The Sierra de Pintas Mountains located on the west coast of the Gulf of Baja California about 10 kilometers south of Mexicali, are an impressive exposure of pyroclastic rock of Cretaceous and Tertiary age. The area mapped contains both the Cretaceous Montezuma Formation (new name) and the Tertiary Sierra de Pintas Formation (new Name), which together make up a stratigraphic thickness of nearly 4,000 feet of pyroclastic rock. The area is highly faulted, with several major faults and smaller faults which form horsts and grabens along the edges of the Sierra de Pintas.
