Abstract Evidence of Cenozoic deformation and sedimentation along the southeasternmost 40 km of the Furnace Creek strike-slip fault zone, in the southwestern Great Basin, is contained in two successions of sedimentary and volcanic rocks. Each indicates a stage in the development of the fault zone and associated basins; each is bracketed by K/Ar age determinations. The older succession, dated at 25 to no less than 14 Ma, occurs in tilted fault blocks of the bordering Funeral Mountains, and predates major crustal extension. The succession is about 1,300 m in maximum exposed thickness, contains remnants of two northeast-sloping alluvial fans, onlaps a Paleozoic basement to the southwest, and includes an unconformity that cuts out progressively older units southwestward. These features indicate that a topographic high persisted where younger formations of the fault-controlled, northwest trending Furnace Creek Basin now occur, and also early vertical movement on the fault zone. The younger succession, comprising the Artist Drive, Furnace Creek, and Funeral Formations of the basin (McAllister, 1970), ranges in age from about 14 Ma to about 4 Ma. It records the subsidence and deformation of the basin, and was associated with right-lateral slip on northwest-striking faults and with basin-range extension expressed in part by abundant north-to northeast-striking normal faults. The three formations have a composite maximum thickness of about 3,600 m, but the combined thickness varies greatly from place to place, owing to contemporaneous faulting, to changes in depocenters related to the fault movements and to a general thinning southeastward. The sedimentation and faulting also were accompanied by abundant plutonism and volcanism in the Greenwater Range and Black Mountains southwest of the fault zone. The fact that the normal faulting is regional, affecting terranes on both sides of the fault zone, qualifies the Furnace Creek as a special type of divergent strike-slip fault zone. The contemporaneous strike slip within the 40-km segment of the fault zone probably increases northwestward from zero to no more than a few kilometers, but continues to increase farther northwestward. In the area of Furnace Creek Wash, strike slip is indicated by low-angle grooves and fault mullions, west-northwest-trending en echelon folds, north-northeast-striking normal faults, and by evidence that west-northwest-directed extension was greater on the southwest side of the fault zone than on the northeast side. Vertical movements are recorded by marginal conglomerates in each of the three formations and by northwest-trending folds with features characteristic of drag folds and forced folds. That the fault zone may penetrate deeply into the crust is suggested by the abundance of basalt flows and sills in the three formations of the basin as compared with the bordering terranes.

Abstract The Furnace Creek Basin is a northwest-southeast oriented structural trough, bordered to the northeast by the Furnace Creek fault zone (FCFZ), which separates the basin from the Funeral Mountains, and to the southwest by the Green water Range and the Grand View fault, which borders the Black Mountains (Figure1). Subsidence of the Furnace Creek Basin was controlled by movement on the pre-existing dextral strike-slip FCFZ beginning in the Miocene, coincident with regional extension (Cemen et al., 1985). The Centra lDeath Valley basin is a pull-apart basin with the form of an east-tilting half-graben (Ellis and Trexler,1991) formed largely by dip-slip movement along the Death Valley fault zone concurrent with northwest textension starting in the Miocene (Christie-Blick and Biddle, 1985; Cemen and Wright, 1994; Wright, 1994). Tertiary strata of these two basins comprise three formations: the Miocene Artist Drive Formation, Miocene-Pliocene Furnace Creek Formation (FCF),and the Pliocene Funeral Formation (Figure 2). TheArtist Drive Formation is an assemblage of variegated conglomerates, sandstones, and minor siltstones and claystones with a total thickness of 1300 m (McAllister,1970; Cemen et al., 1985; Cemen and Wright,1988). Up to 2100 m of FCF conglomerates, basalt flows and breccias, sandstones, mudstones, clay stones, marls, and borates unconformably overlie the Artist Drive Formation. Dates of 7.5 Ma for tuff in the upper Artist Drive Formation (Cemen and Wright,1988) and 4.03 0.12 Ma for a basalt flow in the overlying Funeral Formation (Cemen et al., 1985) partiallyconstrain the age of the FCF, which spans the Miocene Plioceneboundary established by the

The late Miocene to Pliocene Silver Peak–Lone Mountain extensional complex in the western Great Basin is part of a structural stepover that links dextral transcurrent motion between the Furnace Creek fault system and northwest-striking transcurrent faults in the central Walker Lane. In the Silver Peak Range, the extensional complex is exposed as a west-northwest–trending turtleback structure that consists of a folded detachment fault separating a metamorphic lower-plate assemblage from unmetamorphosed upper-plate rocks. The upper plate preserves structurally attenuated lower Paleozoic carbonate and clastic rocks, upper Oligocene to lower Miocene volcanic rocks, and a synextensional mid-Miocene to Pliocene clastic and volcanic succession. The three-dimensional geometry of fault-bounded extensional basins formed during displacement on the detachment is preserved, and the synextensional units comprise five sequences separated by unconformities. The locus of deposition migrated spatially as dimensions of small basins changed through time. The entire extensional complex is deformed in two generations of late Cenozoic folds. North-northeast–trending folds formed first with axial traces oriented at a high-angle to upper-plate extension, and these are preferentially developed in proximity to thrusts and partially inverted extensional faults. Younger, west-northwest–trending folds parallel the axis of the turtleback structure and involve all lithologic units, several syndepositional high-angle faults, and the basal detachment. Pliocene growth of west-northwest–trending folds marked the end of slip on the exposed parts of the basal décollement and the cessation of deposition in the fault-bounded basins. Today, upper and lower plates of the extensional complex are dissected by north- to northeast-striking normal faults that cut alluvium and cross-cut and locally reactivate earlier Cenozoic structures.