Cool Cretaceous climates: new data from the Albian of Western Australia

Although previous geological, palaeobotanical and geochemical data from the Albian of Australia have suggested the possibility of cool palaeoclimates, there are few well-constrained stable isotope palaeotemperatures studies from this region. In this paper we present the results of stable isotope analyses of dimitobelid belemnites from the Albian Gearle Siltstone, Carnarvon Basin, Western Australia. Oxygen isotope values for diagenetically least-altered samples give values ranging between delta(18)O - 0.02 and 0.85 parts per thousand PDB, which equate to a mean palaeotemperature of 10.08 degrees C (assuming delta(w), of - 1.2 parts per thousand SMOW). This value is broadly consistent with recently published isotope data from the Albian Antarctic and with estimates for mid-Cretaceous latitudinal temperature gradients, implying that cool palaeoclimates occurred during a period of 'Greenhouse' Earth.