Geology of Lincoln Co., S. D. — Bcndrat. 69 
from several heads in the upper slope of the divide and also 
from a number of brooklets, which rise in the west in shallow 
sags in the watershed. The narrowness of the spur thrown out 
by the divide in its southern side and mentioned above is nearly 
entirely due to the simultaneous cutting down agency of the 
headwaters of East and West Brule creeks which attack the 
readily yielding deposits of the spur from both sides. 
Geological Features of the Region. 
Algonkian. 
From the circumstance, that the red Sioux quartzyte is 
found exposed immediately north of the northern line of Lin- 
coln county in and by Sioux Falls and also about 10 miles 
farther west in the neighborhood of Parker and up to the north- 
ern boundary of Turner county, it may be assumed, that it is 
Algonkian rock which forms at least for the northern part 
of Lincoln county the "bed rock," a suggestion which has been 
verified by a number of borings in that part of the country, , 
Within section 11 of Perry township, about 3 miles south 
and I mile east of Tea, the Sioux quartzyte was struck at a 
depth of 102 feet, while a little farther N.W. it was found ris- 
ing to 92 feet below the surface and still farther N.N.W., in the 
southwest corner of section 25 of Delapre township falling 
again to a depth of 135 feet, that is to say 43 feet within 4 miles. 
About II miles S.W. of the latter locality, at Chancellor in 
Turner county the Sioux quartzyte was revealed at a depth of 
80 and 100 feet. 
All these data fairly harmonize with the existence of a sub- 
terranean quartzyte peninsula traced by N. H. Darton through 
the eastern part of North and South Dakota, in the latter es- 
pecially through Minnehaha. McCook and Hudson counties, 
and through Nebraska. The contours of this ridge are nicely 
brought out by Darton in his "Contour map of bed rock surface 
in a portion of the Dakota Artesian Basin" in his paper on the 
"Artesian W^aters of a portion of the Dakotas" (part II of 
17th Annual Report of the U. S. Geological Survey), which 
map has been amended by J. E. Todd in plate XI of Bulletin 
No. 2 of the "South Dakota Geological Survey." It is the 
southern slope of the ridge, which underlies at least to some 
extent the other deposits of the area under discussion ; and that 
the surface of this slope is very irregular, probably throwing 
