Tectonic implications of new Pennsylvanian-Permian conodont data from the Diamond Mountains, Nevada

An unstable Late Paleozoic Cordilleran margin has been recognized by several authors, however, detailed data documented the timing of individual tectonic episodes have been unavailable. In the central and northern Great Basin, a regional unconformity separates Lower and Middle Pennsylvanian strata from overlying Permian units. The timing and extent of this unconformity vary within the region, raising questions about the paleotopography. The hiatus represented by the Pennsylvanian-Permian unconformity may have resulted from Late Paleozoic tectonism, yet available age dates have been insufficient to bracket its duration with the resolution required to test this tectonic hypothesis. New conodont and lithostratigraphic data from central Nevada document the nature and extent of the hiatus locally, and suggest definitions of regional tectonic episodes. Variation in the magnitude of the hiatus between Pennsylvanian and Permian units, rapid facies shifts and variation in the thickness of Permian strata are recorded in three stratigraphic sections along the 45 mile length of the Diamond Mountains, north of Eureka, Nevada. Differences in the duration of this hiatus can be recognized using Pennsylvanian conodont lineages of Streptogathodus and Idiognathodus, and the Permian Mesogondollela bisseli-Sweetognathus whitei and Neostreptognathodus pequopensis-Sweetognathus behnkeni assemblage zones. The hiatus in the northern Diamond Mountains ranges frommore » Atokan to latest Wolfcampian; in the central Diamonds, Morrowan to Leonardian ; in the southern Diamonds, Atokan to late Wolfcampian or Leonardian. Immediately south of the Diamond Mountains, at Secret Canyon, the hiatus spans Late Mississippian to lower upper Wolfcampian. Early Permian sedimentation in the region seems to have been strongly influenced by tectonically produced Late Pennsylvanian topography.« less