Abstract

In contrast to the classical interpretation of the Cretaceous as typical greenhouse scenario, recent research has proposed certain cold intervals (glaciations?) in the early Cretaceous (Valanginian) in high-latitudes of the northern hemisphere, based on Glendonite and other geochemical proxies. Until now from the southern hemisphere no indications for climatic cooling are known from that time. Recent studies of the late Jurassic to early Cretaceous in central Chile and Antarctica and the late Cretaceous in Patagonia give evidence for climatic variations during the Tithonian to Valanginian and also Maastrichtian in the southern hemisphere also. Preliminary results of palynofacies analysis indicate mainly shallow marine, shelf environments with a high input of terrestrial organic matter. In mineral residues of some samples microscopic glendonite crystals were found. Glendonites are recorded from time-equivalent intervals in different sections from central Chile and Antarctica in the lower Cretaceous (Valanginian). This clearly indicates, that glendonite occurrence is stratigraphicaly controlled and not by facies or lithology. Also in the upper Cretaceous first glendonites are found in Patagonia and Antarctica. In shallow marine shelf environments, as indicated by palynofacies analysis, glendonite indicates very low surface temperatures, unaffected by palaeo-oceanographical effects of mixing with cold bottom-waters. Thus the repeated occurrence of glendonite indicates alternating periods of cold and warmer ocean surface-waters in the lower and upper Cretaceous of Chile and Antarctica. Therefore our data indicate, that periods of climatic cooling also existed in the early Cretaceous of the southern hemisphere similar to the northern hemisphere and also in the upper Cretaceous.