COLLABORATIVE RESEARCH: Chemostratigraphic Analysis of Panthalassic and Tethyan Permian-Triassic Boundary Sections: Assessment of Global Paleoceanographic Dynamics

合作研究：泛地中海和特提斯二叠-三叠纪界线剖面化学地层学分析全球古海洋动力学评估Thomas Algeo，辛辛那提大学Brooks B. Ellwood，路易斯安那州立大学Katherine Freeman，宾夕法尼亚州立大学Timothy Lyons，加州大学河滨分校Arne Winguth和Harry Rowe，德克萨斯大学阿灵顿分校地球历史上最大规模的二叠纪-三叠纪边界（PTB）大灭绝的原因和动力学仍然不确定。晚二叠世期间海洋和陆地环境的逐渐恶化以及早三叠世时期不适宜生存的条件的持续存在表明，内在因素是重要的，但灭绝率峰值、岩相突变和与二叠世末期事件界相关的地球化学异常是灾难性事件（如大规模火山喷发、火山撞击和/或大规模海洋翻转）的证据。尽管对PTB进行了长期的研究，但对海洋边界剖面进行的综合、高分辨率化学地层学研究却非常少，这些研究可以解决与二叠纪-三叠纪深海缺氧的程度和强度、有毒深海水上涌到浅海架和平台的模式、这些事件与同期海水碳酸盐饱和度变化和海洋生物群落延迟恢复的关系等关键问题。灭绝后全球负c同位素转移的控制因素，以及海洋和陆地领域PTB危机的相对时间和因果关系。在本项目中，我们拟生成地球化学代理数据集，包括磁化率、元素浓度、TOC-TIC、Ô13Ccarb-？Ô13Corg， S-Fe形成，Ô34Ssulfide-？在8个研究区共19个剖面中，包括前泛大洋4个剖面（加拿大的Cache Creek地体、西部沉积盆地、Sverdrup盆地和新西兰的Maitai-Waipapa地体）的8个剖面和前特提斯洋4个剖面（越南、中国、印度、伊朗和意大利）的11个剖面。牙形石生物地层学结合c同位素和MS事件地层学有助于研究区内和研究区之间的对比。古海洋学模拟将用于研究潜在强迫对二叠纪-三叠纪海洋化学和沉积通量的影响，并与全球综合化学地层学数据集进行比较，将使模式模拟更加精细。该项目有可能产生关于二叠纪-三叠纪边界事件的重要新发现，以及关于同期化学海洋扰动的近似和最终控制的关键见解。对与地球历史上最大规模的物种灭绝有关的灾难性气候和环境变化的调查应该引起地球科学界和有科学素养的公众的极大兴趣。该项目的更广泛影响是多种多样的，包括项目成果的公众宣传和传播、本科生和研究生的指导、不同地球科学专业人员群体之间研究协同效应的发展，以及具有广泛科学意义的成果的潜力。pi致力于培养下一代科学家（他们总共指导了大约60名研究生，并且都积极参与指导和培训本科生），推进公立学校的科学教育，并在这些未来的学者中实现更大的种族和性别多样性（Algeo和Ellwood都参与了招募少数民族学生的计划）。由NSF资助的项目数据集将通过CHRONOS和palestrat提供给更大的科学界。

COLLABORATIVE RESEARCH: Chemostratigraphic Analysis of Panthalassic and Tethyan Permian-Triassic Boundary Sections: Assessment of Global Paleoceanographic DynamicsEAR-0745574 Thomas Algeo, University of Cincinnati¡XLeadEAR-0745393 Brooks B. Ellwood, Louisiana State UniversityEAR-0746189 Katherine Freeman, Pennsylvania State UniversityEAR-0745592 Timothy Lyons, University of California, RiversideEAR-0745817 Arne Winguth and Harry Rowe, University of Texas, ArlingtonABSTRACTThe causes and dynamics of the Permian-Triassic boundary (PTB) mass extinction, the largest in Earth history, remain uncertain. Gradual deterioration of marine and terrestrial environments during the Late Permian and persistence of inhospitable conditions through the Early Triassic suggest that intrinsic factors were important, but an extinction rate peak, abrupt lithofacies changes, and geochemical anomalies associated with the end-Permian event horizon are evidence of a catastrophic event (e.g., massive volcanic eruption, bolide impact, and/or large-scale oceanic overturn). Despite long study of the PTB, there are remarkably few integrated, high-resolution chemostratigraphic studies of marine boundary sections that can address critical questions related to the extent and intensity of Permo-Triassic deep-ocean anoxia, patterns of upwelling of toxic deep-ocean waters onto shallow-marine shelves and platforms, the relationship of such events to contemporaneous changes in seawater carbonate saturation and to the delayed recovery of marine biotas, controls on the post-extinction global negative C-isotope shift, and the relative timing and causal relationship of PTB crises in the marine and terrestrial realms. In this project, we propose to generate geochemical proxy datasets consisting of magnetic susceptibility, elemental concentrations, TOC-TIC, ?Ô13Ccarb-?Ô13Corg, S-Fe speciation, ?Ô34Ssulfide-?Ô34Ssulfate, REEs, and biomarkers for a total of 19 sections in eight study areas, including 8 sections in four areas of the former Panthalassic Ocean (the Cache Creek terrane, Western Sedimentary Basin, and Sverdrup Basin of Canada, and the Maitai-Waipapa terranes of New Zealand) and 11 sections in four areas of the former Tethys Ocean (Vietnam-China, India, Iran, and Italy). Conodont biostratigraphy combined with C-isotope and MS event stratigraphy will facilitate correlations within and between study areas. Paleoceanographic modeling will be used to investigate the effects of potential forcings on Permo-Triassic ocean chemistry and sedimentary fluxes, and comparisons with globally integrated chemostratigraphic datasets will allow refinement of model simulations. This project has the potential to yield important new findings regarding events at the Permian-Triassic boundary and key insights regarding proximate and ultimate controls on contemporaneous chemical oceanographic perturbations. Investigation of catastrophic climate and environmental change associated with the largest mass extinction in Earth history should be of considerable interest to both the Earth-science community and the scientifically literate public. The broader impacts of the project are varied and include public outreach and dissemination of project results, mentoring of undergraduate and graduate students, development of research synergies among a diverse group of geoscience professionals, and the potential for results of broad scientific significance. The PIs are committed to training the next generation of scientists (they have collectively supervised ~60 graduate students, and all are actively engaged in advising and training undergraduate students), to advancing science education in the public schools, and to achieving greater ethnic and gender diversity among these future scholars (Algeo and Ellwood are both involved in programs to recruit minority students). Project datasets funded through NSF will be made available to the larger scientific community through CHRONOS and PaleoStrat.