Download or read book Geochronologic and Chemostratigraphic Record of Cenomanian-Turonian Eagle Ford, South Texas written by Michael Anthony Nieto and published by . This book was released on 2016 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Eagle Ford Shale of South Texas is an organic-rich, calcareous mudrock succession which was deposited on the Comanche Platform during the earliest Late Cretaceous. Many academic and industry sponsored Eagle Ford studies over the past 10 years have concentrated their efforts on trying to understand the rock fabrics, facies architecture and heterogeneities present in the succession. However, despite heavy economic and academic interest in the system, few studies focus on trying to understand timing and source of the many bentonite ash beds present in the Eagle Ford; which serve as regional chronostratigraphic markers across South Texas. One of the primary goals of the study is the determination of U-Pb age dates in bentonite-rich ash beds from a group of subsurface cores that penetrate the Eagle Ford Formation in Atascosa County, Texas. Absolute age dates provide a chronostratigraphic framework that is used to estimate the depositional timing of variable Eagle Ford facies, as well as define the timing, duration and magnitude of isotopic events in the region. Secondly, age estimates are utilized to determine and calculate Eagle Ford accumulation rates across South Texas. Absolute age dates are incorporated with lithofacies definitions to better 1) understand the cyclic relationship between dominant Eagle Ford lithologies, 2) identify the controls responsible for the cyclic mode of deposition, and 3) determine the lateral continuity of key lithofacies and lithologic units. Lastly, elemental (XRF) data are utilized to describe the subtle paleoceanographic and sediment source conditions that persisted across the entire Eagle Ford section. These findings are integrated with stable carbon ([delta]13C) isotopic data, which allow for the accurate definition of Ocean Anoxic Event 2 (OAE 2) in the study area and provide a basis for regional correlation with previous studies. Recent studies have suggested that anoxic conditions experienced within the Western Interior Seaway during this time were asynchronous with the well-documented global OAE 2 event. The present study compares local U-Pb age dates, isotopic and elemental results with regional studies to better define the onset timing and paleoceanograpic conditions associated with Eagle Ford Shale deposition.