Paleo-redox context of the Mid-Devonian Appalachian Basin and its relevance to biocrises
Paleo-redox context of the Mid-Devonian Appalachian Basin and its relevance to biocrises
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DOI：
10.1016/j.gca.2019.12.019
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发表时间：
2020-10
影响因子：
5
通讯作者：
Ruliang He;Wanyi Lu;C. Junium;C. Ver Straeten;Zunli Lu
中科院分区：
文献类型：
--
作者：
Ruliang He;Wanyi Lu;C. Junium;C. Ver Straeten;Zunli Lu
泥盆纪见证了维管陆生植物的扩张和与有机质团埋增强相关的大气氧化事件。富有机质页岩的沉积（如Marcellus亚群的黑色页岩）和海洋领域的几种生物危机与泥盆纪海洋缺氧有关。然而，在这种大气-海洋系统动态变化的背景下，水柱不同部分的氧化还原条件是如何演变的尚不清楚。为了解决这个问题，我们对来自纽约州Yates县的岩心样品使用了大量碳酸盐I/Ca代理，以重建通过Onondaga石灰岩进入Marcellus页岩下部的水柱氧化还原历史。在长期尺度上，相对于古生代早期的时间间隔，I/Ca值的范围支持泥盆纪大气氧上升的概念。在Eifelian期地层趋势上，Onondaga组I/Ca比值总体稳定且较高，但Marcellus组下地层I/Ca比值波动较大。在富有机质页岩沉积开始附近发现低I/Ca比值，表明地下水相对减少。氧化还原变化的模式与同期海平面变化的模式相似。最后，重建的氧合变化与泥盆纪海洋系统的三个生物转变有关。
The Devonian Period witnessed the expansion of vascular land plants and an atmospheric oxygenation event associated with enhanced organic mass burial. The deposition of organic-rich shales (e.g. black shales of the Marcellus subgroup) and several biotic crises in the marine realm have been linked to Devonian ocean anoxia. However, it is not clear how redox conditions evolved in different parts of the water column in such a context of dynamic changes in the atmosphere-ocean system. To address this problem, we use the bulk carbonate I/Ca proxy on core samples from Yates County, NY, in order to reconstruct the water column redox history through the Onondaga Limestone into the lower Marcellus shale. On the secular scale, the range of I/Ca values support the notion of a Devonian rise in atmospheric oxygen, relative to time intervals earlier in the Paleozoic. In terms of Eifelian Stage stratigraphic trends, I/Ca ratios are generally stable and high in the Onondaga Formation but show large fluctuations in lower Marcellus strata. Low I/Ca ratios are found near the onset of organic-rich shale deposition indicating relatively reducing subsurface waters. The pattern of redox changes resembles that of contemporaneous sea-level changes. Finally, the reconstructed oxygenation changes are correlated to three biotic transitions in Devonian marine systems.