76 PROTOZOIC ROCKS OF THE NORTHWEST 
times; but Dr. Shumard, who was instructed to collect evidence of any ancient 
river deposits at a higher level, observed, over the limestone at the Falls, a bed of 
drift of about eleven feet in thickness, and, resting thereon, a bed of sand containing 
Cyclas, Limnea, Physa, and Planorbis, and this deposit he traced on to the same 
level for nearly half a mile below the present position of the Falls. 
The same gentleman also observed, half a mile below the Falls, and about a 
quarter of a mile east of the gorge, on rising ground, over which runs the trail to 
St. Paul’s, a white marl charged with the same genera of shells, but of different 
species. 
The former of these deposits is doubtless of fluviatile origin, and affords viens 
of the river having flowed, at one time, for a short distance, at least, above the 
gorge; the latter seems to be a lacustrine deposit, the bottom of some drained lake, 
of which there are numerous instances in the Chippewa Land District. 
If we except these beds and the underlying drift, no formations of more recent 
date than the shell limestones of St. Peter’s were observed along the Mississippi, 
from the Wisconsin River to the Falls of St. Anthony. This statement will apply 
also to the country east of the Mississippi, as far as the water-shed between that 
stream and Lake Superior, except along the valley of the St. Croix above the Falls. 
SECTION V. 
ITS RANGE, EXTENT, AND BEARING. 
Or this formation, together with its associated member, F. 2 c, the southern 
portion is confined to a belt, narrow, but of considerable length, ranging nearly 
west, on both sides of the lower portion of the Wisconsin River, but chiefly south 
of that stream, together with a continuation of the same belt west of the Mississippi, 
and ranging towards and beyond the forks of Turkey River. 
Its appearance, in the north, is still more limited; being restricted to a few miles 
in the immediate vicinity of the Falls of St. Anthony, 
In the high lands lying on both sides of the Lower St. Croix, near the Kinni- 
kinick, also between Yellow River and the Upper Iowa, this formation occurs in 
outliers, assuming much the same symmetrical, mound-like forms as described and 
represented in the preceding section. 
