THE BURIED ROCK SURFACE AND PRE-GLACIAL RIVER 

 VALLEYS OF MINNEAPOLIS AND VICINITY 



E. K. SOPER 

 University of Minnesota 



CONTENTS 



I. Introduction and Summary 

 II. Rock Formations beneath the Drift 



III. The Surface of the Buried Rock 



IV. Relations of Buried Rock Surface to Existing Drift Surface 

 V. The Buried River Channels 



VI. The Drift 

 VII. Influence of Buried River Channels upon Building Construction 



I. INTRODUCTION AND SUMMARY 



The rock formations underlying the mantle of glacial drift which 

 covers the region around Minneapolis have been studied and de- 

 scribed in detail by N. H. Winchell/ Warren Upham,^ C. W. Hall,^ 

 F. W. Sardeson,4 C. P. Berkey,^ and others. The character of the 

 surface of this buried rock floor has been known only in a general 

 way as revealed by local post-glacial erosion and, in part, by the 

 present surface topography. The definite relations of this buried 

 topography to the present one ; the undulations of its surface; and 

 the depth and courses of the buried river channels have been known 

 only at scattered points where data have become available through 

 occasional well borings or other artificial or natural excavations. 

 In the investigations herein described an attempt has been made: 

 (i) to show in detail, so far as available data will justify, the exact 

 nature of the surface of the bed rock; (2) to determine the depth 



* Final Report Geol. and Nat. Hist. Survey of Minn. 

 ^ Ibid. 



3 " Geology and Underground Waters of Southern Minnesota" : Water Supply 

 Paper, U.S. Geol. Survey No. 2j6. 



4 "Galena Series," Bull. Geol. Society of America, XVIII (1907), 179-94. 



5 "Paleography of Saint Peter Time," ibid., XVII (1906), 229-50. 



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