MIDDLE PENNSYLVANIAN THROUGH EARLY PERMIAN REGIONAL TECTONIC UNCONFORMITIES IN NORTHEASTERN AND EASTERN NEVADA

A succession of unconformities within the late Paleozoic strata of northeastern and eastern Nevada record a series of tectonic events. The first unconformity, C5 separates late Atokan from middle Desmoinesian strata. At Buck Mountain and the Central Pequop Mountains (CPM), the C5 boundary is associated with pre-unconformity deformation. At both localities, the deformation is constrained to the uppermost 20-100 m of the Ely Limestone (late Atokan) and is characterized by small-scale thrusts (10's of meters displacement) and outcrop scale folding. Sweet et al., (2001) documented a northwest directed shortening for C5 deformation in the CPM and field observations at Buck Mountain, also, suggest a northwest shortening direction. At Moorman Ranch, the C5 boundary is also present, but, to date, sub-unconformity deformation has not been documented. The C6 and P1 unconformities are only locally preserved. The C6 boundary separates as old as Atokan from early Missourian strata. The P1 boundary separates as old as Virgillian from Asselian strata. The P2 boundary is present at numerous localities in NE and E Nevada and separates strata as old as Atokan from late Sakmarian to early Artinskian strata. In the CPM, the P2 boundary separates late to medial Sakmarian strata from late Desmoinesian strata and regionally represents the oldest strata observed above the boundary. In the Diamond Range, the P2 boundary separates early Artinskian strata from Desmoinesian and Atokan strata. At Carlin Canyon and Buck Mountain, the P2 boundary separates early Artinskian strata from medial Sakmarian strata. At most localities where the P2 boundary is present, a basal chert-pebble conglomerate with a carbonaceous matrix occurs. The C5 boundary represents a short interval of time and displays unique sub-unconformity deformation. It is uncertain, whether or not, the P2 event reflects a more significant tectonic event than the C6 and P1 events.