Smith Lecture: Evolution of Cretaceous climate at southern high latitudes: Initial results from IODP Expedition 369 offshore southern Australia
Brian Huber, Smithsonian Institution
International Ocean Discovery Program Expedition 369 recovered an extensive succession of Cretaceous sediments from 60°S paleolatitude, south and southwest of Australia, that provide new insights to the evolution of the high latitude climate and oceanography during the last phase of Gondwana continental breakup. Four sites recovered a nearly continuous record from the late Albian through early Campanian and two recovered Oceanic Anoxic Event 2 (94-93 Ma), which contains laminated black shales with up to 12% total organic carbon. Negative shifts in osmium isotopes and foraminiferal oxygen isotopes across the OAE 2 black shales demonstrates that volcanic outgassing of CO2 was the trigger for global warming, increased plankton productivity and enhanced preservation of organic matter. Compilations of southern high latitude foraminiferal δ18O and TEX86 paleotemperature data demonstrate warm greenhouse conditions from the Albian-Cenomanian, extreme warmth during the Turonian through late Santonian, and long-term cooling from the Campanian-Maastrichtian. Comparison of the paleotemperature compilations with estimates of variation in pCO2, crustal production at mid-ocean ridges and Large Igneous Provinces, and lengths of continental and island arcs demonstrates that links between Cretaceous temperature variations and presumed forcing factors are not well established.
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