DEFORMATIONAL HISTORY AND KINEMATIC RECONSTRUCTION OF POLETA FOLDS, WHITE-INYO RANGE, CALIFORNIA

The White-Inyo Range of eastern California records multiple Paleozoic-Mesozoic deformation events, but the style and magnitude of contractional deformation is not fully known. Timing of deformation and its relationship to the regional plate tectonic setting and local pluton development is also poorly understood. Previous studies have described two to three episodes of contractional deformation resulting in small scale NE trending folds in the central White-Inyo Range and major N to NW trending anticlinoria that define the White Mountains and the Inyo Mountains. Some studies suggest that NE trending structures are related to the Antler Orogeny, while N and NW trending structures are the result of later events. However, the exact timing of deformation in the White-Inyo Mountains is unknown and has not been conclusively correlated to regional tectonic events. To address this problem the Poleta folds area of the southern White Mountains was mapped at a scale (about 1:7700) that allows a detailed structural and kinematic analysis. Eight units can be easily distinguished within the Poleta Formation, and lithologic variations within each unit allow for detailed mapping of faults between and within the units. The area contains several NE striking major thrust faults and NE trending folds. Most folds are plunging, and at least one is doubly plunging forming a basin structure. Small duplex thrusts cause repetition of Poleta units and larger duplex structures place much of the Poleta Formation on top of the younger Harkless Formation. The Harkless is often highly deformed by small-scale folds and faults as evidenced by repetition of key marker beds. Additionally, NW striking right lateral faults appear to be active and offset older structures. A preliminary balanced cross-section through the area reveals shortening of about 35%, from 3.1 km of restored section length to just over 2km presently. Once dated, a dike in the northwest corner of the field area that is displaced by faults will provide a key constraint on the timing and sequence of thrusting. The kinematic reconstruction and deformational timing constraints of the Poleta folds are a first step towards better understanding the complex history of the White-Inyo Mountain Range during the Paleozoic to Mesozoic, and its correlation to tectonic events of western North America.