.07E-16 + 3.63E-19 3.2E-19 + 3.08E-20 1.6E-18 + 5.2E-19 1.4E-19 + 4.3E-20 96% 9.6949 49.4 + 0.7 1.33% 
22 6.9677E-15 + 7.6E-18 2.54E-16 + 6.7E-19 7.4E-19 + 2.34E-20 9.8E-19 + 4.7E-19 1.2E-19 + 3.7E-20 100% 27.2805 135.8 + 0.4 0.33% 
23 7.6207E-15 + 1.1E-17 6.12E-17 + 7.6E-19 5.1E-19 + 2.85E-20 6.3E-19 + 3.9E-19 1.3E-19 + 3.8E-20 99% 123.8114 547.7 + 6.9 1.26% 
24 2.4564E-15 + 2.6E-18 2.39E-17 + 2.85E-19 2.3E-19 + 3.46E-20 2.1E-18 + 4.8E-19 2E-19 + 4.4E-20 98% 100.2078 455.3 + 6.1 1.34% 
25 2.522E-14 + 2E-17 1.14E-16 + 1.01E-18 1.7E-18 + 1.9E-19 6.5E-18 + 5E-19 5.5E-19 + 6.4E-20 99% 219.8737 881.4 + 7.9 0.90% 
 
 
 
 
186
 
APPENDIX G: Photographs of detrital muscovite grains analyzed for argon dating. 
 
Sample 26-8 (Katari Group, eastern Nepal) 
 
Sample 16-3 (Sisne Formation, western Nepal) 
 
Sample 15-8 (Bhainskati Formation, western Nepal)