EVIDENCE THAT THE BEDS ARE AFTONIAN 405 



In many other cases the sub-Aftonian is not in sight, but the overlying 

 Kansan is clearly shown. This is well illustrated in the Cox pit, near 

 Missouri Valley, 33 and in a pit near Grant Center, in section 7, township 

 85 north, range 44 west, 34 but the same relation is shown clearly in nearly 

 all the exposures studied in Harrison and Monona counties. 



Even in the few cases in which the Aftonian is not in contact with the 

 sub-Aftonian or the Kansan, the position of the beds is stratigraphically 

 consistent. Thus at Logan the bed of gravel 2 feet in thickness, with 

 overlying sands 10 feet in thickness, lies directly on the Missouri an lime- 

 stone, no sub-Aftonian being present. 35 Besting on the sand is a bed of 

 reddish joint clay, 36 and above this is fossiliferous loess. While there is 

 no Kansan till in this section, the presence of the Loveland makes the 

 position of the Aftonian beds consistent. 



At Denison, in Crawford county, a bed of cross-bedded sand and gravel 

 35 feet in thickness lies immediately below a bed of fossiliferous loess, 

 evidently post-Kansan, on which rests, a layer of dune sand, possibly de- 

 rived from the Iowan, and over this appears another deposit of later loess. 

 While neither Kansan nor sub-Aftonian appear in this section, the posi- 

 tion of the bed below the older loess, the similarity of its cross-bedding, 

 etcetera, to that of undoubted Aftonian, and the presence of Aftonian 

 fossils, such as fragments of Sphcerium, and bones of large mammals, 

 such as Elephas and Cervdlces, all indicate that the beds are Aftonian. 



That the beds herein discussed are not merely a comparatively recent 

 outwash covered by a slumping of the Kansan along the bluffs of modern 

 valleys is demonstrated by the fact that well-sections show that they run 

 well back into the bluffs. 



Thus about 15 rods back from the Cox pit a well excavation revealed 

 Aftonian beds 40 feet below the surface, which is here about 60 feet above 

 the top of the Aftonian in the pit. 



At Logan, a well dug about 5 rods from the face of the bluff showed 

 Aftonian sand at a depth of about 28 feet. The exposure shown in plate 

 35, figure 2, is only a short distance above (north) of this well, and also 

 furnishes evidence of the same kind, for the excavation here extends at 

 least 3 or 4 rods into the bluff, yet the Aftonian is well developed. 



A well east of the Wallace pit, near Little Sioux, Iowa, penetrated into 

 a bed of gravel at a depth of about 90 feet. The well is on a high bench 



33 See plate 33, figure 2. 



34 See plate 35, figure 1. 



35 See plate 35, figure 2. 



36 This has heen referred to as "gumbo" in the type locality at Loveland by Udden and 

 the writer (see Bulletins from the Laboratories of Natural History of the State Univer- 

 sity of Iowa, vol. 5, 1904, p. 348). It evidently bears the same relation to the Kansan 

 as the Buchanan gravels, and tbe name Loveland is here proposed for it. 



