[B-PT04] Biotic History

[BPT04-P03] Diversity crises in planktic foraminifers and organic carbon deposition in the late Cretaceous north-western Atlantic

*Kazuyoshi Moriya¹, Toshikazu Furuya¹, Yasuko Miyakura¹ (1.Department of Earth Sciences, Faculty of Education and Integrated Arts and Sciences, Waseda University)

Keywords:Cretaceous, Planktic foraminifers, Diversity crises, Organic carbon deposition

Abundance and diversity of planktic foraminifers in the late Cretaceous north-western Atlantic show distinctive decrease at the Cenomanian/Turonian boundary (CTB) and the Santonian/Campanian boundary (SCB). Both boundaries are marked by positive excursions in stable carbon isotopes, known as the Cenomanian Turonian Boundary Event and the Santonian Campanian Boundary Event. Planktic foraminiferal assemblages recovered by IODP Exp. 342 at Newfoundland Ridge indicate sudden decrease in abundance. Abundances became less than 1 individual/cm^2/kyr at both boundaries. After these boundary crises, abundances have not been reached to pre-boundary levels. While total organic carbon content (TOC) at CTB become more than 10 wt%, the highest TOC at SCB is less than 1 wt% throughout the boundary event.