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Evolution of depositional settings in the Torrey area during the Smithian (Early Triassic, Utah, USA) and their significance for the biotic recovery.

Abstract : This work focuses on well-exposed Lower Triassic sedimentary rocks in the area of Torrey (south-central Utah, USA). The studied Smithian deposits record a large-scale third-order sea-level cycle, which permits a detailed reconstruction of the evolution of depositional settings. During the middle Smithian, peritidal microbial limestones associated with a rather low-diversity benthic fauna were deposited seaward of the tidal flat siliciclastic red beds. Associated with siliceous sponges, microbial limestones formed small m-scale patch reefs. During the late middle to late Smithian interval, the sedimentary system is characterized by tidal flat dolostones of an interior platform, ooid-bioclastic deposits of a tide-dominated shoal complex, and mid-shelf bioclastic limestones. Microbial deposits, corresponding to sparse stromatolites formed in the interior platform, are contemporaneous with a well-diversified marine fauna living in a seaward shoal complex and mid-shelf area. The nature and distribution of these Smithian microbial deposits are not related to any particular deleterious environmental condition, highlighting that observed patterns of biotic recovery after the end-Permian mass extinction were directly influenced by depositional settings. Facies evolution and stratal stacking patterns allow us to identify large, medium and small-scale, as well as elementary depositional sequences. Large- and medium-scale sequences are consistent with sea-level changes, whereas small-scale and elementary sequences are better explained by autocyclic processes.
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https://hal.archives-ouvertes.fr/hal-01345780
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Submitted on : Tuesday, April 5, 2022 - 3:47:29 PM
Last modification on : Wednesday, April 6, 2022 - 3:07:23 AM

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Nicolas Olivier, Arnaud Brayard, Emmanuelle Vennin, Gilles Escarguel, Emmanuel Fara, et al.. Evolution of depositional settings in the Torrey area during the Smithian (Early Triassic, Utah, USA) and their significance for the biotic recovery.. Geological Journal, Wiley, 2016, 51 (4), pp.600-626. ⟨10.1002/gj.2663⟩. ⟨hal-01345780⟩

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