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Two cores from the Cretaceous Second White Speckled (2WS) formation, the underlying Belle Fourche and the overlying Carlile formations, and the interval of the Oceanic Anoxic Event 2 (OAE2) were studied. The 2WS oil shale consists of limestone and marlstone. The limestone is associated with shallow marine facies. It contains Inoceramid shell debris deposited during enhanced water column mixing periods that promoted benthic carbonate productivity, increased bottom-water oxygenation, and reworking. The marlstone is associated with the open marine facies and includes sand-sized coccolith aggregates with varying planktonic foraminifera deposited under low oxygen conditions. Hierarchical component analysis identified two main families. The Belle Fourche and Carlile family is referred to as coastal marine facies. The 2WS oil shale is divided into three sub-facies, namely deep marine, open shelf-lower, and shallow shelf-upper. Bioturbation, lack of lamination, and scarcity of fossils in the Carlile indicate deposition in a restricted basin with minimal circulation. Sand laminae and higher bioturbation in the Belle Fourche indicate higher energy and shallow water facies with high riverine and terrigenous input. Variations in Cr, Ni+V, and Th/U vs. authigenic U show that the coastal facies reflect an anoxic environment, those in the shallow and open shelf marine facies in a suboxic-anoxic, and those in the deep marine facies in a suboxic environment. The coastal facies have high AI2O3, SiO2, and low CaCO3 content. Based on Mn/Ca vs. Sr/Ca, the temperature of water decreased from the coastal facies toward the shallow shelf and open shelf facies. The P/Ti ratio, an indication of OM production and preservation, is greater in the shallow shelf and open shelf marine facies and the highest in the deep marine facies. Clays decreased from 80% to 5% in the shallow shelf and open shelf facies. The 2WS shale was deposited during a long-lived transgression comprised of higher order shallowing upward parasequences that are accompanied by a shift from pelagic to benthic carbonate productivity. There is an increase in carbonates and decrease in siliciclastics (SiO2, clays) toward the eastern shoreline. Facies associations show an overall decrease in grain size, energy level, and bioturbation from east to west within the study area, with increasing distance from the eastern shoreline. Lateral changes of similar facies are controlled by water depth (i.e., sea level fluctuations). During deposition of the limestone lithofacies, the abundance of pelagic activity and oxygenated bottom water conditions resulted in very low TOC quantity of dominantly Type III kerogen. During deposition of the marlstone lithofacies, high marine productivity, coupled with low oxygen bottom water conditions, resulted in an enrichment of micronutrient trace elements (Zn, Ni) and the effective OM preservation with high contribution of oil-prone type II kerogen. The 2WS oil shale present along the eastern margin of the Western Interior Seaway was deposited on a low gradient shallow and broad carbonate ramp, marked by wave energy, minimal fluvial input, and under moderate climatic conditions. [ABSTRACT FROM AUTHOR]