Bragdon FoniuUioii iji N, IV. California. — Ilcrshcy. 359 
volcanic series was spread over llic land. By depression, in 
the TriasL^ic period, the sea began to invade the land from the 
eastward or (preferably) northeastward and the Pit shales 
began to form in the conntry now eastward of the Sacramento 
river. Sedimentation continued in that territory to late in the 
Jurassic period. How far westward of the Sacramento river 
these formations may have extended it is impossible to deter- 
mine, but it is not likely that they were developed far in that 
direction or some remnants would be found in Trinity and Sis- 
kivou counties l^etween the volcanic series and the Bragdon 
slates. 
During ])art of the time at least in which the Triassic and 
Jurassic sedimentation was in progress in the Pit River region 
the volcanic series in the country west of the Sacramento river 
was being leveled off by ordinary subaerial erosion, reducing it 
to a comparatively plane area. 
Then ensued a remarkable physical disturbance. Probably 
it began at the close of deposition of the Bend formation and 
ma\- have given rise to the coarser sediments of the Morrison 
sandstone and conglomerate. But the effect was not pro- 
nounced until the close of the ]\Iorrison epoch. Then a large 
part of the sea-bottom was raised and nearly all of the -territory 
now included in the Klamath region east of the Sacramento 
river and in the northern and higher Sierra Xevadas became 
land. The movement was one of westward tilting and what 
had formerly been land now was depressed and submerged 
and in the body of water thus formed the Mariposa-Bragdon 
strata were laid down. 
The eastern shore-line. I feel . some confidence, was not 
many miles east of the present site of Delta and probably thence 
trended in a southeasterly direction. The Mariposa that I ob- 
served along the Mother Lode belt I should say was deposited 
from 10 to 20 miles distant from the shore-line, judging by 
the position of Bragdon strata of corresponding texture. There 
are some features about the Bragdon formation which indicate 
that it was not deposited in the open sea, but in a broad inland 
water-basin, perhaps in part brackish. It is in that manner 
that I account for the absence of marine animal remains. The 
Mariposa portion may have been more favorably situated for 
the life of marine animals and thus it derived its spare fossils 
of that class. 
