Magnitudes of sea-level lowstands of the past 500,000 years

Article Abstract:

Techniques to estimate natural fluctuations in seal-level and global ice-volumes use fossil coral-reef terraces or oxygen-isotope records from benthic foraminifera. Significant values for minima, or lowstands, before the Last Glacial Maximum (LGM) are not produced by fossil reefs. However improved lowstand estimates, extending back to 500,000 years before present, are presented, based on evidence of extreme high-salinity conditions in the glacial Red Sea, combined with a simple hydraulic control model of water flow through the Strait of Bab-el-Mandab.

Ice, Sea level

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Foraminiferal boron isotope ratio as a proxy for surface ocean pH over the past 21 Myr

Article Abstract:

Data on foraminiferal boron isotopes can be used to determine past ocean pH for the past 21 Myr. Analysis of samples from a deep-sea sediment core shows that seawater boron concentrations and isotopic composition were both constant for the past 21 Myr. Based on foraminiferal isotope data, ocean pH was found to be 7.4 +/- 0.2. This value increased to 8. 2 +/- 0.2 about 7.5 Myr ago, and is almost the same today.

Measurement, Foraminifera, Fossil, Fossil foraminifera, Oceanography, Hydrogen-ion concentration, pH measurement

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Past temperature and delta-18O of surface ocean waters inferred from foraminiferal Mg/Ca ratios

Article Abstract:

It has been established that, in a field-based calibration experiment, the variation of MG/Ca ratios with temperature is similar for eight species of planktonic foraminifera. Past temperatures reconstructed from Mg/Ca ratios followed faunal abundance and alkenone saturation.

Research, Ocean-atmosphere interaction, Oceanographic research

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