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formation. He named this older unit the Tick Canyon formation. This

distinction between the Tick Canyon and Mint Canyon formations

resolved the apparent association of primitive and advanced forms of

vertebrate remains within the original Mint Canyon formation as

defined by Kew. During the course of his studies, Jahns found that the

Vasquez Canyon fault is buried by the Tick Canyon beds; this was the

first published suggestion that faults of earlier Tertiary age exist in

the Soledad basin.

In an earlier unpublished thesis, Sharp (1935a, p. 66)

recognized two distinct periods of faulting farther east in the Ravenna

quadrangle (pl. 1). The older east-trending Soledad fault, a normal

fault, was found to be offset by younger northeast-trending left-hand

faults. He also suggested the name Vasquez (1935b, p. 314) for the

unit that was termed Escondido by Hershey; inasmuch as the name

Escondido is preoccupied, the more appropriate term Vasquez is used

in this paper.

Wallace ~1949 pp. 781-806) studied the San Andreas fault
1
between Palmdale and Elizabeth Lake during the period 1940-1942. He

provided (1944, pp. 6-18) an excellent discussion of the theories

regarding the history and behavior of the San Andreas fault. For a

distance of about six miles westward from the San Andreas fault,

Simpson had mapped the Pelona fault as separating the Pelona schist

from a block of gneissic rocks that lies to the south. Wallace's dis-

cussion (1944, p. 95) of the contacts of these two units is quoted here: