RPG: Organic Geochemistry of Fossil Non-Marine Molluscs with Applications to Amino Acid Racemization Dating

有机溶剂中保留的氨基酸的对映体（D/L）值 软体动物化石基质被用来表征第四纪 地层单位，为地层对比提供依据 和相对年龄的估计。 D/L值作为函数增加 的时间（称为外消旋化），在一定程度上控制的速率 化石沉积后的热历史。 蛋白 水解也对氨基酸产生速率控制作用 外消旋化，因为蛋白质末端的氨基酸 优先于位于蛋白质链内的那些。 水解对保留的D/L值的影响程度 软体动物壳蛋白的定义不明确。 水解产物的浸出 氨基酸（主要是D-对映体）可以影响 氨基酸消旋化（AAR）测年法。 这项工作的重点 化石软体动物外壳的物理和化学条件 蛋白质影响AAR方法的分辨率。 化石有机物 将使用分子量分离方法研究基质 来定义“抵抗”和“不稳定”的成分。 对映 将使用HPLC方法测定各组分的值， 了解水解作用对成岩消旋作用的影响。 将使用扫描观察沥滤的物理证据 电镜 这项研究将主要集中在软体动物 动物群来自南部高平原的第四纪单位， 代表了蛋白质成岩作用的漫长地质记录 可以研究。

Enantiomeric (D/L) values of amino acids preserved in the organic matrix of molluscan fossils are used to characterize Quaternary stratigraphic units, and provide a basis for correlation of strata and estimation of relative age. D/L values increase as a function of time (termed racemization), at a rate controlled to some extent by post-depositional thermal history of the fossil. Protein hydrolysis also exerts a rate-controlling effect on amino acid racemization, because amino acids on protein termini racemize preferentially to those located within the protein chain. The extent to which hydrolysis affects D/L values preserved in mollusc shell protein is not well-defined. Leaching of hydrolyzed amino acids (primarily D-enantionmers) can affect resolution of the amino acid racemizaton (AAR) dating method. The focus of this work is how the physical and chemical condition of fossil mollusc shell protein affects resolution of the AAR method. Fossil organic matrix will be studied using molecular weight separation methods to define "resistant" versus "labile" components. Enantiomeric values will be determined in each component using HPLC methods, to understand the influence of hydrolysis on diagenetic racemization. Physical evidence of leaching will be observed using scanning electron microscopy. This study will focus primarily of molluscan fauna from Quaternary units of the southern High Plains, which represent a long geologic record during which protein diagenesis can be studied.