Recent tectonic reinterpretations of the Late Paleozoic Southwest Laurentian margins recognize widespread Late Paleozoic deformation as a critical component in the boundary region development. Overprinted late Paleozoic structures record repeated shortening events in both northern and southern Nevada, but spatial and temporal data are currently lacking to resolve the evolution of this margin. The Timpahute Range, south-central Nevada, bridges part of the spatial gap between previous detailed studies of Late Paleozoic deformation. The purpose here is to (1) evaluate structures in the area that do not appear to fit with recognized Sevier hinterland structures (the Central Nevada thrust belt [CNTB]) and (2) consider whether these contractional structures may be Late Paleozoic and possibly link, or not, structures to the north and south. New mapping in the Timpahute Range documents four geometrically or kinematically distinct sets of structures: Tempiute Ridge folds, Schofield Pass fault zone (SPFZ), structures of the CNTB, and Cenozoic extensional faults. The first three are interpreted to represent separate shortening events based on cross-cutting relations and differences in orientations of the Tempiute Ridge folds and SPFZ (north [N]), and structures of the CNTB (northwest [NW]). The Tempiute Ridge folds represent the oldest event, D 1 . These folds are large, trend N and verge east (E). The SPFZ is west (W)-vergent, cuts across the limb of a D 1 fold and represents D 2 . The SPFZ is interpreted to be older than the CNTB structures, D 3 , based on positions of fault cut offs, and differences in footwall and hangingwall facies. All of the shortening events predate the newly dated 102.9 ± 3.2 Ma Lincoln stock and its contact metamorphic aureole. New and previous correlations suggest that a belt of Permian deformation extends from southeast (SE) California northward at least to the Timpahute Range. The Tempiute Ridge folds and SPFZ have the same distinctive geometries, styles, and kinematics as structures in the Nevada National Security Site. The mountain-size, E-vergent Tempiute Ridge folds and the W-vergent SPFZ correlate to structures associated with the Belted Range thrust and the W-vergent CP thrust, respectively. The Belted Range thrust previously has been correlated southward into the Death Valley region. Thus, convergence created large-amplitude folds and thrusts for ~200 km along strike. Structures of this age are exposed in northern Nevada but are smaller. These new relations fill a data gap and suggest differences in the size and structural style of Permian structures along strike and corresponding variations in the plate boundary configuration.

ABSTRACT In a reconnaissance investigation aimed at interrogating the changing topography and paleogeography of the western United States prior to Basin and Range faulting, a preliminary study made use of U-Pb ages of detrital zircon suites from 16 samples from the Eocene–Oligocene Titus Canyon Formation, its overlying units, and correlatives near Death Valley. The Titus Canyon Formation unconformably overlies Neoproterozoic to Devonian strata in the Funeral and Grapevine Mountains of California and Nevada. Samples were collected from (1) the type area in Titus Canyon, (2) the headwaters of Monarch Canyon, and (3) unnamed Cenozoic strata exposed in a klippe of the Boundary Canyon fault in the central Funeral Mountains. Red beds and conglomerates at the base of the Titus Canyon Formation at locations 1 and 2, which contain previously reported 38–37 Ma fossils, yielded mostly Sierran batholith–age detrital zircons (defined by Triassic, Jurassic, and Cretaceous peaks). Overlying channelized fluvial sandstones, conglomerates, and minor lacustrine shale, marl, and limestone record an abrupt change in source region around 38–36 Ma or slightly later, from more local, Sierran arc–derived sediment to extraregional sources to the north. Clasts of red radiolarian-bearing chert, dark radiolarian chert, and quartzite indicate sources in the region of the Golconda and Roberts Mountains allochthons of northern Nevada. Sandstones intercalated with conglomerate contain increasing proportions of Cenozoic zircon sourced from south-migrating, caldera-forming eruptions at the latitude of Austin and Ely in Nevada with maximum depositional ages (MDAs) ranging from 36 to 24 Ma at the top of the Titus Canyon Formation. Carbonate clasts and ash-rich horizons become more prevalent in the overlying conglomeratic Panuga Formation (which contains a previously dated 15.7 Ma ash-flow tuff). The base of the higher, ash-dominated Wahguyhe Formation yielded a MDA of 14.4 Ma. The central Funeral Mountains section exposes a different sequence of units that, based on new data, are correlative to the Titus Canyon, Panuga, and Wahguyhe Formations at locations 1 and 2. An ash-flow tuff above its (unexposed) base provided a MDA of 34 Ma, and the youngest sample yielded a MDA of 12.7 Ma. The striking differences between age-correlative sections, together with map-based evidence for channelization, indicate that the Titus Canyon Formation and overlying units likely represent fluvial channel, floodplain, and lacustrine deposits as sediments mostly bypassed the region, moving south toward the Paleogene shoreline in the Mojave Desert. The profound changes in source regions and sedimentary facies documented in the Titus Canyon Formation took place during ignimbrite flareup magmatism and a proposed eastward shift of the continental divide from the axis of the Cretaceous arc to a new divide in central Nevada in response to thermal uplift and addition of magma to the crust. This uplift initiated south-flowing fluvial systems that supplied sediments to the Titus Canyon Formation and higher units.