COMPLEXITY AND TRANSTENSION IN THE WALKER LANE BELT DUE TO SUPERPOSITION OF NEOGENE STRAIN FIELDS: PANAMINT VALLEY, CALIFORNIA

Deformation within the Walker Lane belt is notable for the presence of many oblique displacement faults and geometrically complicated regional fault systems. These complications are interspersed with other structures which fit with simplistic fault geometries formed in the active regional stress field. Panamint Valley, in the southern Walker Lane, is dominated by a relatively large displacement, shallowly dipping, detachment fault. Recent movement on this structure is right-lateral oblique normal. This detachment fault has a 5 km right step via a sinistral oblique fault. The hanging wall rocks are notable for an intricate system of relatively small displacement faults which cut Neogene rocks and deposits and can be easily traced into older bedrock. The kinematics of this deformation are northwest dextral transtension. This zone of deformation cuts Quaternary deposits and also juxtaposes these deposits with bedrock at the detachment fault. These observations along with seismic and GPS data show that the deformation is currently active. This odd and complicated geometry and the obliquity of deformation in Panamint Valley are a result of overprinting of a new stress field onto faults formed during an earlier stress field. Extensional deformation began prior to extensive ~14 Ma volcanics and continued during the ~2 m.y. life of this volcanic field, which is exposed in both the hanging and footwall rocks. This deformation has distinctly different kinematics from the active deformation which is east-west extension. Both the Miocene and Pliocene volcanics are tilted to similar, moderately east-northeast dips, and are capped by rock avalanche deposits. These observations indicate a relatively time-distinct tilting event in the late Pliocene. This tilting event could represent the initiation of the new strain field.