加拿大科迪勒拉山系晚三叠世碳同位素异常:与纪元/雷蒂纪边界和三叠纪末大灭绝事件相关的古环境扰动

IF 4 1区 地球科学 Q1 GEOGRAPHY, PHYSICAL
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引用次数: 0

摘要

晚三叠世是地质历史上一个特别动荡的时期,其特点是反复出现古环境不稳定,最终导致三叠纪末大灭绝(ETME)。这些动荡与火山活动的增强有关,而火山活动是泛大陆最终解体的先兆。海洋碳同位素记录中的地球化学信号证明,这些事件往往足以破坏全球碳循环。然而,三叠纪/侏罗纪边界(TJB)之前与 ETME 相关的扰动的持续时间和范围仍然存在争议。本研究调查了整个不列颠哥伦比亚省的八个地层剖面,以建立一个全面的泛塔拉桑碳同位素记录,时间跨度从诺森纪到赫坦纪早期。研究观察到三个明显的负偏移:一个偏移靠近纪/雷蒂边界(NRB),另一个偏移在雷蒂内,最后一个偏移与TJB相吻合。这与之前的研究基本一致,但表明与 NRB 相关的负偏移和被认为与 TJB 相关的最古老的雷蒂 "前体 "偏移之间可能没有明确的区别。本研究中观察到的一些偏移幅度过大,无法合理地反映全球海洋水化学(∼10 ‰,而预期为∼3 ‰),这表明某些局部机制正在放大这些碳同位素偏移。一种可能的解释是,在古环境干扰期间,受限海洋环境中的有机碳呼吸作用增强。无论如何,这些重复碳同位素偏移的证据支持了古生物学数据,表明ETME并不是TJB的一个单一的地质瞬时事件,而是早在NRB时期就开始的几次转折的综合。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Late Triassic carbon isotope anomalies in the Canadian Cordillera: Paleoenvironmental disturbances associated with the Norian/Rhaetian boundary and end-Triassic mass extinction event

The Late Triassic was a particularly turbulent interval of the geologic past, marked by repeated paleoenvironmental instability culminating in the end-Triassic mass extinction (ETME). These episodes of disturbance are associated with enhanced volcanism, harbinger of the eventual break-up of Pangea. As evidenced by geochemical signals in the marine carbon isotope record, these events were often significant enough to disrupt the global carbon cycle. However, the duration and extent of ETME-associated disturbances leading up to the Triassic/Jurassic boundary (TJB) remain contentious. The present study investigates eight stratigraphic sections from across British Columbia to create a comprehensive Panthalassan carbon isotope record spanning the Norian to early Hettangian. Three distinct negative excursions are observed: an excursion proximal to the Norian/Rhaetian boundary (NRB), another excursion within the Rhaetian, and a final excursion coinciding with the TJB. This is generally consistent with prior studies, but suggests there may be no clear distinction between the negative excursion associated with the NRB, and the oldest Rhaetian “precursor” excursion proposed to be associated with the TJB. Several of the excursions observed in the present study are too large in magnitude to plausibly reflect global ocean water chemistry (∼10 ‰ compared to the expected ∼3 ‰), indicating some local mechanism was amplifying these carbon isotope excursions. A potential explanation is increased organic carbon respiration in restricted marine environments, triggered during episodes of paleoenvironmental disturbance. Regardless, this evidence for repeated carbon isotope excursions supports paleontological data suggesting that the ETME is not a singular and geologically instantaneous event at the TJB, but is instead the amalgamation of several turnovers beginning as early as the NRB.

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来源期刊
Global and Planetary Change
Global and Planetary Change 地学天文-地球科学综合
CiteScore
7.40
自引率
10.30%
发文量
226
审稿时长
63 days
期刊介绍: The objective of the journal Global and Planetary Change is to provide a multi-disciplinary overview of the processes taking place in the Earth System and involved in planetary change over time. The journal focuses on records of the past and current state of the earth system, and future scenarios , and their link to global environmental change. Regional or process-oriented studies are welcome if they discuss global implications. Topics include, but are not limited to, changes in the dynamics and composition of the atmosphere, oceans and cryosphere, as well as climate change, sea level variation, observations/modelling of Earth processes from deep to (near-)surface and their coupling, global ecology, biogeography and the resilience/thresholds in ecosystems. Key criteria for the consideration of manuscripts are (a) the relevance for the global scientific community and/or (b) the wider implications for global scale problems, preferably combined with (c) having a significance beyond a single discipline. A clear focus on key processes associated with planetary scale change is strongly encouraged. Manuscripts can be submitted as either research contributions or as a review article. Every effort should be made towards the presentation of research outcomes in an understandable way for a broad readership.
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