09 May 2019
 | 09 May 2019
Status: this discussion paper is a preprint. It has been under review for the journal Climate of the Past (CP). The manuscript was not accepted for further review after discussion.

Anoxia and salinity changes: a new Permian catastrophe record

Marlise C. Cassel, Ernesto L. C. Lavina, Joice Cagliari, René Rodrigues, and Egberto Pereira

Abstract. Bituminous shales are associated to worldwide geological events, such as mass extinction, anoxia and climatic changes, mainly when preserved in carbonate ramps, and constitute reliable records of this dynamics. However, a minority of data still exist that measure the Permian, especially in the Southern Hemisphere associated to Panthalassic Ocean as compared to numerous studies of Oceanic Anoxic Events in the Cretaceous or associated to Tethys. The Late Permian extinction was the most severe extinction of the past 500 million years, which wiped out over 90 % of marine species. Before the Permian-Triassic boundary (e.g. Early-Middle Permian successions) geochemical and geological anomalous aspects has received more attention due the information about the Late Paleozoic icehouse-greenhous transitions, which is one of the triggers for the catastrophic ectinction. Therefore the Irati Formation, Permian interval of Paraná Basin in southern Brazil, is suitable for the study of these intricate processes due to the presence of Permian bituminous shales and carbonates. Based on core descriptions, spectral gamma ray data and organic geochemistry, a stratigraphic scheme is here proposed to support paleoenvironmental inferences. We identified three depositional sequences formed internally by T-R cycles of highest frequency. The sedimentary facies analysis indicates a carbonate ramp subdivided into outer, middle and inner. Climatic and sea level changes are defined, and also oscillations in the salinity, oxygenation and organic matter source. Bituminous shales record normal salinity, with anoxia levels and even euxinia, associated to the increase in bioproductivity. Carbonate facies register periods of hypersalinity under oxic environment and semi-arid conditions. The accumulation of Mesosaurus skeletal remains results from the action of reworking fluxes, creating an endemic facies in this region. Climatic versus eustatic influence were differentiated, and also the controlling hierarchies. These results are evidence for the environmental dynamics from the Permian, that generated extreme global events, mainly in Gondwana.

Marlise C. Cassel et al.

Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement

Marlise C. Cassel et al.

Marlise C. Cassel et al.


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Short summary
This manuscript proposes a new occurrence of anoxic events deposits (e.g. anomalous black shale) and other climatic extremes (e.g. hypersalinity) as the record of one of the triggers studied for the Permian-Triassic extinction. Although there are models that explain the extinction of P-T boundary, their triggers need more detailing. This study is also innovative due to the importance of oceanic anoxic events beyond of Crataceous and due to deposits in a intracratonic restricted basin.