The sweeney pass area of southeastern San Diego County is underlain by the Julian Schist of probable Mississippian to Triassic age, and the early Late Cretaceous Stonewall Granodiorite and La Posta Quartz Diorite of the Peninsular Range Batholith. The conglomerates of the Split Mountain Formation and the volcanic rocks of the Alverson Canyon Formation were deposited nonconformably upon this crystal-line basement complex. The Pliocene Palm Spring Formation and Canebrake conglomerate, commonly associated with the sedimentary rock series of the Salton Basin, were only laid down over the northeastern part of the area. Three groups of faults were determined which control the attitudes of the rock units. The oldest, trending northeast, has not affected the miocene rocks and is probably Late Cretaceous or Eocene in are. North-trending faults in Carrizo Canyon and northwest-trending antithetic faults in the central and eastern parts have developed blocks tilted down on the eastern edge. The fault in Carrizo Canyon has a probably right-lateral slip component of 2,000 feet, and a dip-slip component of feet.
