308 CONTRIBUTIONS TO ECONOMIC GEOLOGY, 1902. [bull. 213. 
ates of the San Pablo. It is estimated that approximately 1,500 feet 
of measures separate the two horizons. Owing- to this distribution 
there are two distinct areas of wells — an inner, in immediate prox- 
imity to the axis of the anticline; and an outer, of more extended 
area, encircling the point of the anticline in the San Pablo formation, 
and extending well along the southwest side of the general fold. The 
oil from the shales regarded as Tejon is of greenish color and varies 
in gravity from 33° to 38° B. ; that from horizons in the San Pablo is 
brownish black and of a gravity from 16° to 24° B., the higher in the 
eastern portion of the field. The production from both horizons is 
large. The depth of wells varies from 800 to 2,000 feet. 
M'KITTRICK DISTRICT. 
This district lies on the edge of the desert at the eastern base of the 
Coast Range, about 50 miles west of Bakersfield. The railway station 
is McKittrick. The Coast Range in the vicinity embraces a number 
of parallel ridges, the highest constituting the eastern border of thJ 
Carriso Plains. From this each succeeding ridge attains a lower 
altitude, until the outermost line of hills is but a gentle elevation 
above the general valley. The developed oil field in the region of 
McKittrick lies along an interior ridge, separated from the outer ridge 
by a valley 1.1 miles wide. The Length of this district is about 25 
miles. 
The formations involved in the occurrence of oil are the Monterey 
and the San Pablo, an unconformity existing between the two. The 
Monterey consists principally of siliceous shales, with their chalky, 
earthy, or more argillaceous modifications. Gypsiferous clays, lime- 
stones, and sandstones are but slightly developed, except in the north- 
western portion of the field, where certain beds have the general 
aspect of the Lower division of the Miocene. The siliceous shales 
within a zone 200 or 300 feet in width extending for S or 10 miles 
along the middle portion of the field, have, in a great degree, lost 
their stratified nature and become tissile by reason of the severe crush- 
ing to which they have been subjected in the sharp folding and fault- 
ing that has here taken place. Along this line of faulting the shales 
are of a chocolate brown, from the dried bitumen with which they 
have been infiltrated. 
The San Pablo, consisting of the conglomerates, sandstones, and 
clays typical of it, is well develoj^ed, and the terrane is marked, as else- 
where, by a deep deposit of dust wherever weathering has been car- 
ried to an extreme. The lowest stratum of the formation exposed in 
the field is a sandstone, conglomeratic in layers, the pebbles of which 
are of granite, siliceous shale, quartzite, and occasionally a pyritic 
rock that has been derived, perhaps, from some bed of much earlier 
age. This sandstone and conglomerate is generally exposed in close 
