246 The American Geologist. ^p"^- ^^'^2- 
SOME RESULTS OF THE LATE MINNESOTA 
GEOLOGICAL SURVEY.* 
' By N. H. WiNCHELL, Minneapolis. 
This Jtopic has been chosen at the suggestion of the chair- 
man of the Section (Prof. W. M. Davis), but with reluctance. 
The results of the survey have been published fully. Owing, 
however, to the volume of literature devoted to the Minnesota 
Survey, it is believed that a condensed enumeration of the chief 
scientific and economical results of that survey may be of use. 
(i). At the commencement of the survey, the rocks that 
are now included in the Upper Cambrian were embraced under 
the two terms "Lower Magnesian limestone" and "Potsdam 
sandstone." It soon became apparent that the former embraced 
three parts, which had been unknown to D. D. Owen and his 
predecessors. Two of these were individually designated Shak- 
opee limestone, and New Richmond sandstone (a term adopted 
from the Wisconsin survey) and the term Lower Magnesian 
(since rejected by the Iowa Survey in favor of a new term 
Oneota) was restricted to the main body of the limestone ex- 
posed in the cliffs of the Mississippi between Hastings and 
Winona. That these two new parts do not Ijelong in the over- 
lying St. Peter sandstone is evident from the fact that at var- 
ious places, as at Red Rock and at Shakopee. The Shakopee 
was included by Owen, who gave the original names, in his 
term Lower Magnesian limestone, while the Richmond sand- 
stone, which lies below the Shakopee was never by him referred 
to as St. Peter sandstone. 
The term "Potsdam sandstone" Avas also entirely changed 
from its early application in the Mississippi valley. It was 
found by stratigraphic studies that the Potsdam sandstone of 
Potsdam, New York, was represented in Minnesota by a more 
firm, even quartzitic, sandstone whose habit more nearly re- 
sembles the original Potsdam, and the term was applied to that. 
With this transfer it became necessary to apply new names to 
the friable white sandstones of the Mississippi valley. In de- 
scending order the parts thus named are, Jordan sandstone, St. 
Lawrence limestone, Dresbach sandrock, and Hinckley sand- 
rock, with unnamed shales both above and below the Dresbach 
sandstone. The term St. Croix was given to these sandstones, 
* Read Dec. 31, 1902, A. A. A. S., Washington, D. C. 
