California Tertiary Formations.—Hershey. 353 
2. A massive sheet of dark reddish brown basic lava seem- 
ingly a typical basalt, in places very vesicular or 
amygdaloidal, abounding in secondary chalcedony, .. 2000 feet. 
3. Red and yellow sandstones and coarse breccia-con- 
glomerate of granitic and gneissic material, ........ 200 feet. 
4. Dark basic lava passing upward into dark red tuff, .. 200 feet. 
5. A great series of dull red and yellowish coarse sand- 
stones and coarse breccia-conglomerate of granitic 
BIC SN EISSI Cam ATCE Ian recite trate Cpe aid. e.s od) a sac apices 3000 feet. 
tale ete eRe acres ek en id pad ale heeds 6 59co0 feet. 
No. 2 may be correlated with No. 4 of the Tick canyon sec- 
tion, No. 3 with Nos. 5-11 inclusive and No. 4 is similar to 
Nos. 12-13, the coarse red tuff being a characteristic and 
easily recognized stratum. No. 5 of the Escondido canyon sec- 
tion is remarkable for its heavy beds of coarse breccia-con- 
glomerate which recur at frequent intervals throughout the 
series. Blocks of granite and gneiss up to three feet in diam- 
eter may occur anywhere, even in the sandstones compara- 
tively free from conglomerate. It is a characteristic of this 
sandstone and conglomerate series that although overlying and 
newer than the vast mass of lava, the material is essentially all 
debris from the schist-gneiss-granite complex. The material 
grows finer to the westward, and at the valley of the Agua- 
dulce, the very coarse breccia-conglomerates have been re- 
duced to ordinary conglomerates. A local source of much of 
the material is indicated by the abundance of Ravenna dior- 
ytes in the conglomerates on the south side of the trough and 
their rarity on the north side. 
The Escondido series was deposited under static water 
conditions and apparently in the sea. The bedding is regular 
and the pebbles in most layers are well rovwnded. In Mint 
canyon there is, close under a lava sheet, a well-marked gyp- 
sum-bearing stratum about 50 feet in thickness. It is main- 
ly a dark gray sandy silt and clay or shale, heavily impregnat- 
ed with gypsum; but several layers aggregating 10 feet in 
thickness are mainly of gypsum in thin regular layers, trav- 
ersed by veinlets of satin-spar of a secondary character. Ap- 
parently there is along 2000 ft., 1oft. in thickness of 50 per 
cent gypsum rock, which may be depended on to go down 1000 
feet—say a million tons. This gypsum ‘bed seems to repre- 
sent a bay cut off temporarily from the main body of water 
