Some middle Cenozoic freshwater ostracoda from Western Nevada

• F.M. Swain ^[1]
  1. [1] University of Delaware

     University of Delaware

     Estados Unidos

     
• Localización: Revista española de micropaleontología, ISSN 0556-655X, Vol. 17, Nº. 3, 1985, págs. 413-446
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • A fauna of 34 species of freshwater Ostracoda is described and illustrated from the Esmeralda Formation of Stewart and Ione Valleys, Mineral and Nye Counties, western Nevada. One genus and ten species are newly described. Eight species are assigned to previously described forms and the remaining 16 species are given affiinitive assignment or are left in open nomenclature.

    The new genus is Pactolocypris, n. gen., and the new species are Pactolocypris pactolensis, n. gen., n. sp., P. biprojectus, n. sp., P. suborbicularis, n. sp., Eucypris fingerrockensis, n. sp., Cypricercus? minensis, n. sp., Cypricercus mineralensis, n. sp., Procyprois? gracilis, n. sp., Advenocypris concinnus, n. sp., Hemicyprinotus ionensis, n. sp., and Dongyingia? lariversi, n. sp.

    Most of the species are indicative of a lacustrine habitat representing waters having low content of dissolved solids. Four of the species suggest brackish, alkaline or saline lake waters: Dongyingia? lariversi, n. sp.; Xiyingia? sp. aff. X. elliptica Hou et al., 1978, Elkocythereis sp. aff. E. bramletti Dickinson and Swain, and Cytheromorpha? sp.

    The age of the Esmeralda Formation has been designated Miocene by K-Ar dating of igneous rocks associated with it (11-23 m.y.). In several respects the aspect of the fauna is Paleogene rather than Neogene, and although the assemblage is here left in the Miocene, the writer believes it may range in age from Oligocene to Miocene. In other areas of western Nevada the Esmeralda Formation has been designated Miocene and Pliocene.

    The assemblages from the five localities studied in Stewart and Ione Valleys differ significantly from each other, although they have several species in common. Whether these variations the the result of facies controls or age differences cannot be determined satisfactorily at present.