Historical Background of the Geology of the Castaic-Newhall Basin: ABSTRACT

Abstract

The Castaic-Newhall basin is a local name given to describe the eastern part of the Ventura basin, one of the major geologic features of California. It extends from the San Gabriel Mountains to Point Concepcion, a distance of 130 miles and contains a thick section of sedimentary strata ranging in age from Cretaceous to Recent. There are no widespread unconformities, though locally marked changes End_Page 2630------------------------------ in thicknesses occur due to marginal variations in sea level and source of sediments. Structurally the basin is complex and the compressive forces which prevailed caused tight folding and thrusting. Oil permeates zones in the Eocene, Miocene, and lower Pliocene. Control for the accumulation of the oil is largely structural, though the variations in sedimentary conditions naturally have a decided bearing on the details of occurrence and volume of production. Studies of the geologic conditions in the Ventura basin have been carried on since 1856. These first reports were concerned mainly with general observations on the character of the rocks, though evidence of bitumens were noted. After 1865 when the importance of the large seepages in California were advertised by Professor Silliman, the public became more interested in petroleum. Actual drilling commenced in 1870 and, as this activity increased, it led to exploration through the use of geology. W. L. Watts began his surveys in California in 1902 and in 1906 published his first work dealing with the petroleum geology of Los Angeles and Ventura counties in a bulletin of the California State Mining Bureau. Following this George H. Eldridge of the U. S. Geological Survey began a systematic study of the geology in relation to petroleum and this was published in 1907. A second geological survey was made by Kew in 1917 and published by the U. S. Geological Survey in 1925. Since then numerous intensive studies have been made by various oil companies and some reports have been published on specific areas. End_of_Article - Last_Page 2631------------