Geochemistry of the Cretaceous Mowry Shale in the Wind River Basin, Wyoming

The siliceous nature of the Mowry Shale distinguishes it from many well-studied organic-rich mudstones Cretaceous Western Interior Seaway. Available models organic enrichment in rarely incorporate detailed biomarker, bulk organic, inorganic, and mineralogy data. Here, we used these data to evaluate how variations matter source, productivity, dilution, preservation modulated accumulation during deposition Shale, while also demonstrating benefits this integrated approach. An stable carbon isotope vertical profile for is presented test whether was deposited oceanic anoxic event 1d (OAE 1d), thereby contributing Shale. Samples were analyzed three thermally immature drill cores collected Wind River Basin, Wyoming advance our understanding conditions that led formation Results inorganic geochemistry biomarkers show redox-driven closely coupled with stratigraphic changes content intermediate distal settings Biogenic silica dilution decouples productivity enrichment, such interval highest offset containing maximum content. These findings contrast previous studies identified as primary driver middle lower contain primarily marine matter, whereas relative contribution terrestrial increases upper overlying Frontier Formation sea level declined western shoreline prograded eastward. Finally, together recent radioisotopic dating suggest postdates OAE by ∼1−2 million years (m.y.), providing another example temporal between Seaway compared other regions record global OAEs.