CHEMOSTRATIGRAPHIC ANALYSIS AND CORRELATION OF EAGLE FORD GROUP-EQUIVALENT STRATIGRAPHY ACROSS WEST TEXAS

The Ernst Member of the Boquillas Formation, deposited near the southern aperture of the Cretaceous Western Interior Seaway (KWIS), reflects the time-transgressive onset of sediment accumulation following subaerial exposure of the Buda Limestone. The Ernst Member within Big Bend National Park, Brewster County, Texas is a unique intermediary between the Ojinaga Formation and Eagle Ford Group of Hudspeth and Terrell counties, respectively. We present a chemostratigraphic analysis of the Ernst Member’s type section in Ernst Tinaja, Big Bend National Park and correlate spectral gamma ray (U, Th and K), δ¹³C stable isotopes, Total Organic Content (TOC%) and U/Pb Isotope Dilution – Thermal Ionization Mass Spectrometry (ID-TIMS) bentonite ages across west Texas. X-Ray Fluorescence (XRF) data, including Si, Ca, Al and trace element concentrations, are presented. Biostratigraphic data (nannofossil and formaniferal) are presented as additional proxies to add robustness to correlation, with consideration made to old and new Geologic Time Scales (GTSs).