Cretaceous climatic oscillations in the Bering area (Alaska and Koryak Upland): Isotopic and palaeontological evidence

New isotopic palaeotemperatures, estimated from δ18O values of Early Albian, latest Campanian and Early Maastrichtian ammonoid shells of Southern Alaska, as well as our previously published data on the Cretaceous of the Koryak Upland, have been used to reconstruct palaeonvironmental changes in the Bering area. Significant seasonal contrast, marked in Alaska and the adjacent area during the Early Albian, as well as the Coniacian, was partly connected apparently with the possible penetration of cooler waters from the polar area via the Strait of Alaska. Data suggest that the Bering Land Bridge existed during the post-Aptian Cretaceous, with the exception of the Early Albian and Coniacian. Both the stable isotope and the floral data on the post-Aptian Cretaceous of the Bering area suggest the existence of warm climatic conditions in the Late Albian, latest Cenomanian, Coniacian, Santonian to Early Campanian, latest Campanian, and also late Early Maastrichtian. Recurrent terrestrial cooling in northern Alaska, reflected in the composition of corresponding floras, took place possibly because of a barrier to poleward oceanic heat-transport via the Western Interior Seaway (WIS) of North America during the Turonian and Santonian through Early Campanian, then during the Late Maastrichtian through Danian.