Early cenozoic glaciation, antarctic weathering, and seawater ⁸⁷Sr/⁸⁶Sr: Is there a link?

Stable and radiogenic isotopic and sedimentological data from sub-Antarctic deep sea sediment cores reveal a temporal link between changes in seawater ⁸⁷Sr/⁸⁶Sr ratios and major episodes of late Eocene-early Oligocene climate change. The ⁸⁷Sr/⁸⁶Sr records show two major inflections, one at 38-39 Ma near the middle/late 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 and/or 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 early Oligocene (30-33 Ma) three to four inferred peaks in glacial activity appear to coincide with subtle steps in the ⁸⁷Sr/⁸⁶Sr record. The coupled variations in climate and seawater Sr isotope ratios during the Eocene/Oligocene imply a strong causal link between the two. Either changes in climate directly influenced patterns of continental weathering and hence seawater chemistry, and/or a tectonic event (e.g., uplift) as reflected in weathering and seawater chemistry triggered relatively abrupt changes in global climate.