Download or read book Stratigraphic Architecture and Associated Sedimentological and Geochemical Variability in the Upper Cretaceous Eagle Ford Group, South Texas written by Ahmed Wasel Alnahwi and published by . This book was released on 2018 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: A detailed, rock-based investigation of three Upper Cretaceous Eagle Ford Group cores situated behind (L1), at (L2), and downdip (L3) of the Lower Cretaceous Stuart City paleoreef-shelf margin in south Texas was conducted to understand stratigraphic, sedimentological, and geochemical relationships. An understanding of stratigraphic, sedimentological, and geochemical variability across the ancestral shelf margin is currently lacking. The Cenomanian–Turonian Eagle Ford Group is composed predominantly of calcareous mudstones that were deposited below storm-wave base on the drowned South Texas Shelf. The Lower to Upper Eagle Ford contact approximates the Cenomanian–Turonian boundary, at which the OAE-2 occurred and was identified in all three cores. The low-relief raised rim of the paleoshelf margin may have acted as a barrier, dividing the Eagle Ford Group into two sedimentological systems: (1) a restricted drowned shelf to the north and (2) an open-marine basinal setting to the south. Pre-OAE-2 Eagle Ford strata on the drowned shelf are cyclic and enriched in molybdenum, suggesting anoxic to euxinic water masses. Anoxic basinward strata are less cyclical and have a lower molybdenum content. The cores were investigated to quantify mineralogical composition and TOC. Machine learning of XRF dataset was conducted using neural-network analysis to predict mineralogies and TOC. Quantitative laboratory-measured XRD mineralogies and TOC were used to conduct the training and develop high-resolution quantitative models. Derived mineralogic and organic matter quantitative models represent continuous relative abundances. This method allows for the utilization of the relatively inexpensive and nondestructive XRF analysis that requires minimal sample preparation to construct high-resolution mineral abundances and TOC content. Hyperspectral imagery was used to generate mineral maps of the L1 core. The used hyperspectral imaging system uses the SWIR (shortwave infrared) and LWIR (longwave infrared) spectrometers. The introduction of the LWIR made it possible to identify minerals that were not detected by previous SWIR systems such as quartz and feldspars. Hyperspectral imaging facilitates the study of textural and fabric relationships. The diagnostic cyclicity of the Lower Eagle Ford is closely related to calcite compositional variations and coccolithophore productivity. Strontium-rich calcite indicates smaller allochem size dominance as well as lower sedimentation rates.