Testing the Utility of Geochemical Proxies for Interpretation of Reduced Oxygen Sediments Using Body and Trace Fossil Data from Devonian Black Shales

使用泥盆纪黑色页岩的尸体和痕量化石数据测试地球化学代理在解释含氧量减少的沉积物中的效用

• 批准号: 0719841
• 负责人: Mary Droser
• 金额: $ 9.06万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0719841&HistoricalAwards=false
• 关键词: Testing; Utility; Geochemical; Proxies; Interpretation

Geochemical proxies, widely used in Precambrian sedimentary units to infer paleo-oxygen levels, have been well studied and well constrained in modern low oxygen environments. However in modern dysoxic settings, bioturbation, or the reworking of the sediment by infauna, is pervasive with even the slightest amounts of oxygen. Bioturbation has a profound effect on the geochemistry of the sediments, and importantly for widely used redox proxies, results in an increased rate of decomposition of organic matter and oxidation of HB2BS. As a result modern reduced oxygen settings are not an appropriate analog for Precambrian reduced oxygen settings that are devoid of bioturbation. However, Devonian aged sedimentary rocks provide a unique biogeochemical window in which trace and body fossils are widespread and abundant across reduced oxygen depositional settings, allowing for the interpretation of relative paleo-oxygen levels at very high resolution. At the same time, the burrows are shallow and small enough to minimize the dominating infaunal overprints that characterize the geochemical properties of younger sedimentary rocks. This research will test the hypothesis that DOP, TOC, trace metal compositions including Mo, Mn, and Fe, and sulfur isotope data (deltaP34PSBsulfideB) vary in a systematic and predictable manner along a gradient, as identified by the trace and body fossil record in Devonian black shales. The goal of this research is to determine the utility of these proxies as paleo-oxygen indicators in anoxic through dysoxic settings, and thus their applicability for interpretation of paleo-oxygen in the absence of a biological record.

地球化学代理广泛用于前寒武纪沉积单元来推断古氧水平，在现代低氧环境中已得到充分研究和良好约束。然而，在现代缺氧环境中，即使是最少量的氧气，生物扰动或底物对沉积物的改造也很普遍。生物扰动对沉积物的地球化学具有深远的影响，对于广泛使用的氧化还原代理而言，重要的是，生物扰动会导致有机物分解和 HB2BS 氧化的速率增加。因此，现代的低氧环境并不适合模拟没有生物扰动的前寒武纪低氧环境。然而，泥盆纪老化的沉积岩提供了一个独特的生物地球化学窗口，其中痕迹化石和尸体化石在低氧沉积环境中广泛且丰富，从而可以以非常高的分辨率解释相对古氧水平。与此同时，洞穴又浅又小，足以最大限度地减少主要的动物区系印记，而这些印记是较年轻沉积岩地球化学特性的特征。这项研究将检验以下假设：DOP、TOC、痕量金属成分（包括 Mo、Mn 和 Fe）以及硫同位素数据 (deltaP34PSBsulfideB) 沿梯度以系统且可预测的方式变化，正如泥盆纪黑色页岩中的痕量和人体化石记录所识别的那样。这项研究的目的是确定这些指标作为缺氧和缺氧环境中古氧指标的效用，从而确定它们在没有生物记录的情况下解释古氧的适用性。