Greenhouse climate and ocean during the Cretaceous

Abstract：The Cretaceous greenhouse climate and paleoceanography is one of hot topics in the Earth sciences during the past twenty years. Observations and ocean models suggest that the climate system and oceanic dynamics during the greenhouse Cretaceous were quite different from their present icehouse patterns. Based on a wealth of geological, geochemical and paleontological data and climatic and oceanographic modeling data obtained in recent years, this paper reviews new advances in the study of the Cretaceous climate and paleoceanography. The fossils and oxygen isotope data reveal that the global mean annual temperature during the Cretaceous was generally 3–10℃ higher than today, and that the mean latitudinal temperature gradient of the ocean is estimated at only　0.15℃/1°– 0.3 ℃/1°. The global oceanic structures and ocean circulation were possibly completely different from those of today, since the forcing of ocean circulation was very likely to be the change in salinity, rather than temperature. Study of Cretaceous abyssal deposits suggests the transformation from the extensive occurrence of carbonate platform facies, black shale interbeds, black shale and oceanic red beds in the Early Cretaceous to predominance of oceanic red beds in the Late Cretaceous. The study of the mechanism of transformation of deposits and its relations to paleo-oceanography and paleoclimate is the main scientific objective of IGCP463/494.