Early cenozoic glaciation, antarctic weathering, and seawater

Stable and radiogenic isotopic and sedimentological data from sub-Antarctic deep sea sediment cores reveal a temporal link between changes in seawater SrrSr ratios and major episodes of late Eocene–early Oligocene climate change. The SrrSr records show two major inflections, one at 38–39 Ma near the middlerlate Eocene boundary, followed by another at 33.4 Ma. Similarly, the oxygen isotope, ice-rafted debris, and clay assemblage records indicate two important climatic events: the appearance of alpine glaciers andror small ice-sheets on Antarctica in the late Eocene at 38–39 Ma, followed by a rapid transition to larger and more permanent temperate ice-sheets in the early Oligocene at 33.4 Ma. Moreover, during the Ž . early Oligocene 30–33 Ma three to four inferred peaks in glacial activity appear to coincide with subtle steps in the SrrSr record. The coupled variations in climate and seawater Sr isotope ratios during the EocenerOligocene imply a strong causal link between the two. Either changes in climate directly influenced patterns of continental weathering and Ž . hence seawater chemistry, andror a tectonic event e.g., uplift as reflected in weathering and seawater chemistry triggered relatively abrupt changes in global climate. q 1999 Elsevier Science B.V. All rights reserved.