Antarctic Peninsula Late Cretaceous-Early Cenozoic palaeoenvironments and Gondwana palaeogeographies
A review is made of stratigraphical, geochemical and palaeogeographical data from the northern Antarctic Peninsula and the Southern Ocean for Late Mesozoic-Early Cenozoic times. Clay mineral and S/total organic C ratios are used to re-assess earlier scenarios, and it is suggested that eight climatic episodes affected the northern Antarctic Peninsula between Late Aptian and Palaeogene times. Evolving palaeogeographies in southern Gondwana allowed the connection of the inter-continental western Weddell Basin to the proto-Indian Ocean during Albian to Cenomanian times, and it is suggested that this caused an initial cooling of ambient temperatures in the northern Antarctic Peninsula area. This situation altered when the South Atlantic seaway was opened to equatorial regions, producing a Campanian warm episode. Throughout this period, the climate was humid and non-seasonal (ever-wet) and the adjacent seas were dominated by mineral-walled phytoplankton. A Maastrichtian to Mid-Palaeocene cool period is postulated following the establishment of more-polar ocean circulation routes along the southern edge of the Pacific Basin, and the climate became seasonally humid with phytoplankton production switching to organic-walled dominant. The global Palaeogene climatic optimum was a warm, ever-wet episode but as it waned from Mid-Eocene times, a further, relatively short, period of marked seasonality is recognised. Later, Eocene climates were again ever-wet and became progressively cooler. The Late Eocene-Early Oligocene opening of the Tasman Sea and Drake Passage seaways caused cold conditions on Seymour Island, followed rapidly by the earliest glacial sediments on King George Island and the establishment of mineral-walled phytoplankton dominance in the seas. (C) 2000 Elsevier Science Limited. All rights reserved.