Swiss Journal of Palaeontology

, Volume 132, Issue 2, pp 141–219

Smithian ammonoid faunas from Utah: implications for Early Triassic biostratigraphy, correlation and basinal paleogeography

  • Arnaud Brayard
  • Kevin G. Bylund
  • James F. Jenks
  • Daniel A. Stephen
  • Nicolas Olivier
  • Gilles Escarguel
  • Emmanuel Fara
  • Emmanuelle Vennin
Article

DOI: 10.1007/s13358-013-0058-y

Cite this article as:
Brayard, A., Bylund, K.G., Jenks, J.F. et al. Swiss J Palaeontol (2013) 132: 141. doi:10.1007/s13358-013-0058-y

Abstract

Intensive sampling of the lower portion of the Thaynes and Moenkopi Groups (Lower Triassic) at separate localities within the Confusion Range, Pahvant Range, Mineral Mountains, Star Range, Kanarraville, Cedar City, Torrey and San Rafael Swell areas (mainly central and southern Utah, USA) leads to the recognition of a new key regional Smithian ammonoid succession. The new biostratigraphical sequence, which is more precise than the long-recognized Meekocerasgracilitatis and Anasibiriteskingianus Zones, comprises twelve subdivisions, thus resulting in a sequence with much higher resolution that can be correlated not only with other western USA sites, but also with major worldwide localities as well. Middle and late Smithian faunas contain many taxa with wide geographic distribution, thus enabling long-distance correlation with faunal successions from other regions (e.g., British Columbia, Canadian Arctic, South China, Spiti and Oman). New assemblages from the lowermost beds are the least diversified and poorest preserved; they represent the earliest early/middle Smithian ammonoid faunas reported from the western North American basin. They highlight (a) the sudden Smithian advancement of the marine transgression within this epicontinental sea, (b) that this event is diachronous, and (c) that the paleotopography of the basin most likely was highly irregular. The newly obtained ammonoid succession also allows us to date and follow the transgression from the northern and central part of the basin to the southwesternmost and southeasternmost parts, which were reached during the late Smithian (Anasibiriteskingianus beds). In addition, we briefly discuss the now-limited previous regional biozonation in the light of these new results. One new genus (Minersvillites) and nine new species (Kashmirites utahensis, Kashmirites confusionensis, Kashmirites stepheni, ?Xiaoqiaoceras americanum, Minersvillites farai, Inyoites beaverensis, Meekoceras olivieri, Meekoceras millardense, Vercherites undulatus) are also described.

Keywords

Ammonoids Early Triassic Smithian Utah Biostratigraphy Paleogeography New genus and species 

Copyright information

© Akademie der Naturwissenschaften Schweiz (SCNAT) 2013

Authors and Affiliations

  • Arnaud Brayard
    • 1
  • Kevin G. Bylund
    • 2
  • James F. Jenks
    • 3
  • Daniel A. Stephen
    • 4
  • Nicolas Olivier
    • 5
  • Gilles Escarguel
    • 5
  • Emmanuel Fara
    • 1
  • Emmanuelle Vennin
    • 1
  1. 1.UMR CNRS 6282 BiogéosciencesUniversité de BourgogneDijonFrance
  2. 2.Spanish ForkUSA
  3. 3.West JordanUSA
  4. 4.Department of Earth ScienceUtah Valley UniversityOremUSA
  5. 5.Laboratoire de Géologie de Lyon: Terre, Planètes, EnvironnementUMR CNRS 5276, Université Claude Bernard Lyon 1Villeurbanne CedexFrance

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