PREVIOUS STUDIES AND CONCLUSIONS 127 



outside of the outer moraine, to the l^uus beds, which he places in the 

 Pliocene. He also describes (page 111 )\ Pleistocene section near Fair- 

 view, gives a good description of what is evidently Kansan drift (page 

 113), and reports the finding of remains of Eleplvas and mastodon near 

 Sioux Falls. 



In 1898 Bain, who had worked in the field with Todd, reported* a great 

 "Wisconsin gravel train, occupying the valley of the Big Sioux," and in 

 the same paper (page 350) he argues that the predominating drift of 

 northw^estern Iowa "clearly is not Kansan," but adds that "there are 

 traces of Kansan drift at several points in the region discussed. At Sioux 

 City there are certain old gravels which can hardly be referred to any- 

 thing younger. Near Sioux Falls similar old material has been noted." 



In 1899 Todd published^ a revised view of the drift of the region, rec- 

 ognizing two drifts between which lie gravels, and also a dark soil con- 

 taining shells of modern mollusks, a vertebra of a horse and remains of a 

 turtle. 



The most complete report on the geology of the region was presented 

 by Todd in 1899.^ The map, plate I, shows morainic ridges east of Sioux 

 Falls, and morainic knobs northeast of Canton, but does not represent 

 any part of the moraine as extending into the northwestern part of Lyon 

 County, Iowa. Speaking of the first (outer) or Altamont moraine he 

 says (page 19) : "About 5 miles east-southeast of Sioux Falls it reappears 

 on the west bank of the Big Sioux, and curves around the bend of the Big 

 Sioux at Sioux Falls." He describes four knobs northeast of Canton as 

 forming a part of the same moraine (page 34). He also discusses the 

 terraces along the Big Sioux Eiver (pages 138-140), and concludes that 

 they belong to the earlier Glacial Epoch. The report also contains a 

 record of the Pleistocene section west (erroneously printed east) of Fair- 

 view (page 83), of a section northeast of Sioux Falls (page 84), and 

 another east of Canton on the Big Sioux (page 86). The sands and clays 

 under the drift are again referred to the Pliocene (page 67). It is evi- 

 dent that he considered the upper till Wisconsin, and specifically (page 

 128) referred to the "Altamont moraine of the Wisconsin Epoch." 



Wilder was the next to take up the discussion of this region in his 

 report on the geology of Lyon and Sioux counties, lowa.^ 



These counties border the Sioux River on the Iowa side, and their west- 

 ern portions are included in our territory. Wilder attempted to connect 



* Iowa Geological Survey, vol. vili, p. 339. 



^ New light on the drift in South Dakota. Proceedings of the Iowa Academy of 

 Sciences, vol. vi, pp. 122-130. 



« Bulletin No. 158 of the U. S. Geological Survey. 



f Frank A. Wilder : Iowa Geological Survey, vol. x, J900, 



