David K Watkins
Date of this Version
Hermosillo, Bryan, and Watkins, D.K., 2018, Calcareous nannofossil biostratigraphy and paleoecology of the Fort Hays limestone of western Kansas, Western Interior Basin (WIB), Unpublished M.S. thesis, University of Nebraska-Lincoln, Nebraska. p. 1-36.
Investigations of Upper Cretaceous hemi-pelagic sediments from the Western Interior Basin suggest that high surface water fertility caused increased production of biogenic carbonate, resulting in the deposition of limestone. We examined calcareous nannofossils from the Turonian/Coniacian Fort Hays Member of the Niobrara Formation to evaluate the correlation between nannofossil surface water fertility proxies and associated lithology. Our paleoecology results indicate that oligotrophic surface water conditions were present during limestone deposition. This stands at odds with existing depositional models for the Western Interior Seaway (WIS). Paleoecological data within the interbedded marls was artificially skewed due to the prevalence of etching caused by diagenetic overprinting. This occurred during burial and caused the remobilization of calcite from marls into the adjacent limestones, resulting in δ18O excursions within the marls. The first occurrence datum FAD of the species Micula cubiformis is proposed as a proximal nannofossil substitute for the FAD of the inoceramid biomarker Cremnoceramid deformis erectus throughout the Western Interior Basin (WIB).
Advisor: David K. Watkins