THE 
AMERICAN GEOLOGIST. 
Vol. XXXIII. FEBRUARY, 1904. No. 2. 
THE GEOLOGY OF LINCOLN COUNTY, SOUTH 
DAKOTA AND ADJACENT PORTIONS. 
By T. A. Bendrat, M. S., Spencer, South Dakota. 
PLATES II-III. 
As a portion of southeastern South Dakota, limited by the 
Big Sioux river and the 97° of west longitude and extending 
from 43° to 43° 30' north latitude, Lincoln county bears the 
stamp of the Quaternary period and more especially of the 
Glacial epoch. While there are no Archean or Palaeozoic rocks 
to be found outcropping and only here and there some expos- 
ures of the [Nlesozoic, the drift formation, has contributed the 
greatest share to the present topography. 
Topography and Dramage. 
This area may be described as a very shallow trough, the 
axis of which runs in a S. W.-N. E. direction, from about 
north of Ccnterville to south of Canton. Its deepest depres-. 
sions below the outermost edges of the trough, toward the 
N. \\\ and S. E. vary from 160 to 200 feet. It is, however, 
far from being equilateral, as its S. E. side rises abruptly 
toward the rim at about 27 feet per mile, while the region N.W. 
of the axis shows a gentler rise at an average rate of 6 feet per 
mile for the first 10 miles and 20 feet per mile for the last 5.5 
miles. The real bottom of the trough is triangular, one side of 
which is formed by the axis of the trough, another by an imag- 
inary line passing about 3 miles N. of Canton and 2 miles N. of 
Lennox, while the third side has to be sought for bevond the 
Vermillion river perhaps not far from the eastern flank of Tur- 
key ridge. This triangle covers approximately 200 square 
miles, while that portion of the bottom of the trough which lies 
