468 J. E. TODD PRE- WISCONSIN CHANNELS IN DAKOTA-NEBRASKA 



a half a mile farther northeast, in the bottom of a watercourse, a cut bank 

 showed 20 feet of gravel. 



There are deep wells in southwest one-quarter of section 21, northeast 

 one-quarter and northwest one-quarter of section 28, and northeast one- 

 quarter of section 29, township 93 north, range 61 west, which show 

 much sand, while farther east deep wells show only chalk. Xorthwest 

 of Springfield, where the broad valley in which Perkins is located merges 

 into Emmanuel Creek Valley, the bluffs on the west side are less abrupt, 

 and they are composed of till above and of sand below, while on the east 

 side the chalk bluffs are prominent. Farther south, in southeast one- 

 quarter of section 21, township 93 north, range 60 west, an isolated hill 

 near the creek shows chalk extending high up its east side, while its west 

 side is a thick mass of sand. Below this place there are chalk cliffs on 

 both sides of the creek valley, and opposite Springfield depot the chalk 

 cliffs rise 90 feet above the creek, or to an altitude of 1,300 feet. About 

 half a mile west of Springfield the surface of the chalk passes under a 

 thick deposit of sand and gravel. Springs at an altitude of about 1,245 

 feet probably mark the bottom of the sand in this locality. The sand- 

 filled valley was traced only a little farther south, and the point where it 

 crosses the chalk cliffs adjoining the Missouri Valley was not ascertained. 



THE AXCIEXT MOSQUITO 



The ancient Mosquito Creek flowed through the fertile valley north 

 of Greenwood and along the upper 2:>ortion of Slaughter Creek. This 

 valley and the low divide separating it from the Missouri Eiver was 

 first^ regarded by the writer as forming a high terrace of the Missouri, 

 but later observations have led to the view that it was an old channel. 



1. The topographic evidence of the Mosquito Creek channel has not 

 been obscured by glacial action, as in the case of some of the other 

 channels, because it ]io^ outside of tlu^ outermost inoi'aine. On the othei- 

 hand, however, the divide between it and the Missouri is less prominent, 

 only rising alx)ut 100 feet above the old channel, or about 300 above the 

 Missouri. The channel reaches the edge of the Missouri Valley near 

 latitude 40 degrees in a col about 190 feet higher than the river. It 

 follows Mosquito Creek to the junction with' Slaughter Creek, then con- 

 tinues southeast through a slough to the lower course of Cold Springs 

 'Creek, which has the same direction, and finally it opens into the bottom 

 lands of the Missouri. Instead, however, of uniting with the present 

 river channel it extends across the lowlands to Choteau Creek Valley 

 and, crossing that valley near its mouth, passes up a small tributary 



sRiill. T'. S. Geol. Survey. No. 158. p. in2. Washin,si:ton. 188G. 



