PERMIAN TECTONOSTRATIGRAPHY OF EASTERN NEVADA

The Permian stratigraphy of eastern Nevada is punctuated by a series of unconformities, some of which correspond to recognized phases of sedimentary basin development and associated tectonic uplift, and in a few instances with folds and thrust faults. All, however, reflect the effects of regional tectonics. Although a more refined biostratigraphy will continue to sharpen our understanding of the timing of these events, sufficient data exist to allow us to describe the nature of most of them. A minimum of five tectonic episodes have been recognized to date, beginning with the late Asselian-early Sakmarian P1 or upper Strathearn event. This was followed in the latest Sakmarian - early Artinskian by the regionally significant P2 or Dry Mountain-Pequop event. The Kungurian P4 or Part City event marks the initiation of the Park City and Phosphoria basins. Until now, we have assumed that the youngest phase of Permian deformation is associated with the classic Sonoma orogeny (Tr1), but whether or not there is an older Permian phase of deformation that precedes the Sonoma orogeny has yet to be assessed. Importantly, many of these tectonic events can be traced westward into the Antler highlands. Furthermore, P2 (the 'Dry Mountain-Pequop event') may have expression within the Golconda allochthon - shedding light on, or perhaps complicating our understanding of the tectonics of that terrane. Finally, we have just initiated studies to determine if the conglomerates of the Garden Valley Formation and their apparent equivalents in the Edna Mountain Formation, record a significant Middle-Late Permian event; the relationship of these conglomerates to the Park City event is unknown at this point.