Controls on the accumulation of organic matter in the Eagle Ford Group, Central Texas, USA.

The Upper Cretaceous Eagle Ford Formation is an organic rich marine mudrock which outcrops across central Texas. This study documents the chemostratigraphic character of the Pepper and Eagle Ford Formations in central Texas using major and trace elements, organic matter abundance, and the isotopic and stoichiometric character of organic matter. The chemical data allow the identification of six distinct chemofacies that are potentially useful for correlation purposes. Based on these data, changing paleoceanographic conditions were documented ranging from normal marine conditions associated with the Pepper Formation, anoxic conditions associated with the Lower Eagle Ford Formation, suboxic conditions associated with most of the upper Eagle Fords, and then a return to normal marine conditions at the top of the Eagle Ford Formation. The high TOC content of the lower Eagle Ford was most likely caused by high productivity which in turn drove conditions to anoxia.M.S