Cenomanian-Santonian Calcareous Nannofossil Biostratigraphy of a Transect of Cores Drilled Across the Western Interior Seaway
Timothy J. Bralower, James A. Bergen, 1998. "Cenomanian-Santonian Calcareous Nannofossil Biostratigraphy of a Transect of Cores Drilled Across the Western Interior Seaway", Stratigraphy and Paleoenvironments of the Cretaceous Western Interior Seaway, USA, Walter E. Dean, Michael A. Arthur
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The Cenomanian-Santonian calcareous nannofossil biostratigraphy of the Rebecca Bounds, Portland, and Escalante cores was investigated. Zonal markers were used to correlate the Cenomanian-Turonian boundary interval in the cores with outcrop sections in the Western Interior basin. However, it is difficult to apply existing zonations in the remainder of the section. We determined several new biohorizons that are useful for drawing correlations between the cores. These biohorizons are combined with some of the standard zonal markers in defining informal zonal units. Environmental factors appear to have reduced nannofossil diversity along the western margin of the basin and led to the premature extinction of several nannofossil markers in the Cenomanian-Turonian boundary interval.
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This volume presents the results of a coordinated, multidisciplinary study of Cretaceous carbonate and clastic rocks in cores collected along a transect across the old Cretaceous seaway that extended from the Gulf Coast to the Arctic by a team of academic, industry and U.S. Geological Survey scientists. The overall goal was to construct a subsurface transect of mid-Cretaceous strata that were deposited in the U.S. Western Interior Seaway. In particular, the papers in this volume focus on the Graneros Shale, Greenhorn Formation, Carlile Shale, and Niobrara Formation and equivalents in cores from six drillholes from western Kansas, southeastern Colorado and eastern Utah.