The Sierra Santa Rosa and the adjacent areas are the southerly part of a northwest trending structural system which extends for over 100 kilometers on the east side of the Sierra San Pedro Martir, Baja California, Mexico. Batholithic rocks of Jurassic (?) through Late Cretaceous age are surrounded by discontinuous bands and masses of schist, gneiss, quartzites, marbles, metaconglomerates, skarn, and meta-sandstone, and meta-limestone. These pre-batholithic rocks may range in age from Paleozoic to Mesozoic, certainly Early Cretaceous or older. Post-batholithic rocks are dominated by coarse clastic sediments, which locally are obscured by various types of volcanic rocks. The volcanic rocks range from Eocene through Pleistocene and roughly correlate the clastic sediments with which they occur.
