Paleo-redox context of the Mid-Devonian Appalachian Basin and its relevance to biocrises

Ruliang He, Wanyi Lu, Christopher K. Junium, Charles A. Ver Straeten, Zunli Lu

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


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.

Original languageEnglish (US)
Pages (from-to)328-340
Number of pages13
JournalGeochimica et Cosmochimica Acta
StatePublished - Oct 15 2020


  • Atmospheric oxygen
  • Devonian
  • I/Ca
  • Marcellus shale

ASJC Scopus subject areas

  • Geochemistry and Petrology


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