Thermal-maturity trends within Franciscan rocks near Big Sur, California: Implications for offset along the San Gregorio–San Simeon–Hosgri fault zone

Abstract

Conventional neotectonic interpretations place the Lucia and Point Sur subterranes of the Franciscan subduction complex on opposite sides of the San Gregorio–San Simeon–Hosgri dextral fault system and connect that system through the Sur fault zone. Our reconstructed paleotemperature contours, however, are not offset across the San Simeon segment, so differential displacement between the subterranes after peak heating appears to have been negligible. One explanation is that dextral slip on the faults has totaled only 5–10 km. A second possibility is that a discrete Hosgri–San Simeon segment extends offshore of the amalgamated Point Sur and Lucia subterranes and that an en echelon stepover transfers dextral slip eastward to the San Gregorio–Palo Colorado segment. In either case, the Sur fault zone appears to play a relatively insignificant role in the late Cenozoic tectonic evolution of central California.