CAMBRIAN ROCKS IN SOUTHEASTERN CALIFORNIA 471 
intrusion. Therefore the granites are of pre-Cambrian age. At one 
locality the granite is traversed by a dike of black basic rock on which 
the basal Cambrian conglomerates lie. As some of the granites of 
southern California are post-Paleozoic, it was of interest to find that 
the granite in Iron Mountain, at least, is of pre-Cambrian age. 
In the vicinity of the gold mine, 2 miles southeast of Siam and 
almost in the line of strike of Iron Mountain, another high ridge con- 
sists of limestone and quartzite cut by a dark-colored, coarse-grained 
—— 
= gembrian Tocks 
Fic. I. gaia map of op southern ae region showing occurrences of 
Cambrian rocks. GW, Grand Wash escarpment; K, Kingston Range; F, south end 
of Funeral Range; S, Slate Range. 
granite. The exposure shows 200 feet or more of quartzite, overlain 
by greenish shale, capped by 800 feet of semi-crystalline limestone. 
No fossils were found, but some features of the limestone suggest that 
it may represent the Red Wall limestone of the Grand Canyon region 
200 miles northeast. The quartzite lies on granite at this locality, 
but granite also cuts irregularly across the limestone, and apparently 
has caused its alteration. 
The rocks above described are in the middle of a wide area of 
which the geology has never been studied. The location is shown in 
