Fig. 1. Map of Santa Rosa mylonite zone south of Palm Springs, California, and north of Highway 74 (Pines to Palms Road). Symbols: v = biotite-hornblende diorite; parallel lines = mylonite zone; solid black = intense mylonite zone; solid triangles along line = west-directed thrust-fault plane. Numbers 1, 3, 6, 9, 16, 17, and 20 represent sites among 21 samples collected north of Highway 74 at various intervals on a continuous traverse at right angles to the strike of the foliation. A medium-grained biotite-hornblende diorite at site 1 lack deformation, but cataclasis begins at site 3 and increases in intensity to site 16 where abruptly the rocks become fine-grained and obviously mylonitic. The site studied by Simpson and Wintsch (1989) is south of Palm Springs, California, and can be found in the SE 1/4, NW 1/4, Section 14, of the Palm View Peak 7 1/2 Minute Quadrangle, California, west of the Indian Reservation Visitor Center. Map is modified after Simpson and Wintsch (1989).