|;C,4 THE GEOLOGY OF MINNESOTA. 



The river from its source passes through a morainic tract extending over the eastern part of 

 Le Sueur county and into Rice county, ou both sides, as far as the center of Morristowu town- 

 ship, and in this portion of its course its terraces are less distinct. The highest terrace is not well 

 deiined continuously, even after passing Morristown, but the lower is very marked and persistent. 

 The following are the only points in Rice county at which the upper terrace deposits of gravel, 

 probably pertaining to the earlier portion of the time of the eastward outflow of the Minnesota 

 river, have been noticed. On sec. 24, Morristown, and thence extending toward Warsaw, this 

 upper terrace exhibits an undulating upper outline, consisting of gravel, and reaches a higlit of 

 about sixty feet above Cannon lake. This terrace-like outline blends upward with the till, at 

 least superficially, which at once ascends forty feet still higher and stretches off southward indefi- 

 nitely as a smooth prairie. This till is covered with a copious yellow loam (or clay). West of 

 Morristown, in sees. 20 and 21, the railroad enters an old valley apparently cut through the depos- 

 its of this upper terrace,' leaving between it and the river (which lies farther north) an island 

 which rises now about 105 feet. It is undulating, and apparently contains much till as well as 

 gravel. The highest point on the railroad is in the south part of sec. l!0, where the grade is 1056 

 feet above the sea, and the natural surface is 1067. The hill north of the Polar Star mill, S. E. J 

 of sec. 26, Wells, near the Cannon river, rises to 1095 feet, but consists mostly of St. Peter sand- 

 stone, capped with about twenty feet of yellow loam, semi-stratified. The top of the limerock at 

 Doyle's quarry, on the west side of Straight river, sec. 81, Faribault, is 1080 feet above the sea. 

 This quarry is covered by fifteen feet of fine mortar-sand, overlain by four or five feet of stony 

 and pebbly loam. The rock is changed in color and water-worn. There is a terraced projection 

 of high land jutting northward in section 27, Bridgewater, lying between the present valley of the 

 Cannon and the old valley passing through sec. 28. The uppermost flat, which is approximately 

 1060 feet above the sea, is probably due to the action of the Cannon river when its waters flowed 

 nearly at that hight. At Northfield the highest gravel deposits seem to be about 980 feet above 

 the sea, but the site of the city is an undulating, ascending, terrace-like plateau, in which the 

 strike of the Shakopee limestone, as cut by the Cannon river, remnants of the St. Peter sandstone, 

 and the gravel deposits of the ice-period, though elsewhere exhibiting two distinct terraces, are 

 all concerned as causes. The highest part of this plain, in the southeastern suburbs, rises fifty 

 feet above the Milwaukee depot. The west side of the valley is similar to the east, rising by an 

 undulating plain to sixty feet above the Milwaukee depot, where there is a rather more flat and 

 terrace-like expanse. This is 975 feet above the sea, and wells here enter gravel. Beyond this, 

 toward St. Olaf college, there is a further abrupt ascent to 125 feet above the same depot, or 

 1040 feet above the sea, passing over the St. Peter saudrock. Back of St. Olaf college, on the rein- 

 nunt of the Trenton limestone there quarried, at 1063 feet above the sea, the rock is simply over- 

 lain by a yellow loam four feet thick. This isolated area of the Trenton limestone is remarkable 

 for having no signs of foreign drift strewn over it. The Trenton is simply covered with a spread 

 ing of yellow loam, varying to black, making a red brick. The rock itself is rotted and yellow 

 with age and exposure, and only five feet thick, 'and water-worn on the upper surface. There is 

 some drift visible on the St. Peter slope surrounding this plateau, appearing mainly as boulders 

 of granite, but the great blue moraine must have passed to the west of this point. The water- 

 worn condition of this Trenton limestone, which rises higher than the surrounding country toward 

 the north and northwest, indicates that at some time during the flood-stage of the Cannon river, 

 its waters spread widely over Bridgewater and Greenvale in Dakota county, and eastward over 

 much of Northfield, forming rather a lake than a river; but a lake which though slowly flowing 

 eastward, was annually frozen over in the winter. Ice thus annually formed would easily remove 

 any boulders that may have once lain on the St.. Olaf plateau, since the waters probably did not 

 rise much above that level, and would have congealed about them. On the movement of the ice 

 in the spring they would be carried away, and be dropped at lower levels. 



These highest water-signs in the Cannon valley are doubtless much more numerous than 

 here enumerated, but as these are the only definite field-observations that have been made respect- 

 ing them, the outline of this terrace is not attempted on the plate representing Rice county. 

 These gravel deposits and terraced forms in the bluffs of the river, between Morristown and 

 Northfield require an elevation of at least 1066 feet for the surface of the river at Northfield. As 

 there would ba some slope northward, the same water surface would necessarily be at least 1070 

 feet at the Le Sueur county line. The gravel which is spread over the Trenton plateau at Doyle's 



