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Most sequence biostratigraphic methods were established in expanded, siliciclastic-dominated, continental margin deposits. As the oil and gas industry increasingly focuses on unconventional shale plays, there is a greater need to understand the depositional patterns of organic-rich mudrocks. To determine the applicability of sequence biostratigraphic methods to organic-rich mudrocks, several techniques were tested on biostratigraphic data from four cores of the Cenomanian–Turonian Eagle Ford Group taken in south Texas.

One of the more common methods of sequence biostratigraphy is to use planktic microfossil abundance peaks to identify maximum flooding surfaces (MFSs), based on the assumption that microfossil abundances are related to siliciclastic input and rock accumulation rates. However, because the rocks of the distal Eagle Ford Group found in south Texas are often condensed, planktic abundances are predominantly a function of paleoceanography, bottom-water currents, diagenesis, and microfossil recovery, and so cannot be used to identify MFSs. Likewise, much of the Eagle Ford Group in south Texas was deposited under anoxic to euxinic paleoredox conditions, so benthic microfossils are rare to absent in most samples, precluding their use to detect paleobathymetric shifts, another popular sequence biostratigraphic technique. The most useful techniques were the Wheeler diagram and age-depth plots, which were used to identify hiatuses and changes in rock accumulation rates. Correlation into the more proximal settings found in the outcrop belts of west, central, and east Texas, along with integration with other stratigraphic data sets, including petrophysical, bulk geochemical, stable carbon isotopes, and core descriptions, will be needed to definitively establish the precise nature of the stratal surfaces identified in this distal setting.

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