308 THE GEOLOGY OF MINNESOTA. 



[Cretaceous strata 



reliably indicated by the surface features, in the absence of actual outcrops. 

 Guided by this only, it is supposed to occupy the flat and prairie portion 

 of Sumner township, stretching southward through Spring Valley and 

 Bloomtield and crossing the most of Beaver, and perhaps portions of York. 

 Judging from the prevalence of Cretaceous features in the drift-clay exposed 

 in the railroad cut at Lime Springs, it has played an important part in ori- 

 ginating the materials of the heavy drift-covering that spreads over not 

 only the western portion of Fillmore county, but all the counties of the 

 state further west. 



The lower portion of the Cretaceous, which seems to be that represented 

 in this county, consists of sandstones and lignitiferous clays or shales, the 

 sandstones lying at the base of the formation and being the same that Dr. 

 White has denominated in Iowa the Nishnabotany sandstone, and belong- 

 ing to the Dakota group, of Messrs. Meek and Hayden. Above this sand- 

 stone, which is often white and incoherent, with a thickness of about 

 one hundred feet, so far as observed, is a clayey member of the Cretaceous 

 which has been identified by Mr. F. B. Meek* as the Fort Benton group, of 

 Messrs. Meek and Hayden. These rocks are well exposed in the region of 

 the upper Minnesota valley and contain some impure lignite, and are found 

 in small pieces disseminated, with fossils, through the drift-clay cut at Lime 

 Springs, a couple of miles south of Fillmore county, in Iowa. The Niobrara 

 or chalky member of the Cretaceous, may also exist in the western portion 

 of the state. So far as Fillmore county is concerned the presence of the 

 Cretaceous is known more by certain indirect or secondary evidences, than 

 by the actual discovery of its beds in situ. 



Near Spring Valley, on David Higby's farm, S. W. ^ sec. 32, is a very 

 fine and tough clay, of a generally bluish color, almost entirely free from 

 grit, which is spread out over a wide area, lying but few feet below the sur- 

 face. The overlying soil, which is annually plowed, is a black loam (rather 

 clayey), varying below to a yellow, clayey loam. This clay was discovered 

 several years ago, but nothing has been seen that will demonstrate its 

 real origin, though it is evidently not a part of the drift. It has the appear- 

 ance of being suitable for pottery, or for brick, but would require some 

 sand. A soapy, variegated clay also occurs at J. W. Smith's brick-yard, 



American Journal of Science, (3) III. 23. 



