The biotic response to the late Cenomanian oceanic anoxic event;

Abstract: The late Cenomanian sea-level rise was coupled with an expansion of the oxygen-minimum zone. The position of its upper surface may be discerned from the sequential effects on the benthonic and planktonic biota. The near-global existence of organic-rich mudrocks of late Cenomanian age is well documented (Schlanger et al. 1987). The widespread nature of this facies was used by Schlanger & Jenkyns (1976) as evidence that a significant part of the world ocean became temporarily oxygen-deficient, brought about by an expansion in the oxygen-minimum zone. This oceanic anoxic event (OAE) in the latest Cenomanian-earliest Turonian is marked by a positive 6I3C excursion in limestones (Scholle & Arthur 1980). This is believed to be (Arthur et al. 1987) the result of the preferential extraction of 12C from seawater by marine plankton whose organic components were not recycled due to enhanced rates o