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

海洋沉积物中保存的有孔虫方解石壳的微量元素和同位素化学（测试）通过氧同位素和Mg/Ca比值等地球化学指标揭示了我们对过去地质时期全球气候系统的了解。这些信息对于了解大气二氧化碳在气候变化中的作用以及地球系统调节大气二氧化碳的能力至关重要。然而，古代有孔虫测试可以在沉积后通过一个过程来改变，在这个过程中，原始方解石被采用测试形式的次级晶体所取代。这一过程被称为“新晶重结晶”，人们对其了解甚少，但有地球化学证据表明，次生方解石可以保留一些原始的地球化学信号。IODP 320/321考察队沿年龄样带回收沉积物，其中年龄相近的沉积物经历了不同的成岩历史。对该天然成岩实验室选定区间的孔隙水、整体碳酸盐组分和有孔虫测试进行多组分研究，将有助于量化有孔虫的新形态再结晶和地球化学指标的保存。

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.