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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Environmental changes during Frasnian-Famennian transition in south China: A multiproxy approach
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Environmental changes during Frasnian-Famennian transition in south China: A multiproxy approach

机译：华南地区弗拉斯曼-法门尼过渡时期的环境变化：一种多代理方法

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摘要

This study presents high-resolution multiproxy analyses on two Late Devonian sequences for characterizing the environmental changes during the Frasnian-Famennian (F-F) transition in south China. Carbon isotope signatures of the carbonate and organic matter consistently show two positive excursions in the late rhenana zone and around the F-F boundary, implying two increased organic carbon burial events. These observations are consistent with the records from other continents, providing further support for the documented perturbations of the global carbon cycle. Redox indices, mainly of the Cu/Al and U/Al ratios, and hydrothermal-volcanic proxies, Al/(Al + Fe) and Zr/Al, indicate reducing conditions and increased hydrothermal-volcanic activities during these carbon isotope excursions. High-resolution investigations revealed that the reducing conditions predate the onset of the carbon isotope excursions, suggesting that the two positive carbon isotope shifts are likely caused by the expansion of anoxic conditions. The low Al/(Al + Fe) ratio around the F-F boundary leads the U/Al and Cu/Al anomalies in timing, implying that this anoxic event might have resulted from a long-term cumulative effect of intense hydrothermal-volcanic activities. In the late rhenana zone, enhanced hydrothermal activity also seems responsible for the reducing conditions.
机译：这项研究提出了两个晚泥盆纪序列的高分辨率多代理分析，以表征中国南部弗拉西尼亚—法门​​尼过渡时期的环境变化。碳酸盐和有机物的碳同位素特征在雷纳纳后期和F-F边界附近始终显示出两次正偏移，这意味着增加了两次有机碳埋藏事件。这些观察结果与其他大陆的记录一致，为全球碳循环的文献记载的扰动提供了进一步的支持。氧化还原指数主要是Cu / Al和U / Al比率，以及热液火山代理Al /（Al + Fe）和Zr / Al，表明这些碳同位素漂移期间的还原条件和增加的热液火山活动。高分辨率研究表明，还原条件早于碳同位素偏移的发生，这表明两个正碳同位素偏移很可能是由缺氧条件的扩展引起的。 F-F边界附近的低Al /（Al + Fe）比导致时间上的U / Al和Cu / Al异常，这表明这种缺氧事件可能是由于强烈的热液-火山活动的长期累积效应造成的。在雷纳纳地区晚期，热液活动的增强似乎也是造成还原条件的原因。

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