The lfesa Redonda area includes about 34 square miles lying approximately 12 mi es south of Tijuana, Baja California. The rocks in the area range in age from Early Cretaceous to Quaternary. Two Cretaceous formations are present: the metavolcanic Alisitos Formation and the Rosario Formation of interbedded sandstone and conglomerate. Plutons intruded the Alisitos during ¥.iddle Cretaceous. Prior to Tertiary deposition, a paleosol was developed on an irregular surface. Formation A, an =ocene marine mudstone, was deposited over the paleosol, followed by Formation B, a sandstone, and Formation C, a conglomerate. Exact age of Tertiary ormation D, a basalt, is undeterminable.
