01995nas a2200181   4500008004100000022001300041245009300054210006900147300001200216490000800228520141300236100001601649700001401665700002801679700002501707700001401732856006701746       2020                        eng d  a0016703700aPaleo-redox context of the Mid-Devonian Appalachian Basin and its relevance to biocrises0 aPaleoredox context of the MidDevonian Appalachian Basin and its   a328-3400 v2873 a<div id="as005">
<p id="sp0005">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.</p>
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1 aHe, Ruliang1 aLu, Wanyi1 aJunium, Christopher, K.1 aVer Straeten, C., A.1 aLu, Zunli  uhttps://linkinghub.elsevier.com/retrieve/pii/S0016703719307768