HIGH-LATITUDE PALEOTEMPERATURE VARIATION - NEW DATA FROM THE TITHONIAN TO EOCENE OF JAMES-ROSS-ISLAND, ANTARCTICA

An oxygen stable isotope study of molluscan macrofossils from the Tith onian to the Eocene of the James Ross Island and Alexander Island area s, Antarctica, was carried out in conjunction with careful petrographi c, mineralogical and geochemical analyses to assess the state of fossi l preservation. The Alexander Island samples all showed evidence of al teration whilst samples from James Ross Island were variably preserved . The isotopic composition of those samples which met the textural and chemical criteria for well preserved primary skeletal carbonate mater ial were then used to construct a record of high latitude marine water temperature variation. This record shows a marked cooling of palaeote mperatures from the late Jurassic to the Albian, a warming in recorded palaeotemperatures during the mid Cretaceous and a gradual cooling fr om the mid Cretaceous to the Eocene. The isotopic pattern parallels th at from low latitude sites and suggests that climatic change was globa l and that relatively uniform latitudinal palaeotemperature gradients may have been maintained during a time of greenhouse climate. Using th e James Ross Island data to calculate probable polar temperatures over the adjacent Antarctic continent shows that cold temperate or sub-pol ar conditions would have been established during the Albian, late Maas trichtian and Eocene.