The post-mortem history of a bone revealed by its trace element signature: the case of a fossil whale rostrum
Decree, S.; Herwartz, D.; Mercadier, J.; Miján, I.; de Buffrénil, V.; Leduc, T.; Lambert, O. (2018). The post-mortem history of a bone revealed by its trace element signature: the case of a fossil whale rostrum. Chem. Geol. 477: 137-150. https://dx.doi.org/10.1016/j.chemgeo.2017.12.021
In: Chemical Geology. Elsevier: New York; London; Amsterdam. ISSN 0009-2541; e-ISSN 1872-6836
Studies dedicated to palaeoenvironments and taphonomy have made wide use of rare earth elements (REE) contents of fossil bones as proxies. However, the complex diagenetic history of individual specimens combined with intra-bone REE fractionation and the uncertain timing of REE uptake generally prevents the robust interpretation of REE patterns. In this case study we show that combining REE analysis with, on the one hand, histology and microstructural observations and, on the other hand, additional analyses of other trace elements, allows deciphering at least three distinct trace element uptake stages, as well as one leaching event.More than 35 trace elements (including the REE) are analysed using laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) within compact rostrum bones of the Miocene-Pliocene beaked whale Globicetus hiberus from deep-sea deposits and a comparable extant specimen (Blainville's beaked whale Mesoplodon densirostris). Comparison of the extinct and the extant bones allows a better quantification of the diagenetic trace element content.This study highlights the crucial role played by diagenetic minerals such as the Fe-Mn oxyhydroxides in the uptake and release of trace elements (Co, Ni, Ti, V, Zr, Hf and Nb) and REE by bones, in response to changes of the diagenetic fluid redox conditions over time. Such changes of the geochemical environment help constraining the post-mortem history of the bone and its interaction with diagenetic fluids. We conclude that the unique interpretation of geochemical proxies within individual fossil bones requires a thorough investigation of each individual specimen.
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