The Surface of Crystalline Basement, Great Valley and Sierra Nevada, California: A Digital Map Database

Crystalline basement in central California extends westward from the
exposed Sierra Nevada beneath the sedimentary fill of the Great
Valley and under the eastern edge of the Coast Ranges at mid-crustal
depth. The surface of this basement is defined from three types of
control: in the Sierra Nevada from the topography itself, beneath
the eastern two thirds of the Great Valley in considerable detail
from numerous wells drilled for oil and gas, and beneath the
western San Joaquin Valley in less detail from seismic reflection
and refraction profiles. Together, these data demonstrate that the
surface of crystalline rock is continuous from the exposed rock in
the mountains to the top of high-velocity rock buried deep beneath
the eastern front of the southern Coast Ranges.