Bragdon Formation in N. II'. Calif or )iia. — Hershey. 349 
At several places in the Trinity valley I have encountered 
quartz porphyry dikes (cont..ining quartz [)hcnocrysts) rising 
through the greenstone and cut off abruptly and squarely by 
the shale contact. I will mention one on the east side of Trin- 
ity river, near the mouth of Bear gulch, about three miles south 
of Bragdon. There is never any indication of contact meta- 
morphism where these dikes adjoin the shales. Nor are there 
any fragments of 'he shale in the porphyry. None of the rock 
types which are characteristic of the Clear Creek series ever 
rise into the shales. The only intrusives which are ever found 
in the Bragdon formation belong to systems which are known 
to be post-Jurassic in age. Serpentine occurs on its borders 
ajid possibly in a few cases as dikes intruded into the shales. 
Granite adjoins it between Lewiston and the Tower House and 
has produced within it a typical contact metamorphic zone.* 
Apophyses from this granite occur in the shales. Along the 
Trinity range at many places, as near Deadwood, French Gulch 
and east of Bragdon, there are in the shales dikes of a granite 
porphyry related to the granite batholiths. The foregoing are 
rfearly all the intrusives observed in the eastern Bragdon area, 
Dut there are a few small dikes of a fine-grained dioritic rock, 
a system aij-o occurring in the granite areas. One example may 
be seen near the Ivanhoe quartz prospect on the west side of 
Trinity river about three miles south of Bragdon. In general, 
the formation is remarkably free from intrusives of any kind, a 
fact which has to be explained by those who consider the green- 
stone under it as an intruded mass, a sill or laccolite. 
The Western Bragdon Areas. 
Emerging from beneath the Cretaceous rocks near Harri- 
son Gulch in western Shasta county and trending northwest- 
ward by Hay Fork, Hawkin's Bar and Willow Creek to Hoopa 
valley, there is a belt of Mesozoic rocks consisting of the Clear 
Creek volcanic series and the Bragdon formation. It has a 
known length of 65 miles but probably extends far to the north- 
west in the lower Klamath river region. It has a width of from 
three to five miles. Southeastward from Hay Fork it has been 
sharply folded and the two formations outcrop in long narrow 
belts. Without a careful examination the igneous belts might 
• Ambr. Gbol., vol. xxxi, April, 1903, p. 242. 
