180 The American Geologist. March, 1892 
Continued study and search may result in bringing organic 
remains to light. Let us hope. 
The natural outcrops of this formation are rare. In places the 
creeks of the bluffs have cut through the superincumbent loessian 
and thus revealed the clays and sands. This rarity of natural 
outcrop is not strange when we think of the extent and thickness 
of the loessian blanket. But where revealed, whether by creek 
erosion or railroad cutting, there is exhibited always a non-con- 
formity. Not abrupt, as upon the Tertiary buttes, but having 
more undulation, as though the beds sank quietly below the 
water and received a uniform precipitation. However, such a 
deposition of sediment as did not effectually conceal the previous 
contour. Upon the emergence of the land the drainage at once 
assumed almost the identical conditions that had previously ob- 
tained, and in many places we find streams running on loessian 
beds in channels marked out for them prior to the deposition of 
this formation. The Loups are not rapid eroders, on account of 
the load of sediment they carry. They have not hence cut 
through the loessian blanket. 
In the lower of these two divisions above the Tertiary buttes 
we have no vertical cleavage. In this respect it. differs pro- 
nouncedly from the formation immediately above. The com- 
mon calcium carbonate nodules are also wanting. In summation, 
then, the cardinal characteristics for recognition are the presence 
of iron and the iron stain; the presence of gravel, some particles 
being quite coarse; absence of fossils; absence of calcium car- 
bonate, both in nodules and disseminated; absence of vertical 
cleavage, and presence of manganese. ‘The last perhaps rather 
more local than general. These data obtain for all of the many 
outcrops thus far examined in the counties of Valley, Greeley, 
Howard and Sherman. 
Turning to the superincumbent deposit then, let us still further 
note the differences. This formation has a uniform buffish to 
drabbish appearance. The particles are smaller and more uni- 
form, showing greater attrition. Calcium carbonate present in 
nodules and disseminated throughout the mass. Vertical cleav- 
age always found, and becomes one of the most important means 
of identification. The formation is fossiliferous, having such 
forms as Succtnea, Zonites, Helix, Pupa, Vallonia, Helicodiscus, 
ete., of which /Hel/codiscus and Sucecinea occur in great numbers. 
