Uppermost Triassic phosphorites from Williston Lake, Canada: link to fluctuating euxinic-anoxic conditions in northeastern Panthalassa before the end-Triassic mass extinction
Uppermost Triassic phosphorites from Williston Lake, Canada: link to fluctuating euxinic-anoxic conditions in northeastern Panthalassa before the end-Triassic mass extinction
复制标题
加拿大威利斯顿湖最上层三叠纪磷矿：与三叠纪末大规模灭绝之前 Panthalassa 东北部波动的缺氧缺氧条件有关
作者：
E. Larina;D. Bottjer;F. Corsetti;J. Zonneveld;A. Celestian;J. Bailey
三叠纪末期大规模灭绝 (ETE) 与中大西洋岩浆区 (CAMP) 喷发导致的二氧化碳浓度上升有关，并对现代动物群产生了特别显着的影响，因此了解导致 ETE 的条件与当前二氧化碳浓度上升有关。在这里，我们报告了加拿大威利斯顿湖 ETE 之前地层中的多个磷矿矿床，这使得我们能够对导致大规模灭绝的古环境条件进行调查。磷矿中磷酸盐涂层颗粒的主导地位表明在浅水环境中进行了返工。拉曼光谱表明磷矿含有有机碳，岩相学和扫描电子显微镜分析表明磷矿含有推定的微化石，这可能表明微生物以直接或间接的方式参与其中。因此，我们支持一种涉及微生物多磷酸盐代谢的磷生成机制，其中磷酸盐沉积物通常在常氧/缺氧和有氧条件的界面处形成。当与西南较深的水沉积物（肯尼科特角）的数据相结合时，Panthalassa东北部的一个非常广阔的区域似乎经历了缺氧到缺氧的底层水条件，直接导致了三叠纪末的大规模灭绝。这种情况意味着潘塔拉萨东北部广阔区域的最低含氧区扩大和变浅，这可能会给底栖后生动物群落带来压力。需要对全球不同地点的灭绝前间隔进行研究，以解决导致 ETE 的重大环境崩溃之前所控制过程的时间顺序和空间分布。这项研究的结果表明，波动的缺氧和缺氧条件可能是 CAMP 火山爆发之前生态系统稳定性降低的潜在原因，至少在区域范围内是如此。
The end-Triassic mass extinction (ETE) is associated with a rise in CO2 due to eruptions of the Central Atlantic Magmatic Province (CAMP), and had a particularly dramatic effect on the Modern Fauna, so an understanding of the conditions that led to the ETE has relevance to current rising CO2 levels. Here, we report multiple phosphorite deposits in strata that immediately precede the ETE at Williston Lake, Canada, which allow the paleoenvironmental conditions leading up to the mass extinction to be investigated. The predominance of phosphatic coated grains within phoshorites indicates reworking in shallow water environments. Raman spectroscopy reveals that the phosphorites contain organic carbon, and petrographic and scanning electron microscopic analyses reveal that the phosphorites contain putative microfossils, potentially suggesting microbial involvement in a direct or indirect way. Thus, we favor a mechanism of phosphogenesis that involves microbial polyphosphate metabolism in which phosphatic deposits typically form at the interface of euxinic/anoxic and oxic conditions. When combined with data from deeper water deposits (Kennecott Point) far to the southwest, it would appear a very broad area of northeastern Panthalassa experienced anoxic to euxinic bottom water conditions in the direct lead up to the end-Triassic mass extinction. Such a scenario implies expansion and shallowing of the oxygen minimum zone across a very broad area of northeastern Panthalassa, which potentially created a stressful environment for benthic metazoan communities. Studies of the pre-extinction interval from different sites across the globe are required to resolve the chronology and spatial distribution of processes that governed before the major environmental collapse that caused the ETE. Results from this study demonstrate that fluctuating anoxic and euxinic conditions could have been potentially responsible for reduced ecosystem stability before the onset of CAMP volcanism, at least at the regional scale.
影响因子：
18.3
作者：
Goldhammer, Tobias;Bruchert, Volker;Zabel, Matthias
通讯作者：
Zabel, Matthias