BROWN AND REDWOOD COUNTIES. 581 



Terminal moraines.] 



of the Red river basin to take its course northward, as now, to Hudson bay, this being indicated 

 by fossiliferous beds enclosed between deposits of till within the area that had been covered by 

 this interglacial lake and was afterward occupied by lake Agassiz at the close of the last glacial 

 epoch. 



Again a severely cold climate prevailed , accumulating a vast sheet of ice upon Bi itish America 

 and the greater part of Minnesota. By this glacial sheet the valley of the Minnesota river was 

 partly refilled with till, but it evidently remained an important feature in the contour of the land 

 surface. During the final melting of this ice-sheet, its waters, discharged in this channel, quickly 

 removed whatever obstructing deposits of drift it had received, and undermined its bluffs, giving 

 them again the steep slopes produced by fluvial erosion. This partial re excavation and sculpture 

 were then followed immediately, during the retreat of the ice-sheet, by the deposition of the strati- 

 fied gravel, sand and clay, 75 to 150 feet deep, remnants of which occur as terraces on the sides of 

 this valley, from its mouth to New Ulm, and less distinctly beyond. Had not the great valley 

 existed nearly in its present form through the last glacial epoch, it could not have become filled 

 with this modified drift, which must belong to the era of melting of the last ice-sheet. After the 

 departure of the ice, the supply of both water and sediment was so diminished that the river could 

 no longer overspread the former flood- plain of modified drift and add to its depth, but has been 

 occupied mainly in slow excavation and removal of these deposits, leaving remnants of them as 

 elevated plains or terraces.* 



Terminal moraines. The morainic tract in Stately (page 565) is probably a portion of the 

 third terminal moraine, formed at the boundary of the ice of the last glacial epoch during a pause 

 in its recession. This moraine is well exhibited in Martin county and thence to Forest City and 

 Pilot mound in Hancock county, Iowa, as described on page 478. In Redwood county it is not 

 prominent, and its course, which is believed to coincide approximately with that of the Cottonwood 

 river, has not been traced. Close south of the valley of this river in the N. W. J of section 14, 

 Gales, numerous small hillocks and ridges, 10 to 20 feet high, rough with abundant boulders, were 

 observed to occupy a width from a few rods to an eighth of a mile, reaching a half mile or more 

 in length from east to west; and from a bridge in section 10, Gales, a noteworthy hill, perhaps 60 

 feet high, is seen in the view westward, situated not far from where the Cottonwood river crosses 

 the county line. Farther northwest, this morainic belt is clearly traced across Yellow Medicine 

 and Lac qui Parle counties, its most conspicuous accumulations being the Antelope hills. 



During later stages in the recession of this ice-sheet, when the fourth and fifth terminal 

 moraines of its Minnesota lobe were formed, its southern extremity was successively at Kiester in 

 Faribault county and at Elysian in Le Sueur county, and its southwest boundary doubtless crossed 

 Brown and Redwood counties, but the marginal accumulations of drift belonging to these stages 

 have not been traced here. A shallow lake extended along the edge of the ice-sheet across these 

 counties (page 461), and acted to partially level down and smooth the morainic deposits. It seems 

 likely, however, that they are still recognizable, and by careful observation might be mapped 

 approximately. At the time of the fourth or Kiester moraine, the ice-margin probably extended 

 through the central part of Brown and Redwood counties; and the kame-like deposits (page 582) 

 near Sleepy Eye, and in T. Ill, R. 38, and the northwest part of Vesta, may in part represent 

 this moraine. The fifth or Elysian moraine is probably indicated similarly in section 33, Swede's 

 Forest. 



The valley of Mound creek, across the morainic area in Stately, has a level bottom from 500 

 to 1000 feet wide, and appears as if in some former time, which was doubtless the epoch of melting 

 of the last ice-sheet, it had been the water-course of floods pouring southeastward from the upper 

 part of the basin of the Big Cottonwood river into the Little Cottonwood valley. 



Modified drift of the earlier glacial epoch. Thick deposits of stratified sand and gravel, found 

 enclosed in the till near New Ulm, and occurring below a considerable depth of till ten miles far- 

 ther southeast in Courtland, Nicollet county, are believed to be portions of the modified drift which 

 was deposited at the close of the earlier glacial i-eriod, as explained in the foregoing brief history 

 of the ice age. The locality first mentioned is on the extension of Center street a half mile west 

 of New Ulm, where it rises to the top of the bluff, 180 feet above the river, but only some 100 feet 

 above its old channel which lies between New Ulm and this bluff (fig. 47). The hight here 



See pages 44o, 576 and 583; also, compare arlicle on the Minnesota valley in the ice aite. Proc. of Amer Auoc for 

 Adv. of Science, 1W3, and Am. Jour. Sci. (3), xxvii, is<*4. 



