Clay, quartz sand, elastic limestone, and a thick section of clay and very fine grained sand were deposited in the area of Northern Rancho Agua Caliente prior to late Cretaceous time. A hypabyssal intrusion of quartz monzon ite caused the country rock to outward tilt and generally northwest trending faults along and parallel to the pluton borders, probably during the early part of Late Cretaceous time. Numerous dikes intrude the massive slate unit, some of these intrude the granitic rock, and a few cut the limestone and quartzite. With Late Cretaceous(?) isoclinal folding, small folds occurred in the plastic dikerock and foliation developed in the sedimentary rocks. A horizontal terrace of locally derived fluvil conglomerate lies with angular unconformity on the metsedimentary sequence. These conlomerates, of probable Tertiary age, are separated by over one hundred feet of vertical movement along northwest-southeast trending faults which traverse the map area.
