Preservation assessment of Miocene–Pliocene tooth enamel from Tugen Hills (Kenyan Rift Valley) through FTIR, chemical and stable-isotope analyses
Preservation assessment of Miocene–Pliocene tooth enamel from Tugen Hills (Kenyan Rift Valley) through FTIR, chemical and stable-isotope analyses
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通过 FTIR、化学和稳定同位素分析对图根山（肯尼亚裂谷）中新世至上新世牙釉质的保存进行评估
DOI：
10.1016/j.jas.2010.01.029
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发表时间：
2010
影响因子：
2.8
通讯作者：
S. Delattre
中科院分区：
文献类型：
--
作者：
Damien Roche;Loïc Ségalen;E. Balan;S. Delattre
我们对东非两个中上新世地层(Lukeino和Mabaget FMS)的哺乳动物和鳄鱼的牙齿釉质化石进行了红外光谱、化学和稳定同位素分析。红外光谱表明，该化石珐琅中含有生物磷灰石(生物磷灰石)，没有明显的次生碳酸盐污染。用几种经验红外指标分析了釉质的晶体化学特征。与现代珐琅相比，化石珐琅的有机质、水和磷灰石结构碳酸盐的含量较少。化石磷灰石比生物磷灰石具有更好的结晶度。化石磷灰石的钙磷质量比和氟含量介于生物磷灰石和地质氟磷灰石之间。这些样本还显示出显著的晶体化学差异，这取决于脊椎动物群体(哺乳动物与爬行动物)和蚕丝生态环境(Lukeino FM与Mabaget FM)。尽管有这些变化，但化石釉质中的化学成分(碳酸盐和氟)与碳酸盐的稳定同位素比值(δ13C和δ18O)之间没有关系。所研究的三个哺乳动物化石类群的稳定同位素组成与它们的生态特征一致，这有力地支持了古环境信号的保存。例如，典型的C3-和C4-植物同位素组成分别反映在野马和马科动物中，两栖河马的δ18O值低于陆地草食动物，正如预期的那样。
We investigated fossil tooth enamel of mammals and crocodiles from two Mio-Pliocene East-African formations (Lukeino and Mabaget Fms) using infrared spectroscopy and chemical and stable-isotope analyses. Infrared spectra indicate that the fossil enamel contains biological apatite (bioapatite), without significant secondary carbonate contaminations. Several empirical infrared indexes were used to analyze the crystal–chemical characteristics of enamel. Fossil enamel has less organic matter, water and structural carbonate of apatite than modern enamel with which it was compared. Fossil apatite has a better crystallinity than bioapatite. The calcium/phosphorus mass ratio and the fluorine content of fossil apatite show intermediate values between bioapatite and geological fluorapatite. The samples also display significant crystal-chemical variations, depending on the vertebrate group (mammals vs. reptiles) and the taphonomic context (Lukeino Fm vs. Mabaget Fm). In spite of these changes, no relationship was observed between the chemical contents (carbonate and fluorine) and the stable-isotope ratios of carbonate (δ13C and δ18O) in fossil enamel. Preservation of the palaeoenvironmental signals is strongly supported by the fact that the stable-isotope composition of the three investigated fossil mammalian taxa (deinotheres, equids and hippos) is consistent with their ecological features. For instance, typical C3- and C4-plant isotope compositions are reflected in the deinotheres and equids, respectively, and amphibious hippos display lower δ18O values than terrestrial herbivores, as expected.