(2020) The Seawater Sr/Ca Ratio in the Past 50 Myr from Bulk Carbonate Sediments Corrected for Diagenesis
Zhang S, Zhou R & DePaolo D
14b: Plenary Hall, Monday 22nd June 22:24 - 22:27
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Hi. How safe is the assumption of a consistent biogenic partitioning over these time scales? Is there any evidence for a constant contribution to the biogenic carbonate from different organisms i.e. foraminifer / coccolith ratio? Thanks!
This is a great question. The Ksr for foram is around 0.15 while for coccolith is around 0.35. So a change in foraminifer/coccolith ratio will affect the average partitioning coefficient between bulk sediment and seawater. Unfortunately this assumption has to be made for any reconstruction of paleoseawater Sr. Our results are consistent with the Sr/Ca ratio reconstructed using pure forams, indicating that the assumption here does not cause too much inaccuracy.
Great talk, Shuo. I wanted to ask how the reconstructed K_Sr partition coefficient values compared with experimental results, and whether the variability of K_Sr after diagenesis from "initial" K_Sr can be explained via differences in carbonate mineralogy, etc. Thank you!
Hi Kim, the global average Ksr is reconstructed from seawater Sr/Ca ratio and represents the average removal of Sr/Ca by calcite and aragonite. This is different from the Ksr used to infer the seawater Sr/Ca ratio from carbonate sediments which is assumed to be a constant. Hope this clarifies the issue.
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