SOUTHWEST
Tbf   BASALT FLOWS AND INTRUSIVE IGNEOUS ROCKS--West side of Sierra Madre
Tm    MIOCENE ROCKS 2
Tmu   UPPER MIOCENE ROCKS 2

                                    CENTRAL
Tm    MIOCENE ROCKS 2
Tmu   UPPER MIOCENE ROCKS 2
Tml   LOWER MIOCENE ROCKS
Tu    POST-EOCENE SANDSTONE AND CONGLOMERATE

                                     EAST
Tmu   UPPER MIOCENE ROCKS 2
Tmo   LOWER MIOCENE AND UPPER OLIGOCENE ROCKS OR ROCKS EQUIVALENT TO
            UPPER AND LOWER MIOCENE ROCKS AND WHITE RIVER FORMATION