EFFECTS OF OCEAN REDUCTION-OXIDATION CONDITIONS ON ORGANIC MATTER PRESERVATION IN THE UPPER EAGLE FORD FORMATION: MOLECULAR CHARACTERIZATION OF KEROGEN

Kerogen is the organic matter preserved in sedimentary rocks that is insoluble in organic solvents. Kerogen is comprised of a mixture of organic biomolecules and tends to be dominated by the polymeric components of cell walls and cellular membranes. This study seeks to evaluate the influence on redox depositional conditions, organic matter source type, and extent of biotic degradation on bulk molecular composition of kerogen isolates of the Eagle Ford formation of central Texas. Kerogen composition was determined through ¹³C nuclear magnetic resonance (NMR) spectroscopy, while source delineation and reconstruction of depositional conditions was undertaken by a combination of molecular biomarker and trace element enrichment proxies. Samples were collected from 9 Eagle Ford outcrops in McLennan county Texas, USA that represent 20m.y. of Late Cretaceous sediment paleogeographically located on the continental shelf at the gateway to the western interior sea. Samples from a number of outcropping late Cretaceous mudstones of the Eagleford Formation were chosen spanning a gradient of paleo-redox depositional conditions (oxic/suboxic to anoxic). We will attempt to reconcile biomarker information obtained from gas chromatography/mass spectrometry analysis of the extractable lipids with the chemical composition of the kerogen to indentify preservational biases caused by redox conditions, differing source types, and biotic degradation extent.