In Situ Geochemical Analysis of Organics in Growth Lines of Antarctic Scallop Shells: Implications for Sclerochronology
In Situ Geochemical Analysis of Organics in Growth Lines of Antarctic Scallop Shells: Implications for Sclerochronology
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DOI：
10.3390/min10060529
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发表时间：
2020-06
期刊：
影响因子：
2.5
通讯作者：
A. Pérez-Huerta;S. Walker;Chiara Cappelli
中科院分区：
文献类型：
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作者：
A. Pérez-Huerta;S. Walker;Chiara Cappelli
双壳贝壳广泛用作古气候和古环境重建的生物档案。最近贝壳中的代理校准是硬化年代学和地球化学数据在化石中的应用的基础。然而，壳地球化学信息可能会随着早期成岩过程中晶间有机基质成分的消失而改变，包括那些与壳生长增量相关的成分。因此，为了正确使用化石壳中的硬化年代记录，需要对此类有机物的化学性质进行评估。在这里，我们使用原子探针断层扫描 (APT) 对南极扇贝 Adamussium colbecki 壳生长增量中的不溶性有机基质进行原位地球化学表征。我们证实存在羧化的富含硫的蛋白聚糖，可能与这些扇贝中方解石的成核和生长有关，并且含有显着浓度的镁和钙。这些有机成分的成岩作用修改可能会影响基于 Mg/Ca 比率的代理数据，但更重要的是 δ15N 代理的使用，因为大多数壳氮可能与蛋白质的酰胺基团结合。总体而言，我们的研究结果强化了这样的观点：在理解地球化学替代物时需要考虑贝壳有机物。
Bivalve shells are extensively used as bioarchives for paleoclimate and paleoenvironmental reconstructions. Proxy calibrations in recent shells are the basis for sclerochronology and the applications of geochemistry data to fossils. Shell geochemical information, however, could be altered with the disappearance of intercrystalline organic matrix components, including those linked to shell growth increments, during early diagenesis. Thus, an evaluation of the chemistry of such organics is needed for the correct use of sclerochronological records in fossil shells. Here, we use atom probe tomography (APT) for in situ geochemical characterization of the insoluble organic matrix in shell growth increments in the Antarctic scallop, Adamussium colbecki. We confirm the presence of carboxylated S-rich proteoglycans, possibly involved in calcite nucleation and growth in these scallops, with significant concentrations of magnesium and calcium. Diagenetic modification of these organic components could impact proxy data based on Mg/Ca ratios, but more importantly the use of the δ15N proxy, since most of the shell nitrogen is likely bound to the amide groups of proteins. Overall, our findings reinforce the idea that shell organics need to be accounted for in the understanding of geochemical proxies.