PRECAMBRIAN - Upper Proterozoic; mafic dikes - Middle Proterozoic; mafic dikes, diabase, metadiabase, metadiorite mainly of Burro Mountains; age not well constrained - Middle Proterozoic sedimentary rocks of the Sacramento Mountains - Middle Proterozoic plutonic rocks (younger than 1600 Ma) - Middle and Lower Proterozoic plutonic rocks, undivided - Lower Proterozoic rocks, undivided - Lower Proterozoic metasedimentary rocks (1650-1700 Ma). Essentially equivalent to Hondo Group; locally includes high-grade quartzite-pelitic schist of unknown age - Lower Proterozoic metamorphic rocks, dominantly felsic volcanic, volcaniclastic and plutonic rocks (1650-1700+ Ma); includes Vadito Group; locally includes high-grade felsic gneisses of unknown age - Lower Proterozoic plutonic rocks (older than 1600 Ma) - Lower Proterozoic metamorphic rocks, dominantly mafic (1720-1760 Ma) - Lower Proterozoic metamorphic rocks, undivided