IGPP Seminar Series

High Productivity During Cretaceous Ocean Anoxic Events

by Adina Paytan
Stanford

Abstract

Several events of wide spread deposition of organic-carbon-rich marine sediments referred to as Oceanic Anoxic Events (OAEs) occur in the middle of the Cretaceous (about 125-80 million years ago). High biological productivity and/or ocean stagnation have been invoked as possible causes for this widespread oceanic anoxia. Barite accumulation rates in several deep-sea cores coupled with Sr and S isotope analyses indicate that marine productivity was significantly higher during these intervals. The high productivity may have served as a feedback mechanism to lower the impact of greenhouse warming. Oceanic productivity started rising before the initiation of OAEs and peaked during these events. The accumulation and good preservation of biogenic barite in deep oceanic sediments of that age indicate that sulfate reducing conditions were not prevalent throughout the Mid-Cretaceous oceans.
Tuesday, 12 June 2007
3853 Slichter Hall
Refreshments at 3:45 PM
Lecture at 4:00 PM