Vol. 4] Lawson. — Tehachapi Valley System. 437 



of the China Hill Creek cone. But the black adobe clay is the 

 product of more recent accumulation, under marshy conditions, 

 due to springs, on the narrow flood plain of the modern creek 

 where it has trenched the cone. 



Bocks of the Surrounding Mountains. — The prevailing rocks 

 of the mountains which encircle Tehachapi Valley, as well as the 



■ 



other valleys to the west of it which are described in this paper, 

 are those of the Bed-rock Complex of the Sierra Nevada. They 

 comprise a series of metamorphie rocks, represented chiefly by 

 crystalline limestones and mica schists with quartzites, and vari- 

 ous plutonic irruptives of granitic habit which have invaded the 

 metamorphie series. The limestones occur in isolated patches in 

 numerous localities and appear for the most part to be large 

 inclusions which sank down into the granite when the latter was 

 viscous. The mica schists occur in more persistent belts of no 

 great width. Both limestones and schists have a persistent north 

 and south strike with easterly dip at angles of from 45° to 60°, 

 though sometimes vertical. The granitic rocks, however, greatly 

 preponderate throughout the region, and constitute the great 

 bulk of the mountains. The limestone is quarried at a number 

 of localities, but most extensively at the mouth of Antelope 

 Canon to the south of the town of Tehachapi where it is burnt 

 for lime. 



The superjacent series of the northern portion of the Sierra 

 Nevada is represented in this region by two formations of strati- 

 fied rocks, which rest unconformably upon the Bed-rock Com- 

 plex. The lower of these is well exposed in the middle and 

 upper parts of the tributary valley of Cache Creek. It consists 

 of a great volume of coarse arkose sandstones and conglomer- 

 ates with some thin beds of sandy shale. On the northwest side 

 of the middle part of Cache Creek they dip at an angle of 60° 

 to the southeast, and their superposition upon the granite is well 

 exposed. On the east side of Cache Creek these sandstones 

 appear to dip to the northwest and to strike to the northeast, 

 curving around the granite traversed by the creek in its lower 

 part. In certain of the shale beds referred to there are abundant 

 fossil leaves in a good state of preservation, and their occur- 

 rence here renders it probable that the formation is a fresh-water 



