180 EDWARD STEIDTMANN 
Smith and Packard’ state that certain rocks possibly of pre- 
Cambrian age have been found in Oregon. ‘They include a grano- 
diorite near the head of John Day River and certain amphibolite, 
hornblendite, mica quartz schists, and talc schists near the 
California-Oregon boundary. 
Smith? states that the pre-Cambrian of California comprises 
schists and gneisses of Inyo, San Bernardino, and Riverside 
counties. These underlie Olenellus beds. They also include the 
Pelona schists of San Bernardino County, the Abrams and Salmon 
schists of Trinity and Siskiyou counties, the South Fork Mountain 
schists, and certain old schists and gneisses mapped with the Sierra 
batholith. Similar rocks also occur in the Sierra Madre. 
Somers? states that the pre-Cambrian rocks of the Burro 
Copper district of southwestern New Mexico consist of a complex 
of granites. 
Umpleby reports that in a reconnaissance survey of north- 
western Custer County, Idaho, he has found highly metamor- 
phosed schists, slates, and quartzites of Algonkian age, which 
probably represent a part of the Coeur d’Alene section. The 
sequence in Custer County was not worked out in detail. 
Walcott’ cites evidence for the unconformity of the Cambrian 
and pre-Cambrian at Helena, Montana. The specific facts 
referred to are slight angular discordance, in places an erosion sur- 
face on the pre-Cambrian formations, and fossil relationship. . 
Walcott® regards the pre-Cambrian Algonkian limestones of the 
Cordilleran region of North America as owing their origin chiefly 
=W. D. Smith and E. L. Packard, ‘‘The Salient Features of the Geology of 
Oregon,” Jour. Geol., Vol. XXVII (1919), pp. 79-120. 
2J. P. Smith, ‘“‘The Geologic Formations of California with Reconnaissance 
Geologic Map,” Cal. State Min. Bur. Bull. No. 72 (1916), 47 pp., tables. 
3 R. E. Somers, ‘‘ Geology of the Burro Mountains Copper District, New Mexico,” 
Am. Inst. Min. Eng. Bull. No. tor (May, 1915), pp. 957-96, 25 figs.; Bull- 
No. 108, p. 2476. 
4 Joseph B. Umpleby, ““Some Ore Deposits in Northwestern Custer County, 
Idaho,” U.S. Geol. Surv. Bull. 539 (1913), 100 pp., to pls., 4 figs. 
5C. D. Walcott, ‘“‘Relations between the Cambrian and Pre-Cambrian Forma- 
tions in the Vicinity of Helena, Montana,”’ Smithsonian Misc. Coll., Vol. LXTX, No. 4 
(June 24, 1916), pp. 259-301, 6 pls., 4 figs. 
6C. D. Walcott, ‘‘Pre-Cambrian Algonkian Algal Flora,” Smithsonian Misc. 
Coll., Vol. LXIV, No. 2 (1914), pp. 77-156, pls. 4-23. 
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