Structural analysis of the San Simeon fault zone, California : implications for transform tectonics

• Main Author: Coppersmith, Ryan Thomas
• Other Authors: Cloos, Mark
• Format: Thesis
• Language: English
• Published: 2008
• Subjects: San Simeon fault zone; California; Transform tectonics; Structural analysis; San Andreas fault; Movement; Fault kinematics; Andreas; Ragged Point; Elephant Seals
• Online Access: https://hdl.handle.net/2152/115381; https://doi.org/10.26153/tsw/42281

The San Gregorio-Hosgri fault zone (SGH), located in the Southern Coast Ranges of California is a 420 kilometer long right-lateral strand of the San Andreas fault system. The San Simeon fault zone is a segment of the SGH that cross-cuts the Nacimiento block which is primarily composed of Franciscan Complex accretionary prism. The Nacimiento block is juxtaposed against the Salinian block, a portion of the Sierra Nevada batholith, by the Nacimiento Fault. The Nacimiento and Salinian blocks have been displaced from the south in a right lateral sense as part of movements within the San Andreas fault system. The San Simeon segment juxtaposes mid-Jurassic Coast Range Ophiolite with Cretaceous Franciscan accretionary prism material. These units are locally overlain by the Oligocene Lospe Formation and Miocene Monterey Formation. To better understand the movement history near the San Simeon fault zone, 33 kilometers of outcrop were examined along the sea-cliff between Ragged Point in the north and Pico Creek to the south. Of this transect, 4 kilometers were buried under marine terrace and sand dunes. No data was collected along 1 kilometer of transect due to the presence of elephant seals. The 28 kilometers of bedrock examined include: 7 kilometers of ophiolitic material, 16 kilometers of Franciscan Complex, 2 kilometers of Lospe Formation, and 3 kilometers of Monterey Formation. In all, 466 minor faults and 254 major (≥0.5 meters exposure length) faults were mapped, and 22 of these major faults juxtapose different formations (n=8) or different units within the ophiolite (n=14). Slickenlines were measured on 517 faults, of which 237 record sense of slip. Of the faults measured, 199 are strike-slip (0-30° rake), 179 are dip-slip (60-90° rake), and 139 are oblique-slip (31-59° rake). Sense of slip indicators record a wide range of movements: 49 right-lateral, 47 left-lateral, 40 normal, 38 reverse, 18 reverse left-lateral, 17 normal left-lateral, 15 normal right-lateral and 13 reverse right-lateral faults. The study ...