64 IOWA ACADEMY OP SCIENCES. 



THE INTERGLACIAL DEPOSITS OF NORTHEASTERN 



IOWA. 



BY SAMUEL CALVIN. 



The interglacial deposits of northeastern Iowa embrace (1) the 

 peat and forest bed which has been known to well diggers since 

 the early settlement of the region, but which, for this region, 

 was first brought prominently to the attention of science by the 

 writings of McGee,and(2)the Buchanan gravels of Calvin. These 

 deposits represent two distinct horizons in the glacial series. 

 The Pleistocene formations of northeastern Iowa have received 

 more or less attention from geologists since first the region 

 was traversed by Owen. The great lowan bowlders of this region 

 impressed Owen as they have impressed every intelligent 

 observer since, but he believed that these enormous masses of 

 granite could only have been transported to their present posi- 

 tion by floating ice ' ' drifted by currents setting in from the 

 north, before the land emerged from the ocean."* 



Hall, while state geologist of Iowa, seems to have devoted 

 his attention almost exclusively to the indurated rocks and 

 their fossil contents, but A. H. Worthen, who was then acting 

 as assistant on the Iowa survey, discussed briefly the drift of 

 some of the counties which he examined, f though he offered 

 no explanation of the phenomena. 



Dr. C. A. Whitet was the first geologist to consider the drift 

 phenomena of Iowa at any great length. He recognized the glacial 

 origin of the deposits, and referred some of the materials to their 

 true sources in granitic and quartzitic ledges of regions lying to 

 the northward. The time had not yet come, however, for rec- 

 ognizing the complex nature of the Pleistocene deposits of 



*Rept. of a GeoloKlcal Reconnolssance, etc., p. 69. Ordered printed July 3, 1848. 



Kept, of a Geot. Sur. of Wisconsin, Iowa, and Minnesota, p 144. Philadelphia, 1853. 



tRept. on the Geol, Sur. of the State of Iowa, by James Hall and J. D.Whitney, pp. 

 187, 200, 210, and 221. 1858. 



*Rept. on the Geol. Sur. of the State of Iowa, by Charles A. White, M.D., Vol. I, pp. 

 82-103. Des Moines, 1870. 



