T249 Alluvial Records: Numerical Dating and Archives of Climatic, Environmental, and Neotectonic Change (Posters)

Wednesday, 21 October 2009
9:00 AM - 6:00 PM
Hall A

LATE PLEISTOCENE SLIP RATES ALONG THE PANAMINT VALLEY FAULT ZONE, EASTERN CALIFORNIA

Paper number: T249-13
Program: Technical Sessions
Time: 9:00 AM – 6:00 PM

Authors

Abstract

The evolution of right-lateral shear across the Sierra Nevada-Death Valley corridor through space and time remains uncertain. Despite intensive efforts to determine slip rates on major fault systems over the Late Pleistocene – Holocene, significant differences between these rates and the present-day geodetic velocity field remain. One gap in the slip-rate catalogue exists along the Panamint Valley fault zone (PVFZ); current estimates either rely on undated alluvial deposits (Zhang et al., 1990; Oswald and Wesnousky, 2002) or represent long-term estimates based on total offset of the system and bounds on the initiation of fault slip (Burchfiel et al., 1987; Lee et al., 2009). To determine the rate of slip during the Late Pleistocene, we utilize displaced alluvial deposits at two localities along the southern portion of the fault system and reconstruct fault slip from field surveys and airborne LiDAR topography. Chronologic control is provided by radiocarbon dating of tufa associated with lacustrine shorelines, soil characteristics, and terrestrial cosmogenic nuclide (10Be) dating of alluvial fan surfaces.

Near Happy Canyon, a releasing step in the fault zone forms a 2-3 km long embayment where displacement on NE-trending faults is dip-slip, affording an opportunity to constrain fault displacement directly from the vertical offset of varying fan surfaces. Cosmogenic 10Be surface clast dating of the oldest fan suggests a surface age of 30-35 ka, whereas the youngest inset surface appears to have been deposited synchronously with a shallow MIS stage 2 lake (~15-25 ka). We are working to refine this estimate with additional dating and soil characterization, but our preliminary estimates suggest a minimum oblique- slip rate of 1.5-2 mm/yr at Happy Canyon.

Near Manly Canyon, oblique-slip appears to be partitioned into fault strands with primarily lateral and normal slip. The fan surface is displaced by ~10m along the normal fault and debris-flow levees are right-laterally offset by ~26m. 10Be ages from unweathered boulders suggest a maximum surface age of 14 ka, consistent with soil characteristics and cross-cutting relationships with shoreline features. Our results suggest a minimum slip rate ~ 1.75-2 mm/yr at Manly Canyon. Ongoing work will assess whether the PVFZ exhibits temporal variations in slip rate between the Late Pleistocene and Holocene.