The Chemical Composition of Ostracod Shells. Applications in Quaternary Palaeoclimatology

Abstract

Ostracod shells, formed from a complex arrangement of low-Mg calcite crystals around organic fibrils that include protein and chitin, have been the subject of geochemical investigations for over 50 years. Trace-element (especially Mg and Sr) and stable-isotope (δ18O and δ13C, δ11B and 87Sr/86Sr) determinations have been used extensively to reconstruct lake hydrochemistry and temperature and, to a lesser degree, ocean bottom-water temperatures. Additional developments include analyses of Fe, Mn and U for palaeoredox reconstructions, geochronological investigations (e.g. radiocarbon, U-series and amino-acid racemisation) and the use of Sr, Na and Sr-isotopes as water-mass tracers. We trace the history of these developments, outline the principles of ostracod shell geochemistry and discuss challenges that users must address if they are to derive meaningful interpretations from their data, such as the complexities surrounding trace-element uptake and isotope fractionation, the importance of hydrochemistry (especially in lakes) and analytical issues such as sample preparation.