512 



LOCAL SECTIONS 



feet above the river, intercalations of magnesian limestone and thick-bedded sand- 

 stone occur, nearly as white as in the slope below Fort Snelling, though of course 

 they occupy a lower position, being part of F. 1,/. The whole is surmounted by a 

 perpendicular escarpment of one hundred and seventy-eight feet of Lower Magne- 

 sian Limestone. 



This range of bluffs continues on the right bank of the river for about five miles. 

 Thirty-one miles, by estimation, above the mouth, the bluffs measured two hundred 

 and forty-four feet in height, and present a wall of forty feet of F. 2 near the top, 

 with occasional exposures of sandstone seen beneath the slope. On the opposite side, 

 a fine level plain extends, two miles wide, bounded on the south by a wooded range 

 of corresponding bluffs, having a very regular outline. In this vicinity, the bottom- 

 lands are generally well wooded and elevated four to eight feet above the water. 



Near a ferry-house, eight miles below English Prairie, soft white sandstone, six 

 feet in thickness, with thin shaly layers interstratified is shown, on the left bank ; 

 the former are in beds from three inches to a foot thick. These strata increase in 

 elevation up stream, having a slight dip to the southwest. Thicker beds of white 

 and brown sandstone rise to view one mile above the first exposure, where the 

 ledges attain a height of twenty feet. The succession is 



Feet. 



1. Coarse brown sandstone, in thin beds, broken by vertical rents or seams, 3 



2. Thicker beds of the same, ...... 5 



3. Thin-bedded, ripple-marked sandstone, with marly partings, . . 12 



I found here, in some of the loose slabs of sandstone, the pygidium of Trilobites, 

 and a small, finely-striated Ortlds, like the species which occurs in the third Trilo- 

 bite bed near the mouth of the Miniskah. These ledges continue for a mile, with 

 a slight southwest dip, and rise to the height of thirty feet. The lower strata 

 resemble beds near the base of the Lawrence Creek Section ; the superior layers 

 seem to correspond with the inferior portion of the coarse Lingula and Obolus grit, 

 F. 1, c. These bluffs prevail on the right bank for about half a mile, when well- 

 timbered alluvial lands set in. 



At English Prairie, the white and brown sandstone of the last section is seen 

 near the water's edge, ten feet of it extending for half a mile. From one to two 

 miles above the English Prairie Settlement, the Lower Magnesian Limestone 

 is exposed, in a mural bench of fifty-six feet, near the top of the ranges of hills, 

 which are three hundred and fifty to three hundred and sixty feet high, with eight 

 feet of F. 1 above the river on the north side. Some outcrops of sandstone are 

 seen projecting from the slope to the height of three hundred and two feet. For 

 two miles, thick beds of sandstone can be traced, ten to twenty feet exposed. Some 

 of the beds are so very white that they might well be mistaken for F. 2, c, if the 

 associate beds could not be seen. At some points the lower beds have crumbled 

 away, and left the upper projecting like an overhanging cornice. Half a mile 

 higher up is a good exposure of the different strata, in the following order : 



