Structural Evolution of Santa Lucia Range, California: ABSTRACT

Abstract

The rocks of the Santa Lucia Range are divisible into a bedrock complex and a superjacent series, separated by a major unconformity which represents early Late Cretaceous deformation (Santa Lucia orogeny). Decollement tectonics, involving gravity sliding of the Franciscan rocks over carbonate rocks of the Gabilan mesa, played an important role in the deformation of the bedrock complex during Late Jurassic and middle Cretaceous times (Hsu, 1965). The superjacent rocks were deformed by wrench faulting, and by folding during several Cenozoic orogenic episodes. Thrust faults have been observed in wrench-fault zones. Local changes from wrench to thrust faulting are related to slight changes in the magnitude of the vertical and horizontal principal stresses. These thrusts sho ld not be confused with the decollement tectonics which affected only the bedrock complex. The Franciscan-Recent succession of the region is illustrated and discussed. The stratigraphy of the superjacent sediments is based on the work of previous investigators. The stratigraphy of the bedrock complex is based mainly on the writer's structural interpretations. Although the Franciscan rocks were deformed during late Mesozoic and denuded during early Tertiary, they furnished very little debris to the Cretaceous and early Tertiary sedimentary formations of California. End_Page 648------------------------------ Nevertheless, large volumes of Franciscan debris must have been removed from the Santa Lucia Range before the Miocene transgression. This debris probably was transported west and deposited as thick early Tertiary clastic sequences in offshore basins. End_of_Article - Last_Page 649------------