Characterizing the Quaternary expression of active faulting along the Olinghouse, Carson, and Wabuska lineaments of the Walker Lane
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The northern Walker Lane (southwestern USA) accommodates similar to 5-7 mm/yr of right-lateral Pacific-North America relative plate motion. The northwest trend of major right-lateral faults in the Walker Lane is interrupted by the presence of northeast-striking left-lateral faults within the Carson and Excelsior domains. Previous studies in the Carson domain have suggested that left-lateral slip on the northeast-striking Olinghouse, Carson, and Wabuska lineaments accommodates Walker Lane transtensional dextral shear through the clockwise rotation of intervening crustal blocks. Our observations confirm and document the presence of late Pleistocene-Holocene faulting along each of these lineaments. Fault scarps along the Carson and Wabuska lineaments are discontinuous and sparse, and show evidence for left-lateral faulting, locally including linear fault traces, alternating scarp face directions, and lateral offsets of small gullies and ridges. The trends of scarps that define these lineaments link at their western ends with north-trending active normal faults. In this manner, it appears that the 5-7 mm/yr of right slip taking place across the northern Walker Lane is being accommodated by the combined processes of basin opening in the west and block rotation to the east. This mode of slip transfer differs from the Excelsior domain, where active left-slip faults and clockwise rotation of crustal blocks are confined to, and the result of, a distinct right step between right-lateral faults of the southern Walker Lane and central Walker Lane, respectively. The observation of these apparently diverse modes of development of left-slip faults and vertical axis rotations provides an example of the complexity that may be expected in the structural development of continental shear zones that have been characterized by transtension.
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