Abstract

The region comprising the Candelaria Hills and Excelsior Mountains, Nevada, is structurally anomalous with respect to surrounding tracts of the Basin and Range Province. Its major faults strike east, and some, if not all of them, have undergone significant left slip. Ratios of lateral to vertical displacement components on strands of such faults vary from 2 to 6.5. The region of left-oblique slip faulting seems to constitute the intermediate leg of a gigantic Z pattern of Basin and Range faults.

One of these faults, the Candelaria fault system, has been studied closely in pursuit of kinematic details that might characterize the regional faulting. The Candelaria system consists of three en echelon faults of 5 to 10 km trace length joined by connector zones that possess compressional features. The amount of lateral slip transferred from one en echelon fault to another is uncertain; analysis of a complex of faults in one connector zone indicates at least some degree of integrated motion. The same connector zone is the site of a bulge that has an uplift estimated to have been 275 m since 2.8 m.y. B.P. On the basis of fault-plane striae, the extension direction is ∼ N82°W. We propose that the Candelaria fault system and a major asymmetric trough in its northern wall were created in Oligocene time by a regional left-lateral shear system oriented in the extension direction. The connector zones may be kinematic impediments which, at shallow levels at least, have prevented the system from maturing into a single plane fault. The existence of the bulge and the estimated rate of slip on part of the Candelaria fault system suggest that the system is still active.

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