MIDDLE-LATE CRETACEOUS CLIMATE OF THE SOUTHERN HIGH-LATITUDES - STABLE ISOTOPIC EVIDENCE FOR MINIMAL EQUATOR-TO-POLE THERMAL-GRADIENTS

A detailed delta(18)O and delta(13)C stratigraphy has been generated f rom analysis of well-preserved Albian-early Maastrichtian foraminifera from Deep Sea Drilling Project (DSDP) Sites 511 and 327 (Falkland Pla teau; approximate to 58 degrees S-62 degrees S paleolatitude) in the s outhern South Atlantic, and Cenomanian and Coniacian-Santonian foramin ifera from DSDP Site 258 (Naturaliste Plateau; approximate to 58 degre es S paleolatitude) in the southern Indian Ocean. These results, when combined with previously published Maastrichtian stable isotope data f rom Ocean Drilling Program (ODP) Site 690 (Weddell Sea, approximate to 65 degrees S paleolatitude), pro,ide new insight into the climatic an d oceanographic history of the southern high latitudes during middle-l ate Cretaceous time. The planktonic foraminifer delta(18)O curves reve al a gradual warming of surface waters from the Albian through the Cen omanian follow-ed by extremely warm surface waters from the Turonian t hrough the early Campanian. Long-term cooling of surface waters began in the late early Campanian and continued through the end of the Maast richtian. The benthic foraminifer delta(18)O record generally parallel s changes in the oxygen isotopic curves defined by shallow-dwelling pl anktonic foraminifera. The vertical oxygen and carbon isotopic gradien ts were relatively low during the Albian-Cenomanian, high from the Tur onian-early Campanian, and then low during the late Campanian and Maas trichtian. Foraminiferal oxygen isotopic data from published sources a nd this study are averaged for each site, corrected for latitudinal ch anges in salinity based on modern-day surface-water values, and plotte d versus paleolatitude for the late Albian, Coniacian-Santonian, and l ate Maastrichtian. Differences between low- and high-latitude surface- water paleotemperatures are estimated at approximate to 14 degrees C d uring the late Albian and late Maastrichtian, but the Coniacian-Santon ian reconstruction reveals only a 0-4 degrees C latitudinal temperatur e gradient. Uncertainty regarding Cretaceous salinity gradients and po ssible diagenetic alteration of delta(18)O values introduce error into our estimates of paleolatitudinal thermal gradients; however, apparen t low equator-to-pole temperature differences could indicate much high er poleward heat transport than at present.