EVALUATION OF THE BIG PINE VOLCANIC FIELD CONTACT RELATIONSHIPS ALONG THE SIERRA NEVADA FRONTAL FAULT ZONE NORTH OF GOODALE CREEK IN OWENS VALLEY, CALIFORNIA

This study investigates the contact relationships between basalt flows and cones of the Quaternary Big Pine Volcanic field (BPV) and the predominantly granitic rocks of the eastern Sierra Nevada Mountains between Goodale and Taboose Creeks along the Sierra Nevada Frontal Fault Zone (SNFFZ). The SNFFZ marks the western boundary of the Basin and Range Province and separates the Sierra Nevada Mountains from Owens Valley. This zone is composed mostly of NNW-striking, east-dipping normal faults, which generally are assumed to dip 60°. However, previous work north of Bishop and farther south near Lone Pine and Independence has shown that the SNFFZ faults dip much shallower (26 to 52°). The BPV contact with the Sierra Nevada Mountains generally trends NNW and is parallel to the mountain front. The contact locally V’s up and over ridges at the range front and along the SNFFZ and is consistent with an overall east dip. Our working hypotheses are that the contact formed by (1) basaltic flow deposition buttressed against the mountain front; (2) localized basalt emplacement and extrusion along the SNFFZ; and (3) faulting after emplacement of the basaltic rocks. Field and GPS mapping along the contact combined with Google Earth map analysis are being used to test the hypotheses. Field mapping and preliminary 3-point analysis along the contact yields an average dip of 24° E. This dip is similar to the dip of SNFFZ faults farther north and south suggesting that the contact may locally be a fault. Plane-fitting analysis of GPS- and Google Earth-derived x,y,z positions will be utilized for a more precise orientation of the contact and to assess its potential as a fault. A shallow SNFFZ dip affects long-term extension rate calculations and the kinematic history of this part of the western Basin and Range and Eastern California Shear Zone.