222 S. W. SARDESON TliE ftEDSTONE QIlARTZlTE 



about 175 feet high above the river's level and extends out from the north- 

 east side of the valley so far as to turn the river from a direct course. 

 The valley widens opposite this quartzite barrier — that is, on the other 

 side of the river. None of this quartzite is seen on that side of the river 

 and no such outcrops of it appear elsewhere along the valley, so that the 

 Eedstone has the appearance of an isolated block. 



On the north side the quartzite extends under glacial deposits at the 

 foot of a scarp which is the side of the valley. The highest point on the 

 Eedstone quartzite hill is in fact below the general surface level of the 

 glacial drift on either side of the valley, and its position is such as to 

 clearly indicate that it was once covered by glacial deposits, and that its 

 uncovering from the drift has been due to the great glacial river Warren, 

 which excavated the Minnesota valley to its present size. The quartzite 

 being very resistant to erosion, the great river, which at first flowed over 

 Eedstone hill, later worked out an easier course around the south side of 

 this rock mass. The Eedstone quartzite has thus been left obtruding 

 above the bottom of the valley. In similar manner, river silts of Cre- 

 taceous age, on the sides of the quartzite mass, show that in that age also 

 it formed a prominence above a river. The Cambrian sedimentary rocks 

 in turn appear as laid down about its foot, on the shores of an encroach- 

 ing sea. 



The Eedstone, or Courtland quartzite, has therefore this distinction, 

 that it stands in close relation, although unconformably with recent and 

 Pleistocene deposits, with Cretaceous and with Cambrian, as well as with 

 supposed Archean formations. These diverse formations are uncon- 

 formable also, each to the other. The geologic history of the Eedstone 

 quartzite mass is to a large extent a key to the geologic history of the sur- 

 rounding territory. Detailed account of these formations and their rela- 

 tions is given in following chapters. 



In regard to literature concerning the Courtland quartzite and the for- 

 mations about it, the work of C. W. Hall, Warren Upham, N. H. Win- 

 chell, and Leo Lesquereux are important. The first named author has 

 summarized all the earlier literature on the quartzite and the granitic or 

 gneissic rock in particular, and the other authors named embody the 

 knowledge of the Cambrian, Cretaceous, and Pleistocene formations. A 

 list of the works to which reference has been made is found at the end of 

 this paper. 



For opportunity to study closely the geologic formations around New 

 Ulm, Minnesota, I am indebted to Dr 0. C. Strickler and the New Ulm 

 Commercial Association. For assistance and valuable geologic informa- 

 tion, I am under obligation to Mr Benedict Juni, of New Ulm. 



