Paper No. 3
Presentation Time: 8:00 AM-5:00 PM
FAULT SLIP RATES ALONG THE QUEEN VALLEY FAULT SYSTEM, CALIFORNIA: SLIP PARTITIONING IN THE EASTERN CALIFORNIA SHEAR ZONE/WALKER LANE BELT
The Eastern California Shear Zone (ECSZ)/Walker Lane Belt (WLB), a zone of intracontinental deformation, accounts for ~25% of the total relative plate motion between the Pacific and North America plates. The ECSZ/WLB is characterized by NW-striking dextral faults, NE-striking connecting displacement transfer normal faults, and ENE-striking sinistral faults. New geological investigations along the Queen Valley fault system, which connects the dextral White Mountains fault zone (WMFZ) to the south with the sinistral Coaldale fault to the northeast, provide insight into the kinematics of fault slip transfer in the ECSZ/WLB. Queen Valley is a ~16 km long, NE-trending basin bounded to the south by the White Mountains and underlain by four major Pliocene(?) to Holocene alluvial fan surfaces: isolated remnants of Q1, relatively smooth Q2 surfaces, Q3 surfaces with bar and swale topography, and Q4 defining present-day drainages. Beryllium-10 cosmogenic radionuclide dating methods on in situ boulders demonstrate that the ages of the Q2 and Q3 surfaces are ~74 ka and ~11 ka, respectively. Four fault types and orientations cut these surfaces: (1) A series of NE-striking, NW- and SE-dipping normal fault scarps cut across the SE-side of the valley and offset Q1, Q2, and Q3 surfaces; (2) A set of NE-striking, sinistral faults cut Q2 surfaces on the N-side of the valley; and (3) A NW-striking dextral fault, which merges into an EW-striking thrust fault, cuts and offsets Q1, Q2, and Q3 surfaces at the S-end of the valley. Topographic profiling of normal fault scarps developed within Q2 and younger surfaces yields a minimum net surface offset of 45 m, indicating a minimum vertical slip rate of ~0.6 mm/yr and, assuming fault dips of 60°, a horizontal extension rate of ~0.4 mm/yr. Measurement of left-laterally deflected and offset channels in Q2 surfaces yields minimum net lateral offset of 85.1 m, indicating a minimum sinistral slip rate of ~1.1 mm/yr. These results suggests that transfer of >2.5 ± 0.3 mm/yr dextral slip (Schroeder et al., 2003) from the WMFZ is not simply to a right-stepping pull-apart structure, rather it is partitioned into three different components: ~0.4 mm/yr horizontal extension along NW-dipping normal faults, ~1.1 mm/yr sinistral slip along NE-striking faults, and the remaining ~1.0 mm/yr dextral slip along NW-striking faults.