SUPPLEMENT. 
NOTES ON THE GEOLOGIC AGE OF SOME OF THE ROCKS OF THE 
KLAMATH MOUNTAINS, 
The Klamath Mountains were early recognized by the Geological 
Survey of California 1 as composed of rocks essentially the same as 
those of the Sierra Nevada, and definite horizon determinations began 
in the eastern extension of the group in Shasta County with the Car- 
boniferous. IT. W. Fairbanks, 2 Charles Schuchert, 3 and others, 4 but 
more especially J. P. Smith, 5 greatly extended the recognition of 
definite horizons in the same region, but the higher portions of the 
group in Trinity County have received less attention. Concerning 
that district, however, we have a comprehensive paper by Mr. O. H. 
Hershey/' who has kindly supplemented it by furnishing me a manu- 
script copy of his preliminaiy map of this region, based on the Pun- 
nett Brothers' sectional map of Trinity and bordering counties. The 
oldest formations recognized are a series of mica- and hornblende- 
schists, which are succeeded by a mass of slates, in part radiolarian, 
and limestones, all of which are more or less intimately related to a 
wide range of plutonic and volcanic rocks. 
The oldest fossiliferous rocks 7 yet recognized in the region are 
Devonian, and have been found in a belt at the eastern base of, and 
in, the Scott Mountains west of Gazelle, Cal. The belt extends south- 
ward more or less continuously by the well-known Kennett locality 
to the northern end of the Sacramento Valley near Horsetown. 
Northward from Gazelle they have not certainly been recognized. 
In a limestone 3 miles northeast of Kerby, Josephine County, Oreg., 
a number of fossils were discovered, but their affinities could not be 
definitely determined. 
West of this belt Devonian rocks have not been recognized with 
certainty, so far as the writer is aware, unless it be at Three Creeks, 
on the load to Hoopa Valley, in Humboldt County. These are, how- 
ever, nearly in line with the supposed Juratrias limestones southeast 
of Ilyampom. 
1 Geol. Survey California, Vol. I. 
2 Bull. Geol. Soc. America, Vol. VI, p. 71. 
8 Am. Jour. Sci., 3d scries. Vol. XLVII, p. 416. 
4 Fourteenth Ann. Rept. U. S. Geol. Survey, Pt. II, L894, PI. XLV. 
5 Jour. Geol., Vol. II, 1894, p. 588. 
Am. Geologist, April, 1901, Vol. XXVII, p. 225. 
7 The Silurian of the Sierra Nevada in the Taylorville region has not yet been discovered in 
the Klamath Mountains. (Bull. Geol. Soc. America, Vol. Ill, p. 376.) 
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