Early Cenozoic Glaciation, Antarctic Weathering, and seawater 87Sr/86Sr: is there a Link?

• Main Authors: Zachos, James, Opdyke, Bradley, Quinn, Terrence, Jones, Cynthia, Halliday, Alexander
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier
• Subjects: Keywords: Cenozoic; Eocene; glaciation; Oligocene; paleoclimate; seawater; strontium isotope; weathering Antarctic weathering; Early cenozoic glaciation; Antarctic; Antarc*; Antarctica
• Online Access: http://hdl.handle.net/1885/92434; https://openresearch-repository.anu.edu.au/bitstream/1885/92434/5/MigratedxPub23540_RSD_1999.pdf.jpg; https://openresearch-repository.anu.edu.au/bitstream/1885/92434/7/01_Zachos_Early__Cenozoic_Glaciation,_1999.pdf.jpg

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.