Geology of Lincoln Co., S. D. — Bcndrat. 71 
tion of slates with the quartzytes in the region of the Black 
Hills, where they have been observed by the writer and others 
to form the core of the mountains. The circumstance, that the 
red Sioux quartzyte, wherever it crops to the surface in and by 
Sioux Falls, is not associated with slates of any sort, is not 
deemed sufficient to invalidate the suggestion. Future borings 
in the neighborhood may throw, it is hoped, more light upon 
the question and furnish further data of interest. 
Cretaceous. 
As there have as yet been found in the county not the slight- 
est traces of the Palaeozoic or of any Triassic or Jurassic rocks 
nor in the region farther west (compare U. S. G. S., Irrigation 
Paper No. 34, p. 12), the nearest localities, where the Carbon- 
iferous limestone was revealed by extensive borings being 
Sioux City, Iowa, and Ponca, Nebraska, we turn immediately 
to the discussion of the Cretaceous and more precisely to the 
Upper Cretaceous. The Lower Cretaceous has either been re- 
moved altogether or has never been deposited in this part of the 
Dakotas. 
a : The Dakota Sandstone : 
has obtained great importance in the w^ater supply of the Da- 
kotas, although the eastern limit of the Artesian wa- 
ters falls without the area, being drawn by Darton about 
25 to 38 miles west of it. No outcrops of the Dakota 
sandstone have been observed by the writer within the 
limits of the county in spite of its being recorded by Darton 
along the Big Sioux from Sioux Falls southward to Sioux City 
and even farther south, on his "Contour Map of the Upper 
Missouri River Region" (U. S. G. S., XVII Annual Report, 
p. 676), while J. E. Todd in his able paper on "The Moraines 
of Southeastern South Dakota" (U. S. G. S.. Bull. No. 158). 
reports the Dakota sandstone only on the James river and its 
tributaries as well as on the Missouri. The Dakota sandstone 
is, however, revealed by borings, abutting, it is supposed 
against the red Sioux quartzyte farther north. In T.99N., 
R.51W., sec. 4 of Perry township the Dakota sandstone was 
struck at a depth of 150 feet, the head of the flow being 50 feet 
from the surface, while in sec. 9 of same township, about one 
mile farther south, the sandstone, struck at nearly the same 
