Isotopic Evolution of Proterozoic Sediments and Seawater

最近的研究指向晚元古代（0.5-0.9 Ga）是一个巨大的进化变化的时代。 保存完好 纳米比亚、斯匹次卑尔根群岛、南非和 中国已被详细研究，因为它们包含重要的 第一后生动物群的经济沉积物和残余物。 在 此外，强烈的碳和锶同位素变化是 在这些序列中发现，并可能是有用的相关性， 世界范围内的同时代地层 我们建议继续研究 C、Sr和Nd的同位素变化， 保存下来的地层样品来自纳马，波利布雷恩和 Kango群以及陡山沱组和灯影组， 更好地表征同位素变化率在后者 元古宙的一部分 如果更好地了解 我们的目标是， 收件人： 1)追踪外生地球化学循环中的主要物质通量 并理解人类进化与 沉积储层、海洋和大气 晚元古代，2）确定侵蚀速率，有机碳 埋藏和热液蚀变及其与全球 3）探讨了强同位素的关系 已知的冰川、磷块岩和带状事件的变化 铁形成沉积，和4）加强化学之间的联系， 晚白垩世和晚白垩世之间的地层和生物地层对比 元古界的继承。 在元古代，海水Nd和Sr收支似乎 已经从主要的热液输入（如在 太古代），以大陆（河流）输入为主。 建模 从这项研究中获得的数据将被用来限制 热液循环速率的变化，大陆侵蚀 有机碳的埋藏速率和平均值的变化 大陆侵蚀产物的时代贯穿元古代晚期。 对地球大气中O2和CO2演变的影响 大气层也将被考虑。 我们已经证明了我们的 以前的工作，高分辨率的Sr和C同位素曲线， 获得晚元古代沉积序列， 相信这项研究将导致重大突破， 我们对晚元古代演化的理解

Recent investigation point to the latest Proterozoic (0.5-0.9 Ga) as being a time of vast evolutionary change. Well-preserved sedimentary successions in Namibia, Spitsbergen, South Africa and China have been studied in detail as they contain important economic deposits and remnants of the first metazoan faunas. In addition, strong carbon- and strontium-isotopic variations are found in these sequences and may be useful for the correlation of coeval strata world-wide. We propose to continue research on the isotopic variations in C, Sr and Nd in well-characterized and well- preserved stratigraphic samples from the Nama, Polarisbreen and Kango groups as well as the Doushantuo and Dengying formations to better characterize the rate of isotopic change during the latter part of the Proterozoic Eon. Given a better knowledge of the rate of isotopic changes in latest Proterozoic seawater our goals are to: 1) trace the major mass fluxes in the exogenic geochemical cycle and understand the relationship between the evolution of the sedimentary reservoir, the oceans and the atmosphere during the Late Proterozoic, 2) determine rates of erosion, organic carbon burial and hydrothermal alteration and their relation to global tectonics, 3) investigate the relationship of strong isotopic variations to known events of glaciations, phosphorite and banded iron-formation deposition, and 4) strengthen the tie between chemo- stratigraphic and bio-stratigraphic correlations between these Late Proterozoic successions. During the Proterozoic, seawater Nd and Sr budgets appear to have changed from dominantly hydrothermal inputs (as in the Archean) to dominantly continental (river) inputs. Modeling of the data obtained from this research will be used to constrain the changes in rates of hydrothermal circulation, continental erosion rates, burial rates of organic carbon and variations in the mean age of continental erosion products through the late Proterozoic. Implications for the evolution of O2 and CO2 in the Earth's atmosphere will also be considered. We have demonstrated with our previous work that high resolution Sr and C isotopic curves may be obtained for late Proterozoic sedimentary successions and are confident that this research will lead to major breakthroughs in our understanding of Late Proterozoic evolution.