Geochemical paleoredox indicators in organic-rich shales of the Irati Formation, Permian of the Parana Basin, southern Brazil

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dc.contributor.author Goldberg, Karin
dc.contributor.author Humayun, M.
dc.date.accessioned 2017-11-30T21:43:54Z
dc.date.available 2017-11-30T21:43:54Z
dc.identifier.uri http://hdl.handle.net/2097/38351
dc.description Citation: Goldberg, K., & Humayun, M. (2016). Geochemical paleoredox indicators in organic-rich shales of the Irati Formation, Permian of the Parana Basin, southern Brazil. Brazilian Journal of Geology, 46(3), 377-393. doi:10.1590/2317-4889201620160001
dc.description.abstract Paleoredox indicators were used to assess the depositional environment of the Permian Irati Formation, and discuss the controls on the accumulation of organic-rich sediments. Geochemical data were measured for 43 drill-core samples in southern Parana Basin. We infer that redox boundary was located at the sediment-water interface during the accumulation of these sediments. Trace-element data demonstrate that Irati shales were similar to average shales, except during deposition of two organic-rich beds in which U and Mo are enriched, suggesting fully anoxic conditions. The variable degree of oxygenation of bottom waters is also attested by DOPT, Fe-T/Al, and sedimentological indicators of episodic ventilation. DOPT and Fe and S correlation points to an iron-limited environment, where the main sulfur sink is organic matter rather than pyrite. Cu and Cu/Mo ratio suggests bottom-water anoxia driven by increased organic flux. The Irati Formation was probably deposited in a salinity-stratified body of water, with positive water balance. The main control on the accumulation of the organic-rich sediments was the high organic carbon flux resultant from high primary productivity in surface waters. Anoxia arose as a consequence of increased productivity, not as the primary driver in the formation of these organic-rich rocks.
dc.relation.uri https://doi.org/10.1590/2317-4889201620160001
dc.rights Attribution 4.0 International (CC BY 4.0)
dc.rights.uri https://creativecommons.org/licenses/by/4.0/
dc.subject Black Shales
dc.subject Paleoredox Proxies
dc.subject Irati Formation
dc.subject Permian
dc.subject Earth-Element Geochemistry
dc.title Geochemical paleoredox indicators in organic-rich shales of the Irati Formation, Permian of the Parana Basin, southern Brazil
dc.type Article
dc.date.published 2016
dc.citation.doi 10.1590/2317-4889201620160001
dc.citation.epage 393
dc.citation.issn 2317-4889
dc.citation.issue 3
dc.citation.jtitle Brazilian Journal of Geology
dc.citation.spage 377
dc.citation.volume 46
dc.contributor.authoreid kgoldberg
dc.contributor.kstate Goldberg, Karin


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