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Anachronistic facies and carbon isotopes during the end-Permian biocrisis : Evidence from the mid-Tethys (Kisejin, Iran)

Author:
  • Mahdi Maaleki-Moghadam
  • Behrouz Rafiei
  • Sylvain Richoz
  • Adam D. Woods
  • Leopold Krystyn
Publishing year: 2019-02-15
Language: English
Pages: 364-383
Publication/Series: Palaeogeography, Palaeoclimatology, Palaeoecology
Volume: 516
Document type: Journal article
Publisher: Elsevier

Abstract english

Late Permian mass extinction (LPME) research has focused primarily on Tethyan sections because it is believed that these successions are more complete than those from other localities, and provide a more comprehensive record of the largest, most devastating extinction event in Earth history. The Kisejin section, a previously undocumented mid-Tethyan, Upper Permian-Lower Triassic succession located in the Central-Iran Plate. The Kisejin section contains a continuous Permian-Triassic sequence with only small breaks in sedimentation and was examined in order to determine sedimentologic, biostratigraphic, and carbon isotopic trends across the Permian-Triassic transition. Abnormal (anachronistic) carbonates developed in the study area following the LPME, and include microbialites, edgewise conglomerates, sparitic microspheres, and microbially-coated grains; microbialites occur as thrombolites, stromatolites, and as agglutinated forms. Renalcis-type calcimicrobes are documented for the first time from Permian-Triassic boundary microbialites (PTBMs) of Iran. Coated grains fall into two groups, and include pre-PTBM ooids, which are dense and cloudy, and possibly microbial in origin, and post-PTBM cortoids with destructive and constructive micrite envelopes. Latest Permian conodonts (H. praeparvus, M. ultima), coupled with carbon isotopic values, place the Permian-Triassic boundary within the lowermost thrombolite unit, about 2.1 m above the boundary between the Nessen Formation and the Elika Formation, and indicate that microbialite growth began during the latest Permian. Our study of this previously unknown section shows that, unlike other well-known PTB sections from Iran, the microbialite pattern is complicated, and is more similar to PTBM successions from Turkey. In addition, we note a similarity between the unusual facies of the Kisejin section and those of eastern Tethyan sections from China (i.e. sparry microspheres and Renalcis-type calcimicrobes); these unusual facies have not been previously reported from other well-known Iranian sections, including Julfa and Abadeh, which are thick and have been extensively studied.

Keywords

  • Calcimicrobes
  • Coated grains
  • Conodonts
  • Mass extinction
  • Microbialites
  • Permian-Triassic boundary

Other

Published
  • ISSN: 0031-0182
Sylvain Richoz
E-mail: sylvain [dot] richoz [at] geol [dot] lu [dot] se

Senior lecturer

Lithosphere and Biosphere Science

+46 46 222 78 89

Sölvegatan 12, Lund

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