Great Valley-Coast Range Formation

Around 150 - 160 million years ago, the Great Valley-Coast Range ophiolite, a fragment of ocean crust and mantle rock, is thrust eastward over the western edge of the Sierra Nevada. About 14-16 million years ago, volcanic rocks flow southwest from Thompson Peak in the Diamond Mountains (northeast of the Sierra Nevada) past present-day Oroville to Orland Buttes and onward into the "black rocks" area along Putah Creek. This lava lies in the subsurface beneath Cache Creek