DISCOVERY OF CAMBRIAN ROCKS IN SOUTHEASTERN 
CALIFORNIA 
N. H. DARTON: 
During a recent trip in the desert region of southeastern California, 
I discovered an extensive series of fossiliferous Cambrian rocks in 
the vicinity of the Santa Fé Railroad. The locality is on the south 
end of a ridge known as Iron Mountain, 2 miles northwest of Siam 
Siding, in the eastern part of San Bernardino County. The rocks 
constitute the summit of the ridge and dip down its eastern slope. 
They lie on granite which rises several hundred feet up the western 
side. The adjoining country is a desert plain, but the ridge extends 
far to the northward. My opportunities for determining the structure 
and stratigraphy were limited, and only a partial section was measured. 
It comprises the following beds: 
Feet 
Shalesvandsandstomes | a4) eee) a) arenes Se eRZOOrs 
TEWMESEOTIE ele oie, Oeil Ge silczat ce uy, cence g mseniee ec 6 
Gray shales yo 902 1 oy Siam aces SUR Me Aerie say eget eos © 
Limestone . . nee 8 
G.ay shales with fo Haesione an Sandscone assis Ba eg. 250 
Nodular limestone Ne hat ENG eran ca eeneaP ty craton Riser” 1p NOS, 
Massive hard dark-blue laneeiene a Re eRe onset = Lie) 
Gray shales with calcareous sandstone eer sit nee ce GeO 
Gray sandstones and quartzites. . . 5 altbe piace aera §IGOO 
Dark hard quartzites, conglomeratic at nee RCO e RPE MNT Ge ee HOTS) 
Granite 
Fossils were found in the limestone layers in the gray shales above 
the nodular limestone, and also in the gray shales below the 50-foot 
bed of dark-blue limestone. They consisted of fragments of trilo- 
bites and molluscs, which proved to be not specifically determinable, 
but Mr. C. D. Walcott believes them to be undoubtedly of Cambrian 
age, probably Middle Cambrian. 
The contact with the granite is clearly exposed and was traced for 
about a mile. It is unquestionably a shore line and not a contact of 
t Published by permission of the Director of the U. S. Geological Survey. 
47° 
