Brian T. Huber, David A. Hodell, and Christopher P. Hamilton
Middle-Late Cretaceous climate of the southern high latitudes; stable isotopic evidence for minimal equator-to-pole thermal gradients
Geological Society of America Bulletin (October 1995), 107(10):1164-1191

Abstract:
A detailed delta ¹⁸ O and delta ¹³ C stratigraphy has been generated from analysis of well-preserved Albian-early Maastrichtian foraminifera from Deep Sea Drilling Project (DSDP) Sites 511 and 327 (Falkland Plateau; nearly equal 58 degrees S-62 degrees S paleolatitude) in the southern South Atlantic, and Cenomanian and Coniacian-Santonian foraminifera from DSDP Site 258 (Naturaliste Plateau; nearly equal 58 degrees S paleolatitude) in the southern Indian Ocean. These results, when combined with previously published Maastrichtian stable isotope data from Ocean Drilling Program (ODP) Site 690 (Weddell Sea, nearly equal 65 degrees S paleolatitude), provide new insight into the climatic and oceanographic history of the southern high latitudes during middle-Late Cretaceous time. The planktonic foraminifer delta ¹⁸ O curves reveal a gradual warming of surface waters from the Albian through the Cenomanian followed by extremely warm surface waters from the Turonian through the early Campanian. Long-term cooling of surface waters began in the late early Campanian and continued through the end of the Maastrichtian. The benthic foraminifer delta ¹⁸ O record generally parallels changes in the oxygen isotopic curves defined by shallow-dwelling planktonic foraminifera. The vertical oxygen and carbon isotopic gradients were relatively low during the Albian-Cenomanian, high from the Turonian-early Campanian, and then low during the late Campanian and Maastrichtian. Foraminiferal oxygen isotopic data from published sources and this study are averaged for each site, corrected for latitudinal changes in salinity based on modern-day surface-water values, and plotted versus paleolatitude for the late Albian, Coniacian-Santonian, and late Maastrichtian. Differences between low- and high-latitude surface-water paleotemperatures are estimated at nearly equal 14 degrees C during the late Albian and late Maastrichtian, but the Coniacian-Santonian reconstruction reveals only a 0-4 degrees C latitudinal temperature gradient. Uncertainty regarding Cretaceous salinity gradients and possible diagenetic alteration of delta ¹⁸ O values introduce error into our estimates of paleolatitudinal thermal gradients; however, apparent low equator-to-pole temperature differences could indicate much higher poleward heat transport than at present.