Facies and depositional settings during the Smithin in the Torrey area (Early Triassic, Utah, USA)

• Main Authors: Caravaca, Gwénaël, Olivier, Nicolas, Brayard, Arnaud, Vennin, Emmanuelle, Escarguel, Gilles, Fara, Emmanuel, Bylund, Kevin G., Jenks, James F., Stephen, Daniel A.
• Other Authors: Laboratoire de Géologie de Lyon - Terre, Planètes, Environnement Lyon (LGL-TPE), École normale supérieure - Lyon (ENS Lyon)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Biogéosciences UMR 6282 (BGS), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Utah Valley University (UVU)
• Format: Conference Object
• Language: English
• Published: HAL CCSD 2014
• Subjects: [SDU]Sciences of the Universe [physics]; [SDU.STU]Sciences of the Universe [physics]/Earth Sciences; [SDU.STU.PL]Sciences of the Universe [physics]/Earth Sciences/Planetology; [SDU.STU.ST]Sciences of the Universe [physics]/Earth Sciences/Stratigraphy; Ocean acidification
• Online Access: https://hal.science/hal-03922923

International audience The Permian-Triassic transition records the most devastating biotic crisis of the Phanerozoic with 90% of the marine genera being eradicated. The aftermath of this extinction is usually portrayed by large environmental perturbations such as ocean acidification, anoxia, euxinia and fluctuating productivity. However, these fluctuating conditions and their impact on the nature and tempo of the biotic recovery are still under debate. Thus, it is important to decipher the nature of the depositional settings and their putative spatio-temporal variations in order to improve our knowledge of post-crisis environments. The present work focuses on well-exposed Lower Triassic sedimentary rocks in the Torrey area (south-central Utah, USA). The studied Smithian deposits record a large-scale 3rd order sea-level cycle allowing a detailed reconstruction of the depositional setting evolution. In the middle Smithian, peritidal microbial limestones associated to a rather low-diversity benthic fauna deposited seaward of siliciclastic red beds of a tidal flat. Associated with siliceous sponges, microbial limestones formed small dm-scale patch reefs. During the late middle to late Smithian interval, tidal flat dolostones of interior platform, ooid-bioclastic deposits of tide-dominated shoal complexes, and mid-shelf bioclastic limestones characterize the sedimentary system. Microbial deposits correspond to sparse stromatolites that formed in the interior platform. They are contemporaneous of a well-diversified marine fauna found in seaward shoal complexes and mid-shelf area. The nature and the distribution of these Smithian microbial deposits were triggered by the depositional setting and did not support any peculiar deleterious environmental conditions.