Global Controls on the Carbon Isotopic Composition of Carbonate Platforms: Unrelated to the Glocal Carbon Cycle

PI将检验这样一种假设，即在过去25年中，边缘台地碳酸盐岩碳同位素组成的变化并不像人们普遍认为的那样与全球碳循环的变化有关，而是与全球海平面波动的变化有关，并反映了邻近台地浅水中生产的同位素富集碳酸盐岩的相对输入。这一假设将通过分析从DSDP和ODP地点采集的大量碳酸盐材料中的ä13C来验证，这些地点位于现代碳酸盐台地附近。π吗?s的初步数据表明：(i)在巴哈马等与碳酸盐台地相邻的许多地点采集的这些序列中提取的块状碳酸盐沉积物的ä13C可以相互关联，但这些变化与全球碳循环的变化无关；（ii）在过去10万年中，在马尔代夫和澳大利亚的一些地点可以识别出类似的变化。PI将进一步研究这一现象，通过(i)将研究扩展到其他地点，（ii）将样品的时间范围延长到25 Ma， （iii）调查海平面高幅度冰川-上升变化的现象，（iv）增加有机物质ä13C的变化，作为浅水碳酸盐岩平台生产的代理。(v)结合来自浅海碳酸盐台地的输入随着方解石-文石海洋的变化和有机物埋藏的变化而改变ä13C的概念，开发一个模型。更广泛的影响：认识到碳循环以外的其他因素可以控制碳酸盐的ä13C，将提高对有机碳埋藏历史的理解，但也会使人们了解这些记录与当前增加大气二氧化碳分压和将碳从有机储集层转移到无机储集层的人为实验之间的关系。该项目将支持一篇博士论文以及RSMAS地球化学实验室中本科生、高中生和高中教师的互动。

The PI will test the hypothesis that over the past 25 yrs the variations in the carbon isotopic composition of marginal platform carbonates are not related to changes in the global carbon cycle as widely believed, but are instead related to the variations in global sea-level fluctuations and reflect the relative input of isotopically enriched carbonate produced in shallow water on the adjacent platforms. This hypothesis will be tested by analyzing the ä13C in bulk carbonate material sampled from DSDP and ODP sites cored adjacent to modern carbonate platforms. PI?s preliminary data has shown that (i) the ä13C of bulk carbonate sediments retrieved from such sequences cored at a number of sites adjacent to carbonate platforms such as the Bahamas can be correlated with each other, but that these variations are unrelated to changes in the global carbon cycle, and (ii) similar change can be recognized at locations in the Maldives and Australia over the past 10myrs. The PI will further investigate this phenomenon, by (i) extending the study to additional sites, (ii) extending the time range of samples back to 25 Ma, (iii) investigating the phenomenon over high amplitude glacio-eustatic changes in sea level, (iv) adding variations in the ä13C of organic material as a proxy of production from shallow-water carbonate platforms, and (v) developing a model combining the notion that input from shallow marine carbonate platforms alters the ä13C with changes in calcite-aragonite seas, and the varying burial of organic material. Broader Impacts: Recognition that other factors than the carbon cycle can control the ä13C of carbonates will improve the understanding of the history of the burial of organic carbon, but also lead to understanding of how such records relate to the present anthropogenic experiment of increasing the pCO2 of the atmosphere and transferring carbon from the organic to inorganic reservoirs. The project will support a Ph.D. thesis as well as the interaction of undergraduates, high-school students, and high-school teachers in the geochemical laboratories at RSMAS.