THE SAN JUAN FAULT, AN E-W TRENDING LEFT-LATERAL STRIKE SLIP FAULT ZONE INFERRED FROM ANALYSIS OF KINEMATIC INDICATORS; VANCOUVER ISLAND, CANADA

We present data on the kinematics and geometry of a western segment of the San Juan Fault, which strikes east-west near the southern tip of Vancouver Island, British Columbia, Canada. This fault delineates the boundary between metamorphosed volcanic and plutonic rocks of the Wrangellia terrane to the north from the altered Pandora Peak unit and Leech River Complex of the Pacific Rim terrane to the south, but the kinematic history of this fault remains poorly understood. Detailed geologic mapping of the study area suggests the San Juan Fault is not a discrete fault, but rather a distributed shear zone. Fault kinematic data from six locations, including a total of 203 slickenlines measured and shear-sense indicators from both slickensides and thin sections of fault surfaces, all suggest left-lateral oblique slip with a minor component of oblique thrust motion. Thus, the San Juan fault is an east-west trending, left-lateral high angle strike-slip fault with a minor oblique thrust component, and is as much as 2,400 meters wide.