684 F. W. SARDESON 
distant toward the northeast. The Cretaceous lies on one of 
the higher hills of the prairie. It is covered by the loess five 
to ten feet thick, which also covers the Kansan eskers, the Saint 
Peter sandstone of the butte-like hills and, at lower levels, the 
Shakopee dolomite hills, and then, on the steep sides of the 
valleys, the Oneota dolomite and Jordan sandstone. The glacial 
till or gravel is spread beneath the loess, over the same Creta- 
ceous, Ordovician and Cambrian formations. Under this drift, 
the dolomite formations are commonly protected by a dark- 
colored residuary clay, containing chert and iron concretions. 
Two or three miles to the westward from the Cretaceous patch, 
the Saint Peter sandstone is conformably overlaid by the Galena 
(Trenton), and upon that may once have rested the Maquoketa 
(Hudson) strata.. Now at the particular locality where the 
Cretaceous patch occurs, there is neither Galena nor Maquoketa 
extant, but the Cretaceous rests upon the Saint Peter sandstone 
or possibly in part upon the Shakopee dolomite. Further, it is 
evident, as shown by N. H. Winchell (of. cet.) and others, that 
all the geologic formations, from the Galena down to and below 
the Jordan sandstone, were once, in this region at least, uniform, 
coextensive, sedimentary deposits, and that all the valleys are 
due to later erosion. This valley cutting was accomplished 
before the glacial deposits were spread on them. The erosion 
of the loess and glacial till and gravels now going on is very 
slight as compared to that which produced the valleys over 
which those deposits have since been spread. 
The Cretaceous strata lie where erosion had already obtained. 
The Galena series, at least, must have been eroded away before 
Cretaceous deposit could be laid upon Saint Peter sandstone. 
Again, the valleys on either side of this Cretaceous, as we now 
see it, must be younger than such a sedimentary formation if the 
same is 27 stu, else the formation should lie in the valley and 
not on a hill. This Cretaceous patch, like the hills of Saint 
Peter sandstone and of other older formations in the same 
locality, must be the outlier or eroded remnant of a once more 
extensive sedimentary deposit; unless, like the bowlders of 
