Our previous study of the paleoenvironments of the southwestern margin of the Cretaceous Western Interior Seaway used a joint investigation of clay minerals and foraminifera to yield some new ideas on the interaction of sedimentation, tectonics, climate and oceanography on a regional scale. Specifically, we have been able to discriminate between eustatic and climatic influences on sediment distribution during the Late Cretaceous, and we have correlated changes in source area and circulation patterns to foraminiferal populations. In this study, we intend to expand the scope of our scrutiny to more rigorously evaluate short-term changes in depositional conditions, water-column stratification, and the development of oxygen-minimum zones at a proximal basin locality spanning the upper Cenomanian to basal Campanian (Mesa Verde, CO). The principal methods to be used will be sedimentary geochemistry (Fe, Mn, S, CaCO3, TOC and Rock-Eval pyrolysis) coupled with foraminiferal population and shape studies, and integrated into the detailed stratigraphy gathered previously during two field seasons. Moreover, we will correlate the environments at this site to those at a neritic basin site (Lohali Point, AZ) further west where we have a detailed section from the Cenomanian to the upper Turonian. This will provide us with the basis for comparing conditions in this nearshore locale with those that have been documented for distal basin sites to the east, (such as at Pueblo, CO) and will enable us to reconstruct the comprehensive paleoceanography of this southwestern sector of the Western Interior Seaway.
