248 A OLMOKS PAB STMCA GIES, 
this is a slight unconformity, followed by conglomerates, sandstones, 
and clays of the Livingston formation, 12,000 feet thick. Near the base 
the conglomerate consists largely of volcanic material. ‘True tuff- 
breccia of volcanic rocks occurs intercalated near the base of the 
series on Boulder River. 
Neocene lake beds occur in Gallatin Valley, and on Yellowstone 
River, opposite Fridley. 
Superficial deposits of the Pleistocene period occur as alluvium over 
all the broader river valleys. Glacial drift, consisting of gravel, sand, 
and bowlders, is scattered over the higher parts of the country, and 
covers the Yellowstone Valley south of Chicory. 
Igneous rocks occupy a large part of the area of this sheet. They 
consist of subaérial breccias or agglomerates, with tuffs and lava- 
flows, and of intrusive bodies, such as dikes, sheets, laccolites, and 
stocks or necks. They occur extensively in the southeastern corner of 
the district, and form the Gallatin Range along the southwestern bor- 
der, and another area east of Boulder River. In the Crazy Mountains 
the igneous rocks are wholly intrusive. ‘The extrusive rocks are ande- 
sitic breccia, acid and basic; trachytic rhyolite, rhyolite, and basalt. 
The intrusive rocks are gabbro, diorite, theralite, basic and acid por- 
phyries, basic and acid andesites and dacites. Several centers of 
volcanic eruption, active in early Tertiary time, occur in the region. 
They are at Emigrant Gulch, Haystack Mountain, and Crazy Moun- 
tains. Other centers are just outside of the limits of the atlas sheet. 
The chief economic deposits of the district are the gold-bearing 
gravels of Emigrant, Bear, and Crevice gulches. ‘They have been 
worked on a small scale. Gold veins occur in Emigrant Gulch, Crev- 
ice Gulch, and Haystack Mountain. Copper ores in small quantities 
have been found at the head of Boulder River and of Slough Creek. 
Clays serviceable for brick-building occur in the alluvium near Living- 
ston, and in the lake-beds near Bozeman, also in the Cretaceous strata. 
Two coal fields exist within the district, the Cinnabar field and the 
Bozeman field. The aggregate thickness of the coal is twelve to 
eighteen feet, made up of a number of seams, only three of which are 
workable. The coal is bituminous, of variable character, and in 
places is a fair coking coal. The output in 1889 was 49,400 tons. 
U. S. Geologic Atlas, Folio 3, Placerville, California, 1804. 
This folio consists of one and one-half pages of text descriptive 
of the Gold Belt and one and one-half pages descriptive of the 
