GeoJofji) of the St. Croix Dalles. — Berkey . 369 
Wisconsin with the 4th or Kiester moraine,* is not necessaril}^ 
substantiated by the evidence herein set forth. In fact the 
morainic development due to western accumulation seems to 
disappear gradually as it approaches this area. 
Wisconsin geologists refer to the Kettle range, of which the 
moraine immediately east of St. Croix Falls is apart, as prob- 
ably belonging to the same stage as the accumulation known 
as the Leaf Hills moraine in Minnesota, j- Such correlation is 
not jT^et substantiated andean not be so long as the glacial ac- 
cumulations immediately south and southwest of the extremity 
of lake Superior are so imperfectly known. 
Observations in this district indicate that the erosion of the 
St. Croix Dalles is post-glacial. 
Chapter III. 8trati(jraphic Geology. 
The exposed sedimentary rocks in the St. Croix Dalles area 
vary from a few feet to 225 feet in thickness. An equal thick- 
ness probably lies below the level of the St. Croix river, upon 
the very irregular floor formed b}^ the Keweenawan rocks. If 
the dip of the igneous rocks were constant, however, a thick- 
ness of 1,500 to 2,000 feet could be attained along the western 
margin of the area. 
The dip of tlie several subdivisions is fairly uniform 
southward at a very gentle inclination, amounting to 50 to 75 
feet per mile.;j; While varying slightly at different places, the 
dip is fairly constant to a considerable distance beyond the 
bounds of the area. Approaching the district from the south 
and west, it is noted that the successive members of the Mag- 
nesian series disappear one by one until, at Eagle Point, near 
Osceola village, the Oneota dolomite constitutes the cap and 
surface formation. Within the bounds of the district this 
formation also is lacking, and the Jordan sandstone becomes 
for some distance the uppermost formation. No attempt to 
follow the subdivisions toward the north beyond Osceola has 
heretofore been attempted. The subdivisions of the Magne- 
sian series§ recognized at Osceola are, approximately : Oneota 
*Geol, and Nat. Hist. Survey of Minn., Final Report, vol. ii, p. 415. 
tGeology of Wisconsin, vol. xii, 1880, p, 385. 
JGeol. and Nat. Hist. Survey of Minn., Final Report, vol. ii, 1888, p. 
409. 
§The Magnosian Series of the N. W. States, by Hall and Sardeson. 
Bull. Geol. Soc. of America, vol. 6, 1895, pp. 167-198. 
