Geology of Mount Pinos area, Ventura County

Abstract

This paper is written on the geology of the northern half of Lockwood Valley, which is located in northern Ventura County. The area in general is mountainous, and includes Mt. Pinos (8826 feet) as its highest peak. The rocks consist of two igneous member (granite and basalt) and many sedimentary ones (shales, sandstones, and conglomerates). The oldest rock is granite intruded in the Jurassic. This is overlain by a series of continuous, marine sediments of Eocene age. These are overlain by a basalt flow which was extruded in early Miocene times. Both marine and terrestrial beds of the same age overlie the basalt. The only subsequent deposits are of terrace gravels and alluvium. Faulting is the most prominent type of structure. Voiding is present, but plays a very minor part on the area studied. There are two sets of faults, one running concentrically about the other radially to Mt. Pinos. The second set is of little importance, The first set, is made up of four large faults, which uplift sediments and granite along the southern side of Mt, Pinos. From an economic standpoint this is a place of both recent and historical interest. The region was one of the first localities in which borax was mined (1899), and mining was continued intermittently until 1913. Gold has been taken in large quantities from the southern side of Lockwood Valley since the early 18801s. At the present time the area has a new business in the mining of rotary mud. This is done by steam shovel from one of the valley's many clay beds.