38 SANTA MARIA OIL DISTRICT, CALIFORNIA. 
DIATOMACEOUS EARTH DEPOSITS.® 
The infusorial earth, diatomaceous earth, diatomaceous shale, or 
tripoli, as the same material is variously called, of which the upper 
division of the Monterey is chiefly composed, is of fairly pure quality 
in this region and of' considerable economic value, especially as it 
occurs in inexhaustible quantities close to transportation facilities. 
The areas of it are extended and the series of strata very thick. 
Deposits suitable for working occur in the hills immediately south 
of Lompoc; southwest and west of Lompoc; along the river east of 
Lompoc; in the northeastern and southeastern portions of Burton 
Mesa and over the Purisima Hills east of it; over wide areas in the 
Purisima Hills southwest, south, and southeast of Los Alamos; on 
the southern flanks of the Santa Rita Hills; 1J miles north of the 
Santa Ynez Mission; in smaller amounts near the east edge of the 
area mapped, a mile north of Santa Ynez River; underlying the San 
Antonio terrace south of Casmalia; over a wide region southeast, 
east, and north of Casmalia; on Graciosa Ridge, and in the region 
extending from the head of Howard Canyon to a point southeast of 
Sisquoc. The uses to which this material can be put are numerous 
and the demand for it is increasing. 
COMPOSITION OF THE MONTEREY SHALE. 
MATERIAL OF SHALE. 
The composition of the Monterey shale is of especial interest. 
One is able to see on examining the soft unaltered variety with a 
hand lens, or sometimes even with the naked eye, that it is full of 
small round dots ranging, to speak roughly, from 0.1 mm. to 1 mm. 
in diameter. These are the skeletons of minute marine organisms 
called diatoms. They are a low order of plants or algae having a 
framework of silica. They are locally so closely packed together 
that they seem to form the bulk of the deposit. In some of the rock 
they are so well preserved that the details of their structure can be 
made out with the aid of higher magnification. But elsewhere they 
appear crushed and almost unrecognizable. It is a question how 
much of the shale is formed of the diatom frustules that have been 
thus crushed. The shale in which the remains are well preserved 
and abundant is extremely soft and white and may be rubbed at a 
touch into a powder like flour. The round diatom disks are white 
and soft just like the matrix surrounding them, which looks as if it, 
too, were made up of diatom remains that had preserved their form 
less perfectly. Shale in which the remains are less prominent has 
a A more extended description of these diatomaceous deposits is published in “Contributions to 
Economic Geology, 1900” (Bull. U. S. Geol. Survey No. 315, 1907, pp. 438-447), under the title “Diato¬ 
maceous deposits of northern Santa Barbara County, Cal.” 
