Pennsylvanian brachiopods of Nevada
AuthorRai, Vijai Narain
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Highly fossiliferous Pennsylvanian rocks crop out extensively in mountain ranges of eastern Nevada. Brachio- pods and corals are uniformly distributed in these rocks in contrast to erratic lateral distribution of fusulinids. Correlation of the Pennsylvanian System in this area is better served Dy using tnegafaunal elements and a biostratigraphical scheme is presented. Faunal elements of the basal Moleen and Ely Formations in northeastern and east-central Nevada respectively, and extreme upper units of BSb member of the Bird Spring Group in southern Nevada have close affinity to the early Morrowan fauna from other areas in Nevada, Utah and the mid-continent region. These basal units also represent the upper range limit of brachiopcds, Rhipidomella nevadensis and Diaphragmus fasciculatus which are primarily upper Mississippian species. The presence of these two late Mississippian species and Gvatia aff. 0. elongate, Splrifer ocelduus, S. oplmus, Hus ted la miseri, Aiitiquatonia lintzi n. sp., and other early Pennsylvanian fauna in the basal units is indicative of an early Morrowan age. A widespread unconformity indicating local orogenies and epiero- genic upwarping is evident for late middle and upper Pennsylvanian time in northeastern and east-central Nevada. In southern Nevada, uninterrupted faunal and lithologic sequences indicate continuous deposition. Faunal analysis revealed that 9 taxa are index fossils, 27 axa have short vertical range but poor to moderate lateral distribution, 8 have poor vertical distribution, but good lateral distribution and the rest are stratigraphically unimpoi'tant. More than oO taxa of brachiopods are described. Nine brachiopods Wellerella dekalbensis var. elkoensis n. var., Composite nevadensis n. sp. , Composite elorigata var. elyensls n. var., C1e io thyr i d in a orbicularis var. brogani n. var., Antlquatonia llntzi n. sp., Antiquatonia lintzi var. costatus n. var., Linoproductus firbyi n, sp., Desmoinesia muricatina var. nevadensis n. var., and Retichonetes larsoni n. sp. are described for the first time.
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