The Importance of Diagenesis upon the C, S, and B Isotopic Composition of Carbonates: Implication for Reading the Rock Record

碳酸盐岩成岩作用的研究使用了碳、氧同位素和微量元素的经典工具，现在有许多其他的地球化学替代方法和潜在可用的方法。PI建议研究成岩作用对硫和硼两种代用品的同位素系统学的影响，并重新审视控制有机质和无机碳酸盐碳同位素的因素。这项工作将主要在上更新世沉积物中进行，使用浅水和陆地钻探收集的材料以及ODP值。材料将包括未改变的样品以及那些受涉及淡水和海洋流体的成岩作用影响的样品。除了更现代的样品，PI还将研究新元古代更老的剖面中的B，一些人认为这些剖面既保留了原始的地球化学，也被另一些人认为受到了成岩作用的影响。PI将测试确定碳同位素信号是原始的，而不是成岩作用的最成熟的标准之一，主要是有机和无机材料的碳同位素之间是否存在相关性，这一点最近受到了质疑。这项工作对古气候和古海洋研究具有重要意义。其他更广泛的影响包括研究生和本科生培训，对高中生的推广，以及与迈阿密的创造性学习和参与机会计划的合作。PI建议，利用地球化学研究碳酸盐岩的成岩作用正处于一个令人兴奋的点。不仅碳、氧同位素和微量元素的传统工具在准确度、灵敏度和微采样能力方面不断改进，而且还可能有一些额外的地球化学替代物和应用这些替代物的方法。这些代理中的一些需要改进，而另一些则等待发现和开发。PI将研究成岩作用对硫和硼两种同位素体系的影响，并重新审视控制有机物质和无机碳酸盐碳同位素的因素。这项工作将主要在碳酸盐平台侧面和表面沉积的年轻碳酸盐沉积物(上更新世)中进行，使用浅水和陆地钻探收集的材料以及ODP值。材料将包括据称没有改变的样品，以及受到涉及淡水和海洋流体的成岩作用的明确影响的材料。提出这一建议的理由是，C、B和S的同位素已经在广泛的地质时间尺度上被用来解释地球-S地球化学系统的变化。这样的工作是在没有对可能改变这些代理的过程的一些基本了解的情况下进行的。除了更现代的样品外，PI还将研究新元古代剖面中的B，一些人认为这些剖面既保留了原始的地球化学，也有人认为受到成岩作用的影响。最后，确定碳同位素信号是原始的，而不是成岩作用的最成熟的标准之一，主要是有机和无机材料的碳同位素之间是否存在相关性，最近受到了质疑。因此，需要确定这种相关性在多大程度上表明这些信号是原始的，或者相关性的存在是否实际上表明成岩作用实际上已经发生。这项工作对古气候和古海洋研究具有重要意义。其他更广泛的影响包括研究生和本科生培训，对高中生的接触，以及与迈阿密的创造性学习和参与机会计划的合作。

The study of diagenesis in carbonates uses classic tools of C and O isotopes and trace elements and now there are a number of additional geochemical proxies and methods that are potentially available. The PI proposes to examine the influence of diagenetic process upon the isotopic systematics of two of these proxies, sulfur and boron, as well as take a new look at factors controlling the carbon isotopes of organic material and inorganic carbonates. This work will be carried out mainly in Plio-Pleistocene sediments using material collected by shallow water and land drilling as well as the ODP. Material will include unaltered samples as well as those affected by diagenesis involving freshwater and marine fluids. In addition to the more Modern samples, the PI will also study B within older, Neoproterozoic, sections which have been proposed by some to have both retained their original geochemistry and by others to have been influenced by diagenesis. The PI will test one of the most established criteria for determining that the carbon isotopic signals are original, rather than diagenetic, mainly the presence of a correlation between the carbon isotopes of organic and inorganic material, which has recently been questioned. The work has implications for paleoclimatic and paleoceanographic studies. Other broader impacts include graduate and undergraduate training, outreach to high school students and collaboration with the Miami-based Creative Learning and Engagement Opportunities program.The PI suggests that the study of diagenesis in carbonate rocks using geochemistry is at an exciting point. Not only have the classic tools of C and O isotopes and trace elements continued to improve in terms of their accuracy, sensitivity and microsampling ability, but there are a number of additional geochemical proxies and methods of applying these proxies potentially available. Some of these proxies need to be refined while others wait to be discovered and developed. The PI will examine the influence of diagenetic process upon the isotopic systematics of two of these, sulfur and boron, as well as take a new look at factors controlling the carbon isotopes of organic material and inorganic carbonates. This work will be carried out mainly in young carbonate sediments (Plio-Pleistocene) deposited on the flanks and surface of carbonate platforms using material collected by shallow water and land drilling as well as the ODP. Material will include supposedly unaltered samples as well as materials which have been unequivocally affected by diagenesis involving freshwater and marine fluids. The rationale for this proposal is that the isotopes of C, B, and S have already been used over a wide ranges of geological time scales to interpret changes in the Earth?s geochemical systems. Such work is being undertaken without some of the fundamental understanding of the processes which may alter these proxies. In addition to the more Modern samples, the PI will also study B within Neoproterozoic sections which have been proposed by some to have both retained their original geochemistry and by others to have been influenced by diagenesis. Finally, one of the most established criteria for determining that the carbon isotopic signals are original, rather than diagenetic, mainly the presence of a correlation between the carbon isotopes of organic and inorganic material, has recently been questioned. Hence there is a need to establish to what extent such correlations indicate that the signals are original or whether in fact the presence of a correlation indicates that diagenesis has actually occurred. The work has implications for paleoclimatic and paleoceanographic studies. Other broader impacts include graduate and undergraduate training, outreach to high school students and collaboration with the Miami-based Creative Learning and Engagement Opportunities program.