University of Missouri at Columbia, United States

Oxygen isotope analyses of well-preserved foraminifera from Blake Nose (30 degrees N paleolatitude, North Atlantic) and globally distributed deep-sea sites provide a long-term paleotemperature record for the late Albian-Maastrichtian interval that is difficult to reconcile with the existence of significant Cretaceous ice sheets. Given reasonable assumptions about the isotopic composition of Cretaceous seawater, our results suggest that middle bathyal water temperatures at Blake Nose increased from approximately 12 degrees C in the late Albian through middle Cenomanian to a maximum of 20 degrees C during the latest Cenomanian and earliest Turonian. Bottom waters were again approximately 12 degrees C during the middle Campanian and cooled to a minimum of 9 degrees C during the Maastrichtian. Correlative middle bathyal foraminifera from other ocean basins yield paleotemperature estimates that are very similar to those from Blake Nose. Comparison of global bottom-water temperatures and latitudinal thermal gradients suggests that global climate changed from a warm greenhouse state during the late Albian through late Cenomanian to a hot greenhouse phase during the latest Cenomanian through early Campanian, then to cool greenhouse conditions during the mid-Campanian through Maastrichtian.