Erhaltung geochemischer Proxies in Foraminiferen - Karbonatdiagenese im natürlichen Labor des IODP Pacific Equatorial Age Transect (PEAT)

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The trace element and isotopic chemistry of the calcite shells (tests) of foraminifera preserved in marine sediments has revealed, via geochemical proxies like oxygen isotope and Mg/Ca ratios, much of what we know about the global climate system in the geologic past. Such information is crucial for the understanding of the role of atmospheric CO2 in climate change and the ability of the Earth system to regulate atmospheric CO2. However, ancient foraminifera tests can be altered post deposition by a process where the original calcite is replaced by secondary crystals which take the form of the test. This process, termed “neomorphic recrystallisation”, is poorly understood but there is geochemical evidence that the secondary calcite can retain some of the original geochemical signal. IODP Expedition 320/321 recovered sediments along an age transect where sediments of similar age have been subjected to different diagenetic histories. A multi-component study of the pore waters, bulk carbonate components and foraminifera tests from selected intervals of this natural diagenetic laboratory would help quantify neomorphic recrystallisation and the preservation of geochemical proxies in foraminifera.