GEOMETRY OF MESOZOIC(?) CONTRACTIONAL STRUCTURES: IMPLICATIONS FOR THE TECTONIC DEVELOPMENT OF THE CENTRAL NEVADA THRUST BELT, EAST-CENTRAL GREAT BASIN, NEVADA

The Central Nevada Thrust belt (CNTB) is a N/S trending fold and thrust belt located in the hinterland of the Sevier orogenic belt. Subsequent dissection by Cenozoic normal faults makes delineation of CNTB structures difficult. Some workers suggest the southern portion of the CNTB is an early Mesozoic pulse of contraction related the Sevier orogenic belt. Therefore, the CNTB is important to the regional tectonic evolution of the western Cordillera from late Paleozoic to Eocene time. The purpose of this study is to document contractional structures and Cenozoic normal faults in the central Pancake Range, Nye County, Nevada, and correlate contractional structures to the CNTB.

Map, cross section, and stereonet data suggest a minimum of three sets of Cenozoic normal faults: pre-33 Ma, 33 Ma to 31.3 Ma, and post- 31.3 Ma sets. Normal fault sets strike N/S, however, several transverse left-lateral oblique-slip faults were mapped that are younger than 35.34 ± 0.07 Ma.

Field relations document the presence of an E-vergent, N-striking (N23°E, 46°W) thrust fault, the Ike Springs thrust. This fault lies structurally above southern CNTB thrust faults mapped in the Grant and Quinn Canyon ranges. The Ike Springs thrust places Devonian strata over Mississippian/Pennsylvanian Antler foredeep deposits with a maximum stratigraphic offset of 2037 m. This is consistent with CNTB faults mapped further north. In contrast, previous workers attribute deformation of Paleozoic strata to a Cenozoic low-angle normal fault. The documentation of the Ike Springs thrust provides a better explanation for the deformation of Paleozoic strata exposed within the area.

Field mapping and structural analysis documents contractional deformation that lies structurally above southern CNTB structures exposed to the southeast, and shares consistent offset and strike of CNTB structures mapped to the north. Structures exposed in the Pancake Range therefore link the CNTB through central Nevada.