PLATE XXXV. 



CARVER AND SCOTT COUNTIES, 1888. WARREN UPHAM. 



The Minnesota river and its attendant geology compose the chief geological 

 features of these counties. A morainic belt, that of the latest glacier, appears on 

 each side of the river, passing through these counties in an approximate north-south 

 course. It is the same that occupies western Dakota and Rice counties, to the ice 

 of which must be referred the obstruction of the Minnesota river at the date of the 

 existence of the glacial lakes of the Minnesota valley mentioned in connection with 

 Le Sueur and other counties. While the ice margin crossed the Minnesota valley at 

 this place the Minnesota's waters, in whole or in part, reached the Mississippi valley 

 by way of the Cannon or other valleys lying further south. But it is apparent that 

 the water of the valley was so abundant that the drift was subjected to more thor- 

 ough washing within the valley than elsewhere, this probably being the cause of the 

 extensive gravel and sand terraces that mark the valleys that carried water from 

 the glacier. 



Prior to the accumulation of this till and moraine an earlier glacial epoch had 

 deposited an earlier sheet of drift over these counties, and it is certain that similar con- 

 ditions existed in Carver and Scott counties, at some part of that earlier epoch, as 

 existed at corresponding portions of the later epoch. Hence some of the lower till of 

 the region, and most of the-brick clay seen at Carver, Chaska and Jordan, are attrib- 

 uted to that earlier epoch. The later epoch buried the deposits of the earlier under 

 fresh accumulations, but did not materially reduce their bulk by erosion or transpor- 

 tation. 



Earlier still, the region had been buried under the Cretaceous ocean. The shale 

 and lignite of the Cretaceous are quite common in the till of these counties, and its 

 kaolinic lower beds went easily into the general drift, augmenting its clayey element. 



For a very long period prior to the Cretaceous the region had been dry land. 

 This period extended, as appears from the record of the rocks, from the close of 

 the Trenton in the Lower Silurian, to the Cretaceous submergence. This enormous 

 interval of time, covering Upper Silurian, Devonian, Carboniferous and much of 

 Mesozoic, was sufficient to cause the superficial decay of the old strata that happened 

 to be at the surface in these counties. The region was brought almost to the condi- 

 tion of the base-level of the Archean lying a few miles further north. The kaolinic 

 residuum of the older rocks, whether Archean or Silurian, went into the bottom beds 

 of the Cretaceous, giving the bottom Cretaceous a well-known kaolinic character. 



It was during this long exposure that the great gorges in which lie now the 

 Mississippi river and the lower part of the Minnesota, were excavated. In these 



