Structural geology and kinematic history of rocks formed along low-angle normal faults, Death Valley, California

摘要

Several late Cenozoic low-angle normal, or detachment, faults on the western flank of the Black Mountains are each characterized by the following, in descending structural order: (1) a hanging wall of upper Tertiary to Quaternary sedimentary and volcanic strata that displays little evidence for fault-related damage other than widely spaced planar or listric normal faults; (2) a sharp, planar, and locally striated principal slip plane forming the lower boundary of the hanging wall; (3) an upper zone—zone I—of very fine grained, fault-generated rocks composed dominantly of gouge; (4) a lower zone—zone II—of coarser-grained fault rocks consisting chiefly of foliated breccia; and (5) a variably damaged footwall, consisting of partly mylonitic Precambrian units or Tertiary plutonic rocks, that has been exhumed from depths of 10–12 km since late Miocene time. The fault rocks, which were mostly derived from the footwalls, preserve evidence for cataclastic and particulate flow. Fault rocks contain authigenic minerals but lack the cyclically deformed, mineral-filled syntectonic veins that are abundant in some other late Cenozoic high-angle and strike-slip faults.