TJie Kcivccnazvan in Mi/mcsota. — Elftman. 91 
PART I. 
GLACIAL GEOLOGY. 
General Statement. — Certain important features of the gla- 
cial geology of northeastern Alinnesota are found within the 
areal Kmits of the Keweenawan series. The glacial drift oc- 
curs in: ist, well defined moraines; 2nd, rolling till, and 3rd, 
modified deposits. The chief moraines are limited to the cen- 
tral part of this region, extending from Pigeon river to Saint 
Louis river, with the northern and southern boundaries of the 
morainic area equi-distant between the international bound- 
ary and lake Superior. The till and modified drift is abund- 
ant, and hence in this area the underlying rock is for the most 
part concealed, appearing only in isolated outcrops often sev- 
eral miles apart. In the rest of the region the drift is either 
present in small quantities occupying the depressions and cov- 
ering the rocks with a thin veneer only, or it is entirely want- 
ing. The drift of northeastern Minnesota is regarded as 
belonging to the Wisconsin stage of the Glacial Epoch. 
MORAINES. 
Mr. Warren Upham has mapped the moraines of northern 
Minnesota in the twenty-second annual report of the Minne- 
sota Geological and Natural History Survey, plate I. In that 
portion of the state north of lake Superior widely separated 
known areas of morainic drift were provisionally correlated 
by Mr. Upham with the Leaf Hills, Itasca, Mesabi and \'er- 
milion moraines found in the central and western parts of the 
state. The moraines thus mapped extend in a general east 
and west direction across Minnesota and appear to have been 
formed successively during a movement of the ice sheet prin- 
cipally from the north. 
Prof. J. E. Todd has called attention to several objections 
to this interpretation;* namely, that the interpretation of Mr. 
Upham does not duly recognize the altitude and that it does 
not represent the ice sheet as retiring in the proper direction 
to explain the formation of Western Superior glacial lake, 
and that it does not agree with the direction of the striae and 
*Revision of the moraines in central Minnesota. Amer. Geol., vol. 
XVIII, 1896, pp. 225-226. 
