Tectonic Implications of Pennsylvanian and Permian Conodont Biostratigraphy at Selected Locations in the Diamond Range, White Pine and Eureka Counties, Nevada

An unstable Late Paleozoic Cordilleran margin has been recognized by several authors. However, detailed data documenting 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 varies within the region, raising questions about Late Pennsylvanian and Early Permian topography. 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 documents the nature and extent of the hiatus locally, and suggests definitions of regional tectonic episodes. Variation in the magnitude of the hiatus between Pennsylvanian and Permian units, variation in the thickness of Pennsylvanian and Permian strata, and rapid facies shifts are recorded in three stratigraphic sections along the 70 km length of the Diamond Mountains, north of Eureka, Nevada. Differences in the duration of this hiatus can be recognized using Pennsylvanian conodont lineages of Neognathodus, Diplognathodus, Mesogondolella, Sweetognathus, and Neostreptognathodus. In the northern Diamond Mountains, the hiatus ranges from Desmoinesian to latest Wolfcampian; in the central Diamonds, Atokan to latest Wolfcampian; in the southern Diamonds, Desmoinesian to earliest Leonardian. This indicates sedimentation from Early Permian seas onlapped from north to south across an area which had been eroded to variable depths during the Late Pennsylvanian. The region in the vicinity of the Diamond Range seems to have been strongly influenced by Late Pennsylvanian topography which is most easily explained by mild tectonism