Abstracts on Global Climate Change
       

Jun 2007

Eustasy and sea water Sr composition: application to high-resolution Sr-isotope stratigraphy of Miocene shallow-water carbonates

Kroeger, KF Reuter, M Forst, MH Breisig, S Hartmann, G Brachert, TC

SEDIMENTOLOGY 54:3 565-585

Oceanic Sr-87/Sr-86-isotope ratios are strongly influenced by rates of silicate weathering and therefore linked not only to glaciation but also to sea-level change. The present study combines analysis of sequence stratigraphy and basin architecture with Sr-isotope stratigraphy in Miocene shallow-water sediments in southern Portugal and Crete (Greece). The common method is to use smoothed global sea water Sr-isotope reference curves but here a different approach is chosen. Instead, measured Sr-isotope curves are correlated with unsmoothed reference curves by identification of similar fluctuations in the order of several 100 kyr. Transgressive intervals are characterized by increasing Sr-isotope ratios interpreted as corresponding to intensified silicate weathering as a consequence of deglaciation, while lowstand deposits have low Sr-isotope ratios. Comparison of Sr-isotope curves and sedimentary sequences in the studied basins with independent global delta O-18 data and data on global sea-level might suggest a general relationship, supporting a connection to global climate change. Because of these relationships, the method presented herein has a high potential for use in high-resolution age dating and is also applicable in shallow-water sediments.

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