BULLETIN OF THE GEOLOGICAL SOCIETY OF AMERICA 



Vol. 12, pp. 313-342, PLS. 27-28 AUGUST 31, 1901 



KEWEENAWAN AREA OF EASTERN MINNESOTA 



BY C. W. HALL 



(Presented before the Society December 30, 1899, and December 28, 1900) 



CONTENTS 



Page 



Topography and physiography. 314 



The area defined 314 



Surface features , 314 



River erosion 314 



Erosion of the Dalles of the Saint Croix 315 



A pre-Glacial Saint Croix valley 316 



Absence of lakes 317 



Relation to the associated formations 317 



The underlying formations , 317 



The overlying Cambrian sandstones 317 



Stratigraphic relationships 318 



The fault line 318 



Extent of the fault 318 



Minnesota localities 319 



The evidence of artesian vy^ells 320 



Exposures of the Keweenawan 321 



Eastern Pine and Carlton counties , 321 



Taylors Falls 321 



The Saint Croix River section ' 322 



The Saint Croix Copper range 324 



Kettle river 324 



The Snake River localities 327 



The Chengwatana series 327 



General structural characters 327 



The lava flows 327 



The conglomerate beds 329 



Attitude of the series .- 330 



The limits of the series 330 



Thickness of the Chengwatana series 330 



Petrography of the series 331 



Structural characters 331 



.Textural characters 332 



Lithologic characters 332 



Rock alteration 335 



The secondary minerals 335 



XLV— Bull. Geol. Soc. Am., Vol. 12, 1900 (313) 



