FROM ST. PAUL TO THE WESTERN PART OF THE STATE. 



333 



mens had been found there ; and at another place on the Cottonwood I found them to be 

 quite common. Near the previous exposure, and partly from an old digging, I obtained 

 a similar section. At still another point I noticed a similar exposure, leaving no doubt 

 of the character and order of arrangement of the materials composing this formation. 



The character of the vegetation obtained from the sandstone of the shaft and elsewhere, 

 resembling the leaves of Salix, Poplar, Liriodendron, Tupelo, etc., induced me to refer this 

 formation to the Cretaceous period. A single indistinct shell was the only animal fossil 

 I was able to obtain. The aspect of the calcareous concretions is similar to those from 

 the Cretaceous formation of the Upper Missouri; and the green argillaceous clay is like- 

 wise similar. 



Leaving this place on the Cottonwood, we proceeded westward on the low prairie, 

 crossing Mount Creek, going towards the sources of the Little Cottonwood ; when at a 

 point ten or twelve miles from the place of the last examinations on the Big Cottonwood, 

 we came to an abrupt elevation in the prairie, the upper part of which presented a verti- 

 cal escarpment of red quartzite, which trends northwest and southeast, dipping to the 

 southwest. The surface of the rock above was nearly destitute of vegetation over seve- 

 ral acres, and presented a most beautiful exhibition of ripple-marked layers. On its 

 higher exposed surfaces the rock is thinly bedded, and easily separated into krainee often 

 an inch or less in thickness. In the larger exposures it is red, grayish, or mottled, and 

 in all essential characters is similar to the lower beds at Redstone Ferry, on the Minne- 

 sota. 



It is impossible to resist the conclusion that we have here the eastern outcrop of strata 

 similar to those at Redstone Ferry, and which, dipping in opposite directions, have once 

 been continuous across this interval of forty miles, originally forming a great anticlinal 

 axis, which has been eroded to an unknown depth, and subsequently partially filled 

 with the deposits of cretaceous and other modern formations. 



This outcrop, forming a sort of terrace, is the commencement of the Cotcau des Prai- 

 ries ; and I am informed by Mr. Back, the chief of scouts, that lie has traced this rock, 

 sometimes uninterruptedly, for twelve or fifteen miles, and that it is constantly rising to 

 the northwestward. From the point where I stood, the course of the outcrop could be 

 traced for many miles towards the northern limits of Iowa. Farther away to the north- 

 west, the great table land of the Coteau des Prairies rises several hundred feet above the 

 prairie on the cast. 



I was also informed by Mr. Back, that the famous Pipestone locality presented an 

 escarpment precisely like the one on which we stood, except that the strata were dipping 

 to the eastward; that the upper beds arc; hard and quartzose like those we examined; and 

 that the pipestone is at a lower level, of about eighty feet below the crest of the outcrop. 



