Detrital Zircon U-Pb Age Constraints on the Sandstone Provenance of the Upper Cretaceous Eutaw Formation from Central Alabama to Western Georgia

Abstract

Sandstone provenance analysis of the Tombigbee Sand Member and Eutaw Formation is vital to discerning source material of clastic detrital sediments found in eastern Alabama and western Georgia along the Upper Cretaceous coastal plain boundary. Geochemical methods and grain-size analysis give insight into the relationship between Upper Cretaceous coastal plain boundary clastic sediment accumulations and potential erosional sources. Utilizing detrital zircon grains in U-Pb radiometric dating, detrital zircon age populations were analyzed to determine erosional sources of the Eutaw Formation. Their overall zircon age distributions are dominated by Grenvillian zircons (44-46%) followed by Taconian zircons (23-33%) with minor Acadian and Alleghanian zircons. Their age distributions are similar to the detrital zircon age distributions of Appalachian rivers suggesting their origin from the Appalachian mountain. The lack of zircon age peaks at greater than 1.8 Ga indicates that Ouachitas were not a significant source for the sandstones in this study. Geochemical and grain-size analysis revealed a well-sorted, quartz dominated sediment composition included in the Eutaw Formation suggesting increased sediment transport and possible chemical weathering. The results of this study suggest greater sediment influx from older upper-continental sources from the Appalachian Mountains, transported by the Chattahoochee River system. Provenance investigation through geochemical and grain-size analysis of the Eutaw Formation has helped to further constrain our depositional understanding of eastern Alabama and western Georgia along the Upper Cretaceous coastal plain outcrop belt.