Bragdon Formation in A^ IV. California. — Ilcrshey. 357 
the Franciscan series. Typical Franciscan rocks occur in the 
valley of Mad river in riunil)oklt county where they rest un- 
conformably on the pre-Devonian schists of the South Fork 
Mountain belt. They contain conglomerates in which are peb- 
bles which seem to have been derived from porphyry dikes 
of a system occurring in the neighboring Klamath region and 
there are black grains in abundance which seem to me referable 
for an origin to the silicified Bragdon slates occurring on the 
opposite side of South Fork mountain. The Bragdon forma- 
tion was involved by the orogenic activity of the Appalachian 
type which acted on the California rocks at the close of the 
Jurassic period and its pre-Cretaceous age is beyond dispute. 
It is now cornered into the last epoch of the Jurassic period. 
In the Sierra Nevada region there is a formation which is 
remarkably like the Bragdon formation. It is the Mariposa 
formation wb.ich is placed in the Jurassic period but later than 
the Morrison sandstone. The Mariposa which I have studied 
along the I\lother Lode belt, more closely resembles the Brag- 
don in the western areas than in the eastern. It appears that 
what is preserved of the Mariposa formation is the deep- water 
and not the litoral portion. ^Mariposa areas are bordered usu- 
ally by amphibolite schist and less altered surface volcanic 
rocks very similar to the Clear Creek series. The Weitchpec 
schists resemble the most highly metamorphosed Calaveras 
schists, and the schistose slates of the Bragdon areas crossed by 
the Klamath river resemble the moderatelv altered ^lariposa 
schists. 
In the toot-hills of the central and southern Sierras, the 
sedimentary series are distributed in long narrow belts as in 
the western Klamath region. In the northern Sierras they are 
distributed in broader and more irregular belts as in the cen- 
tral and eastern Klamath region. A line drawn from the 
mouth of the Klamath river southeastward through Weaver- 
ville and Red Bluft and thence prolonged into the Sierra Ne- 
vada region will roughly separate the territory in which the 
pre-Cretaceous rocks arc in long narrow, northwest-southeast 
belts from that in which they arc differently distributeil. This 
line will 1)c oblique to the strike of the rocks. 
It is true that no Mariposa fossils have been found in the 
Bragdon rocks, but that is no difficulty in referring them to 
