| Summary: | Mg/Ca and d 18 O derived from marine biogenic carbonates have been widely used as reliable paleoenvironmental proxy for seawater temperature, salinity and water mass circulation reconstructions. The use of Mg/Ca is based on long residence time in seawater and uniform distribution with habitat depth of planktonic foraminifera. Fluid Mg/Ca affects mineralogy of CaCO 3 , thus high seawater Mg/Ca favors precipitation of aragonite instead of calcite. The records of d 18 O in carbonates yield strong correlation with seawater temperature, salinity and d 18 O. Distribution of d 18 O in water is highly heterogeneous within longitude, latitude and depth. Therefore a combination of foraminieral d 18 O and Mg/Ca could resolve temperature, d1 18 Owater, and hence salinity, which is linked to variability in fresh water balance and glacial ice volume throughout geologic history. In this work we study the effects of important seawater/fluid parameters on Mg/Ca in inorganic and d 18 O in natural samples and provide data for improving paleoceanographic reconstructions.
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