Geologic map: Supplement 2 from "Geology of the southern Santa Ana Mountains, Orange County, California" (Thesis)

Description

The area studied lies on the southwestern slope of the Santa Ana Mountains in the southeastern quarter of the Corona Quadrangle. The oldest rocks are a series of slates and sandstones with some lenses of limestone and intruded by andesite porphyry dikes. Unconformably overlying the slates is a coarse conglomerate and in part of the area a series of basic lavas and tuffs. All these rocks have been metamorphosed by andesite granodiorite and diabase intrusions. Triassic fossils have been reported from the slates. The rocks overlying the "basement complex" constitute a westward dipping homocline, including upper Cretaceous. Paleocene, and middle Eocene formations, the Vaqueros and Topanga formations, the Puente shales, and the Capistrano formation, each of which is bounded by an unconformity or disconformity. The structure is unusual in that, while the sediments are those typical of the Coast Ranges, the mountains are a tilted fault block, uplift taking place along the Elsinore fault system. The detailed structure consists of a few folds and faults not aligned with the Elsinore system. The physiographic history shows a long series of repeated uplifts. Some of the lower terraces are marine. In the evolution of the present topography the resistance of the rocks has played a large part.

Files

Additional details