Two-phased collapse of the shallow-water carbonate factory during the late Pliensbachian–Toarcian driven by changing climate and enhanced continental weathering in the Northwestern Gondwana Margin
Two-phased collapse of the shallow-water carbonate factory during the late Pliensbachian–Toarcian driven by changing climate and enhanced continental weathering in the Northwestern Gondwana Margin
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DOI：
10.1016/j.earscirev.2020.103254
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发表时间：
2020-06
影响因子：
12.1
通讯作者：
François-Nicolas Krencker;A. Fantasia;Jan Danisch;R. Martindale;L. Kabiri;M. Ouali;S. Bodin
中科院分区：
文献类型：
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作者：
François-Nicolas Krencker;A. Fantasia;Jan Danisch;R. Martindale;L. Kabiri;M. Ouali;S. Bodin
Pliensbachian-Toarcian末期的特征是多次碳循环扰动和动物更替（如菊石和有孔虫），这很可能是由karou - ferrar - chon Aike大火成岩省的脉冲触发的。关于这些事件的大部分信息是基于对深水环境中沉积地点的详细研究，这给浅海生态系统中这些事件的表现和反应留下了巨大的不确定性。本文综合评价了摩洛哥高阿特拉斯盆地中部从Pliensbachian晚期到Toarcian中期的古气候对浅海沉积环境的影响，并与特提斯西部同时期浅海沉积环境的变化进行了比较。在高阿特拉斯盆地中部南部共调查了4个新的地层剖面，并将这些剖面与以前发表的6个剖面进行了综合，分布在8个地区。剖面间的对比基于生物地层学、化学地层学和岩石地层学。在摩洛哥，观察到两次碳酸盐工厂关闭事件，跨越了Pliensbachian/Toarcian边界和Polymorphum/Levisoni过渡。每一次碳酸盐工厂的崩塌都与最新的pliensbachia - Toarcian中期的环境扰动有关，包括Toarcian Oceanic Anoxic Event （T-OAE）。此外，每次碳酸盐工厂关闭都与盆地中粗硅质塑料输入显著增加的间隔相吻合，进一步证明了全球变暖、大陆风化加剧和生态系统翻转之间的联系。此外，这两次碳酸盐岩工厂停产之后都有碳酸盐岩生产的恢复，显示了该地区浅海碳酸盐岩工厂的弹性。第一个恢复层段发生在多晶带晚期，与混合硅-塑性-碳酸盐体系有关。随着T-OAE的发生，碳酸盐的第二次开采很快就会结束。它与非生物主导的碳酸盐生产模式有关，导致了高产量。生物碳酸盐生产的完全恢复只发生在T-OAE的后期。虽然生物更替发生在这两个事件中，但从浅海的角度来看，主要的生物和非生物危机发生在Pliensbachian/Toarcian边界，而不是在T-OAE期间。这与深海记录相反，在深海记录中，T-OAE通常被推断为最重要的事件。在Pliensbachian/Toarcian过渡时期，增强的水文循环和随后大陆养分流失的增加可能引发了碳酸盐生产力的最严重变化；然而，海洋酸化和风暴活动的增加可能在T-OAE开始时发挥了重要作用。
The end Pliensbachian–Toarcian is characterized by several carbon-cycle perturbations and faunal turnovers (e.g., ammonites and foraminifera), which are most likely triggered by pulses of the Karoo-Ferrar-Chon Aike large igneous province. The majority of information about these events is based on detailed studies of sites deposited in deep-water settings, which leaves vast uncertainties about the expression of, and response to, these events in shallow-marine ecosystems. Here, we present a comprehensive assessment of paleoclimatic impacts on neritic depositional environments from the latest Pliensbachian through the middle Toarcian in the central High Atlas Basin, Morocco, and compare those with changes observed in coeval neritic environments within the western Tethyan realm. A total of four new stratigraphic sections were investigated in the southern part of central High Atlas Basin and these new sections are synthesized with six previously published sections, distributed over eight localities. Correlations between sections are based on biostratigraphy, chemostratigraphy and lithostratigraphy. In Morocco, two episodes of carbonate factory shutdown are observed, spanning the Pliensbachian/Toarcian boundary and the Polymorphum/Levisoni transition. Each carbonate factory collapse correlates to well-documented environmental disturbances during the latest Pliensbachian–middle Toarcian interval, including the Toarcian Oceanic Anoxic Event (T-OAE). Moreover, each episode of carbonate factory shutdown coincides with an interval characterized by a significant increase of coarse siliciclastic input in the basin, further demonstrating the link between global warming, increased continental weathering, and ecosystem turnovers. Furthermore, these two episodes of carbonate factory shutdown are each followed by episodes of renewed carbonate production, showing the resilience of the neritic carbonate factory in this region. The first recovery interval, occurring during the late Polymorphum Zone, is associated with a mixed siliciclastic‑carbonate system. The second episode of carbonate recovery quickly follows the shutdown associated with the onset of the T-OAE. It is associated with an abiotic-dominated carbonate production mode, resulting in an elevated ooid production. A full recovery of biotic carbonate production only occurs in the late stage of the T-OAE. Although biotic turnover occurs at both events, from a shallow-marine perspective, the major biotic and abiotic crisis occurred at the Pliensbachian/Toarcian boundary and not during the T-OAE. This is in contrast to the deep-marine record, where the T-OAE is often inferred to be the most significant event. An enhanced hydrological cycle and the subsequent increase of continental nutrient shedding might have triggered the most severe changes of the carbonate productivity at the Pliensbachian/Toarcian transition; whereas, ocean acidification and increased storm activity likely played a significant role at the onset of the T-OAE.