Paleoceanography and Paleoenvironments of the Late Cretaceous Western Interior Seaway: An Integrated Study of Geochemistry and Foraminiferal Paleoecology

我们以前对白垩纪西部内陆海道西南缘古环境的研究，采用粘土矿物和有孔虫的联合研究，在区域尺度上对沉积、构造、气候和海洋的相互作用有了新的认识。具体地说，我们已经能够区分晚白垩纪期间海平面上升和气候对沉积物分布的影响，并且我们已经将源区和环流模式的变化与有孔虫种群联系起来。在这项研究中，我们打算扩大我们的审查范围，以更严格地评估沉积条件的短期变化，水柱分层，以及近端盆地地区横跨上塞诺曼尼亚到基坎帕尼亚的氧最低带的发展（Mesa Verde， CO）。主要方法将是沉积地球化学（Fe, Mn， S, CaCO3， TOC和Rock-Eval热解），结合有孔虫种群和形状研究，并结合之前在两个野外季节收集的详细地层。此外，我们将把这个地点的环境与更西面的一个浅海盆地遗址（Lohali Point， AZ）的环境联系起来，在那里我们有一个从塞诺曼期到上Turonian期的详细剖面。这将为我们提供将近岸地区的条件与东部远端盆地遗址（如科罗拉多州普韦布洛）的条件进行比较的基础，并使我们能够重建西部内陆海道西南部分的综合古海洋学。

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.