The geology of a part of the Ravenna Quadrangle, California

Abstract

The Ravenna quadrangle includes the easternmost part of the Ventura Basin in Los Angeles County, California and together with adjoining quadrangles constitutes an area of which little or no detailed geological work has been published. Ravenna station is situated on the Southern Pacific Railway and the present work involved the investigation of an area or about five square miles surrounding Ravenna and extending about two miles north and the same distance west of the station while at the same time including a narrow strip to the south of and paralleling the Santa Clara River. The area is readily accessible over excellent motor roads from the city of Los Angeles which lies forty to fifty miles to the southwest. Branch roads, in less excellent state of repair, lead from the main highways into the area, relatively little of which cannot be reached by automobile. The object of the present work was to obtain as much information as possible concerning the geological relations or a series of interbedded conglomerates and volcanic flows while at the same time to contribute towards the completion of a detailed study of the entire Ravenna and adjoining quadrangles. Problems requiring solution involved principally the origin of the deposits, their geological relationships to each other, their structural features and their respective ages. All these problems have been attacked but their solution has been met with only varying degrees of success. The field work upon which this report is based was carried on from March to June, 1946. A total of eighteen days was spent in the field during that period. The work was carried out by plotting the geology directly on field maps supplied by the California Institute of Technology. These maps had been enlarged to twice the scale from United States Topographical maps published on a scale of 2000 feet to 1 inch. Rock samples were collected and their locations plotted on the map then a megascopic examination was made in the office. No microscopic examinations were made so that the only descriptions included in this report are megascopic with the exception or certain references where noted.