Publication Date:
2013-09-24
Description:
A shift from the icehouse climate in which humans evolved to a Late Cretaceous–like greenhouse climate is an often-repeated cautionary prediction of the consequences of continued anthropogenic CO 2 emissions. The corollary, that understanding the past might help predict the future, has justified many Late Cretaceous studies, but important questions remain about climate stability and sensitivity. New 18 O measurements of more than 1000 samples of exceptionally well preserved foraminifera (8 planktic and 11 benthic taxa) from two sites in Tanzania indicate that hot and remarkably stable conditions prevailed in the region during the Turonian, including during a proposed greenhouse glacial event. Planktic taxa have 18 O values largely between –4.0 and –5.0, suggesting surface-water temperatures between 30 and 35 °C. Estimates for seafloor temperatures are between 18 and 25 °C. No parallel shifts in 18 O values are observed among planktic and benthic taxa, contradicting an often-cited line of evidence for greenhouse glaciations and supporting an effectively ice-free Turonian world.
Print ISSN:
0091-7613
Electronic ISSN:
1943-2682
Topics:
Geosciences
