Diagenetic carbonates as a tool for reconstructing water temperatures in fossil-poor sections

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Abstract
Reconstructions of ocean temperature through deep time frequently rely on isotopic or elemental compositions biotic carbonates (e.g. foraminifera, coccolithophores, molluscs, brachiopods). But what can be done when fossil carbonate is absent? Several high-latitude early Cenozoic and Mesozoic sites (e.g. Svalbard, Denmark) are characterized by an early dissolution of such biotic carbonates, with rapid reprecipitation of the CaCO3 as diagenetic carbonates, such as ikaite, calcite concretions, and interstitial calcite. Can these be of use in reconstructing palaeotemperature or paleoenvironmental conditions? What exactly do these carbonates represent? We investigate their age relative to their host sediment, and whether the pore waters they formed in could be considered to reflect ocean bottom-waters. We also look at possible kinetic biases and elemental fractionation during their formation, and if we can apply temperature proxies such as Mg/Ca ratios, stable oxygen isotopes, and/or clumped isotope thermometry.