Cenozoic seawater Sr/Ca evolution

[1] Records of seawater chemistry help constrain temporal variations in geochemical processes that impact the global carbon cycle and climate through Earth’s history. Here we reconstruct Cenozoic seawater Sr/Ca (Sr/Casw) using fossil Conus and turritellid gastropod Sr/Ca. Combined with an oxygen isotope paleotem-perature record from the same samples, the gastropod record suggests that Sr/Casw was slightly higher in the Eocene (11.4 3 mmol/mol) than today (8.54 mmol/mol) and remained relatively stable from the mid- to late Cenozoic. We compare our gastropod Cenozoic Sr/Casw record with a published turritellid gas-tropod Sr/Casw record and other published biogenic (benthic foraminifera, fossil fish teeth) and inorganic pre-cipitate (calcite veins) Sr/Casw records. Once the uncertainties with our gastropod-derived Sr/Casw are taken into account the Sr/Casw record agrees reasonably well with biogenic Sr/Casw records. Assuming a seawater [Ca] history derived from marine evaporite inclusions, all biogenic-based Sr/Casw reconstructions imply decreasing seawater [Sr] through the Cenozoic, whereas the calcite vein Sr/Casw reconstruction implies increasing [Sr] through the Cenozoic. We apply a simple geochemical model to examine the implications of divergence among these seawater [Sr] reconstructions and suggest that the interpretation and uncertaintie