Effects of Compositional Differences on Early Diagenetic Pathways of Carbonate Biominerals

拟议的工作将调查序列，速率， 时间和环境控制的成岩变化在两个 控矿蚀变类型：1. 前新形的 生物成因文石的矿物学和成分变化，2。 生物成因的高镁方解石对低镁方解石的稳定作用。 工程材料将从圣萨尔瓦多岛获得， 巴哈马群岛，那里有全新世和更新世沉积的珊瑚礁， 浅潮下、潮三角洲、泻湖、海滩和沙丘相 与现代类似物非常接近， 生物的属和种。 其他人先前和正在进行的工作 在地层学和沉积和成岩历史上， 这些沉积物，以及由各种 技术，为拟议的研究提供了良好的框架。 工具（反射光谱和核磁共振光谱）和 现在有了非破坏性表征技术 骨架中的H2O-、OH-和有机相。 因为 骨骼中这些不稳定相的丰度在分类学上是 控制，工作将集中在少数重要的 产生沉积物的分类群。 现代骨骼与 同一属和种的骨骼化石 其年龄和成岩历史是众所周知的， 矿物学，化学成分，显微和超微结构， 彻底的特点将澄清几个角色 早期成岩作用中的重要矿物相和成分相 蚀变碳酸盐骨架

The proposed work will investigate the sequences, rates, timing, and environmental controls of diagenetic changes in two types of mineral controlled alteration: 1. Preneomorphic mineralogical and compositional changes in biogenic aragonites, 2. The stabilization of biogenic high Mg calcites to low Mg calcites. Materials for the work will be obtained from San Salvador Island, the Bahamas, where Holocene and Pleistocene sediments of reef, shallow subtidal, tidal delta, lagoonal, beach and dune facies exist in close proximity to modern analogs occupied by the same genera and species of organisms. Prior and ongoing work by others on the stratigraphy and depositional and diagenetic histories of these sediments, and age dates determined by a variety of techniques, provide and excellent framework for the proposed study. Tools (reflectance and nuclear magnetic resonance spectroscopy) and techniques are now available for non-destructive characterization of H20-, OH- and organic-containing phase in skeletons. Because abundances of these unstable phases in skeletons are taxonomically controlled, work will focus on a small number of important sediment-producing taxa. Comparisons of modern skeletons with suites of fossil skeletal material of the same genera and species whose ages and diagenetic histories are well-known, and whose mineralogy, chemical composition, and micro- and ultrastructure are thoroughly characterized will clarify the roles of several important mineral and compositional phases in the early diagenetic alteration carbonate skeletons.