Northern Coast Ranges, California: ABSTRACT

ABSTRACT The California Northern Coast Ranges include the mountainous and semi-mountainous areas and intermontane valleys from the Oregon-California boundary on the north to San Francisco Bay on the arbitrary sinuous line which approximately follows the Southern Pacific Railway from Oregon southward to a point about 10 miles southwest of Redding, thence the boundary approximates the western limits of the Cretaceous of the Sacramento Valley province to a point a few miles northeast of Napa and thence, southward to Carquinez Straits. It represents an area of approximately 19,938 square miles, of which about 812%, or 1,700 square miles, are underlain by sedimentary rocks which are common to oil-field provinces. This total of 1,700 square miles is made up of a number of widely separated areas, in many of which the basement is relatively shallow. The calculated volume of sediments of the California Northern Coast Ranges, which might be placed in the classification of possible future oil provinces, is of the order of 500–550 cubic miles. The sedimentary formations, herein considered, are of Tertiary and Cretaceous age, but some of the latter has not been included in our calculations. As explained in the body of the paper, there is an indeterminate quantity of Cretaceous sediments so intimately associated with steeply folded and faulted Franciscan rocks that a separation has not been made and it is believed that such phases of the Cretaceous and the Franciscan sediments of the California Northern Coast Ranges should not be considered in the areas of possible future oil provinces. To date, no major oil or gas fields have been developed in this area; a small dry-gas field containing about 112 square miles with only three producing wells supply gas to the Eureka district. Also, a little oil and gas have been developed in the vicinity of Petaluma but there is no sustained production, and the oil development is included within an area of 20–30 acres and the gas area covers about 12 square mile. The oil production from this area amounted to 1,186 barrels during 1949 and the total cumulative production to date amounts to 3,475 barrels.