KEWEENAWAN ROCKS ON SNAKE AND KETTLE RIVERS. 241 
collections of the Wisconsin Geological Survey, and of the survey made for 
this report. If this evidence does not constitute proof of continuity, then 
no geological formation in the United States has ever been proved to be 
continuous for more than a very few miles—rarely for more than a mile— 
except in the plateau region of the western territories. 
In the distance between Numakagon Lake and the Saint Croix it is 
difficult to estimate the total thickness of the Keweenawan rocks. The 
Upper Division is not exposed on this side of the synclinal, and the position 
of the junction with the older rocks is rendered uncertain by heavy drift 
accumulations. Judging, however, from the dip and strike observations, 
and from the outside limits between which its surface spread must lie, it 
appears probable that the Lower Division of the Keweenaw Series must have 
here a total thickness of from 25,000 to 30,000 feet. 
The Northern Belt; Snake River and Kettle River District, Minnesota.— 
The western end of the trough in the Keweenawan rocks is concealed by 
the unconformably overlying Cambrian sandstone and limestone. The 
final termination southward must lie on the Saint Croix, about half way 
between Hudson and Osceola, the exposures continuing down to the latter 
place. Rounding the turn and moving northward now on the Minnesota 
side of the Saint Croix, we find the Cambrian sandstone completely con- 
cealing the older rocks until Snake River is reached in township 39. Here, 
on the lower portions of Snake and Kettle rivers, and on the Saint Croix 
in the vicinity of the mouths of these streams, typical Keweenawan rocks 
are again exposed on a large scale with a trend but little east of north and 
a high easterly dip. 
Snake River enters the Saint Croix on Sec. 30, T. 39, BR. 19 W... we 
miles below the mouth of the stream, in the N. W. 4 of Sec. 7, T. 38, R. 
19 W., there are cliffs of horizontal Potsdam (Cambrian) sandstone 50 feet 
high, in which the rock is the usual crumbling, quartzose, light-colored 
sandstone commonly seen in the Mississippi Valley. The same rock. is ex- 
posed on the Snake River in the southern part of Sec. 36, T. 39, R. 20 W. 
Above this, Snake River is without rock exposures until Sec. 24, T. 39, R.21 
W. is reached. From here there are exposed continuously in the bed and on 
16LS 
