Collaborative Research: New Chemo- and Biostratigraphic Framework for the Lower Triassic of the Western U.S.: Towards a high-resolution understanding of Early Triassic events

合作研究：美国西部下三叠世的新化学和生物地层框架：对早三叠世事件的高分辨率理解

• 批准号: 0920894
• 负责人: Margaret Fraiser
• 金额: $ 6.92万
• 依托单位: University of Wisconsin-Milwaukee
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-10-01 至 2011-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0920894&HistoricalAwards=false
• 关键词: Collaborative; Research; New; Chemo; Biostratigraphic

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Collaborative Research: New Chemo- and Biostratigraphic Framework forthe Lower Triassic of the Western U.S.: Towards a high-resolutionunderstanding of Early Triassic eventsPedro Marenco, UC Riverside, EAR-0921127Margaret Fraiser, Univ. Wisconsin, Milwaukee, EAR-0920894Matthew Clapham, UC Santa Cruz, Ear-0918184 ABSTRACTThe cause of the end-Permian mass extinction remains controversial. However, some combination of CO2 or H2S toxicity and/or climate change, triggered or catalyzed by the eruption of the Siberian Traps, appears to be the most likely kill mechanism. The biotic recovery from the end-Permian mass extinction has received less attention, despite the fact that the Early Triassic recovery was unusually long (~5m.y.) The occurrence of ?anachronistic facies? (e.g., seafloor precipitated crystals, subtidal stromatolite bioherms, and wrinkle structures), multiple carbon isotopic excursions, and elevated seawater sulfate sulfur isotopic values in Lower Triassic strata suggest a prolonged period of anomalous environmental conditions following the mass extinction that may have delayed the biotic recovery.Multiple lines of evidence imply that the Early Triassic was a time of elevated atmospheric CO2 most likely resulting from the extreme volcanism of the Siberian Traps. At the same time, metazoan reefs disappeared from the fossil record until the Middle Triassic, while calcifying marine invertebrates tended to be small. These observations and experimental work on living organisms have raised concerns about the ecological consequences of ocean acidification, in reef ecosystems in particular. Laboratory experiments with extant corals have demonstrated that as pH drops, corals survive as polyps without skeletons until pH returns to favorable levels. It has been suggested that similar ocean acidification during the Early Triassic inhibited growth of large calcareous shells, favoring small organisms, and prevented corals from forming skeletons. Thus, if the protracted recovery reflects a suppressed ecosystem due to elevated CO2 levels, Early Triassic communities may represent an ancient analog for the effects of greenhouse gas-forced ocean acidification on Earth?s ecosystems. Considering the extreme importance of coral skeletal frameworks in supporting the biodiversity of modern reef ecosystems, the inability of corals to produce skeletons will most likely have severe and negative effects on fisheries and the economies that depend on them. Thus, unusual Early Triassic deposits may provide a preview of marine ecosystems under conditions of increased atmospheric pCO2 and reduced ocean pH.The Lower Triassic of the western U.S. was deposited in two basins on the western coast of Pangaea, which together comprise a nearly complete record of the entire Early Triassic. Studies of the biotic recovery in the western U.S. have largely focused on fossil abundance and diversity patterns and the occurrence of anachronistic facies. These studies have demonstrated that anachronistic facies such as seafloor-precipitated aragonite fans and large subtidal stromatolite bioherms are found exclusively in deeper water settings, below fair-weather wave base (except for the immediate P-T boundary interval). Crystal fans have been reported only from slope or basinal sections while stromatolite bioherms occur on flooding surfaces at the bases of parasequences in more proximal environments. Both seafloor crystal fans and stromatolite bioherms are interpreted to have formed under anaerobic conditions. The facies-dependent occurrence of anachronistic facies has led to the conclusion that anoxia was a deep-ocean phenomenon during the Early Triassic, and that shallower settings were a refuge from anoxia in the aftermath of the mass extinction. The lack of evidence for shallow-water anoxia during the Early Triassic suggests that the biotic recovery in the shallow realm may have been hindered not by anoxia, but by hypercapnia and ocean-acidification due to high atmospheric carbon dioxide.The impact of atmospheric carbon dioxide and ocean acidification during the Early Triassic has received little study. In order to understand the nature of the recovery, the independent and synergistic effects of deep-water anoxia and shallow-water acidification on marine ecosystems need to be examined in greater detail. Because of the different environmental range of each stress, evidence for the two phenomena is rarely found in a single section; thus studies are currently hindered by the lack of a robust stratigraphic framework for the precise correlation of proximal to distal depositional settings both within and between the two Lower Triassic successions. PIs will address this issue by creating a high-resolution bio- and chemostratigraphic framework for the western U.S. and then use those results to test two hypotheses related to the nature of the biotic recovery: 1) The oxygen isotopic composition of conodont phosphate and brachiopod carbonate indicates that the Early Triassic was a time of recurrent climate warming and ocean acidification resulting from increased atmospheric carbon dioxide from Siberian Trap volcanism, and 2) spatially and temporally variable environmental conditions facilitated ecologic change in the Paleozoic Fauna that can be tracked in the immediate extinction aftermath and through the prolonged Early Triassic biotic crisis.

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。合作研究：美国西部下三叠世的化学和生物地层学新框架：对早三叠世事件的高分辨率理解spedro Marenco， UC Riverside, ear - 0921128 margaret Fraiser, university Wisconsin, Milwaukee, EAR-0920894Matthew Clapham, UC Santa Cruz， Ear-0918184摘要二叠纪末大灭绝的原因仍然存在争议。然而，由西伯利亚圈闭火山喷发引发或催化的二氧化碳或硫化氢毒性和/或气候变化的某种组合，似乎是最可能的死亡机制。二叠纪末生物大灭绝后的生物恢复受到的关注较少，尽管三叠纪早期的恢复时间异常长（约5万年）。的发生？过时的相?（例如，海底沉淀晶体、潮下叠层石生物礁和褶皱结构）、多次碳同位素漂移以及下三叠统地层中海水硫酸盐硫同位素值的升高表明，在大灭绝之后，异常环境条件延长了一段时间，这可能推迟了生物的恢复。多种证据表明，早三叠纪是大气中二氧化碳含量升高的时期，极有可能是西伯利亚圈层的极端火山活动造成的。与此同时，直到中三叠世，后生动物珊瑚礁才从化石记录中消失，而钙化的海洋无脊椎动物往往很小。这些对生物体的观察和实验工作引起了人们对海洋酸化，特别是珊瑚礁生态系统的生态后果的关注。对现存珊瑚进行的实验室实验表明，当pH值下降时，珊瑚以没有骨骼的珊瑚虫的形式存活，直到pH值恢复到有利的水平。有人认为，早三叠纪时期类似的海洋酸化抑制了大型钙质贝壳的生长，有利于小型生物，并阻止了珊瑚形成骨骼。因此，如果持续的恢复反映了由于二氧化碳水平升高而抑制的生态系统，那么早三叠纪群落可能代表了温室气体对地球海洋酸化影响的古代模拟。年代的生态系统。考虑到珊瑚骨骼框架在支持现代珊瑚礁生态系统生物多样性方面的极端重要性，珊瑚无法产生骨骼很可能对渔业和依赖它们的经济产生严重的负面影响。因此，不寻常的早三叠纪沉积物可以提供在大气二氧化碳分压增加和海洋ph降低条件下的海洋生态系统的预览。美国西部的下三叠纪沉积在盘古大陆西海岸的两个盆地中，它们一起构成了整个早三叠纪的几乎完整的记录。对美国西部生物恢复的研究主要集中在化石丰度和多样性模式以及时代错误相的发生上。这些研究表明，像海底沉淀文石扇和大型潮下叠层石生物礁这样的逆时代相只存在于较深的水域环境中，在天气良好的波基之下（除了直接的P-T边界间隔）。据报道，晶体扇只出现在斜坡或盆地剖面上，而叠层石生物礁则出现在更近的准层序底部的泛水面。海底晶体扇和叠层石生物泡都是在厌氧条件下形成的。逆时代相的发生依赖于相，由此得出缺氧在早三叠世是一种深海现象，而在大灭绝之后，较浅的环境是缺氧的避难所。早三叠纪时期浅水缺氧证据的缺乏表明，阻碍浅水生物恢复的可能不是缺氧，而是大气中二氧化碳含量高导致的高碳酸血症和海洋酸化。早三叠纪时期大气二氧化碳和海洋酸化的影响很少得到研究。为了了解恢复的性质，需要更详细地研究深水缺氧和浅水酸化对海洋生态系统的独立和协同作用。由于每种应力的环境范围不同，在单个剖面中很少能找到这两种现象的证据；因此，缺乏一个强有力的地层格架来精确对比两个下三叠统内部和之间的近端和远端沉积背景，阻碍了目前的研究。pi将通过为美国西部创建一个高分辨率的生物和化学地层学框架来解决这个问题，然后使用这些结果来测试与生物恢复性质相关的两个假设：1)磷酸盐牙形石和碳酸腕足动物的氧同位素组成表明，早三叠世是西伯利亚圈陷火山活动引起的大气二氧化碳增加导致气候变暖和海洋酸化的周期性时期；2)时空变化的环境条件促进了古生代动物的生态变化，这种变化可以追溯到早三叠世物种灭绝后的直接后果和延长的早三叠世生物危机。