Bragdon Foniiatioii in X. IV. California. — Hershey. 249 
Presently I began to read the reports of the U. S. Geological 
Survey on the rocks of the Sierra Nevada region and recog- 
nized in the descriptions, a similarity of the Calaveras forma- 
tion to the Lower Slate scries and the Mariposa formation to 
the Bragdon formation, while my volcanic material seemed 
to have its counterpart in the '"Diabase and Porphyrite" series 
of the Sierra Nevada province. Because of its evident rather 
close relation to the Bragdon slates, I provisionally classed the 
volcanic series as Jurassic in age. 
In September, 1901, I visited Mr. Diller's camp at Copley, 
going with him to Shasta. In the course of our discussions of 
the rocks of that region, he informed me of his discovery short- 
ly before, that the great volcanic series of tuffs and lavas rests 
unconformably on the Carboniferous and Devonian, but seems 
to pass conformably under the Pit shales of Triassic age, so 
that it seemed pretty definitely to belong in large part to the 
Triassic series of rocks. I then made a reconnaisance trip into 
the Pit River and Squaw Creek country, following an itinerary 
laid out for me by Air. Diller and was able to verify to my en- 
tire satisfaction the evidence of the Triassic age of the volcanic 
series which goes under the Bragdon slates. Since then I have 
considered the Clear Creek volcanic series, wherever it occurs, 
as far west nearly as South Fork mountain, as essentially rath- 
er early Triassic in age, but as the announcement of the discov- 
ery properly belonged to Mr. Diller, I have heretofore avoided 
definite reference to its Triassic age. However, in the treat- 
ment of the subject of this paper, I am compelled to freely 
handle the volcanic series and its structural relations. J\Ir. 
Diller has recently indicated his idea of the age of this series, 
having found Triassic fossils in some of the later tuffs.* 
In October, 1901, while following the "^Mother Lode" from 
Plymouth to Jacksonville and between Mariposa and Princeton, 
I had an opportunity of becoming familiar with the character- 
istics of the Mariposa formation and was impressed by the 
strong resemblance between it and the Bragdon formation. At 
several places I observed conglomerates similar to those in the 
Bragdon formation. The Mariposa formation as developed in 
the Sierra Nevada areas more nearly resembles the southern 
•"Copper Deposits of tbc Reddiog^ Region. California," V. S. Geol. Sar., 
Ball. No. 233, p. 124-. 
