COLLABORATIVE RESEARCH: Organic Carbon Burial, Anoxia, and Ecological-Evolutionary Events in the Appalachian Basin During the Middle to Late Devonian (Eifelian-Famennian)

合作研究：阿巴拉契亚盆地中晚泥盆世（艾菲尔期-法门期）的有机碳埋藏、缺氧和生态进化事件

• 批准号: 9725441
• 负责人: Bradley Sageman
• 金额: $ 16万
• 依托单位: Northwestern University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-01-01 至 2000-12-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9725441&HistoricalAwards=false
• 关键词: COLLABORATIVE; RESEARCH; Organic; Carbon; Burial

9725441 Sageman The widespread but episodic deposition of organic carbon-rich facies (ORF) in marine basins during Earth history has been recognized as an important problem in the geological sciences. Water column stratification and consequent anoxia has commonly been the favored hypothesis to account for ancient ORF deposition, but in recent years alternate hypotheses have emerged that highlight the importance of coupled biogeochemical and sedimentological processes (e.g., high productivity, stratigraphic condensation), and even suggest that water column anoxia may not have been as prevalent as once thought. Yet oxygen deficiency, whether as a cause or consequence of organic carbon burial, has been postulated as a potential driving force for evolutionary change and extinction during the Phanerozoic. For example, it was recently implicated as a possible cause of overturn events punctuating distinct Silurian and Devonian benthic faunas of the Appalachian basin. These benthic faunas are termed ecological-evolutionary subunits. The pattern of long-term stability and punctuated change at the community level is called coordinated stasis, and many of the identified faunal overturns are coincident with ORF deposits. Although coordinated stasis has rapidly become a forefront of research in evolutionary paleoecology, very few studies have integrated anallyses of faunal changes with independent assessments of coeval environmental change, and none have focused on the role of oxidation-reduction chemistry at or near the sediment-water interface (redox dynamics). What are the spatial and temporal relationships between organic matter burial events and oxygen deficiency? How does oxygen depletion relate to evolutionary change within a community, a basin, or an ecosystem? This proposal outlines a plan to re-evaluate hypotheses for the origin of ORF deposits in the Middle to Late Devonian Appalachian basin (late Eifelian through early Famennian), and to use the data collected for this purpose to i nvestigate the causes of faunal stasis and overturn. A preliminary data set of geochemical analyses from core samples has been generated (Fig. 3, Table 2) that illustrates why previous hypotheses for the origin of ORF in the Appalchian basin need to be reconsidered. This data set has provided a foundation for the development of working hypotheses relating ORF deposition and coordinated stasis, as well as a trial for selection of the best paleoenvironmental parameters to employ in the study. The two year project will focus on two cores from west central New York that will be analyzed for sedimentologic and ichnologic trends and sampled for geochemical analyses. Three types of geochemical data sensitive to redox dynamics will be collected (carbon isotopes; abundance of C, Fe, S, and P; and concentrationof trace metals), and the results will be compared to a compilation of published and unpublished data on macrofaunal trends within and around the Appalachian basin. Tests for the statistical covariance of redox sensitive proxies and faunas will allow the fundamental hypothesis, that oxygen depletion controls faunal turnover, to be confirmed or refuted. Alternate mechanisms, such as species-area effects related to relative sea level changes, will also be considered. Past global climate and environmental changes have been linked to variability in ocean circulation and biogeochemical processes/cycles. This study is directed at assessing the linkage between physical, chemical, and biological processes within an ancient marine system, and the results will provide important constraints for currently evolving ideas about past global change. The research will make a significant contribution to the understanding of organic carbon accumulation processes in the evolution of epicontinental foreland basins, and of the relationship between carbon cycling, redox history, and ecological-evolutionary events in the rock record.

小行星9725441 在地球历史时期，海相盆地中普遍存在的富有机碳相（ORF）沉积是地质科学中的一个重要问题。 水柱分层和随后的缺氧通常是解释古代ORF沉积的有利假设，但近年来出现了替代假设，强调了耦合地球化学和沉积学过程的重要性（例如，高生产力，地层浓缩），甚至表明水柱缺氧可能并不像以前认为的那样普遍。 然而，无论是作为有机碳埋藏的原因还是结果，缺氧都被假定为中生代进化变化和灭绝的潜在驱动力。 例如，它最近被认为是阿巴拉契亚盆地志留纪和泥盆纪底栖动物群发生倾覆事件的可能原因。 这些底栖动物群被称为生态进化亚单位。 在群落水平上的长期稳定和间断性变化的模式被称为协调停滞，许多已确定的动物区系翻转与ORF沉积相一致。 虽然协调停滞已迅速成为进化古生态学研究的前沿，但很少有研究将区系变化与独立评估同时代环境变化相结合，而且没有一项研究关注沉积物-水界面处或附近的氧化还原化学作用（氧化还原动力学）。有机质埋藏事件与缺氧之间的时空关系是什么？ 在一个群落、一个盆地或一个生态系统中，氧气消耗与进化变化有什么关系？ 该提案概述了一项计划，以重新评估中泥盆世至晚泥盆世阿巴拉契亚盆地（Eifelian晚期至Famennian早期）ORF沉积物起源的假设，并使用为此目的收集的数据来调查动物群停滞和翻转的原因。 已经生成了一组来自岩心样品的初步地球化学分析数据（图3，表2），说明了为什么需要重新考虑以前关于阿帕尔基亚盆地ORF起源的假设。 这一数据集提供了一个基础的工作假设有关ORF沉积和协调停滞的发展，以及在研究中采用的最佳古环境参数的选择试验。 这个为期两年的项目将集中在纽约中西部的两个岩心上，将对这两个岩心进行沉积学和遗迹学趋势分析，并取样进行地球化学分析。 将收集对氧化还原动力学敏感的三种类型的地球化学数据（碳同位素; C、Fe、S和P的丰度;以及痕量金属的浓度），并将结果与阿巴拉契亚盆地内和周围的大型动物趋势的已发表和未发表数据汇编进行比较。 氧化还原敏感的代理和动物群的统计协方差的测试将允许的基本假设，即氧气消耗控制动物的营业额，被证实或反驳。 还将考虑其他机制，例如与相对海平面变化有关的物种-面积效应。 过去的全球气候和环境变化与海洋环流和海洋地球化学过程/循环的变化有关。 本研究旨在评估古代海洋系统中物理，化学和生物过程之间的联系，其结果将为目前有关过去全球变化的不断发展的想法提供重要的约束。 该研究将为理解陆表海前陆盆地演化过程中有机碳的积累过程，以及岩石记录中碳循环、氧化还原历史和生态演化事件之间的关系做出重要贡献。