The photograph above was taken at Bodega Head in Sonoma County. Dramatic cliffs of granite rise up out of the Pacific Ocean here. This is the northernmost exposed outcrop of granitic rocks west of the San Andreas Fault. Slip on the fault juxtaposes rocks sliced off the Sierra Nevada batholith against the Franciscan subduction complex. But what about the rocks that were between the Sierra Nevada and the Franciscan complex? Shouldn’t those have been translated north also? Instead the granitic rocks meet the sea here, and that forearc basin is missing! This is a clue to events prior to formation of the San Andreas Fault that took place in Southern California during subduction.
