Abstract

The Norian Stage of the Late Triassic represents a long interval from which the benthic faunal succession is poorly understood, particularly from eastern Panthalassa. Fossiliferous bulk samples of shallow marine carbonates were collected from the Luning and Gabbs formations in west-central Nevada to evaluate the changes in faunal composition and paleoecological structure during the Norian Stage. Stationary epifauna dominated the early Norian faunal assemblages but gradually became less common by the late Norian, with the exception of cementing bivalves, which were common in the middle and late Norian. After the early Norian, mobile infauna also became increasingly abundant and diverse. These paleoecological trends are similar to those observed in Tethyan level-bottom carbonate deposits from the Lombardian Basin in northern Italy. Reclining epifauna remained uncommon in the local area until the Early Jurassic, and this Mesozoic decline in recliners preceded the end-Triassic mass extinction in Nevada.

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