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Palmdale 6-minute quadrangles (pl. 1). He mapped the entire Pelona

fault except for the short segment previously mapped by Kew at the

western end of the fault. The Pelona fault was traced by Simpson along

the southern base of the Sierra Pelona from the San Andreas fault west-

ward for a distance of nearly 20 miles to the southern edge of the

quadrangle, one mile west of Bouquet Canyon (pl. 1). Several southwest-

trending branches of the Pelona fault also were mapped. Noting the

abundance of Pelona schist fragments in the Quaternary terrace gravels,

Simpson dated the earliest movement on the Pelona fault as being either

late Tertiary or early Quaternary. He stated that the intrusive rocks

have gradational boundaries, and he also believes (1934, p. 384) that an

"intrusive relationship to Pelona schist series
cannot be proved directly, for the only visible
contacts are along faults. However, the Pelona
schists locally show the effects of superimposed
contact metamorphism at several places along
the Pelona fault, and one must suppose that the
adjacent granitic bodies were the metamorphosing
agents. 11

Simpson retained the name Escondido series for the section described by

Hershey, and rejected Kew' s correlation with the Sespe formation,

Miller, in 1934, published the results of several years of

study of the western San Gabriel Mountains. His reconnaissance map

and detailed petrographic descriptions of the rock types still represent

the only extensive study of that large area.

A detailed stratigraphic study by Jahns fl 939; 1940) enabled

him to distinguish an older unit in the basal part of Kew' s Mint Canyon