Abstract: Compressional Folding and Faulting in the Vicinity of Silver Creek Valley, Southeast San Jose, California

Leo A. De Vito

Mapping of recent grading exposures for developments within Silver Creek Valley in Southeast San Jose have enabled a closer look at bedrock units and structural conditions along the general alignment of the Silver Creek Fault. Prior mapping in the subject area indicated the presence of Serpentines of the Coast Range Ophiolite, the Franciscan Melange, and the Santa Clara Formation as the primary bedrock units, with both the Coast Range Fault and the Silver Creek Fault passing through the area.

New grading exposures and geologic exploration have enabled recognition of the Silver Creek Gravels as a distinct, previously unrecognized Mio-Pliocene unit. Additionally, clarification of the extent and description of the Santa Clara Formation has been undertaken, and a previously unmapped band of the Great Valley Sequence is now recognized. The new outcrop patterns and grading exposures provide evidence of considerable neogene east-west compression in the area. An initial transpressive period along the Silver Creek Fault is revealed, and this movement may have utilized a portion of the older Coast Range Fault. A later episode of transpression resulted in tight folding and additional faulting, followed by possible normal faulting as compressive components relaxed. The compressional c mponent of the current transpressive regime remains to be clarified.

AAPG Search and Discovery Article #90958©1995 AAPG Pacific Section Meeting, San Francisco, California