Cenomanian-Santonian Calcareous Nannofossil Biostratigraphy of Demerara Rise, Western Equatorial Atlantic (ODP Leg 207): Black Shales and a Better Refined Biostratigraphic Framework

Stacie A. Blair
Florida State University, Dept of Geological Sciences, Tallahassee, FL USA;
[email protected]

Calcareous nannofossils are used as biostratigraphic indicators integral for age control in both petroleum industry and academic settings. Increasing the biostratigraphic resolution of Cretaceous stages is becoming crucial as petroleum industries are beginning to invest in new exploration of Cretaceous plays. Cenomanian-Santonian nannofossil biostratigraphies lack fine-scale resolution, primarily due to an absence of cored, deep-water sections, even though this encompasses a period of rapid turnover within several nannofossil families.

Cored sediments recovered during Ocean Drilling Program Leg 207 on Demarara Rise (western equatorial Atlantic) provide a unique opportunity to analyze Cenomanian-Coniacian nannofossil bioevents in a rare, deep-water, nannofossil-rich section. Upper Cretaceous bioevents noted can be used to better corroborate and calibrate nannofossil biostratigraphies developed primarily in shallow water, outcrop sections as well as improve age control in industrial settings. In addition, calcareous nannoplankton are valuable for evaluating fluctuations in primary productivity, surface water dynamics, temperature, and salinity which can provide better insight to paleo-ecologic and -oceanographic transitions between carbonate-rich sediments and carbonate-poor sediments (i.e. black shales) at this locality.

AAPG Search and Discovery Article #90094 © 2009 AAPG Foundation Grants in Aid