Geology of Central California

Ron Crane
139 North 4080 East, Rigby, Idaho 83442

Regional strike-slip faults do not exist in Central California. The San Andreas, Calaveras, Hayward and other designated faults owe their origin to compressional forces, and represent terrane boundaries

The presently accepted concept of strike-slip faulting violates every accepted principle of structural interpretation as well as mapped field data. “Regional” faults have been wrongly correlated from one quadrangle to the next. Geologic mapping has been based on genetic concepts rather than on the geometry of the actual deformation. Three dimensional studies have been neglected and few balanced cross sections have been made. Geologic maps have been ignored. Structural studies are non-existent.

Mini-terranes travelling across the Pacific Ocean have collided with Central California over time, each collision resulting in a fold and thrust belt. Each succeeding collision has deformed earlier thrust belts. The effects of compressive forces are spread across the entire region, with relief along faults occurring in the weaker regions. Basins have opened, filled, and then been destroyed. These basins can be identified by unfolding the many cross-sections constructed across the area. Unfolding demonstrates a minimum of 80,000 meters of horizontal compression. This contrasts to the known 7 meters of horizontal movement in the 1906 earthquake. Deformation has increased in time to the present day.

Geologic mapping in the field and office resulted in the revision of one hundred and twenty two (122) 7 ½ minute quadrangles. This was necessary in order to make the maps geometrically correct. The map is the cross-section. More than 235 cross sections were prepared, each consistent with the geologic map. Additional quadrangles along the San Andreas “Fault” were examined but not corrected.

AAPG Search and Discovery Article #90076©2008 AAPG Pacific Section, Bakersfield, California