GLAUCONITE AS AN INDICATOR OF SEQUENCE STRATIGRAPHIC 
PACKAGES IN A LOWER PALEOCENE PASSIVE-MARGIN  
SHELF SUCCESSION, CENTRAL ALABAMA 
 
 
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 not 
include proprietary or classified information. 
 
 
_____________________________ 
Devi Bhagabati Prasad Udgata 
 
 
 
 
Certificate of Approval: 
 
 
 
______________________     ________________________ 
Ashraf Uddin       Charles E. Savrda, Chair 
Associate Professor      Professor 
Geology       Geology 
 
 
 
______________________     ________________________ 
Willis E. Hames      Joe F. Pittman 
Profesor       Interim Dean 
Geology       Graduate School 
 
 
 
 
 
GLAUCONITE AS AN INDICATOR OF SEQUENCE STRATIGRAPHIC 
PACKAGES IN A LOWER PALEOCENE PASSIVE-MARGIN  
SHELF SUCCESSION, CENTRAL ALABAMA 
 
 
Devi Bhagabati Prasad Udgata 
 
 
 
 
 
 
A Thesis 
Submitted to 
the Graduate Faculty of 
Auburn University 
in partial fulfillment of the 
Requirements for the 
Degree of 
Masters of Science 
 
 
 
 
 
 
 
Auburn, Alabama 
December 17, 2007 
 
 iii
 
 
 
GLAUCONITE AS AN INDICATOR OF SEQUENCE STRATIGRAPHIC 
PACKAGES IN A LOWER PALEOCENE PASSIVE-MARGIN  
SHELF SUCCESSION, CENTRAL ALABAMA 
 
 
Devi Bhagabati Prasad Udgata 
 
Permission is granted to Auburn University to make copies of this thesis at its discretion, 
upon request of individuals or institutions and at their expenses. The author reserves all 
publication rights. 
 
 
 
 
 
 
 
________________________ 
Signature of Author 
 
 
________________________ 
Date of Graduation 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 iv
 
 
 
VITA 
Devi Bhagabati Prasad Udgata, son of Narayan Otta and Gouripriya Otta, was born 
on January 1, 1980, in a small village of the Orissa Province, in eastern India. He 
graduated from Katyayani High School, in Puri, India, in 1993. He attended Utkal 
University, in Bhubaneswar, India, and graduated in July 1998 with a Bachelors of 
Science degree in Geology. He attended the Indian School of Mines, Dhanbad, India, and 
graduated in May 2001 with a Masters of Science and Technology degree in Applied 
Geology. He entered the graduate program in Geology at Auburn University in the Fall of 
2005.    
 
 
 
 
 
 
 
 
 
 
 
 v
 
 
 
THESIS ABSTRACT 
GLAUCONITE AS AN INDICATOR OF SEQUENCE STRATIGRAPHIC 
PACKAGES IN A LOWER PALEOCENE PASSIVE-MARGIN  
SHELF SUCCESSION, CENTRAL ALABAMA 
 
 
Devi Bhagabati Prasad Udgata 
 
Master of Science, December 17, 2007 
(M. Sc. Tech., Indian School of Mines, Dhanbad, India, 2001) 
 
 
 
124 typed pages 
Directed by Charles E. Savrda 
 
The Lower Paleocene Clayton Formation in central Alabama comprises a 
complete third-order depositional sequence that accumulated mainly on a passive-margin 
marine shelf. Glauconite occurs throughout the sequence, providing the opportunity to 
systematically evaluate changes in glauconite abundance and character that resulted from 
sea-level-mediated fluctuations in sedimentation rates expressed at both the systems-tract 
and parasequence scale. To this end, detailed studies of glauconite were carried out using 
a combination of reflected and transmitted light microscopy, microprobe analyses, and x-
ray diffraction studies. 
 vi
 Total glauconite abundance increases upward from lowstand systems tract (LST) 
incised valley-fill sands through the transgressive systems tract (TST) and condensed 
section (CS) and then generally decreases through the highstand systems tract (HST). 
Parasequences in the CS/HST are defined by asymmetrical cycles characterized by abrupt 
increases and gradual decreases in glauconite abundance. Although detrital glauconite is 
common in the LST and TST, most glauconite grains are authigenic. The relative 
abundances of various authigenic glauconite morphotypes vary with total glauconite 
content. Mature morphotypes (e.g., mammillated and lobate grains), as well as 
glauconitized skeletal grains and glauconite-coated detrital grains, are prevalent in the 
condensed section and lower parts of parasequences, while less mature varieties (e.g., 
vermicular grains) dominate parasequence tops. Decreases in glauconite maturity upward 
through parasequences also are indicated by lighter grain colors, decreasing K content, 
and increasing importance of glauconite smectite relative to glauconite mica. 
 Observations from this study indicate that glauconite can be an effective tool for 
delineating sequence stratigraphic packages and bounding surfaces, particularly in 
relatively sediment-starved, passive-margin shelf successions. Notably, in quiet-water 
shelf sequences, sea-level-controlled changes in glauconitization result in fining-upward 
parasequences. 
 
 
 
 
 
 vii
 
 
 
ACKNOWLEDGMENTS 
This study was supported by grants-in-aid of research from the Geological 
Society of America (GSA) and the Gulf Coast Association of Geological Societies 
(GCAGS). I am very much thankful to my research advisor Dr. Charles E. Savrda for his 
constant support, help, and advice. Thanks also due to my thesis committee members Dr. 
Ashraf Uddin, and Dr. Willis E. Hames for their support and encouragement. I thank Dr. 
Uddin for bringing me to Auburn University for a Master?s Degree in Geology. Drs. Joey 
Shaw (Agronomy and Soils) and James Saunders (Geology and Geography) provided 
guidance in the preparation of samples for x-ray diffraction and microprobe analyses, 
respectively. Chris Fleisher facilitated microprobe analysis at the University of Georgia. 
Fellow graduate students Trent Hall, Sean Bingham, Mohammad Shamsudduha, Derick 
Unger, Prakash Dhakal, and Wahidur Rahman assisted in field or laboratory work. I 
dedicate my thesis to my family. 
 
 
 
 
 
 
 
 viii
 
 
 
 
 
Journal style used: Palaios 
 
Computer software used: Microsoft Word 2003, Microsoft Excel 2003, Microsoft 
PowerPoint 2003, Adobe Photoshop 7, Endnote 8 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 ix
 
 
 
 
 
TABLE OF CONTENTS 
 
LIST OF FIGURES .......................................................................................................... xii 
 
LIST OF TABLES.............................................................................................................xv 
 
1.0 OBJECTIVES................................................................................................................1 
 
2.0 GLAUCONITE..............................................................................................................3 
 
2.1 MINERALOGY........................................................................................................... 3 
 
2.2 FORMATION OF GLAUCONITE .............................................................................3 
 
2.3 GRAIN FORMS AND FABRICS...............................................................................4 
 
2.4 GLAUCONITE MATURITY ..................................................................................... 5 
 
2.4.1 Glauconite Chemistry and Color .....................................................6 
 
2.4.2 Glauconite Morphology and Texture.............................................11 
 
2.5 USE OF GLAUCONITE IN SEQUENCE STRATIGRAPHY................................ 12 
 
2.5.1 Glauconite in Passive-Margin Depositional Sequences ................12 
 
2.5.2 Glauconite in Parasequence-Scale Studies ....................................15 
 
3.0 CLAYTON FORMATION..........................................................................................16 
 
3.1 GENERAL STRATIGRAPHY .................................................................................16 
 
3.2 SEQUENCE STRATIGRAPHY ...............................................................................18 
 
3.3 PALEOENVIRONMENT..........................................................................................20 
 
4.0 LOCATION AND METHODS ..................................................................................22 
 
4.1 STUDY LOCALITY ................................................................................................22 
 
4.2 FIELD STUDIES ......................................................................................................24 
 x
4.3 LABORATORY INVESTIGATIONS .....................................................................25 
 
4.3.1 Textural Analyses ............................................................................25 
 
4.3.2 Carbonate and Organic-Carbon Analyses ........................................26 
 
4.3.3 Binocular Microscopic Examination ...............................................26 
 
4.3.4 Thin Section Petrography ................................................................26 
 
4.3.5 X-Ray Diffraction Analyses ............................................................27 
 
4.3.6 Electron Microprobe Analysis and Scanning Electron Microscopy 28 
 
5.0 SEDIMENTOLOGICAL CHARACTER OF THE STUDY SECTION.................... 30 
 
5.1 GENERAL SECTION DESCRIPTIONS ................................................................30 
 
5.1.1 Lowstand Incised Valley Fill (Unit 1, Clayton Sand) ......................30 
 
5.1.2 Transgressive Lag (Unit 2) ..............................................................35 
 
5.1.3 Transgressive Systems Tract (Units 3-8) .........................................35 
 
5.1.4 Condensed Section (Units 9-11) ......................................................35 
 
5.1.5 Highstand Systems Tract (Units 12-30) ...........................................37 
 
5.2 TEXTURAL ANALYSES .......................................................................................38 
 
5.3 CARBONATE AND ORGANIC CARBON ANALYSES .....................................41 
 
5.4 GENERAL PETROGRAPHY AND POINT-COUNT ANALYSES ......................47 
 
5.4.1 General Observations .......................................................................47 
 
5.5 SUMMARY AND INTERPRETATION ................................................................. 54 
 
6.0 CHARACTER OF GLAUCONITE ...........................................................................57 
 
6.1 INTRODUCTION .....................................................................................................57 
 
6.2 MODES OF GLAUCONITE OCCURRENCE .......................................................57 
 
6.2.1 Glauconite Morphotypes ..................................................................57 
 
 xi
6.2.2 Glauconite-Coated Grains.................................................................66 
 
                        6.2.3 Glauconitized Skeletal Grains ..........................................................71  
 
                        6.2.4 Relationships to Systems Tracts and Parasequences .......................71 
   
6.3 GLAUCONITE GRAIN COLOR ............................................................................73 
 
6.4 GLAUCONITE CHEMISTRY .................................................................................74  
 
6.5 XRD ANALYSIS .....................................................................................................80 
 
7.0 DISCUSSION .............................................................................................................85 
 
            7.1 ROLE OF GLAUCONITE IN DELNEATING SEQUENCE  
       STRATIGRAPHIC PACKAGES ............................................................................. 85 
                
         7.2 COMPARISON WITH PREVIOUS PARASEQUENCE-SCALE STUDIES ........86 
 
            7.3 COMPARISON WITH FORELAND BASIN PARASEQUENCES ....................87  
 
            7.4 ORIGIN OF CLAYTON LIMESTONES ................................................................87 
 
8.0 CONCLUSIONS .........................................................................................................89 
 
REFERENCES .................................................................................................................91 
 
APPENDIX  ......................................................................................................................97 
 
 
 
 
 
 
 
 
 
 xii
 
 
 
LIST OF FIGURES 
Figure 1 ? The X-ray diffractogram peaks showing progressive stages of glauconitization 
(from Odin and Matter, 1981) ...........................................................................................10  
 
Figure 2 - Generalized shelf stratigraphic sequence showing systems tracts, bounding 
surfaces, and relations to sedimentation rate and authigenic glauconite content. ............13 
 
Figure 3 ? Distribution of Lower Paleocene strata in Alabama ........................................17 
 
Figure 4 ? Sequence stratigraphic interpretations of the Lower Paleocene Clayton 
Formation and enveloping strata, central Alabama ..........................................................19 
 
Figure 5 ? Location of the Mussel Creek and Highway 263 sections (source: 
www.nationalgeographic.com/topo, 2002)  ......................................................................21 
 
Figure 6 ? Stratigraphic column of study section showing sequence stratigraphic context, 
informal units (1-30), and sampling horizons ...................................................................31  
 
Figure 7 ? Photographs of the study section .....................................................................32 
 
Figure 8 ? Photograph of unit 1 (Clayton sand) associated with underlying Prairie     
Bluff Chalk and overlying transgressive lag unit (unit 2)..................................................33 
 
Figure 9 ? Representative photomicrographs from the study section ...............................34 
 
Figure 10 ? Representative photograph of carbonate cemented transgressive lag bed (unit 
2) with phosphate clasts (P), and quartz pebbles (Q) ........................................................36 
 
Figure 11 ? Representative photograph of Clayton sand (unit 1), transgressive lag bed 
(unit 2), and overlying transgressive systems tract (units 3-8) .........................................36 
 
Figure 12 ? Representative photographs of highstand systems tract ................................39 
 
Figure 13 ? Percent sand and mean grain size of sand in the study section .....................40 
  
Figure 14 ? Percent sand, carbonate and organic carbon in the study section ..................45 
 
Figure 15 ? General inverse relationship between percent carbonate and organic carbon.46 
 
 xiii
 
Figure 16 ? Percent sand, percent glauconite, and percent skeletal grains (including 
glauconitized grains) in the study section .........................................................................50 
 
Figure 17 ? Percent glauconite vs. percent sand in the samples .......................................52 
 
Figure 18 ? Relationship between percent carbonate and percent glauconite...................52 
 
Figure 19 ? Relationship between percent sand, percent phosphate, and percent pyrite in 
the study section.................................................................................................................53 
 
Figure 20 ? Stratigraphic column and inferred sea-level curves for the Clayton 
Formation ..........................................................................................................................55 
 
Figure 21 ? Different grain morphotypes as viewed in reflected light..............................58 
 
Figure 22 ? Photomicrographs showing different glauconite grain types ........................60 
 
Figure 23 ? Backscattered electron images of different glauconite morphotypes ............61 
 
Figure 24 ? Percent total glauconite, percent mammillated/lobate grains, and percent 
capsule-shaped grains in the study section .......................................................................64 
 
Figure 25 ? Percent total glauconite, percent vermicular/tabular grains, and percent 
ovoidal grains in the study section ....................................................................................65 
 
Figure 26 ? Photomicrograph showing glauconite coatings on and fracture fillings in 
quartz (Q) ..........................................................................................................................67 
 
Figure 27 ? Percent total glauconite, percent glauconite-coated detrital grains, and 
percent glauconitized skeletal grains in the study section ................................................70 
 
Figure 28 ? Photomicrographs showing glauconitized fossil fragments ..........................72 
 
Figure 29 ? Reflected light photographs showing color variation of glauconite grains in 
parasequences ...................................................................................................................75 
 
Figure 30 ? Plane-light photomicrographs showing color variation of glauconite grains in 
parasequences ...................................................................................................................76 
 
Figure 31 ? Relationships among average oxide contents for thirteen glauconite  
samples...............................................................................................................................78 
 
Figure 32 ? Percent sand, percent glauconite and K2O % in the study section ................79 
 
 xiv
Figure 33 ? X-ray diffractograms derived from the parasequence 2 ................................81 
 
Figure 34 ? X-ray diffractograms derived from the parasequence 4 ................................82 
 
Figure 35 ? X-ray diffractograms of samples from unit 9 (condensed section; base of 
parasequence 2) and unit 19 (middle of parasequence 4) .................................................83 
 xv
 
 
 
LIST OF TABLES 
Table 1 ? Morphological varieties of glauconite .................................................................6 
Table 2 ? Internal fabrics within glauconite grains .............................................................7 
Table 3 ? Characteristics of glauconite at different stages of maturity ...............................8 
 
Table 4 ? Percent sand, mean sand size, and percent carbonate and organic carbon data.42 
 
Table 5 ? Relative abundance of grain types based on point-counts of selected samples 
from the study section........................................................................................................48 
 
Table 6 ? Normalized percentages of assignable glauconite grain types derived from 
point-count data .................................................................................................................62 
 
Table 7 ? Abundances of glauconitized skeletal grains and glauconite-coated detrital 
grains based on point-count analysis .................................................................................68 
 
Table 8 ? Average abundances (weight percent) of major oxides in glauconite grains as 
determined by microprobe analysis ...................................................................................77 
 
Table TA1 - Abundances (weight percent) of major oxides in glauconite grains as 
determined by microprobe analysis ..................................................................................97 
 
 
 
 
 1
 
 
 
1.0 OBJECTIVES 
The term ?glauconite,? derived from the Greek word glaukos for ?blue-green,? is 
used to collectively refer to a broad spectrum of minerals that fall within what is known 
as the ?glaucony facies.? According to Odin and Matter (1981), the glaucony facies 
includes dark green to greenish brown grains that fall within the spectrum between 
immature ?glauconitic smectite? and mature ?glauconitic mica? end members. Glauconite, 
or glaucony, is an authigenic component that forms via replacement of, or precipitation 
on or within, existing grains (mainly fecal pellets, shells or tests, or phyllosilicate grains) 
within marine sediments. Formation of glauconite is generally restricted to marine 
environments wherein supply of iron (Fe) is high, conditions are suboxic, and, most 
important, sediment influx is very low (McRae, 1972; Odin and Matter, 1981).  
Because glauconite is a sensitive indicator of low sedimentation rate, it constitutes 
a powerful tool for sedimentological interpretation of glauconite-bearing marine 
successions (Amorosi, 1997). By reflecting the residence time of grains at or near the 
seafloor, the presence and compositional maturity of glauconite can help recognize and 
assess the magnitude of relative breaks in sedimentation (Odin and Matter, 1981; 
Amorosi, 1995). This is particularly important for sequence stratigraphic studies. Given 
its link to sediment starvation, authigenic glauconite traditionally has been taken as an 
indicator of transgressive systems tracts and condensed sections (Van Wagoner et al., 
1988). Recent studies of glauconite in a sequence stratigraphic framework (e.g., Amorosi, 
 2
1995; Harris and Whiting, 2000; Hesselbo and Hugget, 2001) show that glauconite may 
be present in almost all systems tracts, but its maturity may vary systematically from one 
systems tract to another. Glauconite also potentially could be used to study shorter-term 
relative sea-level changes reflected at the parasequence scale. However, studies of 
glauconite at the parasequence level are rare (Amorosi, 1995; Urash, 2005).  
The objective of this thesis research is to test two related hypotheses: (1) 
abundance and maturity of glauconite vary systematically through a depositional 
sequence in response to sea-level dynamics and associated changes in sedimentation rate; 
and (2) abundance and maturity of glauconite vary systematically through individual 
parasequences in response to shorter-term changes in relative sea level. These hypotheses 
were evaluated through a detailed study of glauconite and other sedimentary parameters 
in the Lower Paleocene Clayton Formation exposed along Mussel Creek and nearby 
roadcuts in Lowndes County, central Alabama.  
 
 
 
 
 
 
 
 
 
 
 3
 
 
 
2.0 GLAUCONITE 
2.1 Mineralogy  
Minerals placed into the glauconite group are iron- and potassium-rich alumino-
phyllosilicates having the general chemical composition of (K, Na) (Fe, Al, Mg)
2 
(Si, 
Al)
4
O
10
(OH)
2
. These minerals constitute a continuous family with smectite and 
micaceous end members (Odin and Fullagar, 1988). Glauconite mica is a Fe- and K-rich 
dioctahedral mica with tetrahedral Al (or Fe
3+
) usually comprising >0.2 atoms per 
formula unit and octahedral R
3+
 comprising >1.2 atoms (Huggett, 2005). Typically, 5?
12% of the total iron is ferrous. Glauconite mica is chemically distinguished from ferric 
illite by having higher total iron content, and from celadonite by higher levels of 
substitution of aluminum for silicon in the tetrahedral layer and by a higher octahedral 
charge (Duplay and Buatier, 1990). Glauconitic-smectite is a mixed-layer clay that has 
lower K and Fe contents but higher Al contents than glauconite mica. As will be 
described in subsequent sections, the spectrum of glauconite smectite to glauconite mica 
reflects mineralogic maturity (Thompson and Hower, 1975; Odin and Matter, 1981; Odin 
and Fullagar, 1988). 
2.2 Formation of Glauconite  
 The formation of glauconite occurs via authigenesis under a relatively narrow 
range of environmental conditions. It forms at or near the sediment-water interface in 
oxygenated to mildly reducing marine environments wherein sedimentation rates are very 
 4
low (McRae, 1972; Odin and Matter, 1981; Amorosi, 1997). Glauconization mainly 
occurs in fine-grained muds deposited in shelf and slope settings at depths between 30 m 
to 500 m (Bornhold and Giresse, 1985; Amorosi, 1997; Kelly and Webb, 1999).  
Glauconite may precipitate as coatings or films on the walls of fissures, borings, 
and other semi-confined microenvironments associated with carbonate hardgrounds 
(Pemberton et al., 1992; Kitamura, 1998; Ruffel and Wach, 1998). However, it forms 
most commonly in granular siliciclastic substrates via replacement, infilling, or coating of 
individual grains. Fecal pellets are the most common type of precursor substrate. 
Aggregation of clay-rich sediment during passage through the digestive tracts of the 
organisms creates microenvironments that are favorable for glauconitization (Anderson et 
al., 1958; Pryor, 1975; Chafetz and Reid, 2000). In addition to pellets, glauconite may 
replace a variety of other grain types, including micas, quartz, chert, feldspar, calcite, 
dolomite, phosphate, and volcanic rock fragments (McRae, 1972; Pryor, 1975; Odin and 
Matter, 1981). Glauconite also may precipitate as cements within microfossil cavities or 
as coatings or films on other grains (Triplehorn, 1966; McRae, 1972; Odin and Matter, 
1981).  
2.3 Grain Forms and Fabrics 
Glauconite mainly occurs in the form of sand-sized grains in the range of 100-500 
?m (McRae, 1972). Grains typically exhibit an earthy or lustrous appearance (Odin and 
Matter, 1981; Odin and Morton, 1988; Kelly and Webb, 1999). Morphology of these 
grains varies considerably with regard to size, gross shape, and surface characteristics 
(grain smoothness, external ornamentation, and fractures). Based on these attributes, 
Triplehorn (1966) identified nine morphological varieties: (1) spheroidal or ovoidal 
 5
pellets; (2) tabular or discoidal pellets; (3) mammilated pellets; (4) lobate pellets; (5) 
capsule-shaped pellets; (6) composite pellets; (7) vermicular grains; (8) fossil casts and 
internal molds; and (9) pigmentary glauconite. Defining characteristics of these varieties, 
summarized in Table 1, reflect to varying degrees the morphology of the precursor grain 
and the compositional maturity of the glauconite.    
The internal textures and fabrics of glauconite grains, as viewed in cross-sections of 
broken grains or in thin section, are also variable. Previous workers (Triplehorn, 1966; 
McRae, 1972) have employed a variety of terms to describe internal fabrics (Table 2). 
Most fabrics (e.g., micaceous or vermicular fabrics) reflect the structure of replaced 
precursor grains, while others reflect formation of glauconite as a primary precipitate.  
2.4 Glauconite Maturity 
Odin and Matter (1981) recognized four common varieties of glauconite that 
reflect different levels of maturation: nascent, slightly evolved, evolved, and highly 
evolved grains. Level of maturity reached by glauconite depends on residence time of 
grains at or near the sediment-water interface and, hence, sedimentation rate. The 
glauconitization process normally ceases after burial beneath several decimeters of 
sediment, and formation of fully mature grains may require residence times of 10
5
-10
6
 
years (Odin and Matter, 1981). Levels of maturity of glauconite can be assessed based on 
chemical composition, grain color, and morphology (Table 3).  
2.4.1 Glauconite Chemistry and Color 
The formation of glauconite begins at the sediment-water interface with the 
development of iron-rich smectitic clay (nascent glauconite). As the glauconitization 
process proceeds, grains progressively alter towards the glauconite mica end member  
 6
Table 1 ? Morphological varieties of glauconite (after Triplehorn, 1966). 
Glauconite Variety Characteristics 
spheroidal or ovoidal 
pellets 
simple, rounded, equidimensional grains with 
smooth surfaces 
tabular or discoidal pellets flattened, elongate or disk- or bowl-shaped pellets   
mammilated pellets irregular grains with small rounded knobs separated 
by shallow sutures  
lobate pellets very irregular grains with deep radial cracks; 
commonly triangular in cross-section 
capsule-shaped pellets simple cylindrical grains with nearly circular cross-
sections 
composite pellets relatively large (up to 3-4 mm) grains composed of 
smaller grains of glauconite and detrital minerals 
embedded in glauconitic matrix 
vermicular grains accordion-shaped grains; also known as caterpillar, 
zebra, concertina, accordion, or booklet grains 
fossil casts and internal 
molds 
shapes correspond to skeletal fragments or internal 
molds (e.g., foraminiferal tests, sponge spicules, 
echinoderm spines, etc.) 
pigmentary glauconite coatings on surfaces of and/or penetrating 
cracks/cleavage within other minerals 
 
 
 
 
 
 
 
 
 
 
 
 
 7
Table 2 ? Internal fabrics within glauconite grains (after Triplehorn, 1966; McRae, 1972). 
 
Fabrics Characteristics 
random 
microcrystalline  
homogeneous aggregates of overlapping micaceous flakes 
with no preferred orientation  
oriented 
microcrystalline  
lamellar aggregates of oriented microcrystals (exhibit unit 
extinction in polarized light) 
micaceous or 
vermicular  
similar to oriented microcrystalline fabrics but with incipient 
micaceous cleavage  
coatings on grains  accretionary, oolitic textures  
organic replacement 
structures  
various fibrous, perforate, or lamellar structures reflecting 
the internal structure of replaced or infilled skeletal grains  
fibroradiated rims  rims, differing in color and structure from core grains, 
formed by accumulation or precipitation (rather than 
alteration) 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 8
Table 3 ? Characteristics of glauconite at different stages of maturity (after Odin and 
Matter, 1981; Amouric and Parron, 1985; Amorosi, 1995; Huggett and Gale, 1997; Kelly 
and Web, 1999).  
 
Glauconite 
types 
Maturity K
2
O 
content
Mineralogical 
structure 
Color XRD 
peak 
position
nascent low < 4% glauconite 
smectite 
pale 
green 
14? 
slightly      
evolved 
moderate 4-6%  light 
green 
 
evolved high 6-8%  green  
highly        
evolved 
very high > 8% glauconite 
mica 
dark 
green 
10 ? 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 9
(highly evolved grains). This maturation process involves the uptake of Fe at the expense 
of Al and the uptake of K in lattice spaces to balance the remaining charge (McRae, 
1972; Odin and Matter, 1981). Hence, level of maturation can be assessed based on 
mineral chemistry and associated mineral structure.   
 Potassium (K) content, measured via microprobe analysis or other technique, is 
most commonly employed to evaluate compositional maturity of glauconite. Nascent, 
slightly evolved, evolved, and highly evolved stages generally are indicated by K
2
O 
contents of 2-4%, 4-6%, 6-8%, and >8%, respectively (Birch et al., 1976; Odin and 
Matter, 1981; Amorosi, 1995) (Table 3). K
2
O contents of ~7% or more generally are 
indicative of significant breaks in deposition (McRae, 1972; Odin and Matter, 1981; Odin 
and Fullagar, 1988; Chafetz and Reid, 2000). Chemical changes are accompanied by 
structural changes that can be recognized in x-ray diffraction analysis. Increases in 
glauconitic maturity are accompanied by a progressive shift from a glauconite smectite 
peak at ~14 ? to a glauconite mica peak at 10? (Table 3, Fig. 1) (Odin and Matter, 1981; 
Amouric and Parron, 1985; Amorosi, 1995; Huggett and Gale, 1997; Kelly and Web, 
1999).  
Glauconite is generally greenish, as viewed under normal reflected light and in 
thin section under plane-polarized light (McRae, 1972). However, grain color does vary 
with degree of maturation (Table 3). Nascent grains are typically brownish, light green to 
pale greenish-yellow, slightly evolved grains are normally olive green, and evolved and 
highly evolved grains range from dark green to almost black (McRae, 1972; Odin and 
Matter, 1981; Amorosi, 1995). The progressive darkening of grains reflects increasing  
 
 10
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 1 ? The X-ray diffractogram peaks showing progressive stages of glauconitization 
(from Odin and Matter, 1981).  
 
 
 
 
 
 
 
 
 
 
 11
ferrous Fe contents. Where weathering has occurred and glauconite is oxidized to 
kaolinite and/or goethite, grains become rusty brown.  
2.4.2 Glauconite Morphology and Texture 
 Various attempts have been made to link glauconite grain morphology to level of 
maturity. Nascent, weakly evolved grains generally retain the original size, shape, and 
texture of the host grain that has been replaced. With increased maturity, the shape and 
affinity of host grains may be masked (Odin and Matter, 1981). Of the morphological 
varieties listed in Table 1, mammillated, capsule-shaped, lobate, and vermicular grains 
are typically considered as relatively mature grain types, particularly if they exhibit 
marginal fractures and cracks (Odin and Matter, 1981; Odin and Fullagar, 1988; 
Amorosi, 1995, 1997). Cracks in glauconite, which are typically irregular and taper 
inward, are thought to form due to differential expansion during mineral growth (McRae, 
1972; Odin and Morton, 1988; Huggett and Gale, 1997; Kelly and Web, 1999) or 
dehydration during the mineralogical evolution of the grains (McRae, 1972). 
Precipitation of glauconite within grain cracks and fractures is generally indicative of the 
highly evolved stage (Odin and Matter, 1981).   
 Huggett and Gale (1997) have suggested that grains with vermicular fabrics are 
less evolved than grains with fractures and/or healed fractures. They argue that the 
vermicular fabric is inherited from precursor grains (e.g., fecal pellets, micas), and that 
this fabric would be lost with further grain evolution during maturation. In contrast to 
other workers (Odin and Matter, 1981; Odin and Fullagar, 1988; Amorosi, 1995, 1997), 
Huggett and Gale (1997) also suggest that ovoidal pellets are more mature than the other 
morphological varieties.   
 12
 Use of glauconite grain morphology to assess maturity may be complicated by 
grain transport and reworking. Cracks in grains represent zones of weakness. Hence, 
mature fractured grains are vulnerable to mechanical breakdown, during physical 
transport or bioturbation, into smaller, less irregular fragments. Further abrasion of these 
fragments can result in ovoidal or spherical grains (Amorosi, 1997). Such grains, known 
as detrital glauconite, are less reliable for evaluating maturity and, because they are 
transported, may not reflect the authigenic conditions that existed during deposition of 
the host sediment (McRae, 1972; Odin and Matter, 1981; Odin and Fullagar, 1988; 
Amorosi, 1997).  
2.5 Use of Glauconite in Sequence Stratigraphy 
2.5.1 Glauconite in Passive-Margin Depositional Sequences 
Glauconite formation and maturation require prolonged residence at or near the 
sediment-water interface and, hence, are reliable indicators of low sedimentation rate 
(Odin and Matter, 1981; Odin and Fullagar, 1988; Amorosi, 1995). For this reason, 
occurrences of abundant glauconite have traditionally been interpreted to reflect marine 
transgression and associated sediment starvation (Odin and Matter, 1981; Baum and Vail, 
1988; Odin and Fullagar, 1988; Amorosi, 1995, 1997). The link between glauconite and 
sedimentation rate gained significance with the development of sequence stratigraphy 
(Baum and Vail, 1988; Posamentier et al., 1988; Van Wagoner et al., 1988). Depositional 
sequences consist of systems tracts that correspond to distinct phases of sea-level cycles, 
and these phases govern sedimentation rates (Fig. 2).  
Recent studies focusing on passive-margin successions have shown that 
glauconite may be ubiquitous throughout a depositional sequence, but its origins  
 13
Figure 2 ? Generalized shelf stratigraphic sequence showing systems tracts, bounding 
surfaces, and relations to sedimentation rate and authigenic glauconite content.  
 
 
 
 
 
 
 
 
 
 
Surface of 
maximum starvation
Condensed 
Section
Landward
~~~~~~
Sequence Boundary
Sequence Boundary
Transgressive surface
Highstand Systems Tract 
(HST)
Transgressive Systems Tract
(TST)
Lowstand Systems Tract 
(LST)
S
edi
m
ent
ati
on 
ra
t
e
s
A
u
thi
gen
i
c
 
G
l
auc
oni
t
e
TI
M
E
Coastal Onlap Curve
S
edi
m
ent
ati
on 
ra
t
e
s
A
u
thi
gen
i
c
 
G
l
auc
oni
t
e
TI
M
E
 14
(authigenic vs. detrital), abundance, and maturity vary systematically within and through 
systems tracts (Amorosi, 1995, 1997; Huggett and Gale, 1997; Kelly and Web, 1999; 
Harris and Whiting, 2000; Giresse and Weiwi?ra, 2001; Hesselbo and Huggett, 2001).  In 
marine shelf sequences, lowstand systems tracts (LST) normally consist of sediments that 
were deposited relatively rapidly in estuarine, lagoonal, or foreshore-shoreface settings 
wherein conditions are not favorable for glauconitization. Nonetheless, due to the erosion 
of older glauconitic deposits, lowstand sediments (e.g., incised valley fills) may contain 
detrital glauconitic grains (Baum and Vail, 1988).  
Transgressive systems tracts (TST) form during phases of sea-level rise and 
diminished sediment influx. TST deposits typically contain detrital glauconite, 
particularly near the base of the systems tract (e.g., in association with transgressive lags 
on the transgressive surface, TS) and common to abundant authigenic glauconite. 
Abundance and maturity of authigenic glauconite in TST deposits vary as a function of 
specific deposition environments, shorter-term sea-level dynamics, and magnitude of 
sediment starvation but generally increase upwards through the system tract 
(Bhattacharya and Walker, 1991).  
Maximum glauconite abundances and maturity are characteristic of the condensed 
section (CS) and the associated surface of maximum sediment starvation (SMS), which 
occur at the transition between the TST and the highstand systems tract (HST). In 
passive-margin condensed sections, glauconite is commonly associated with 
concentrations of fossil debris, phosphatic grains, sulphides, carbonates horizons, and 
intense bioturbation (Baum and Vail, 1988; Pemberton et al., 1992; Amorosi, 1995; 
Kitamura, 1998; Urash, 2005).  
 15
Vertical successions within highstand systems tracts (HST) generally reflect 
increasing sedimentation rates associated with late transgressive, highstand, and early 
regressive phases. Authigenic glauconite may be most common in the lower parts of the 
HST. However, glauconite abundance and maturity generally decrease upward through 
this systems tract. Authigenic glauconite is typically rare or absent in the upper part of the 
HST.   
2.5.2 Glauconite in Parasequence-Scale Studies 
Parasequences are the building blocks of systems tracts. Parasequences and 
parasequence sets are relatively conformable successions of genetically related beds or 
bedsets that reflect shorter-term sea-level changes. In marine depositional sequences, they 
are upward-shallowing sediment packages bounded by marine-flooding surfaces (Van 
Wagoner et al., 1988). Previous investigations of glauconite at the parasequence scale are 
relatively rare, but indicate that abundance and maturity of authigenic glauconite may 
decrease upward through parasequences in response to sea-level mediated increases in 
sedimentation rate (Amorosi, 1995; Urash, 2005). The Lower Paleocene Clayton 
Formation in central Alabama provides the opportunity to further explore the 
relationships between glauconite and sea-level dynamics at both the systems tract and 
parasequence scales.   
 
 
 
 
 
 16
 
 
 
3.0 CLAYTON FORMATION 
3.1 General Stratigraphy 
The Paleocene (Danian) Clayton Formation, part of the Midway Group, crops out 
in an arcuate belt trending northwest-southeast across Alabama (Fig. 3A, B) and adjacent 
states. Strata dip gently to the south and southwest at less 30-40 ft/mile (0.6-0.8
?
). The 
Clayton Formation overlies the Cretaceous (Maastrichtian) Prairie Bluff Chalk in western 
Alabama and the Providence Sand in eastern Alabama, and is overlain by the Paleocene 
Porters Creek Formation (Baum and Vail, 1988; Donovan et al., 1988).  
The basal contact of Clayton Formation (the Cretaceous-Tertiary boundary) is a 
regional unconformity. At some localities, this unconformity is overlain by a lag bed of 
quartz grains, phosphate pebbles, and shark teeth. In central and western Alabama, the 
unconformity is locally overlain by thin, discontinuous lenses of quartzose fine- to 
coarse-grained sands (e.g., at Moscow Landing, along Shell Creek, at Prairie Bluff 
Landing, and along Mussel Creek) (Mancini et al., 1989, 1993; Savrda, 1993). The latter 
sand bodies, which contain Tertiary macrofossils and reworked Cretaceous microfossils, 
are known collectively as the Clayton basal sands (LaMoreaux and Toulmin, 1959). 
Locally, the sands fill depressions on the eroded surface of the underlying chalk (Mancini 
et al., 1989; Mancini and Tew, 1993).  
 17
Auburn
ALABAMA
Midway Group
Upper Selma Group
Study location
34?
87?
A
N
0 50
miles
Highway 263 section
Mussel Creek section
86
0
32
0
N
B
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 3 ? Distribution of Lower Paleocene strata in Alabama. (A) Map showing the 
location of the study area and distribution of Cretaceous Upper Selma Group and Lower 
Paleocene Midway Group in Alabama. (B) Generalized map showing the distribution of 
Clayton Formation in southern Alabama, and study locations (stars) in Butler and 
Lowndes Counties.   
 
 
 18
The thickness and lithologic character of the Clayton Formation vary along the 
outcrop belt (Baum and Vail, 1988; Donovan et al., 1988; Mancini et al., 1989; Mancini 
and Tew, 1993). In the far eastern and far western parts of Alabama, the Clayton 
Formation is relatively thin and is not differentiated into members. In central Alabama, 
including the area of the current study, the Clayton Formation is relatively thick (up to 60 
m) and is divided into two members; the Pine Barren and McBryde members (Fig. 4). 
The lower Pine Barren Member includes, in ascending order: the localized Clayton sands; 
a thin (~2.5 m) package of alternating glauconitic calcareous muddy sands and sandy 
limestones; a thicker package of alternating sandy, calcareous mudstones and fine-
grained limestones and marls; and a very fossiliferous sandy limestone (informally 
known as the ?Turritella Rock?) (Mancini et al., 1989). The McBryde Member, also 
known informally as the ?Nautilus Rock,? consists of light gray to white, sandy, 
argillaceous limestones (Smith et al., 1894).  
3.2 Sequence Stratigraphy 
 According to previous workers, the Clayton Formation contains parts of two 
marine shelf depositional sequences and, hence, records two sea-level cycles (Fig. 4) 
(Baum and Vail, 1988; Donovan et al., 1988; Mancini et al., 1989). The contact between 
the Clayton Formation and the underlying Prairie Bluff Chalk (or Providence Sand) 
generally is regarded as a sequence boundary that separates the uppermost Cretaceous 
depositional sequence UZAGC- 5.0 from the lowermost Paleocene depositional sequence 
TP 1.1 (Baum and Vail, 1988; Donovan et al., 1988; Mancini and Tew, 1988, 1993; 
Mancini et al., 1989, 1995; Savrda, 1991, 1993).   
  
 19
Pe
ri
o
d
Ag
e
Relative Changes in 
Coastal Onlap
Landward Seaward
Lithostratigraphy
Systems Tracts
C
r
eta
c
e
ous
Ma
as
tr
ic
hti
a
n
T
e
rti
a
ry
Da
n
i
a
n
Clayton sands
Pine Barren 
Member
?Turritella Rock?
McBryde
Member
Porters Creek Formation
Clayton
Formation
lowstand
condensed section
highstand
shelf margin
transgressive
condensed section
highstand 
Prairie Bluff Chalk
SB
transgressive
highstand
condensed section
transgressive
SB
SB
TP1.2
TP1.1
UZAGC-5.0
Pe
ri
o
d
Ag
e
C
r
eta
c
e
ous
Ma
as
tr
ic
hti
a
n
T
e
rti
a
ry
Da
n
i
a
n
 
 
 
 
 
Figure 4 ? Sequence stratigraphic interpretations of the Lower Paleocene Clayton 
Formation and enveloping strata, central Alabama, (light gray area indicates the 
depositional sequence studied herein). Black triangles indicate condensed sections. 
SB- Sequence Boundary; UZAGC 5.0, TP 1.1, and TP 1.2 represent Upper 
Cretaceous and Lower Paleocene depositional sequences, respectively. Lower two 
sequence boundaries are type 1, while upper sequence is type 2, (after Mancini et al., 
1989). 
 
 
 
 
 
 20
Sequence TP 1.1 includes all of the Pine Barren Member except for the Turritella 
Rock. The thin Clayton sand bodies have been interpreted as lowstand incised-valley fill 
deposits, although some of these sand bodies have been attributed to deposition in  
response to a K-T boundary impact event and associated megawave processes (Bourgeois 
et al., 1988; Hildebrand et al., 1991). Where the Clayton sands are absent, the basal  
Clayton contact is inferred to represent a coplanar sequence boundary/transgressive 
surface (SB/TS). Coarse-grained, fossiliferous, phosphatic, quartzose beds that 
immediately overlie the Clayton sand or the coplanar SB/TS are inferred to be 
transgressive lag deposits. Alternating glauconitic calcareous muddy sands and sandy 
limestones in lower parts of the Pine Barren Member are assigned to the transgressive 
systems tract/condensed section. The overlying package of calcareous sandy muds and 
fine limestones has been placed into the highstand systems tract. Decimeter- to meter-
scale beds or bedsets in both transgressive and highstand deposits of sequence TP1.1 
have been interpreted as parasequences formed in response to short-term changes in 
relative sea level (Huchison, 1993).   
 The remainder of the Clayton Formation has been assigned to depositional 
sequence TP1.2. The base of the Turritella Rock is interpreted as a sequence boundary. 
The Turritella Rock, McBryde Member, and Porters Creek Formation represent 
lowstand, transgressive, and highstand deposits, respectively.  
3.3 Paleoenvironment 
 Strata of the Clayton Formation are interpreted to have been deposited in marginal 
marine and shallow marine settings (Mancini et al., 1989). Although some Clayton sand 
bodies are inferred to be impact-related tsunami deposits (e.g., Smit et al., 1996), the 
 21
Clayton sand in the study area likely was deposited in estuarine settings during an early 
stage of transgression (Habib et al., 1992; Savrda, 1993). The bulk of the Clayton 
Formation (Pine Barren and McBryde members) was deposited in passive-margin marine 
shelf settings under variable water depths and energy regimes controlled by sea-level 
dynamics and distance to the paleo-shoreline. As a generalization, deposits exposed in the 
eastern and western portions of the Clayton outcrop belt in Alabama represent relatively 
shallow and deeper shelf facies, respectively (Huchison and Savrda, 1994)  
 
    
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 22
 
 
 
 
 
4.0 LOCATION AND METHODS 
 
4.1 Study Locality 
 
This study concentrated on exposures of the Pine Barren Member of the Clayton 
Formation in southern Lowndes County, central Alabama (Figs. 3A and B). The work 
focused on a relatively continuous section exposed in the banks of Mussel Creek and 
within immediately adjacent road cuts created during construction of a new bridge over 
the creek. However, supplementary observations and sampling were made at an 
equivalent section exposed a few miles north of the Mussel Creek locality along Highway 
263 (Fig. 5).  
Selected exposures were ideal for this study for several reasons. First, they 
include a relatively complete section of the Pine Barren Member for which the sequence 
stratigraphic context has already been established. Based on previous investigations 
(Baum and Vail, 1988; Donovan et al., 1988; Mancini and Tew, 1988; Mancini et al., 
1989; Savrda, 1991), these exposures include, in ascending order: highstand marls (upper 
4 m of Maastrichtian Prairie Bluff Chalk) of sequence UZAGC-5.0;  the basal TP 1.1 
sequence boundary locally separated from a transgressive (ravinement) surface by alleged 
lowstand estuarine incised valley-fill deposits (<1 m thick Paleocene Clayton sands); a 
thin (~ 2.5 m) transgressive systems tract dominated by glauconitic sandy limestones, 
marls, and marly sands; a purported surface of maximum starvation; and highstand 
 23
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 5 ? Location of the Mussel Creek and Highway 263 sections (source: 
www.nationalgeographic.com/topo, 2002).                                                                       
 
 
 
 
 
 
 
 
 24
deposits (~ 8 m) dominated by alternating calcareous muds and muddy limestones. Both 
transgressive and highstand deposits in sequence TP1.1 are characterized by decimeter- 
to meter-scale beds or bedsets that have been interpreted as parasequences formed in 
response to short-term changes in relative sea level (Mancini and Tew, 1993; Huchison 
and Savrda, 1994). Second, glauconite is present throughout the section, providing an 
opportunity to examine variations in the abundance and character of glauconite through a 
depositional sequence and associated parasequences. Finally, the exposures are virtually 
complete and relatively unweathered. Only one interval of the section at Mussel Creek 
was weathered deeply enough to require supplementary sampling from Highway 263 
road-cut exposures.  
4.2 Field Studies 
Field studies involved section description and collection of samples. The Mussel 
Creek section was carefully measured and described using Jacob staff, tape, and line-
level methods. Observations focused on general lithology and sedimentary structures, but 
included associated body and trace fossils. A total of 30 units were delineated in the Pine 
Barren Member of the Clayton Formation; one representing the lowstand incised valley 
fill (unit 1; Clayton sand), twelve in the transgressive systems tract (units 2-11; including 
a transgressive lag and condensed bed), and seventeen in the highstand systems tract 
(units 12-30). Sedimentologic characteristics observed in the field were employed in the 
preliminary delineation of parasequences. 
A total of 110 samples were collected throughout the section for laboratory 
analyses. Generally, only one or two samples were collected from thinner, commonly 
indurated beds. For thicker typically less indurated beds, multiple samples were collected 
 25
in series throughout the beds. Vertical spacing of samples was variable but averaged ~10 
cm. One ~1.5-m-thick interval of the Mussel Creek section (unit 13) was deeply 
weathered and oxidized. Hence, samples for this unit were derived from an unweathered 
outcrop along Highway 263.   
4.3 Laboratory Investigations 
Sediment samples were subjected to various analyses in the laboratory. These 
included general analyses of sediment texture and composition (including carbonate and 
organic carbon contents) and petrographic, XRD, and microprobe studies of glauconite.  
4.3.1 Textural Analyses 
Sediment textures for all samples were determined using a combination of wet- 
and dry-sieve techniques. A small subsample (~25 g) of each sediment sample was dried, 
weighed and disaggregated. Most of the subsamples (muddy sands, sandy muds) could be 
disaggregated in distilled water. However, disaggregation of more indurated carbonate-
rich subsamples required digestion in 10% HCl. Subsamples (or insoluble residues) were 
then wet-sieved through a 4? (63-micron) screen to remove the mud (silt and clay) 
fraction. The sand-sized fraction was removed from the screen, dried, weighed, and then 
dry-sieved (using a Gilson screen shaker) for 15 minutes at 1? intervals through the 
range of 0? (1 mm) to 4? (63 ?). Each size fraction was weighed and retained for latter 
inspection. Sand content (% sand) was determined by weight loss during wet-sieve and 
acid digestion procedures. Graphic mean size of the sand fractions was calculated using 
the GRADISTAT program (Blott, 2000) following Folk and Ward (1957).  
 
 
 26
4.3.2 Carbonate and Organic-Carbon Analyses 
Carbonate and organic-carbon contents were determined using acid digestion and 
a LECO CS-200 carbon/sulfur analyzer, respectively. Subsamples weighing ~3-4 g were 
extracted from each of the field samples, powdered, and then dried for 24 hours. 
Approximately 0.25 g of the powdered subsamples were weighed and digested in 10% 
HCl. Residues were filtered through pre-weighed carbon-free borosilicate filters. The 
filters and residues were then dried for 24 hours and weighed. Carbonate contents of 
subsamples were determined by weight loss during acid digestion. Dried filters and 
residues were then combusted with metal accelerators in a LECO CS-200 carbon/sulfur 
analyzer. Organic carbon content (wt %) was determined by infrared detection of CO
2
 
released during sample combustion.  
4.3.3 Binocular Microscopic Examination 
Sand fractions derived from subsample sieving were examined under a binocular 
microscope. Examination focused on grains contained within the mean sand size range 
for each sample. The mean grain-size fraction was used to visually estimate the relative 
abundance of glauconite in each sample, to identify and describe the glauconite grain 
morphologies, and to qualitatively assess glauconite color.   
4.3.4 Thin Section Petrography 
A total of 110 thin sections, representative of all samples collected in the field, 
were prepared for petrographic analyses. Thin sections were prepared commercially by 
Wagner Petrographic Laboratory. Thin sections were initially examined under a 
petrographic microscope to recognize and generally describe sediment textures and 
various components, including clastic or detrital grains (e.g., quartz, feldspars, micas), 
 27
allochemical grains (e.g., skeletal fragments), matrix and cements, and glauconite (color, 
morphotypes, etc.). Representative fabrics, textures, and grain types were documented via 
digital photography.  
Following general petrographic studies of all thin sections, a total of sixty-one 
representative thin sections were subject to point-count analysis in order to quantify the 
relative abundances of major detrital and authigenic constituents, including various 
glauconite types. A total of 300 grains were counted per thin section. Point counting was 
performed at 50X magnification with the aid of an automatic point-counting stage.  
4.3.5 X-Ray Diffraction Analyses 
Owing to time and cost constraints, only eight samples were selected for X-ray 
diffraction (XRD) analyses. Grains were extracted from the mean sand fraction of these 
samples, wherein glauconite grains were abundant. Grains were powdered using a mortar 
and pestle. Powders were then used to prepare oriented samples using the filter-
membrane peel technique (Drever, 1973, as cited by Moore and Reynolds, 1989, 1997). 
Approximately 150 mg of powder were suspended in water and filtered under vacuum 
through carbon-free borosilicate filters. After the water was removed, three separate 5-ml 
aliquots of a cation-saturating solution [MgCl
2
 of 0.5 M (1N)] were filtered through the 
sample. The sample was then filter washed several times with 5-ml aliquots of deionized 
water to remove the extra salts from the sample. After completion of the saturation 
process, samples were allowed to dry to a moist state. The filter paper was then placed 
with the sediment face down on a clean, ethanol-washed glass slide. Air bubbles between 
the filter paper and the glass slide were removed by rolling a plastic cylinder across the 
 28
filter paper. The filter paper was then gently peeled away, leaving the oriented sample on 
the glass slide.  
Oriented mounts were sprayed with ethylene glycol and placed into a Siemens D 
5000 x-ray diffractometer housed in the Department of Agronomy and Soils at Auburn 
University. Samples were run using a Cu K? radiation source at a speed of 0.05?/3 s. 
through the range of 0 to 60? 2?. X-ray diffractograms were used to evaluate the 
structural states of glauconites (i.e., within the glauconite smectite-glauconite mica 
spectrum). 
4.3.6 Electron Microprobe Analysis and Scanning Electron Microscopy  
As with XRD analysis, time and cost limited the number of samples that were 
subject to electron microprobe analysis (EMPA). A total of thirteen samples were 
strategically selected. Glauconite grains were manually picked from the sand-sized 
fractions of these samples, mixed with an embedding medium (epoxy resin), and set in a 
plastic cylindrical mold. After the epoxy set, lower portions of the molds were hand 
polished with 600 to 1000 grit to expose grains for microprobe analysis.   
EMPA of polished sections were performed using the microprobe facility in the 
Department of Geology at the University of Georgia (Athens, GA). Specifically, analyses 
were performed using a JEOL 8600 Scanning Electron Microprobe fitted with 
wavelength-dispersive spectrometer (WDS). Analyses were run at an accelerating voltage 
of 10 KeV, with a 10 nA (nano-ampere) current flowing for 10 seconds and a fixed beam 
diameter of 10 ?m. A Phi-Rho-Z metric correction was used.  
Samples were pre-coated with carbon using the evaporated carbon-coating 
method to make the samples conductive. Before selecting individual points for EMPA, 
 29
grains were examined using backscattered-electron (BSE) imagery to recognize primary 
and secondary glauconite infillings and compositional variations within single grains. 
Only primary glauconitic parts of grains (those having higher atomic number and brighter 
parts in BSE images) were selected for EMPA.  
Ten grains per sample were analyzed to evaluate major element abundances. Data 
for the 10-grain sets were used to calculate average compositions for each sample. K, Fe, 
and Al were the major elements of interest. Natural and synthetic mineral standards were 
used to calculate K
2
O%. Orthoclase was used as the primary standard, and lemhi biotite 
prepared by USGS was used as secondary standard. Total oxygen content was measured 
by the stochiometry method, and total Fe% was measured as FeO.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 30
 
 
 
 
 
5. 0 SEDIMENTOLOGICAL CHARACTER OF THE STUDY SECTION 
5.1 General Section Descriptions 
The composite Mussel Creek/Highway 263 section provides approximately 12 m 
of continuous vertical exposure that includes the upper part of the Cretaceous Prairie 
Bluff Chalk (~1 m) and much of the Pine Barren Member of the Clayton Formation (~11 
m). Thirty informal units were delineated in the Pine Barren Member (Figs. 6 and 7). The 
general character of these units is described below, in sequence stratigraphic context. 
5.1.1 Lowstand Incised Valley Fill (Unit 1, Clayton Sand) 
Lowstand incised valley-fill deposits are represented by the Clayton sand (unit 1). 
This lenticular sand body, which varies from 0-90 cm in thickness, is composed of 
unconsolidated, yellowish-gray, weakly bioturbated, laminated and cross-laminated, fine- 
to medium-grained, carbonaceous, micaceous, quartzose sand (Figs. 7, 8, 9A).  Although 
burrows attributed to resident organisms are present, most larger burrows pipe down from 
and are filled with sand derived from unit 2. The sand contains reworked Cretaceous 
macrofossils, localized carbonate concretions, plant detritus (including large lignite 
clasts), and detrital glauconite grains (Fig. 9A). The erosional base of the Clayton sand is 
sharp and irregular; locally, large irregular masses of the underlying Prairie Bluff Chalk 
extend upward into the sand bed (Fig. 8).  The upper contact, a transgressive surface of 
erosion or ravinement surface, is also sharp and erosional and truncates stratification 
within the sand (Fig. 8).   
 31
PRAIRIE BLUFF 
CHALK
PINE BARREN MEMBER
CLAYTON FORMATION
MFS
LST
SB
TS
HST
TST
HST
CS
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
a
b
c
Glauconitic sandy mud
Glauconitic carbonate
Glauconitic muddy sand
Carbonate concretions
11
Units
Sample horizons
Samples subject to point count 
analysis
Microprobe samples
XRD samples
SB Sequence boundary
TS Transgressive surface 
TST Transgressive systems tract
MFS Maximum flooding surface
CS Condensed section
HST Highstand systems tract
LST
Lowstand systems tract
Sand
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 6 ? Stratigraphic column of study section showing sequence stratigraphic context, 
informal units (1-30), and sampling horizons. Prairie Bluff Chalk and Pine Barren 
intervals belong to depositional sequences UZAGC 5.0 and TP 1.1, respectively.  
 32
1
2
3
4
5
6
7
8
Prairie Bluff Chalk
A
8
9
10
11
12
13
14
B
14
15
16
17
18
19-30
C
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 7 ? Photographs of the study section. (A) Units 1-8 overlying the Prairie Bluff 
Chalk (Mussel Creek exposure); (B) Units 8-14 (Highway 263 exposure); (C) Units 14-
30 (Mussel Creek exposure). Scale = 1 m.   
 33
1
2
Prairie Bluff Chalk
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 8 ? Photograph of unit 1 (Clayton sand) associated with underlying Prairie     
Bluff Chalk and overlying transgressive lag unit (unit 2).                             
 34
Q
G
P
Py
M
Q
Fe
G
Py
M
P
G
A
B
G
P
Q
M
P
P
F
Ma
Mi
Q
Ma
C
D
Ma
M
Fo
Ma
Ma
Py
Fo
P
E
Ve
Ma
P
Mi
F
G
M
Q
Ma
G
Mi
G
Q
Ve
G
H
Py
P
P
Ve
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 9 ? Representative photomicrographs from the study section. (A) Clayton sand 
(unit 1); (B) Transgressive lag unit (unit 2); (C) lower part of TST (unit 3); (D) upper part 
of TST (unit 6); (E) muddy sand  (unit 9) and (F) sandy limestone (unit 10) from 
condensed section; (G) sandy mud (unit 12) and (H) sandy limestone (unit 18) from HST. 
(G-glauconite; Q-quartz; M-matrix; Mi-microspar; Fe-feldspar; P-phosphate; Py-Pyrite; 
Fo-foraminifera; Ma-mammillated glauconite grain; Ve-vermicular glauconite grain). Bar 
scales are ~ 1 mm.  
 35
5.1.2 Transgressive Lag (Unit 2) 
 
Unit 2 represents a transgressive lag deposit (Figs. 6, 7). This unit, approximately 
45 cm thick, is a light gray, massive, thoroughly bioturbated, micritic calcite-cemented, 
glauconitic, poorly-sorted, medium- to coarse-grained sandstone (Figs. 7, 9B, 10). In 
addition to angular clastic sand grains (quartz and subordinate feldspar), unit 2 contains 
common pebble-sized phosphate clasts (including molluscan steinkerns and rare shark 
teeth), reworked Cretaceous macrofossils (whole and fragmented), and rare quartz 
pebbles (Fig. 10). The contact between units 2 and 3 is irregular and gradational.  
5.1.3 Transgressive Systems Tract (Units 3-8) 
The transgressive systems tract, approximately 2 m thick, comprises six units 
(units 3-8; Figs. 6, 7, and 11). Units 3, 5, and 7 are relatively unconsolidated greenish 
gray glauconitic, calcareous, poorly-sorted, fine- to medium-grained muddy sands (Fig. 
9C). Units 4, 6, and 8 are moderately indurated, variably glauconitic sandy limestones or 
marlstones (Fig. 9D). All of these units are fossiliferous, thoroughly bioturbated, and 
have irregular, gradational contacts (Fig. 11). Fossil assemblages include common 
foraminifers and bivalves (whole and fragmented) and rare bryozoans and echinoids. The 
upper surface of unit 8 is characterized by localized patches of small encrusting oysters 
and rare, intact bryozoan fronds.  
5.1.4 Condensed Section (Units 9-11) 
The condensed section, representing the upper- and lowermost parts of the 
transgressive and highstand systems tracts, respectively (Figs. 6, 7), is herein defined by 
maximum abundance of authigenic glauconite (see below). The glauconite maximum 
corresponds to a thin (<1 m) interval defined by units 9 through 11 (Fig. 7B). Units 9 and  
 36
Q
P
1
2
3
4
5
6
7
8
 
 
 
 
 
 
 
 
 
 
Figure 10 ? Representative photograph of carbonate cemented transgressive lag bed (unit 
2) with phosphate clasts (P), and quartz pebbles (Q). 
 
 
 
 
 
 
 
 
 
Figure 11 ? Representative photograph of Clayton sand (unit 1), transgressive lag bed 
(unit 2), and overlying transgressive systems tract (units 3-8).  
 
 
 37
11 are unconsolidated, dark green, extremely glauconitic, poorly-sorted, fine- to medium-
grained sandy muds (Figs. 6, 7, 9E). Unit 10 is an indurated, light greenish gray, highly 
glauconitic, sandy limestone (Fig. 9F). All of these units are thoroughly bioturbated and 
fossiliferous. Fossil assemblages are the same as that in the underlying units (see section 
5.1.3). However, most fossils in the condensed section are partly to wholly replaced by 
glauconite. Contacts between units 9 through 11 and sub- and superjacent strata are 
relatively sharp but irregular. Irregular contacts reflect both bioturbation and differential 
cementation of limestones. 
5.1.5 Highstand Systems Tract (Units 12-30)  
The portion of the highstand systems tract represented in the composite section is 
characterized by alternating weakly indurated, gray to dark greenish gray, calcareous, 
poorly-sorted, fine- to medium-grained sandy muds (units 13a and c, 15, parts of unit 16, 
and all odd-numbered units from 17 through 29; Figs. 6, 7, 9G) and moderately to well-
indurated, gray to light greenish gray, variably sandy, micritic limestones or marlstones 
(units 12, 13b, 14, parts of unit 16, and all even-numbered units from 18 through 30; 
Figs. 7, 9H). The uppermost four units (27-30) at the Mussel Creek section are deeply 
weathered and oxidized.   
Limestones and marlstones generally form discrete, continuous beds. However, 
those in unit 16 are defined by discontinuous, irregular nodules (Fig. 7), reflecting a 
concretionary origin for at least some of the carbonate-rich units. In most 
limestones/marlstones, micrite has been recrystallized to microspar (Fig. 9H). 
Contacts between sandy muds and limestones/marlstones are generally fairly 
sharp despite thorough bioturbation of the entire package. Large (up to 5 cm in diameter) 
 38
burrows assigned to Thalassinoides are particularly evident in and below nodular 
limestones owing to preferentially cementation of burrow fills (Fig. 12A).  
All units in the highstand systems tract are fossiliferous. Macrofossils include 
common whole and fragmented molluscan remains (bivalves and gastropods) and rare 
shark teeth. Mollusks are most obvious in the limestones where they typically are 
preserved as relatively well preserved shells and as external molds and steinkerns (Fig. 
12B). All of the units of the highstand systems tract contain glauconite. However, as will 
be described below, glauconite contents generally decrease upward through the package, 
in both the sandy muds and carbonate-rich units. 
5.2 Textural Analyses 
Textural analyses were performed on all 110 samples collected from units 1 
through 30 (see Fig. 6). Calculated sand percentage and mean sand size are given in 
Table 4 and are plotted versus stratigraphic height in Figure 12.  
As expected, sand content is highest (78%) in unit 1 (Clayton sand). In the 
remainder of the section, sand percentages vary significantly from 0% to ~60%. Several 
general patterns are observed in the data. First, there is a general trend toward decreasing 
sand content upward through the section. Second, higher-frequency variations in percent 
sand define four fining-upward cycles, one in the transgressive systems tract (units 1-8) 
and three in the condensed section/highstand systems tract (units 9-13, 13-16, and 17-30). 
Hereafter, these are referred to as cycles 1, 2, 3, and 4, in ascending order. Several of 
these cycles appear to contain even higher-frequency fining-upward cycles (e.g., mini-
cyles 4a, b, and c, Fig. 13). 
 39
A
B
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 12 ? Representative photographs of highstand systems tract. (A) Large 
Thalassinoides associated with the nodular limestones (unit 16); (B) Large mollusks in 
marlstone.   
 
 40
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 13 ? Percent sand and mean grain size of sand in the study section. Textural data 
reveals four fining-upward cycles (1-4) and associated mini-cycles (e.g., 4a, b, and c). 
Dashed and dot-dashed lines define boundaries of cycles and mini-cycles, respectively. 
Section legend is shown in figure 6.  
123
Mean phi
1
2
3
4
a
b
c
a
b
c
020406080
% Sand
H
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1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
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t
 
in s
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c
t
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t
 
in s
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 41
Mean sand size ranges from 2.75? (fine sand) to ~1.25? (medium sand) (Table 
4, Fig. 13). As a generalization, mean sand size decreases (increasing ?) upward through 
the section. Higher-frequency cycles of decreasing sand size match the cycles and, in 
some cases, the minicyles, in sand percent; i.e., sand size generally covaries with percent 
sand. Notably, the coarsest sands occur in units 8 through 12 and generally coincide with 
the condensed section.   
 
5.3 Carbonate and Organic Carbon Analyses 
Carbonate and organic carbon data derived from all 110 samples are given in 
Table 4 and plotted against stratigraphic height and percent sand in Figure 14. Carbonate 
contents are lowest (14.8%) in unit 1 (Clayton sand) and range widely from ~20% to 
~80% throughout the remainder of the section. Not surprisingly, carbonate contents are 
highest in the indurated limestones/marlstones (mostly >60% CaCO
3
) and lowest 
(typically <60% CaCO
3
) in the poorly indurated muddy sand and sandy muds. As a 
generalization, carbonate-rich units seem to coincide with the upper parts of the cycles 
and/or minicycles defined from textural data (Fig. 14).  
Organic carbon contents are generally low (0.13% to 0.37%) in the relatively 
carbonate-rich transgressive system tract and condensed section (units 2-12). Values are 
variable but generally higher in the highstand systems tract, with the exception of the 
upper oxidized portion of the section. Organic carbon contents vary inversely with 
carbonate content (Fig. 15). Higher organic contents (up to 1.1%) generally correspond to 
sandy muds (Fig. 14; e.g., lower part of unit 13, unit 15, etc.).   
 
 
 42
Sample 
name
Sample
 number
Height in 
section
 (cm)
% 
Sand Mean 
Phi (?)
% 
Carbonate
% 
Organic 
Carbon
MC-1-1-11 1 10 73.849 2.395 14.799 0.370
MC-2-0-5 2 20.5 32.522 1.995 59.226 0.257
MC-2-23-37 3 48 27.824 1.704 68.222 0.174
MC-2-37-45 4 58 30.470 1.866 60.210 0.199
MC-3-0-15 5 73 37.945 1.859 47.292 0.222
MC-3-28-35 6 94.5 49.798 2.028 34.183 0.245
MC-4-12-17 7 118 31.814 2.030 65.437 0.216
MC-5-0-10 8 128 53.414 2.189 30.313 0.289
MC-5-25-35 9 153 57.985 2.124 46.985 0.233
MC-6-0-12 10 169 37.642 2.105 57.772 0.174
MC-6-18-25 11 184.5 30.547 2.006 69.043 0.139
MC-7-19-23 12 209 0.848 80.383 0.335
MC-8-0-5 13 215.5 33.426 2.014 62.448 0.153
MC-8-10-20 14 228 10.330 1.470 72.841 0.172
MC-8-20-25 15 235.5 23.392 1.505 75.517 0.146
MC-8-30-40 16 248 12.553 1.336 74.742 0.126
MC-9-0-3 17 254.5 57.388 1.598 28.998 0.249
MC-9-13-25 18 273 55.550 1.607 26.993 0.216
MC-10-0-15 19 285.5 17.730 1.648 69.658 0.204
MC-11-0-1
20 293.5 47.889 1.573 34.982 0.272
MC-11-1-5 21 297 37.908 1.590 21.768 0.276
MC-11-5-7 22 299 41.068 1.589 22.020 0.239
MC-11-7-9 23 301 40.051 1.560 20.070 0.268
MC-11-9-12 24 303.5 40.079 1.334 20.212 0.255
MC-11-12-18 25 308 35.863 1.335 24.614 0.270
MC-11-18-23 26 313 33.845 1.283 22.896 0.257
MC-11-24-29 27 319 36.084 1.401 21.818 0.274
MC-12-3-17 28 333 21.785 1.444 68.174 0.213
MC-13a-0-5 29 355.5 50.011 1.970 25.208 0.541
MC-13a-10-20
30 368 23.198 2.243 25.676 1.100
MC-13a-30-40 31 388 8.933 2.458 27.195 1.060
MC-13a-35-45 32 393 9.140 2.507 29.752 1.040
MC-13a-45-55 33 403 13.376 2.559 26.124 1.060
MC-13a-55-65 34 413 7.916 2.620 26.894 1.080
MC-13a-65-70 35 420.5 15.660 2.492 28.038 1.040
MC-13b-70-75 36 425.5 9.739 2.601 30.671 0.921
MC-13b-70-75 37 425.5 2.627 2.638 70.582 0.465
MC-13b-85-95 38 443 15.277 2.093 78.063 0.403
MC-13b-100-115 39 460.5 35.910 1.980 78.847 0.330
MC-13c-115-125 40 473 39.109 2.100 21.805 0.485
Table 4 ? Percent sand, mean sand size, and percent carbonate and organic carbon data.  
  
 
 43
Sample 
name
Sample
 number
Height in 
section
 (cm)
% 
Sand Mean 
Phi (?)
% 
Carbonate
% 
Organic 
Carbon
MC-13c-125-135 41 483 43.554 2.120 21.204 0.537
MC-13c-140-147 42 498 36.549 2.194 20.507 0.644
MC-13c-147-153 43 503 34.189 2.307 21.700 0.546
MC-13c-160-162 44 514 40.414 2.176 31.862 0.504
MC-14-0-15 45 525.5 13.226 2.212 50.489 0.197
MC-15-3-7 46 538 35.039 1.959 31.417 0.718
MC-15-8-13 47 543.5 14.411 2.282 35.324 0.986
MC-15-15-23 48 552 13.101 2.314 32.310 0.942
MC-15-28-38 49 566 9.492 2.340 26.746 1.090
MC-15-40-45 50 575.5 10.504 2.418 25.438 1.070
MC-15-42-50 51 579 10.176 2.612 29.260 1.110
MC-15-50-58 52 587 7.106 2.646 30.958 1.100
MC-15-60-68 53 597 8.957 2.538 33.372 1.100
MC-15-65-72 54 601.5 10.234 2.554 28.655 1.080
MC-15-75-80 55 610.5 8.069 2.566 37.159 0.964
MC-15-85-90 56 620.5 11.346 2.437 51.396 0.848
MC-16a-0-7 57 626.5 3.140 2.575 72.394 0.473
MC-16b-bottom 58 634 4.263 2.576 33.219 1.030
MC-16b-middle 59 643 15.609 2.227 34.012 1.040
MC-16b-top 60 653 7.206 2.741 34.450 0.907
MC-16c-35-42 61 661.5 2.532 2.722 80.434 0.325
MC-16d-42-47 62 667.5 9.420 2.779 32.423 0.904
MC-16e-47-53 63 673 2.674 2.699 73.323 0.410
MC-16f-53-72 64 686 8.702 2.658 30.668 0.998
MC-16g-72-78 65 698 9.977 2.543 72.852 0.443
MC-16h-78-92 66 708 24.412 2.453 28.209 0.729
MC-16i-92-98 67 718 11.361 2.423 48.680 0.430
MC-17-0-15 68 728.5 42.737 2.274 26.283 0.527
MC-17-15-20 69 738.5 45.086 2.204 20.326 0.577
MC-17-20-25 70 743.5 40.385 2.261 20.247 0.818
MC-17-25-45 71 756 46.742 2.290 18.311 0.558
MC-17-35-45 72 761 31.129 2.205 20.362 0.678
MC-17-55-60 73 778.5 26.433 2.427 18.363 0.812
MC-17-60-70 74 786 28.269 2.478 20.101 0.473
MC-17-70-80 75 796 22.098 2.553 18.245 0.661
MC-17-80-90 76 806 18.524 2.446 16.195 0.853
MC-17-90-95 77 813.5 41.077 2.223 37.939 0.391
MC-18-5-20 78 828.5 16.207 2.276 68.456 0.249
MC-19-5-10 79 843.5 50.340 2.279 19.956 0.651
MC-19-10-15 80 848.5 40.924 2.407 19.006 0.420
Table 4 ? Continued.   
 
 
 44
Sample 
name
Sample
 number
Height in 
section
 (cm)
% 
Sand Mean 
Phi (?)
% 
Carbonate
% 
Organic 
Carbon
MC-19-20-25 81 858.5 22.130 2.316 36.202 0.579
MC-19-25-30 82 863.5 47.164 2.064 20.829 0.458
MC-19-30-40 83 871 29.241 2.315 24.028 0.512
MC-19-40-47 84 879.5 35.905 2.139 21.375 0.539
MC-19-47-55 85 887 17.990 2.598 20.271 0.599
MC-19-55-60 86 893.5 23.093 2.561 25.737 0.654
MC-19-60-68 87 900 20.901 2.548 27.836 0.693
MC-19-70-75 88 908.5 21.583 2.517 30.370 0.662
MC-19-75-80 89 913.5 20.132 2.631 35.658 0.657
MC-19-82-86 90 920 14.121 2.659 38.881 0.567
MC-20-0-5 91 928.5 2.820 2.504 46.011 0.245
MC-21-0-10 92 936 11.682 2.673 82.572 0.654
MC-21-10-20 93 946 10.124 2.708 39.040 0.529
MC-21-20-30 94 956 8.599 2.721 30.641 0.961
MC-21-30-37 95 964.5 8.833 2.747 29.880 0.840
MC-22-0-13 96 971.5 3.040 2.814 32.319 0.312
MC-23-5-10 97 991.5 17.721 2.284 74.628 0.154
MC-23-10-15 98 996.5 16.207 2.173 70.689 0.231
MC-23-15-20 99 1001.5 12.036 2.619 60.716 0.300
MC-24-0-12 100 1015 2.889 2.554 39.290 0.127
MC-25-5-10 101 1028.5 12.352 2.297 81.006 0.268
MC-25-15-18 102 1037.5 5.668 2.727 47.789 0.318
MC-26-0-8 103 1045 1.471 2.512 30.578 0.164
MC-27-5-10 104 1056.5 3.245 2.674 69.375 0.377
MC-27-15-20 105 1066.5 2.979 2.739 29.610 0.334
MC-27-20-24 106 1071 6.223 2.328 31.025 0.230
MC-28-1-11 107 1079.5 0.773 2.453 49.606 0.149
MC-29-2-10 108 1091 2.495 2.663 77.152 0.282
MC-29-15-20 109 1102.5 1.056 2. 664 41.048 0.282
MC-30-1-8 110 1108.5 0.574 2.380 79.810 0.152
Table 4 ? Continued.  
 
 
 
 
 
 
 
 
 45
0
1
2
3
4
a
b
c
a
b
c
0 20 40 60 80
% Sand
25 50 75 100
% Carbonate
0
.5 11.5
% Organic Carbon
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1
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9
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13
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15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
Oxidized 
interval
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in
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 (
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s
)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 14 ? Percent sand, carbonate, and organic carbon in the study section. Dashed 
and dot-dashed lines define boundaries of cycles and mini-cycles, respectively. Section 
legend is shown in figure 6. 
 
 46
 
 
 
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 15 ? General inverse relationship between percent carbonate and organic carbon.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
0
20
40
60
80
100
0 0.4 0.8 1.2
% Organic Carbon
%
 C
a
r
b
onat
e
R
2
 = 0.216 
 47
5.4 General Petrography and Point-Count Analyses 
5.4.1 General Observations 
General petrographic observations of thin sections of all samples and point-count 
analyses of selected samples indicate that sediments are composed mostly of matrix (0% 
to 95%), glauconite (0% to 95%), quartz (0.3% to 20.9%), skeletal fragments (0% to 
20%), and other diagenetic minerals (phosphatic grains, 0% to 10%; pyrite, 0% to 3.5%). 
The abundances of these major constituents based on point-count analyses are given in 
Table 5. Minor constituents include feldspars and large micas.  
The matrix fractions in the sandy mud and muddy sand units are characterized by 
very fine-grained, randomly-oriented clay, fine micas, and other unidentifiable 
components. Matrix in carbonate-rich units (marlstones and limestones) is composed of 
micrite or recrystallized micrite (microspar).   
Glauconite of various morphotypes (see Chapter 6) is observed in variable 
abundance in all units except those at the top of the section (units 27-30) (Fig. 16). 
Glauconite contents are relatively low in the Clayton sand (unit 1), transgressive lag (unit 
2), and the transgressive systems tract (units 3-8). Glauconite abundance reaches a 
maximum (up to ~94%) in the condensed section (units 9-11) and trends toward lower 
values through the highstand systems tract (Fig. 16). However, glauconite abundance 
varies cyclically through the condensed section/highstand systems tract interval. These 
asymmetric cycles, marked by relatively rapid increases and gradual decreases in 
glauconite abundance are coincident with textural cycles 2, 3, and 4 and, in some cases, 
associated mini-cycles; above the transgressive systems tract, glauconite abundance 
correlates strongly with, and is responsible for, the observed fining-upward cycles. A  
 48
Sample
 name
Height in 
section
 (cm)
% 
Matrix
% 
Glauconite
%
 Quartz
% Fossil 
Fragments
% 
Phosphate
% 
Pyrite
% 
Other
MC-2-0-5 20.5 57.7 11.2 15.7 6.3 3.9 0.0 5.1
MC-3-28-35 94.5 50.7 22.2 20.9 2.9 1.9 0.0 1.4
MC-4-12-17 118 62.2 5 16.8 7.8 1.3 2.8 4.3
MC-5-25-35 153 39.9 24.1 25.5 7.1 1.3 1.9 0.2
MC-6-18-25 184.5 51.5 9.5 18.5 16.2 0.0 0.6 3.7
MC-8-0-5 215.5 54.3 11.8 19.0 12.0 2.2 0.0 0.6
MC-8-10-20 228 41.7 27.1 14.3 13.0 4.4 0.0 0.0
MC-8-20-25 235.5 37.9 31.2 12.3 8.4 10.1 0.0 0.1
MC-8-30-40 248 2.4 91.2 3.2 13.8 1.6 0.0 0.0
MC-9-0-3 254.5 3.2 94.2 0.6 14.1 0.3 0.0 0.0
MC-9-13-25 273 15.5 76 3.0 14.1 0.0 0.0 0.0
MC-10-0-15 285.5 37.7 55.5 0.9 8.6 1.5 0.3 0.0
MC-11-0-1
293.5 0.0 93.2 1.5 19.9 1.5 0.0 0.0
MC-11-5-7 299 16.7 80.1 0.0 13.4 0.3 0.0 0.0
MC-11-12-18 308 34.6 63.8 1.5 12.6 0.0 0.0 0.0
MC-11-24-29 319 11.4 87.3 0.6 9.2 0.0 0.0 0.0
MC-12-3-17 333 54.4 41.2 0.3 10.3 0.3 0.0 0.0
MC-13a-10-20
368 66.9 27.2 1.9 4.6 0.3 0.0 0.0
MC-13a-35-45 393 83.1 8.8 1.7 3.3 1.4 1.4 0.3
MC-13a-45-55 403 84.1 11.4 1.6 2.2 0.3 0.6 0.0
MC-13a-55-65 413 87.0 8.4 0.3 4.6 0.0 0.0 0.0
MC-13b-70-75 425.5 82.8 10.9 1.7 4.6 0.0 0.0 0.0
MC-13c-115-125 473 33.4 53.5 1.7 8.0 0.0 0.0 3.4
MC-13c-140-147 498 61.4 36.2 0.9 2.6 0.0 0.3 0.0
MC-13c-147-153 503 28.4 64.6 3.1 3.1 0.0 0.0 0.8
MC-13c-160-162 514 45.6 40.1 3.3 6.1 0.0 0.0 4.9
MC-14-0-15 525.5 50.8 37.3 2.6 6.5 0.0 0.7 2.1
      Table 5 ? Relative abundance of grain types based on point-counts of selected samples 
from the study section.  
 
  
             
 
 
 
 49
Sample
 name
Height in 
section
 (cm)
% 
Matrix
% 
Glauconite
%
 Quartz
% Fossil 
Fragments
% 
Phosphate
% 
Pyrite
% 
Other
MC-15-3-7 538 33.0 56.3 2.3 10.3 0.0 0.7 0.0
MC-15-60-68 597 63.4 17.4 2.1 7.4 0.0 2.4 7.4
MC-15-65-72 601.5 77.6 13.3 2.0 5.2 0.0 1.7 0.1
MC-15-75-80 610.5 56.3 35.8 1.7 6.2 0.0 1.4 0.0
MC-15-85-90 620.5 59.7 35.2 3.8 2.0 0.0 3.4 0.0
MC-16b-bottom 634 64.9 32.8 0.3 3.1 0.0 1.6 0.0
MC-16b-top 653 66.6 31.5 0.0 2.8 0.0 0.0 0.0
MC-16c-35-42 661.5 82.5 14.4 0.3 0.6 0.0 2.7 0.0
MC-16d-42-47 667.5 77.0 18.9 0.0 4.8 0.0 3.0 0.0
MC-16f-53-72 686 79.7 17.6 0.3 2.0 0.0 0.7 0.0
MC-16g-72-78 698 84.2 12.2 0.0 1.0 0.0 2.6 0.0
MC-16h-78-92 708 88.1 5.4 0.0 5.4 0.0 1.0 0.0
MC-17-0-15 728.5 18.7 71.8 7.5 6.6 0.0 0.0 0.0
MC-17-15-20 738.5 45.8 53.4 0.0 3.2 0.0 0.0 0.0
MC-17-20-25 743.5 41.9 58.7 0.3 5.6 0.0 0.0 0.0
MC-17-70-80 796 76.6 21.9 0.0 2.5 0.0 0.0 0.0
MC-17-80-90 806 78.6 20 0.0 2.1 0.0 0.0 0.0
MC-17-90-95 813.5 39.2 52.5 6.5 7.2 0.0 0.0 0.0
MC-18-5-20 828.5 74.0 16.9 6.0 3.6 0.0 0.0 0.0
MC-19-47-55 887 61.2 32 5.4 3.4 0.0 0.0 0.0
MC-20-0-5 928.5 80.1 7.9 7.2 4.0 0.0 0.0 0.8
MC-22-0-13 971.5 94.3 0.6 1.9 3.1 0.0 0.0 0.0
MC-23-5-10 991.5 92.9 3 3.3 1.8 0.0 0.0 0.0
MC-23-15-20 1001.5 90.4 2.6 4.5 2.6 0.0 0.0 0.0
MC-24-0-12 1015 90.0 4 2.0 4.0 0.0 0.0 0.0
MC-25-5-10 1028.5 96.0 1.9 0.6 1.5 0.0 0.3 0.0
MC-26-0-8 1045 90.1 1.6 3.3 5.0 0.0 0.0 0.1
MC-27-20-24 1071 97.2 0 1.1 1.7 0.0 0.0 0.0
MC-28-1-11 1079.5 96.8 0 1.4 1.8 0.0 0.0 0.0
MC-29-15-20 1102.5 96.6 0 0.0 3.4 0.0 0.0 0.0
MC-30-1-8 1108.5 95.8 0 4.2 0.0 0.0 0.0 0.0
Table 5 ? Continued.  
 
 
 
 
 
 
 
 50
02550 75 100
% Glauconite
01020
% Skeletal 
grains
1
2
3
4
a
b
c
a
b
c
20 40 60 80
% Sand
H
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t
 
in s
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0
H
e
igh
t
 
in s
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c
t
i
o
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 (
m
et
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)
 
 
 
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
                       
   
 
 
 
 
 
Figure 16 ? Percent sand, percent glauconite, and percent skeletal grains (including 
glauconitized grains) in the study section. Dashed and dot-dashed lines define boundaries 
of cycles and mini-cycles, respectively. Section legend is shown in figure 6. 
 
 
 51
bivariate plot of sand versus glauconite shows a positive correlation (Fig.17). In contrast, 
glauconite shows a weak inverse relationship with carbonate content (Fig. 18).  
Quartz grains fall within the fine- to medium-grained range. They are typically 
angular to subangular, monocrystalline, and nonundulose.  
Skeletal allochems recognized include foraminifers and bivalve, echinoderm 
(echinoid spines), and bryozoan fragments. Skeletal grain abundance increases upward 
through the transgressive systems tract (units 3-8), reaches a peak in the condensed 
section (units 9-11), and generally decreases through the highstand systems tract (units 
12-30) (Fig. 16). In the condensed section and highstand systems tract, abundance of 
skeletal allochems is generally proportional to percent glauconite, particularly within 
cycles 2 and 3. Replacement of fossil fragments by glauconite is common in the 
condensed section and lower part of highstand systems tract (units 8-13) and gradually 
decreases upward (see Chapter 6).  
Diagenetic components other than glauconite include phosphate grains and pyrite. 
Abundance of phosphatic grains decreases gradually upward through the bulk of the 
transgressive systems tract (units 3-7) and then increases abruptly to a maximum in unit 8 
(top of cycle 1) (Fig. 19). Phosphate decreases through the condensed section and 
lowermost part of highstand systems tract. No phosphatic grains were recognized above 
unit 13. Pyrite is common only in units 4-6, 13, and 15-16, in the middle to upper 
portions of cycles 1-3 (Fig. 19). Notably, pyritiferous intervals in cycles 2 and 3 
correspond to relatively glauconite-poor and organic-rich intervals (compare Figs. 14, 16, 
and 19). 
 
 52
0
20
40
60
80
100
2040608010
% Carbonate
%
 Gl
au
co
n
i
te
R
2
 = 0.087 
0
20
40
60
80
100
0 10203040506070
% S a n d
%
 Gl
au
co
n
i
t
e
R
2
 = 0.42 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 17 ? Percent glauconite vs. percent sand in the samples. 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
             Figure 18 ? Relationship between percent carbonate and percent glauconite. 
 
 
 
 
 53
020406080
% Sand
H
e
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g
ht
 
i
n
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m
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19
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1
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7
8
9
10
11
a
b
c
1
2
3
4
a
b
c
a
b
c
0
4 812
% Phosphate
024
% Pyrite
H
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i
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i
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t
i
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n (
m
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t
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r
s
)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 19 ? Relationship between percent sand, percent phosphate, and percent pyrite 
in the study section. Dashed and dot-dashed lines define boundaries of cycles and mini-
cycles, respectively. Section legend is shown in figure 6. 
 
 
 54
5.5 Summary and Interpretation 
The observations described above support the general sequence stratigraphic 
interpretations for the study section. Units 9-11 were identified as the condensed section 
based on peak glauconite abundance (Fig. 16). This interpretation is supported by 
maxima in skeletal grain abundance (Fig. 16) and sand-grain size (Fig. 13) and by 
relatively high concentrations of phosphatic grains (Fig. 19) in this interval. Like 
glauconite, these parameters reflect limited supply of clastic sediment and/or winnowing. 
General trends towards decreased glauconite content, skeletal grain abundance (Fig. 16), 
sand percent, and mean sand size through the interval above unit 11 (Fig. 13) reflect a 
progressive increase in the influx of finer clastic sediments and limited winnowing of 
finer-grained sediments. These trends are consistent with a highstand systems-tract 
succession.  
Observations also help to delineate parasequences that likely record 4
th
?order 
relative sea-level fluctuations. The aforementioned asymmetrical sand/glauconite cycles, 
particularly cycles 2 through 4, are interpreted as parasequences (Fig. 20). In this 
interpretation, the boundaries between cycles 1-4 are inferred to be marine flooding 
surfaces (Fig. 20). Abrupt increases in sand percent, mean sand size, and glauconite 
content (Figs. 13, 14, 20) across these surfaces represent phases of rapid sea-level rise 
and sediment starvation. Gradual decreases in these same parameters above each surface 
reflect progressive increases in clastic sediment flux associated with phases of slower 
transgression, sea-level stillstand, or perhaps minor regression. Parasequence delineation 
is supported by trends in the relative abundance of skeletal allochems and organic carbon. 
Skeletal allochems are generally more common near parasequence bases (Fig. 16),  
 55
02550 75 100
% Glauconite
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
1
2
3
4
a
b
c
a
b
c
020406080
% Sand
SMS/FS
Condensed 
section
HS
T
LS
T
SB/TS
FS
FS
TS
T
HST
Shallowing
Deepening
Parasequence 1
Parasequence 2
Parasequence 3
Parasequence 4
H
e
igh
t
 in 
s
e
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t
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(
m
et
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s
)
H
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igh
t
 in 
s
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t
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(
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et
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s
)
H
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igh
t
 in 
s
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c
t
i
o
n
 
(
m
et
e
r
s
)
HS
T
LS
T
TS
T
HST
HS
T
LS
T
TS
T
HST
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 20 ? Stratigraphic column and inferred sea-level curves for the Clayton 
Formation. HST-Highstand systems tract; LST-Lowstand systems tract; TST-
Transgressive systems tract; SB-Sequence boundary; TS-Transgressive surface; SMS-
Surface of maximum starvation; FS-Flooding surface. Dashed lines define boundaries of 
cycles, here inferred to the parasequence bounding flooding surfaces. Dot-dashed lines 
define boundaries of mini-cycles, which may correspond to higher-order sea-level 
fluctuations. Section legend is shown in figure 6. 
 
 56
reflecting limited dilution by clastic sediments. Organic carbon contents are generally 
higher in upper parts of parasequences (Fig. 14), perhaps reflecting increased 
preservation of organic matter associated with higher sedimentation rates. The 
relationships between inferred parasequences, sea-level dynamics, and limestone 
formation are problematic and will be addressed in subsequent discussion (Chapter 7).  
Two of the sedimentary cycles (parasequences 2 and 4) contain minicycles (2a, b, 
and c; 4a, b, and c) defined by smaller-scale asymmetrical cycles in sand content and 
glauconite. These minicycles are interpreted to reflect shorter-term, 5
th
?order sea-level 
variations (Fig. 20).  
The observations presented thus far indicate that glauconite is nearly ubiquitous 
throughout the study section. However, glauconite abundance varies considerably as a 
function of sea-level changes and can be used to delineate systems tracts and 
parasequences. The following chapter focuses on the relationship between sequence 
stratigraphic packages and glauconite morphotypes, color, and chemistry. 
 
 
 
 
 
 
 
 
 
 57
 
 
 
6.0 CHARACTER OF GLAUCONITE 
6.1 Introduction  
 As noted above, glauconite is nearly ubiquitous throughout the study section, but 
its abundance varies significantly between systems tracts and parasequences. The goal of 
this chapter is to examine variations in the character of glauconite through the section. 
This includes modes of glauconite occurrence, color, chemistry, and x-ray diffraction 
signature.   
6.2 Modes of Glauconite Occurrence  
 Glauconite in the study section occurs mainly as distinct grains of various 
morphotypes for which original precursor grains are not readily apparent. It also occurs 
as coatings on detrital grains, as a product of skeletal grain replacement, and locally as 
part of fine-grained matrix. 
6.2.1 Glauconite Morphotypes  
Examination of sand samples under a binocular microscope indicates that most 
previously recognized glauconite grain morphotypes (Table 1) are represented in the 
study section. These include capsule-shaped, mammillated, lobate, ovoidal, vermicular, 
tabular, and composite grains (Fig. 21). Capsule-shaped grains are crudely cylindrical and 
exhibit relatively deep, commonly transverse surface cracks (Fig. 21A). Mammillated 
grains are highly irregular grains with numerous surface protuberances separated by 
cracks (Fig. 21B). Lobate grains are similar to mammillated grains, but have deeper  
 58
E
C
A B
D
F
 
 
Figure 21 ? Different grain morphotypes as viewed in reflected light. (A) Capsule-shaped 
grains. (B) Mammillated grains. (C) Lobate grains. (D) Ovoidal grains. (E) Vermicular 
grains. (F) Tabular grains (arrows). Bar scales are ~ 1 mm long.  
 
 
 
 59
cracks (Fig. 21C). Cracks observed on capsule-shaped, mammillated, and lobate grains 
typically are partially healed with lighter green glauconite. Ovoidal grains are 
equidimensional and exhibit relatively smooth, rounded surfaces (Fig. 21D). Vermicular 
grains generally are elongate, curved, and are longitudinally segmented (Fig. 21E). 
Tabular grains generally are flat or platy and commonly exhibit smooth surfaces (Fig. 
21F). Composite grains are aggregates of detrital grains cemented by a glauconitic 
matrix.  
Identification of grain morphotypes generally requires three-dimensional views 
and, hence, is difficult in thin-section analysis. Although many glauconite grains 
observed in two-dimensional thin-section views could not be classified based on their 
two-dimensional geometry, most could be placed into four morphological categories. 
These are mammillated/lobate grains (Figs. 22A,C, 23A,B),  capsule-shaped grains (Figs. 
22A,B, 23C), vermicular/tabular grains (Figs. 22C, 23D), and ovoidal grains (Fig. 22D). 
As viewed in thin section, the interiors of most glauconite grains are characterized by 
homogeneous, randomly oriented microcrystalline aggregates. In backscattered scanning 
electron images generated prior to microprobe analysis, compositional zonation is 
observed in some glauconite grains (Fig. 23).   
The normalized percentages of the four glauconite grain types recognized in thin 
section are given in the Table 6. These data are plotted versus stratigraphic height and 
total glauconite abundance in Figures 24 and 25. Overall, mammillated/lobate and 
capsule-shaped grains are the most common grain types observed. The relative 
abundances of these grains types generally are proportional to total glauconite content 
(Fig. 24). Both types are relatively rare in the lowstand incised valley fill (Clayton sand)  
 60
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 22 ? Photomicrographs showing different glauconite grain types.                           
(A) Mammillated/lobate (Ma) and capsule-shaped (Ca) grains. (B) Capsule-shaped grains 
(Ca). (C) Vermicular/tabular (Ve) and mammillated/lobate (Ma) grains. (D) Ovoidal (Ov) 
grain. Bar scales are ~ 1 mm long.  
 
 
 
 
 
 
 
 
 
Ve
Ma
C
Ca
A
Ma
B
Ov
D
Ca
 61
A
B
C
D
E
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 23 ? Backscattered electron images of different glauconite morphotypes. (A and 
B) Mammillated/lobate grains revealing compositional zonation. Brighter areas in the 
grains represent higher average atomic number and Fe content. (C) Capsule-shaped grain. 
(D) Vermicular/tabular grain. (E) Ovoidal grain.  
 
 
 62
Sample
 name
Height in 
section
 (cm)
% 
Mammilated/
Lobate
% 
Vermicular/
Tabular
%
 Capsule-
shaped
%
 Ovoidal
MC-2-0-5 20.5 20.0 6.7 0.0 73.3
MC-3-28-35 94.5 19.0 2.4 9.5 69.0
MC-4-12-17 118 25.0 25.0 25.0 25.0
MC-5-25-35 153 5.1 20.5 7.7 66.7
MC-6-18-25 184.5 0.0 16.7 0.0 83.3
MC-8-0-5 215.5 3.8 15.4 0.0 80.8
MC-8-10-20 228 6.9 10.3 0.0 82.8
MC-8-20-25 235.5 39.6 16.7 10.4 33.3
MC-8-30-40 248 53.3 5.6 39.3 1.9
MC-9-0-3 254.5 52.6 21.6 21.6 4.3
MC-9-13-25 273 56.7 2.2 41.0 0.0
MC-10-0-15 285.5 63.9 6.9 26.4 2.8
MC-11-0-1
293.5 66.4 7.8 25.8 0.0
MC-11-5-7 299 51.9 6.2 42.0 0.0
MC-11-12-18 308 36.4 27.3 36.4 0.0
MC-11-24-29 319 60.7 8.9 30.4 0.0
MC-12-3-17 333 75.9 4.6 19.5 0.0
MC-13a-10-20
368 41.7 45.8 8.3 4.2
MC-13a-35-45 393 30.0 70.0 0.0 0.0
MC-13a-45-55 403 44.4 11.1 11.1 33.3
MC-13a-55-65 413 10.5 57.9 0.0 31.6
MC-13b-70-75 425.5 0.0 100.0 0.0 0.0
MC-13c-115-125 473 52.3 17.4 25.6 4.7
MC-13c-140-147 498 41.5 27.7 27.7 3.1
MC-13c-147-153 503 31.9 41.5 6.4 20.2
MC-13c-160-162 514 25.4 47.6 17.5 9.5
MC-14-0-15 525.5 22.2 66.7 11.1 0.0
Table 6 ? Normalized percentages of assignable glauconite grain types derived from 
point-count data.  
 
 
 
 
 
 63
Sample
 name
Height in 
section
 (cm)
% 
Mammilated/
Lobate
% 
Vermicular/
Tabular
%
 Capsule-
shaped
%
 Ovoidal
MC-15-3-7 538 30.9 41.2 16.5 11.3
MC-15-60-68 597 0.0 20.0 20.0 60.0
MC-15-65-72 601.5 0.0 0.0 0.0 0.0
MC-15-75-80 610.5 12.5 62.5 0.0 25.0
MC-15-85-90 620.5 77.8 22.2 0.0 0.0
MC-16b-bottom 634 0.0 100.0 0.0 0.0
MC-16b-top 653 0.0 0.0 0.0 100.0
MC-16c-35-42 661.5 0.0 100.0 0.0 0.0
MC-16d-42-47 667.5 14.3 85.7 0.0 0.0
MC-16f-53-72 686 0.0 66.7 0.0 33.3
MC-16g-72-78 698 0.0 100.0 0.0 0.0
MC-16h-78-92 708 0.0 100.0 0.0 0.0
MC-17-0-15 728.5 38.8 40.0 20.0 1.3
MC-17-15-20 738.5 40.0 46.7 8.9 4.4
MC-17-20-25 743.5 65.1 30.2 4.7 0.0
MC-17-70-80 796 0.0 100.0 0.0 0.0
MC-17-80-90 806 0.0 100.0 0.0 0.0
MC-17-90-95 813.5 34.6 53.8 7.7 3.8
MC-18-5-20 828.5 33.3 63.0 3.7 0.0
MC-19-47-55 887 14.3 74.3 8.6 2.9
MC-20-0-5 928.5 28.6 57.1 14.3 0.0
MC-22-0-13 971.5 0.0 0.0 0.0 0.0
MC-23-5-10 991.5 50.0 50.0 0.0 0.0
MC-23-15-20 1001.5 0.0 0.0 0.0 0.0
MC-24-0-12 1015 16.7 83.3 0.0 0.0
MC-25-5-10 1028.5 0.0 0.0 0.0 0.0
MC-26-0-8 1045 0.0 0.0 0.0 0.0
MC-27-20-24 1071 0.0 0.0 0.0 0.0
MC-28-1-11 1079.5 0.0 0.0 0.0 0.0
MC-29-15-20 1102.5 0.0 0.0 0.0 0.0
MC-30-1-8 1108.5 0.0 0.0 0.0 0.0
Table 6 ? continued. 
 
 
 
 64
020406080
% Mammillated/lobate
grains
0 25 50
% Capsule-shaped
grains
02550 75 100
% Glauconite
1
2
3
4
a
b
c
a
b
c
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in s
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 (
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11
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13
14
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19
21
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25
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0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
H
e
igh
t
 
in s
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t
i
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 (
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et
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s
)
H
e
igh
t
 
in s
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t
i
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n
 (
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et
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r
s
)
H
e
igh
t
 
in s
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c
t
i
o
n
 (
m
et
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r
s
)
H
e
igh
t
 
in s
e
c
t
i
o
n
 (
m
et
e
r
s
)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 24 ? Percent total glauconite, percent mammillated/lobate grains, and percent 
capsule-shaped grains in the study section. Dashed and dot-dashed lines define 
boundaries of parasequences (1-4) and mini-cycles (2a-c, 4a-c), respectively. Section 
legend is shown in figure 6.   
 
 
 65
0 25 50 75 100
% Vermicular/tabular 
grains
0 25 50 75 100
% Ovoidal grains
0 25 50 75 100
% Glauconite
1
2
3
4
a
b
c
a
b
c
H
e
i
g
ht
 
i
n
 s
e
ctio
n (
m
e
t
e
r
s)
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
H
e
i
g
ht
 
i
n
 s
e
ctio
n (
m
e
t
e
r
s)
H
e
i
g
ht
 
i
n
 s
e
ctio
n (
m
e
t
e
r
s)
H
e
i
g
ht
 
i
n
 s
e
ctio
n (
m
e
t
e
r
s)
H
e
i
g
ht
 
i
n
 s
e
ctio
n (
m
e
t
e
r
s)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 25 ? Percent total glauconite, percent vermicular/tabular grains, and percent 
ovoidal grains in the study section. Dashed and dot-dashed lines define boundaries of 
parasequences (1-4) and mini-cycles (2a-c, 4a-c), respectively. Section legend is shown 
in figure 6. 
 
 66
and transgressive system tract (units 1-8) but increase abruptly to maxima in the 
condensed section. In general, both types progressively decrease in relative abundance 
upward through the highstand systems tract. However, abundances vary systematically 
through parasequences 2 through 4. Within each parasequence, relative abundances of 
mammillated/lobate and capsule-shaped grains are highest in the lower parts and decrease 
upwards (Fig. 24).  
Distribution of vermicular/tabular grains is opposite of that of mammillated/lobate 
and capsule-shaped grains. Relative abundances of vermicular/tabular grains increase 
upward through the section in general, and upward through each parasequence. The latter 
pattern is most obvious in parasequences 2 and 3 (Fig. 25).  
Ovoidal grains have a very different distribution (Fig. 25). They are the dominant 
glauconite grain type in the lowstand incised valley fill (Clayton sand). However, with 
the exception of isolated horizons in the highstand systems tract (e.g., in parasequence 3) 
they are rare or absent altogether in the remainder of the section (Fig. 25). 
6.2.2 Glauconite-Coated Grains 
In thin section, glauconite is observed as grain coatings on detrital grains, 
principally quartz (Fig. 26). Coatings vary in thickness and may be continuous or 
discontinuous around grain perimeters. Glauconite-coated quartz grains also commonly 
contain very thin glauconite-filled fractures (Fig. 26).  
The relative abundances of glauconite-coated detrital grains in point-counted 
samples are provided in Table 7, and the stratigraphic distribution of these grains is 
shown in Figure 27. Relative abundances of coated grains generally vary with total  
 
 67
 
 
 
 
 
 
 
 
 
 
Figure 26 ? Photomicrograph showing glauconite coatings on and fracture fillings in 
quartz (Q). Bar scale is ~ 1 mm long.  
 
 
 
 
 
 
 
 
 
 
 
 
Q
 68
Table 7 ? Abundances of glauconitized skeletal grains and glauconite-coated detrital 
grains based on point-count analysis.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Sample
 name
Height in 
section
 (cm)
% 
Coated detrital 
grains
%
 Replaced Skeletal
 grains
MC-2-0-5 20.5 0.3 0.6
MC-3-28-35 94.5 7.3 1.4
MC-4-12-17 118 0.0 0.0
MC-5-25-35 153 2.9 0.8
MC-6-18-25 184.5 0.3 1.1
MC-8-0-5 215.5 0.6 0.8
MC-8-10-20 228 0.0 1.6
MC-8-20-25 235.5 6.9 1.9
MC-8-30-40 248 2.4 12.3
MC-9-0-3 254.5 4.8 12.5
MC-9-13-25 273 1.7 6.9
MC-10-0-15 285.5 1.5 4.5
MC-11-0-1
293.5 10.2 16.4
MC-11-5-7 299 11.5 10.8
MC-11-12-18 308 6.0 12.7
MC-11-24-29 319 3.6 8.8
MC-12-3-17 333 0.3 6.6
MC-13a-10-20
368 2.8 1.5
MC-13a-35-45 393 0.0 0.0
MC-13a-45-55 403 0.0 0.3
MC-13a-55-65 413 0.0 0.0
MC-13b-70-75 425.5 0.0 0.0
MC-13c-115-125 473 6.7 0.3
MC-13c-140-147 498 2.9 1.4
MC-13c-147-153 503 14.4 0.9
MC-13c-160-162 514 6.7 0.3
MC-14-0-15 525.5 2.0 2.0
 69
Table 7 ? Continued.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Sample
 name
Height in 
section
 (cm)
% 
Coated detrital 
grains
% 
Replaced Skeletal 
grains
MC-15-3-7 538 4.0 2.3
MC-15-60-68 597 0.6 0.0
MC-15-65-72 601.5 2.0 0.0
MC-15-75-80 610.5 9.2 2.8
MC-15-85-90 620.5 0.3 0.3
MC-16b-bottom 634 12.3 2.6
MC-16b-top 653 18.5 1.3
MC-16c-35-42 661.5 0.0 0.3
MC-16d-42-47 667.5 4.4 3.7
MC-16f-53-72 686 5.3 0.0
MC-16g-72-78 698 0.0 0.0
MC-16h-78-92 708 2.6 0.0
MC-17-0-15 728.5 17.0 5.4
MC-17-15-20 738.5 15.1 2.4
MC-17-20-25 743.5 16.8 5.4
MC-17-70-80 796 6.2 1.1
MC-17-80-90 806 5.9 0.7
MC-17-90-95 813.5 10.6 5.3
MC-18-5-20 828.5 0.4 0.8
MC-19-47-55 887 5.8 2.2
MC-20-0-5 928.5 0.0 0.0
MC-22-0-13 971.5 0.0 0.0
MC-23-5-10 991.5 0.0 0.9
MC-23-15-20 1001.5 2.6 0.0
MC-24-0-12 1015 2.0 0.0
MC-25-5-10 1028.5 0.3 0.3
MC-26-0-8 1045 1.3 0.0
MC-27-20-24 1071 0.0 0.0
MC-28-1-11 1079.5 0.0 0.0
MC-29-15-20 1102.5 0.0 0.0
MC-30-1-8 1108.5 0.0 0.0
 70
 
 
Figure 27 ? Percent total glauconite, percent glauconite-coated detrital grains, and 
percent glauconitized skeletal grains in the study section. Dashed and dot-dashed lines 
define boundaries of parasequences and mini-cycles, respectively. Section legend is 
shown in figure 6. 
 
 
01020
% Glauconite-coated 
grains
01020
% Glauconitized skeletal 
grains
0 25 50 75 100
% Glauconite
1
2
3
4
a
b
c
a
b
c
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
H
e
igh
t
 in 
s
e
c
t
i
o
n
 
(
m
et
e
r
s
)
 71
glauconite content. Coated grains are most common in the lower parts of parasequences 
and of mini-cycles therein.  
6.2.3 Glauconitized Skeletal Grains  
A variety of originally carbonate skeletal fragments have been partly or wholly 
replaced by glauconite (Fig. 28). These include foraminifers (Fig. 28A) and bivalve (Fig. 
28B), bryozoan (Fig. 28C), and echinoid spine (Fig. 28D) fragments. In addition to 
replacement of original calcite, glauconite also commonly fills intraparticle pore space 
(e.g., foramenifer chambers, stereom, etc.) within these carbonate grains.  
The relative abundances of glauconitized skeletal grains in point-counted samples 
are provided in Table 7, and the stratigraphic distribution of these grains is shown in 
Figure 27. As with coated grains, the abundance of replaced skeletal fragments generally 
varies with total glauconite content. Notably, peak abundances (>10% of rock volume) 
are associated with the condensed section, which contains the greatest percentage of 
skeletal fragments in general (Fig. 16).  
6.2.4 Relationships to Systems Tracts and Parasequences 
 Observations described above indicate that the relative abundances of glauconite 
grain varieties do vary with inferred changes in sea-level and sedimentation rates and, 
hence, can be of use in delineating systems tracts and parasequences. Capsule-shaped, 
mammillated, and lobate grain morphotypes, all of which contain glauconite-healed 
cracks, are regarded as relative mature varieties and are indicative of relatively slow 
sedimentation rates. In contrast, vermicular grains are considered to be indicative of 
lower maturity (Huggett and Gale, 1997) and, hence, limited sediment starvation. As 
expected, the relative abundances of these grain types (Figs. 24 and 25) clearly reflect  
 72
 
 
 
 
Figure 28 ? Photomicrographs showing glauconitized fossil fragments. (A) Glauconite 
infilling and partially replacing foraminifer (Fo). (B) Glauconite replacing shell fragment 
(SF). (C) Glauconitized bryozoan (Br). (D) Echinoderm fragment (echinoid spine) (Ec) 
partially replaced and infilled with glauconite. Bar scales are ~ 0.5 mm long.     
 
 
 
 
 
 
 
C
D
Fo
A
SF
B
Br Ec
 73
decreasing maturity through the highstand system tract in general and upward through 
each parasequence. 
 Ovoidal grains may acquire their shape in several ways. They may reflect the 
reworking and rounding of other grain morphotypes (detrital glauconite) or inherit their 
shape from precursor grains (Triplehorn, 1966; Hugget and Gale, 1997; Amorosi, 1997).  
The abundance of ovoidal grains in the incised valley fill (unit 1, Clayton sand) and the 
transgressive systems tract (units 2-8) likely reflect reworking of glauconite grains in 
relatively shallow settings during early stages of sea-level rise. Other peaks in abundance 
of ovoidal grains (i.e., in units 15 and 16) also may reflect detrital glauconite associated 
with reworking near the upper part of parasequence 2. Alternatively, these peaks may 
reflect inherited morphologies related to glauconite infilling of foram chambers or other 
fossil cavities or replacement of fecal pellets.  
 Glauconitized skeletal fragments are most abundant in the condensed section. 
However, the abundances of these and glauconite-coated detrital grains are generally 
proportional to total glauconite content and to abundances of relatively mature grain 
morphotypes. Therefore, common glauconitized carbonate grains and coated detrital 
grains also appear to be indicative of significant sediment starvation and could be 
employed in delineating sequence stratigraphic packages.    
6.3 Glauconite Grain Color 
Glauconite color was assessed based on observations of sand fractions under 
reflected light and of thin sections viewed under plane-polarized transmitted light. 
Although quantitative color analyses of glauconite-grain separates may be a productive 
pursuit for future work, only qualitative observations were made for the current study. 
 74
 Although grains in the upper oxidized part of the section tend to be reddish-
brown, most glauconite grains in the study interval are various shades of light to dark 
green. Shades of green may vary within a single grain (e.g., glauconitic fracture fills tend 
to be lighter green than glauconite host grains; see Fig. 21) and among glauconite grains 
within a single sample (Fig. 21F). Nonetheless, some general color trends can be 
discerned throughout the study section and within parasequences. Glauconite grains 
throughout parasequences 1 and 2 are generally medium to dark green. However, 
glauconite grains generally change from medium to dark green to light green to light 
greenish brown from the bases to the tops of parasequences 3 and 4 (Figs. 27, 30). Hence, 
general glauconite color does appear to reflect sea-level controlled changes in 
sedimentation rate and glauconite maturity. 
6.4 Glauconite Chemistry 
Ten grains from each of thirteen samples were subjected to microprobe analysis. 
Three samples fall within the top of parasequence 1, five samples are from parasequence 
2, and five samples are from parasequence 3. Average abundances of major oxides for 
each sample are listed in Table 8. As expected, the data show a strong positive correlation 
between FeO and K
2
O and inverse relationships between Al
2
O
3
 and FeO and K
2
O (Fig. 
31).  
K
2
O contents of glauconite are plotted versus stratigraphic height in Figure 32. 
Averaged K
2
O contents for twelve of the samples fall between 6 and 8%, indicating that 
the glauconite is evolved. The remaining sample, which is stratigraphically highest, has 
an average K
2
O content of 4.8%, indicating slightly evolved glauconite. In the context of 
parasequences 2 and 3, K
2
O contents are highest at the base and decrease significantly  
 75
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 29 ? Reflected light photographs showing color variation of glauconite grains in 
parasequences. (A) Bottom and (B) top of parasequence 2. (C) Bottom and (D) top of 
parasequence 3. (E) Bottom and (F) top of parasequence 4. Samples in A, B, C, D, E, and 
F are from unit 9, lower and upper parts of unit 13, unit 16, unit 17, and unit 23, 
respectively. Bar scales are ~ 1 mm long. 
 
 
 
 
FE
DC
BA
 76
 
 
Figure 30 ? Plane-light photomicrographs showing color variation of glauconite grains in 
parasequences. (A) Bottom and (B) top of parasequence 2. (C) Bottom and (D) top of 
parasequence 3. (E) Bottom and (F) top of parasequence 4. Samples in A, B, C, D, E, and 
F are from unit 9, lower and upper parts of unit 13, unit 16, unit 17, and unit 23, 
respectively. Bar scales are ~ 1 mm long.  
 
 
G
G
G
G
G
G
G
A
B
C
F
E
D
 77
Sample name
Sample 
no.
Height in 
section 
(cm) SiO2 %Al2O3 % FeO % MgO % CaO % Na2O % K2O % Total
MC-8-0-5 13 215.5 47.07 5.87 24.30 3.82 0.44 0.02 6.35 87.87
MC-8-10-20 14 228 49.55 4.33 25.41 4.12 0.31 0.02 7.56 91.29
MC-8-20-25 15 235.5 50.10 5.41 24.25 3.59 0.58 0.02 6.72 90.71
MC-8-30-40 16 248 49.00 4.04 25.31 3.77 0.40 0.02 7.16 89.69
MC-9-0-3 17 254.5 49.59 4.81 25.15 4.03 0.63 0.01 7.29 91.51
MC-9-13-25 18 273 47.43 4.50 25.89 3.93 0.64 0.01 7.18 89.57
MC-11-24-29 27 319 42.34 4.45 23.19 3.79 0.97 0.02 6.29 87.71
MC-13-45-55 33 403 50.73 7.49 22.58 3.95 1.02 0.01 6.20 91.98
MC-13c-147-153 43 503 48.00 4.80 24.60 3.90 0.65 0.03 7.20 89.22
MC-14-0-15 45 525.5 49.50 6.50 22.80 3.85 0.72 0.03 6.00 89.36
MC-15-8-13 47 543.5 47.20 5.70 24.50 3.96 0.86 0.01 6.40 88.75
MC-15-60-68 53 597 48.73 6.85 21.70 3.85 1.03 0.02 6.06 88.24
MC-16b-top 60 653 49.10 9.10 18.80 3.99 1.17 0.04 4.80 86.99
Table 8 ? Average abundances (weight percent) of major oxides in glauconite grains as 
determined by microprobe analysis.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
.  
 
 
 
 
 
 
 
 
 
 
 
 
 78
4
6
8
10
468
Fe
O
%
Al
2
O
3
%
K
2
O%
15
20
25
30
R
2
= 0.79
R
2
= 0.88
Fe
O
%
Al
2
O
3
%
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 31 ? Relationships among average oxide contents for thirteen glauconite samples 
 
 
 
 
 
 
 
 79
468
K
2
O%
02550 75 100
1
2
3
4
a
b
c
a
b
c
020406080
% Sand
H
e
i
g
h
t
 
i
n
 s
e
ct
io
n (
m
e
t
e
r
s)
1
2
3
4
5
6
7
8
9
11
12
13
14
15
16
17
18
19
21
23
25
27
29
0
1
2
3
4
5
6
7
8
9
10
11
a
b
c
% Glauconite
H
e
i
g
h
t
 
i
n
 s
e
ct
io
n (
m
e
t
e
r
s)
H
e
i
g
h
t
 
i
n
 s
e
ct
io
n (
m
e
t
e
r
s)
H
e
i
g
h
t
 
i
n
 s
e
ct
io
n (
m
e
t
e
r
s)
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Figure 32 ? Percent sand, percent glauconite, and K
2
O % in the study section. Dashed 
and dot-dashed lines define boundaries of parasequences and mini-cycles, respectively. 
Section legend is shown in figure 6. 
 
 
 80
towards the middle and top. This is consistent with increasing sedimentation rate and 
associated reduction in glauconite maturity upward through the parasequences. Hence, 
the available data suggest that relative glauconite maturity based on elemental analysis 
may be of use in delineating parasequences. 
6.7 XRD Analysis 
A total of eight samples were selected for XRD analysis. Four of these samples 
are derived from the condensed section and lower part of the highstand systems tract 
(parasequence 2), while the other four are derived from higher in the section 
(parasequence 4).  
Diffractograms for the first four samples, shown in ascending stratigraphic order 
in Figure 33, reveal little obvious differences from the bottom to the top of the 
parasequence 2. All are dominated by glauconite mica peaks centered at ~10 ? and 4.52 
?. Only the diffractogram for the upper sample has a weakly defined smectite peak (at 
~14 ?). Diffractograms from the two middle samples manifest weak peaks (at ~7.05 ?) 
that may reflect berthierine, an Fe-rich clay commonly associated with glauconite.  
Diffractograms for samples from parasequence 4 are shown in ascending 
stratigraphic order in Figure 34. No obvious differences can be detected through the 
parasequence. However, diffractograms for this parasequence do differ from those of 
parasequence 2. In general, peaks inferred to reflect smectite and berthierine are more 
prominent in parasequence 4 (see Fig. 35 for ready comparison).   
X-ray diffraction results reveal little obvious change in structural state of 
glaucony through the two parasequence. This suggests that the XRD approach may not be 
sensitive enough to detect changes in sedimentation rate and glauconite maturity  
 81
 
 
Figure 33 ? X-ray diffractograms derived from the parasequence 2. Note changes in 
expression of glauconite peaks (at ~10? and ~4.55 ?) and eventual appearance of 
smectite peak (at~14?) towards the top of the parasequence. Fe-rich clay mineral 
berthierine often occurs within the glaucony facies.  
 
 
 
Co
u
n
t
s
0
10
20
30
40
50
60
70
Glauconite
10.1
Glauconite 4.55
9-0-3
0
10
20
30
40
50
60
Co
u
n
t
s
Glauconite 
10.04
Glauconite 4.57
Berthierine
7.05 
9-13-25
0
10
20
30
40
50
60
Glauconite 
10.01
Glauconite 4.52
C
o
unt
s
11-24-29
Berthierine
7.05 
2?
0
10
20
30
40
50
60
70
80
90
100
110
Glauconite 10.0
Glauconite 4.52C
o
unt
s
Smectite 
14
13-45-55
4 6810 12 14 16 18 20
P
a
r
a
s
equ
enc
e
 2
top
bottom
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
C
o
unt
s
C
o
unt
s
C
o
unt
s
C
o
unt
s
P
a
r
a
s
equ
enc
e
 2
 82
 
 
 
Figure 34 ? X-ray diffractograms derived from the parasequence 4. Note the decrease of 
glauconite peak (at ~4.55?) peak and increase in smectite peak (at ~14?) towards the top 
of the parasequence.  
 
 
0
10
20
30
40
50
60
70
80
Glauconite
10.04
Smectite
14
Bertheirine
7.05
Glauconite 4.57
Co
u
n
t
s
4 6 810121416 18
20
2?
17-0-15
0
10
20
30
40
50
60
70
80
90
100
Co
u
n
t
s
Glauconite 
10
Smectite 
14
Berthierine
7.05 Glauconite 4.52
17-80-90
0
10
20
30
40
50
60
70
80
Glauconite 
10
Smectite 
14
Berthierine
7.05
Glauconite 4.50
Co
u
n
t
s
17-90-95
0
10
20
30
40
50
60
70
80
90
Glauconite 
10
Smectite
14
Berthierine
7.05 Glauconite 4.5
Co
u
n
t
s
19-82-86
top
P
a
r
a
s
e
qu
enc
e
 4
bottom
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
Co
u
n
t
s
P
a
r
a
s
e
qu
enc
e
 4
 83
 
 
 
 
 
 
 
 
 
Figure 35 ? X-ray diffractograms of samples from unit 9 (condensed section; base of 
parasequence 2) and unit 19 (middle of parasequence 4).  
 
 
 
 
 
 
 
2?
4
6 8 10 12
14 16 18 20
0
10
20
30
40
50
60
70
80
90
Glauconite 
10
Smectite
14
Berthierine
7.05 Glauconite 4.5
Co
u
n
t
s
19-82-86
0
10
20
30
40
50
60
70
Glauconite
10.1
Glauconite 4.55
9-0-3
C
o
unt
s
up s
e
c
t
i
o
n
Co
u
n
t
s
Co
u
n
t
s
C
o
unt
s
C
o
unt
s
up s
e
c
t
i
o
n
 84
associated with 4
th
-order sea-level fluctuations, at least for those recorded in the 
parasequences of the study section. However, following previous authors (Odin and 
Matter, 1981; Hugget and Gale, 1997; Kelly and Web, 1999), relatively high smectite 
contents (and, perhaps, berthierine contents) in the upper part of the section 
(parasequence 4) may be interpreted to reflect limited glauconitization. In this sense, the 
XRD approach may help to detect larger differences in relative sedimentation rate that 
occur at the systems tract scale.   
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 85
   
 
 
7.0 DISCUSSION  
7.1 Role of Glauconite in Delineating Sequence Stratigraphic Packages 
 The main intent of this thesis was to test two hypotheses: (1) the abundance and 
maturity of glauconite vary systematically through a depositional sequence in response to 
sea-level dynamics and associated changes in sedimentation rate; and (2) the abundance 
and maturity of glauconite vary systematically through individual parasequences in 
response to short-term changes in sea-level. Both of these hypotheses are supported by 
studies of a passive-margin sequence in the Lower Paleocene Clayton Formation. 
 Glauconite abundance and character vary in a predictable way through systems 
tracts in the Clayton sequence. Lowstand incised valley fill deposits (Clayton sand) are 
characterized by low abundances of glauconite, most of which is detrital. The bulk of the 
transgressive systems tract contains low to moderate amounts of glauconite, including 
detrital and authigenic grains. The condensed section is characterized by peak 
abundances of highly mature glauconite grains, which occur in association with coarsest 
sands and abundant skeletal debris. The highstand systems tract is characterized by an 
upward decrease in glauconite abundance and maturity as indicated by changes in 
abundance of grain morphotypes, color, and chemistry.   
 The abundance and character of glauconite also varies in a systematic way 
through parasequences. Within the condensed section/highstand system tract, 
paraseqences are expressed as asymmetrical cycles in glauconite abundance and maturity. 
 86
Bases of parasequences are dominated by relatively abundant, darker colored, K and Fe-
rich, mature grains. Total glauconite abundances and K and Fe contents decrease, 
abundances of immature glauconite morphotypes increase, and glauconite becomes 
lighter in color progressively towards parasequence tops.  
 These observations indicate that detailed studies of glauconite can be used to 
decipher changes in sea-level and sedimentation rate. Use of glauconite is best applied to 
relatively condensed passive-margin shelf sequences wherein glauconite is common and 
other sedimentologic evidence for sea-level dynamics is absent. 
7.2 Comparison with Previous Parasequence-Scale Studies 
Previous studies of glauconite at the parasequence scale include those by Ruffell 
and Wach (1998) and Urash (2005). Ruffell and Wach (1998) described two different 
types of parasequences in the Cretaceous Lower Greensand Group in southern England, 
only one of which contains glauconitic sediments (their type A parasequences). They 
noted that glauconite is restricted to the bases of these coarsening upward sequences. 
Urash (2005) focused on parasequences in a condensed sequence of fossiliferous, 
glauconitic muddy sand in the Eocene Lisbon Formation, southern Alabama. He noted 
that parasequences are reflected by transitions from coarser, glauconitic-rich sands at 
bases to finer-grained, less glauconitic sands at tops. In both of these earlier studies, 
workers focused on general sedimentology and ichnology, and they did not address 
glauconite morphotypes or any other indicators of glauconite maturity. Hence, to date, 
the current study of the Clayton Formation represents the most in-depth analysis of 
glauconite at the parasequence scale.  
 
 87
7.3 Comparison with Foreland Basin Parasequences  
As previously noted, parasequences are relatively conformable successions of 
genetically related beds or bedsets that reflect shorter-term sea-level fluctuations  They 
reflect upward shallowing and are bounded by marine flooding surfaces (Van Wagoner et 
al., 1988). In foreland basins, wherein sediment supply is relatively large, parasequences 
typically coarsen upwards in response to a seaward shift in shallow marine facies (e.g., 
Frey and Howard, 1990; Van Wagoner et al., 1990). The parasequences in the condensed 
passive-margin deposits described in the current study deviate from this general trend; 
Clayton parasequences are characterized by fining upward sequences. When viewed by 
itself, this textural pattern could be misinterpreted to reflect a progressive decrease in 
environmental energy or a deepening event. However, sediment textures in the Clayton 
Formation apparently do not reflect primary detrital grain size. Instead, sand fractions are 
composed primarily of authigenic glauconite. Hence, as previously noted by Urash 
(2005) for Eocene deposits, the glauconitization process can result in the formation of 
fining-upward parasequences in deeper shelf settings wherein sea-level controlled facies 
shifts are not recorded.   
7.4 Origin of the Clayton Limestones 
The occurrence of fine-grained, bedded and nodular limestones in the study 
section requires some discussion. In a previous study, Huchison and Savrda (1994) 
attributed limestone/mudstone couplets in the Pine Member of the Clayton Formation to 
sea-level-controlled dilution cycles. They suggested that the limestones represent periods 
of short-term sea-level rise when the supply of clastic sediments was reduced, while 
mudstones record stillstands or minor relative sea-level drops. In this interpretation, each 
 88
limestone/mudstone pair would represent a parasequence.  However, this is inconsistent 
with observations in the current study. As a generalization, most of the limestones in the 
condensed section/highstand systems tract occur in the relatively glauconite-poor upper 
parts of parasequences (or tops of 5
th
-order minicycles) that were deposited at relatively 
high sedimentation rates. Hence, the limestones cannot be attributed to dilution.  
How and why then did the limestones form? Certain limestone intervals (e.g., in 
units 13 and 16) are nodular and clearly diagenetic. Notably, all other limestones in the 
highstand systems tract are characterized by the same microspar textures that are 
observed in the nodular limestones. This may indicate that all limestone units (both 
bedded and nodular) in the highstand systems tract have a common diagenetic origin. 
That is, they all may have formed as concretions well after deposition of the host 
sediments. In this case, carbonate precipitation may be related yet to marine flooding and 
clastic starvation. The position of limestones in upper parts of parasequences is consistent 
with a mechanism whereby marine flooding and associated processes (e.g., 
glauconizitation of carbonate grains) resulted in selective carbonate precipitation in pre-
existing sediments below marine flooding surfaces. The viability of this mechanism is 
worthy of future study.   
 
 
 
 
 
 
 89
 
 
 
8.0 CONCLUSIONS 
The Pine Barren Member of the Lower Paleocene Clayton Formation exposed in 
central Alabama contains a single 3
rd
-order, passive-margin shelf depositional sequence 
composed of glauconitic muddy sands, sandy muds, and limestones. This sequence was 
the subject of a detailed sedimentologic study designed mainly to test relationships 
between glauconite abundance and maturity and sequence stratigraphic context. Major 
conclusions of this study are as follows:  
(1) Glauconite abundance and maturity vary predictably between systems tracts. 
In lowstand incised valley fill sands, glauconite is rare and mainly detrital. Lower parts of 
the transgressive systems tract are characterized by low to moderate abundances of 
glauconite, representing a mixture of detrital and authigenic varieties. The condensed 
section is marked by peak abundances of mature glauconite, as well as by coarsest sand 
fractions and common skeletal debris. Glauconite abundance and maturity generally 
decrease upward through the highstand systems tract.  
(2) Parasequences can be delineated based on asymmetric cycles in sediment 
texture and glauconite content. From bottoms to tops of parasequences, total glauconite 
content, abundance of mature glauconite grain morphotypes, and K and Fe contents of 
glauconite decrease, and glauconite becomes lighter green in color.  
(3) Results generally support observations by previous workers regarding 
glauconite maturity indicators. As proposed by Huggett and Gale (1997), vermicular 
 90
grains represent a lower degree of maturity than mammillated, lobate, and capsule-shaped 
grains.  In the current study, variations in glauconite color and K
2
O contents reflect 
differences in maturity at the parasequence scale. However, structural states of glauconite 
reflected by x-ray diffraction signatures appear to reflect only longer-term changes in 
maturity.  
 (4) Unlike those typical of foreland basin successions, parasequences formed on 
sediment-starved passive margins may be characterized by fining-upward sequences. 
This upward fining reflects the glauconitization process rather than detrital grain texture 
and should not be misinterpreted to represent waning energy or deepening.   
 (5) Observations made in the current study indicate that limestones in the Pine 
Barren Member are most prevalent in upper parts of parasequences and are likely 
diagenetic in origin. They do not reflect primary deposition of carbonate during episodes 
of marine flooding and clastic sediment starvation as previously suggested.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 91
 
 
 
 
 
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 97
 
 
 
 
 
APPENDIX 
 
Table TA1 ? Abundances (weight percent) of major oxides in glauconite grains as 
determined by microprobe analyses. 
Sample MC-8-0-5 
Weight Percent Oxides 
  13a 13b 13c 13d 13e 13f 13g 13h 13i 13j 
SiO
2
 50.50 48.12 46.68 37.40 43.17 47.78 50.08 48.07 48.78 50.10 
TiO
2
Al
2
O
3
 4.60 7.69 6.53 6.88 5.09 6.39 6.06 5.17 5.00 5.24 
FeO 23.74 22.85 23.69 29.39 26.39 21.76 22.91 23.78 24.37 24.15 
MnO  
MgO 3.89 3.54 3.61 3.07 3.90 3.76 3.87 4.10 4.34 4.14 
CaO 0.49 0.43 0.36 0.40 0.50 0.53 0.56 0.31 0.49 0.38 
Na
2
O 0.00 0.05 0.03 0.00 0.02 0.00 0.01 0.03 0.03 0.01 
K
2
O 6.07 6.64 6.66 4.80 5.29 6.19 6.51 7.55 6.49 7.30 
Sum 89.28 89.32 87.56 81.94 84.36 86.41 90.00 89.00 89.50 91.33 
            
Mineral Formulas on Basis of 22 Oxygen 
Si 7.983 7.618 7.620 6.879 7.470 7.776 7.838 7.750 7.78 7.82 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.00 0.00 
iv AL 0.017 0.382 0.380 1.121 0.530 0.224 0.162 0.250 0.22 0.18 
vi AL 0.840 1.053 0.877 0.371 0.508 1.002 0.956 0.732 0.72 0.79 
Fe 3.138 3.025 3.234 4.521 3.819 2.962 2.999 3.206 3.25 3.15 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.00 0.00 
Mg 0.917 0.835 0.878 0.842 1.006 0.912 0.903 0.985 1.03 0.96 
Ca 0.082 0.073 0.064 0.078 0.092 0.093 0.093 0.054 0.08 0.06 
Na 0.000 0.015 0.010 0.001 0.005 0.000 0.002 0.010 0.01 0.00 
K 1.224 1.341 1.387 1.127 1.168 1.285 1.300 1.553 1.32 1.45 
  
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 4.98 4.99 5.05 5.81 5.42 4.97 4.95 4.98 5.09 4.97 
Na+K 1.22 1.36 1.40 1.13 1.17 1.29 1.30 1.56 1.33 1.46 
 
 
 
 
 
 
 98
Table TA1 ? Continued.  
Sample MC-8-10-20 
Weight Percent Oxides 
  14a 14b 14c 14d 14e 14f 14g 14h 14i 14j 
SiO
2
 49.70 48.60 50.02 49.28 50.46 49.90 49.42 48.70 49.30 50.16 
TiO
2
           
Al
2
O
3
 4.40 2.47 4.99 4.66 5.12 2.44 7.24 2.78 2.92 6.32 
FeO 25.37 27.29 22.95 26.04 24.98 27.54 23.24 27.16 26.29 23.21 
MnO           
MgO 4.18 4.01 4.03 4.27 4.14 4.08 4.24 4.22 3.97 4.01 
CaO 0.29 0.23 0.35 0.23 0.40 0.32 0.34 0.22 0.30 0.41 
Na
2
O 0.03 0.00 0.01 0.00 0.00 0.03 0.04 0.04 0.00 0.00 
K
2
O 7.50 7.86 7.18 7.96 7.28 7.69 7.73 7.73 7.37 7.29 
Sum 91.48 90.46 89.52 92.44 92.39 91.99 92.25 90.85 90.15 91.40 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.824 7.883 7.915 7.729 7.811 7.926 7.617 7.847 7.935 7.773 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.176 0.117 0.085 0.271 0.189 0.074 0.383 0.153 0.065 0.227 
vi AL 0.640 0.355 0.846 0.591 0.746 0.383 0.933 0.376 0.489 0.927 
Fe 3.340 3.702 3.037 3.416 3.234 3.658 2.996 3.660 3.539 3.008 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.981 0.970 0.951 0.998 0.955 0.966 0.974 1.014 0.953 0.926 
Ca 0.049 0.041 0.059 0.039 0.067 0.054 0.056 0.038 0.051 0.067 
Na 0.010 0.000 0.002 0.000 0.000 0.010 0.013 0.012 0.000 0.000 
K 1.507 1.627 1.450 1.593 1.438 1.559 1.520 1.589 1.514 1.442 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.01 5.07 4.89 5.04 5.00 5.06 4.96 5.09 5.03 4.93 
Na+K 1.52 1.63 1.45 1.59 1.44 1.57 1.53 1.60 1.51 1.44 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 99
Table TA1 ? Continued.  
Sample MC-8-20-25 
Weight Percent Oxides 
  15a 15b 15c 15d 15e 15f 15g 15h 15i 15j 
SiO
2
 51.46 50.21 49.15 49.22 49.88 50.21 50.14 49.58 50.90 50.26 
TiO
2
           
Al
2
O
3
 6.45 5.23 4.85 6.42 3.88 3.31 7.09 4.35 7.12 5.37 
FeO 24.25 24.11 24.98 22.17 24.93 25.96 23.34 24.77 23.18 24.80 
MnO           
MgO 3.65 3.75 3.55 3.53 3.83 4.03 3.90 3.82 3.89 3.59 
CaO 0.57 0.39 0.50 0.60 0.28 0.40 0.36 0.34 0.48 0.58 
Na
2
O 0.02 0.00 0.02 0.08 0.07 0.02 0.02 0.00 0.01 0.02 
K
2
O 6.11 6.67 6.71 5.70 7.53 7.22 7.41 6.92 6.86 6.03 
Sum 92.50 90.36 89.77 87.72 90.39 91.17 92.26 89.79 92.44 90.65 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.831 7.885 7.841 7.849 7.932 7.944 7.699 7.902 7.751 7.864 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.169 0.115 0.159 0.151 0.068 0.056 0.301 0.098 0.249 0.136 
vi AL 0.988 0.853 0.753 1.056 0.659 0.562 0.982 0.719 1.029 0.855 
Fe 3.086 3.166 3.333 2.957 3.316 3.435 2.997 3.301 2.952 3.245 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.828 0.878 0.844 0.839 0.908 0.951 0.893 0.908 0.883 0.837 
Ca 0.093 0.066 0.085 0.103 0.047 0.067 0.059 0.059 0.079 0.098 
Na 0.005 0.000 0.007 0.024 0.020 0.007 0.005 0.000 0.003 0.006 
K 1.186 1.337 1.366 1.160 1.528 1.458 1.452 1.407 1.333 1.204 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.00 4.96 5.02 4.96 4.93 5.01 4.93 4.99 4.94 5.04 
Na+K 1.19 1.34 1.37 1.18 1.55 1.46 1.46 1.41 1.34 1.21 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 100
Table TA1 ? Continued.  
Sample MC-8-30-40 
Weight Percent Oxides 
  16a 16b 16c 16d 16e 16f 16g 16h 16i 16j 
SiO
2
 51.41 49.92 48.86 48.10 49.23 47.15 49.10 47.59 49.83 48.77 
TiO
2
           
Al
2
O
3
 4.80 3.24 3.69 4.39 4.22 3.42 3.27 4.07 4.30 4.95 
FeO 23.38 25.55 26.47 25.06 27.18 24.68 25.62 23.83 25.76 25.59 
MnO           
MgO 4.27 4.23 3.95 3.37 3.75 3.50 3.97 3.64 3.46 3.59 
CaO 0.42 0.25 0.39 0.42 0.28 0.48 0.25 0.49 0.48 0.53 
Na
2
O 0.00 0.01 0.04 0.00 0.00 0.00 0.04 0.04 0.04 0.01 
K
2
O 7.72 7.62 7.32 7.03 7.72 6.19 7.65 6.33 7.36 6.64 
Sum 92.00 90.82 90.72 88.37 92.38 85.42 89.91 86.00 91.23 90.07 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.931 7.936 7.824 7.845 7.766 7.938 7.913 7.912 7.875 7.783 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.069 0.064 0.176 0.155 0.234 0.062 0.087 0.088 0.125 0.217 
vi AL 0.804 0.543 0.520 0.689 0.550 0.617 0.534 0.709 0.676 0.714 
Fe 3.016 3.397 3.545 3.418 3.586 3.475 3.453 3.313 3.405 3.415 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.982 1.002 0.943 0.819 0.882 0.878 0.954 0.902 0.815 0.854 
Ca 0.070 0.042 0.066 0.074 0.047 0.086 0.043 0.088 0.081 0.090 
Na 0.001 0.004 0.012 0.000 0.000 0.001 0.014 0.011 0.013 0.004 
K 1.520 1.546 1.496 1.463 1.554 1.330 1.573 1.343 1.484 1.352 
  
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 4.87 4.99 5.07 5.00 5.06 5.06 4.98 5.01 4.98 5.07 
Na+K 1.52 1.55 1.51 1.46 1.55 1.33 1.59 1.35 1.50 1.36 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 101
Table TA1 ? Continued.  
Sample MC-9-0-3 
Weight Percent Oxides 
  17a 17b 17c 17d 17e 17f 17g 17h 17i 17j 
SiO
2
 49.17 50.21 50.01 50.78 49.50 49.42 48.78 49.80 49.46 48.77 
TiO
2
           
Al
2
O
3
 3.57 4.55 4.55 5.55 7.07 5.56 4.93 4.31 2.83 5.13 
FeO 26.91 25.06 24.95 24.78 22.75 24.34 25.76 24.73 26.96 25.23 
MnO           
MgO 4.12 3.86 4.20 4.37 3.78 3.76 3.72 4.23 4.15 4.15 
CaO 0.60 0.62 0.53 0.64 0.90 0.55 0.67 0.67 0.57 0.52 
Na
2
O 0.02 0.02 0.01 0.00 0.00 0.01 0.02 0.02 0.01 0.03 
K
2
O 7.55 7.59 7.58 7.17 6.77 7.40 6.99 7.30 7.60 6.98 
Sum 91.93 91.92 91.84 93.28 90.77 91.04 90.86 91.06 91.58 90.81 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.795 7.850 7.825 7.765 7.699 7.768 7.745 7.848 7.878 7.723 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.205 0.150 0.175 0.235 0.301 0.232 0.255 0.152 0.122 0.277 
vi AL 0.462 0.689 0.664 0.765 0.995 0.799 0.668 0.648 0.410 0.680 
Fe 3.568 3.277 3.265 3.169 2.959 3.200 3.421 3.259 3.591 3.341 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.974 0.900 0.980 0.996 0.876 0.881 0.881 0.994 0.985 0.980 
Ca 0.102 0.105 0.089 0.105 0.150 0.093 0.113 0.113 0.097 0.088 
Na 0.005 0.007 0.004 0.000 0.000 0.004 0.005 0.006 0.002 0.008 
K 1.527 1.514 1.513 1.399 1.344 1.484 1.416 1.468 1.545 1.410 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.11 4.97 5.00 5.04 4.98 4.97 5.08 5.01 5.08 5.09 
Na+K 1.53 1.52 1.52 1.40 1.34 1.49 1.42 1.47 1.55 1.42 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 102
Table TA1 ? Continued.  
Sample MC-9-13-25  
Weight Percent Oxides 
  18a 18b 18c 18d 18e 18f 18g 18h 18i 18j 
SiO
2
 48 48.79 48.9 47.82 48.14 47.69 43.85 46.29 44.35 50.4 
TiO
2
           
Al
2
O
3
 4.62 4.8 4.12 3.92 3.74 4.8 6.52 4.61 3.92 3.92 
FeO 26.07 25.79 26.4 25.76 25.62 25.5 23.92 26.2 26.62 27 
MnO           
MgO 3.63 3.66 4.06 3.98 4.06 4.17 3.81 3.97 3.89 4.04 
CaO 0.69 1.04 0.59 0.52 0.66 0.61 0.55 0.53 0.61 0.60 
Na
2
O 0.02 0.00 0.01 0.02 0.00 0.01 0.03 0.00 0.05 0.01 
K
2
O 6.71 6.15 7.54 7.58 7.22 7.28 7.26 7.41 7.22 7.41 
Sum 89.75 90.23 91.6 89.59 89.43 90.04 85.94 89.01 86.66 93.4 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.741 7.770 7.757 7.767 7.805 7.674 7.412 7.608 7.563 7.825 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.259 0.230 0.243 0.233 0.195 0.326 0.588 0.392 0.437 0.175 
vi AL 0.619 0.671 0.527 0.517 0.520 0.585 0.711 0.501 0.351 0.542 
Fe 3.516 3.435 3.506 3.499 3.474 3.432 3.381 3.601 3.797 3.504 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.873 0.869 0.960 0.964 0.981 1.000 0.960 0.973 0.989 0.935 
Ca 0.120 0.178 0.100 0.090 0.115 0.105 0.100 0.093 0.111 0.100 
Na 0.005 0.001 0.004 0.005 0.000 0.002 0.009 0.000 0.017 0.004 
K 1.381 1.250 1.526 1.571 1.494 1.495 1.566 1.554 1.571 1.467 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.13 5.15 5.09 5.07 5.09 5.12 5.15 5.17 5.25 5.08 
Na+K 1.39 1.25 1.53 1.58 1.49 1.50 1.57 1.55 1.59 1.47 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 103
Table TA1 ? Continued.  
Sample MC-11-24-29 
Weight Percent Oxides 
  27a 27b 27c 27d 27e 27f 27g 27h 27i 
SiO
2
 45.93 42.16 47.37 46 46.4 46.5 48.57 45.3 48.26 
TiO
2
          
Al
2
O
3
 5.17 3.69 6.22 5.76 3.35 5.37 4.63 4.52 4.58 
FeO 24.45 25.27 23.53 25.8 26.8 25 25.03 23.6 25.16 
MnO          
MgO 3.78 3.86 3.74 3.52 3.73 3.72 4.01 3.56 4.16 
CaO 0.60 0.49 0.84 0.96 0.62 0.61 0.58 3.55 0.477 
Na
2
O 0.01 0.00 0.01 0.00 0.00 0.03 0.02 0.10 0.004 
K
2
O 6.95 7.23 6.26 6.13 7.43 7.34 7.42 6.04 7.24 
Sum 86.9 82.7 87.98 88.2 88.3 88.6 90.26 86.7 89.86 
          
Mineral Formulas on Basis of 22 Oxygen 
Si 7.645 7.549 7.669 7.553 7.726 7.618 7.765 7.589 7.750 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.355 0.451 0.331 0.447 0.274 0.382 0.235 0.411 0.250 
vi AL 0.659 0.328 0.855 0.669 0.384 0.655 0.637 0.481 0.617 
Fe 3.403 3.784 3.186 3.547 3.734 3.423 3.347 3.298 3.379 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.938 1.030 0.903 0.862 0.926 0.908 0.956 0.888 0.996 
Ca 0.108 0.094 0.146 0.169 0.111 0.106 0.099 0.637 0.082 
Na 0.004 0.000 0.002 0.000 0.001 0.009 0.007 0.033 0.001 
K 1.476 1.652 1.293 1.285 1.579 1.534 1.514 1.290 1.484 
          
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.11 5.24 5.09 5.25 5.15 5.09 5.04 5.30 5.07 
Na+K 1.48 1.65 1.30 1.29 1.58 1.54 1.52 1.32 1.48 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 104
Table TA1 ? Continued.  
Sample MC-13-45-55 
Weight Percent Oxides 
  33a 33b 33c 33d 33e 33f 33g 33h 33i 33j 
SiO
2
 50.70 48.97 50.27 50.83 51.08 51.68 50.67 51.65 50.19 51.23 
TiO
2
           
Al
2
O
3
 6.65 6.18 4.42 8.33 8.83 8.77 8.08 8.42 7.26 7.97 
FeO 23.60 25.50 25.60 20.18 20.62 20.57 21.53 21.35 25.19 21.64 
MnO           
MgO 4.19 4.06 4.11 3.95 3.94 3.89 3.69 3.81 3.90 3.91 
CaO 0.87 0.89 0.45 1.58 1.09 1.28 1.14 1.08 0.71 1.12 
Na
2
O 0.00 0.00 0.00 0.00 0.00 0.00 0.04 0.03 0.01 0.03 
K
2
O 6.75 6.63 7.70 5.58 5.56 5.28 5.61 5.98 7.01 5.92 
Sum 92.76 92.24 92.55 90.45 91.12 91.47 90.77 92.32 94.26 91.82 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.726 7.617 7.827 7.744 7.718 7.755 7.742 7.745 7.597 7.747 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.274 0.383 0.173 0.256 0.282 0.245 0.258 0.255 0.403 0.253 
vi AL 0.920 0.750 0.639 1.240 1.290 1.306 1.198 1.233 0.892 1.168 
Fe 3.008 3.317 3.334 2.571 2.606 2.581 2.751 2.677 3.189 2.737 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.952 0.941 0.954 0.897 0.887 0.870 0.841 0.852 0.880 0.881 
Ca 0.141 0.149 0.076 0.258 0.176 0.206 0.187 0.173 0.115 0.181 
Na 0.000 0.000 0.000 0.000 0.000 0.000 0.012 0.008 0.003 0.009 
K 1.313 1.316 1.530 1.085 1.072 1.011 1.094 1.144 1.354 1.142 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.02 5.16 5.00 4.97 4.96 4.96 4.98 4.94 5.08 4.97 
Na+K 1.31 1.32 1.53 1.08 1.07 1.01 1.11 1.15 1.36 1.15 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 105
Table TA1 ? Continued.  
Sample MC-13c-147-153 
Weight Percent Oxides 
  43a 43b 43c 43d 43e 43f 43g 43h 43i 43j 
SiO
2
 47.67 48.60 47.53 48.27 48.18 47.29 47.93 47.53 49.20 48.11 
TiO
2
           
Al
2
O
3
 5.26 2.98 5.60 4.33 4.95 5.45 4.34 5.66 5.33 3.72 
FeO 25.33 25.23 24.63 24.40 23.89 24.81 24.58 25.11 22.69 25.53 
MnO           
MgO 3.60 4.49 3.62 4.17 3.64 3.87 3.92 3.79 3.86 4.07 
CaO 0.84 0.40 0.88 0.67 0.71 0.60 0.55 0.76 0.66 0.47 
Na
2
O 0.04 0.06 0.01 0.03 0.01 0.01 0.00 0.03 0.00 0.06 
K
2
O 6.42 8.06 6.76 7.51 6.75 7.33 7.75 6.79 7.26 7.61 
Sum 89.15 89.82 89.03 89.38 88.14 89.36 89.06 89.67 89.00 89.58 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.698 7.868 7.676 7.788 7.817 7.646 7.784 7.64 7.849 7.803 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0 0 0.000 
iv AL 0.302 0.132 0.324 0.212 0.183 0.354 0.216 0.36 0.151 0.197 
vi AL 0.700 0.437 0.742 0.611 0.763 0.685 0.615 0.71 0.852 0.515 
Fe 3.421 3.416 3.327 3.292 3.242 3.355 3.339 3.38 3.027 3.463 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0 0 0.000 
Mg 0.867 1.084 0.872 1.003 0.880 0.933 0.949 0.91 0.918 0.984 
Ca 0.145 0.069 0.152 0.117 0.124 0.104 0.095 0.13 0.114 0.082 
Na 0.014 0.019 0.005 0.009 0.003 0.003 0.000 0.01 0 0.019 
K 1.323 1.665 1.393 1.546 1.397 1.512 1.606 1.39 1.478 1.575 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.13 5.01 5.09 5.02 5.01 5.08 5.00 5.12 4.91 5.04 
Na+K 1.34 1.68 1.40 1.56 1.40 1.52 1.61 1.40 1.48 1.59 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 106
Table TA1 ? Continued. 
Sample MC-14-0-15 
Weight Percent Oxides 
  45a 45b 45c 45d 45e 45f 45g 45h 45i 45j 
SiO
2
 50.55 51.21 50.12 50.45 48.98 50.43 47.92 49.65 47.44 48.63 
TiO
2
           
Al
2
O
3
 3.78 8.29 7.80 8.25 5.72 8.77 4.82 3.93 6.51 6.65 
FeO 25.12 19.36 21.38 20.60 25.04 20.44 25.06 24.94 23.61 22.01 
MnO           
MgO 4.12 3.56 3.37 3.84 3.85 3.72 3.90 4.40 3.65 4.05 
CaO 0.39 0.96 0.62 0.92 0.69 0.97 0.67 0.39 0.66 0.89 
Na
2
O 0.01 0.11 0.01 0.00 0.03 0.02 0.05 0.01 0.03 0.02 
K
2
O 7.39 4.84 5.69 5.33 6.13 4.70 6.40 7.69 6.35 5.65 
Sum 91.36 88.34 89.01 89.38 90.45 89.05 88.83 91.01 88.24 87.89 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.939 7.890 7.806 7.771 7.728 7.755 7.753 7.858 7.654 7.751 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0 
iv AL 0.061 0.110 0.194 0.229 0.272 0.245 0.247 0.142 0.346 0.249 
vi AL 0.639 1.395 1.238 1.269 0.792 1.345 0.672 0.591 0.892 1 
Fe 3.299 2.494 2.785 2.654 3.304 2.629 3.391 3.301 3.186 2.934 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0 
Mg 0.965 0.818 0.782 0.882 0.905 0.853 0.941 1.038 0.878 0.962 
Ca 0.066 0.159 0.104 0.151 0.117 0.159 0.117 0.066 0.114 0.151 
Na 0.005 0.032 0.004 0.000 0.010 0.005 0.015 0.003 0.010 0.006 
K 1.481 0.952 1.131 1.048 1.234 0.922 1.321 1.553 1.307 1.149 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 4.97 4.87 4.91 4.96 5.12 4.99 5.12 5.00 5.07 5.05 
Na+K 1.49 0.98 1.14 1.05 1.24 0.93 1.34 1.56 1.32 1.15 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 107
Table TA1 ? Continued.  
Sample MC-15-8-13 
Weight Percent Oxides 
  47a 47b 47c 47d 47e 47f 47g 47h 47i 47j 
SiO
2
 45.87 46.09 47.71 46.81 45.98 47.75 47.02 48.06 48.79 48.26 
TiO
2
           
Al
2
O
3
 4.48 5.40 3.79 6.77 7.37 7.45 5.05 6.60 4.02 6.22 
FeO 25.97 24.73 26.11 25.23 22.87 23.57 25.42 23.16 24.53 23.77 
MnO           
MgO 4.08 4.13 4.09 4.15 3.89 3.79 3.87 3.83 3.89 3.83 
CaO 0.89 0.73 0.57 0.87 0.88 1.10 0.87 1.18 0.56 0.92 
Na
2
O 0.00 0.01 0.01 0.03 0.00 0.00 0.01 0.02 0.00 0.00 
K
2
O 6.73 6.87 7.46 5.83 6.24 5.31 6.63 5.69 7.50 6.20 
Sum 88.03 87.96 89.73 89.70 87.21 88.98 88.88 88.54 89.29 89.19 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.604 7.582 7.750 7.487 7.502 7.579 7.653 7.674 7.870 7.691 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.396 0.418 0.250 0.513 0.498 0.421 0.347 0.326 0.130 0.309 
vi AL 0.480 0.629 0.476 0.763 0.919 0.973 0.621 0.916 0.634 0.859 
Fe 3.601 3.402 3.547 3.375 3.121 3.129 3.460 3.093 3.309 3.168 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 1.008 1.013 0.990 0.989 0.946 0.897 0.939 0.912 0.935 0.910 
Ca 0.158 0.129 0.099 0.149 0.153 0.187 0.152 0.203 0.097 0.157 
Na 0.000 0.002 0.002 0.008 0.000 0.000 0.005 0.006 0.000 0.000 
K 1.424 1.442 1.546 1.190 1.299 1.076 1.377 1.159 1.544 1.261 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.25 5.17 5.11 5.28 5.14 5.19 5.17 5.12 4.98 5.09 
Na+K 1.42 1.44 1.55 1.20 1.30 1.08 1.38 1.16 1.54 1.26 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 108
Table TA1 ? Continued.  
Sample MC-15-60-68 
Weight Percent Oxides 
  53a 53b 53c 53d 53e 53f 53g 53h 53i 53j 
SiO
2
 47.34 49.57 48.6 48.49 47.15 48.49 49.57 49.26 50.2 48.6 
TiO
2
           
Al
2
O
3
 6.79 7.46 5.76 7.32 6.03 6.79 6.02 7.34 7.71 7.26 
FeO 20.13 21.85 22.4 20.68 23.86 21.57 23.21 21.99 19.2 22.1 
MnO           
MgO 3.38 3.99 3.71 4.02 3.86 3.98 4.00 3.95 4.01 3.64 
CaO 1.05 1.10 1.09 1.15 0.82 1.03 0.60 1.19 1.13 1.15 
Na
2
O 0.03 0.00 0.01 0.03 0.06 0.01 0.01 0.00 0.01 0.04 
K
2
O 5.47 5.98 5.99 5.56 6.62 6.07 7.39 5.84 6 5.69 
Sum 84.19 89.94 87.6 87.25 88.4 87.94 90.8 89.56 88.2 88.5 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.819 7.704 7.827 7.729 7.637 7.733 7.760 7.698 7.823 7.701 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.181 0.296 0.173 0.271 0.363 0.267 0.240 0.302 0.177 0.299 
vi AL 1.141 1.071 0.920 1.105 0.788 1.010 0.871 1.050 1.240 1.057 
Fe 2.781 2.840 3.011 2.757 3.232 2.877 3.039 2.874 2.509 2.929 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.832 0.924 0.890 0.955 0.932 0.946 0.934 0.920 0.932 0.860 
Ca 0.185 0.183 0.189 0.196 0.143 0.176 0.101 0.199 0.188 0.195 
Na 0.009 0.001 0.003 0.009 0.019 0.004 0.003 0.000 0.004 0.012 
K 1.153 1.186 1.230 1.131 1.368 1.235 1.476 1.165 1.194 1.150 
           
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 4.94 5.02 5.01 5.01 5.09 5.01 4.94 5.04 4.87 5.04 
Na+K 1.16 1.19 1.23 1.14 1.39 1.24 1.48 1.16 1.20 1.16 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 109
Table TA1 ? Continued.  
Sample MC-16b-top 
Weight Percent Oxides 
  60a 60b 60c 60d 60e 60f 60g 60h 60i 60j 
SiO
2
 49.52 49.75 46.90 49.54 49.15 45.93 49.64 50.32 49.86 50.01 
TiO
2
           
Al
2
O
3
 7.15 8.83 13.20 10.23 10.18 7.78 8.82 6.28 9.57 9.17 
FeO 23.46 19.06 13.54 16 16.61 15.7 21.70 22.41 21.11 18.72 
MnO           
MgO 4.04 3.89 4.05 4.39 3.99 3.38 4.04 4.27 3.69 4.13 
CaO 0.92 1.28 1.27 1.50 1.04 1.02 1.19 0.92 1.31 1.21 
Na
2
O 0.04 0.02 0.08 0.02 0.13 0.05 0.00 0.00 0.03 0.04 
K
2
O 6.51 4.45 2.547 4.45 4.53 4.39 5.33 6.39 4.55 4.67 
Sum 91.63 87.29 81.58 86.2 85.64 78.2 90.73 90.6 90.1 87.95 
           
Mineral Formulas on Basis of 22 Oxygen 
Si 7.645 7.758 7.501 7.697 7.708 7.914 7.599 7.801 7.611 7.729 
Ti 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
iv AL 0.355 0.242 0.499 0.303 0.292 0.086 0.401 0.199 0.389 0.271 
vi AL 0.946 1.381 1.989 1.570 1.590 1.494 1.190 0.949 1.333 1.399 
Fe 3.029 2.486 1.811 2.084 2.179 2.255 2.778 2.906 2.695 2.419 
Mn 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 0.000 
Mg 0.930 0.904 0.966 1.017 0.933 0.868 0.922 0.987 0.840 0.951 
Ca 0.152 0.214 0.217 0.250 0.175 0.188 0.195 0.152 0.214 0.200 
Na 0.012 0.006 0.024 0.007 0.041 0.015 0.000 0.000 0.007 0.013 
K 1.283 0.885 0.520 0.882 0.907 0.965 1.041 1.264 0.886 0.921 
  
Si + iv Al 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 8.00 
Sum vi 5.06 4.98 4.98 4.92 4.88 4.81 5.09 4.99 5.08 4.97 
Na+K 1.29 0.89 0.54 0.89 0.95 0.98 1.04 1.26 0.89 0.93