LoGaN. | The Upper Cretaceous. 209 
thickness from 6 to 26 inches. In Republic county it occurs from 
80 to 100 feet below the Benton limestone. In Lincoln county 
it is only 60 feet below that horizon, and in Russell county it is 
90 feet. The thickest vein occurs in the mines on Little Timber 
creek in Lincoln county where the lignite rests between beds of shale 
and gray sandstone, the shale adjacent the coal being extremely 
bituminous in character. In Republic county near Minersville, two 
9 inch veins are intercalated with shales which are argillaceous, and 
not bituminous in character. Above the lignite bed in Mitchell 
county rests a thick bed of bituminoous shales which seem to pass 
conformably into lignite. In Coal cafion thin layers of lignite are in- 
terealated with sandstone and shale. The lignite is mined in this 
locality by tunneling into the drift of the creek bed. Shafts have 
been sunk to a depth of 80 feet in Republic county and 50 feet in 
Lincoln county. Lignite is mined and used for fuel in Republic, 
Mitchell, Lincoln, Russell and Ellsworth counties. The lignite con- 
tains much ash in the form of pyrite, shale, etc. The principal 
mines are located on Wolf creek and Coal canon in Russell county; 
on Coal creek and Elkhorn in Ellsworth county; on Spillman creek, 
Little Timber creek, Bacon creek, Rattlesnake creek and Elkhorn 
creek in Lincoln county; on Rock creek and Solomon river in 
Mitchell county; on West creek in Republic and Cloud counties. 
The strata adjacent the lignite vary with the locality. In some 
localities the lignite rests between beds of shale, in others between 
layers of sandstone, and still in other localities it is found resting 
upon sandstone and covered with shale. In many places it is. 
entirely wanting. Its place, however, may be occupied by a thin 
bed of bituminous shale. 
Salt Marsh Horizon.—Resting upon the lignite is a bed of shales 
which are, in the majority of instances, highly saliferous in charac- 
ter. They vary in thickness from 15 to 30 feet. By the disintegra- 
tion of these shales salt marshes have been formed in many 
localities along the exposure of the upper Dakota horizon. The 
marshes occur on the Rattlesnake creek in Lincoln county; on Rock 
ereek and Salt creek in Mitchell county; on Marsh creek in Cloud 
county; on West creek, Marsh creek and Salt creek in Republic 
—14 
