PLATE XXIX. 



BIG STONE AND LAC QUI PARLE COUNTIES, 1884. WARREN UPHAM. 



These counties, lying on opposite sides of the Minnesota river, at the western 

 border of the state, were affected differently by the retirement of the ice border 

 across them. They both slope slightly toward the Minnesota river, and as long as 

 that valley was obstructed by the glacier in its slow northward retreat, the drainage 

 water resulting from the ice was embayed, after the ice border left the third or 

 Antelope moraine, in a shallow lake that covered at least the greater part of Lac 

 qui Parle county. By this water not only was the till which was deposited by the 

 glacier smoothed out more evenly, but a distribution of the clayey portions was 

 more or less spread later over the surface of the till proper. This makes this a 

 smooth county with fine soil. On the other hand, while the ice margin was passing 

 still further north and over Big Stone county, the drainage was toward the south, 

 and found easy escape to the Minnesota valley, leaving the till more nearly in the 

 pose given it by the glacier itself. This county, therefore, has more numerous small 

 hills and undulations, frequent lakes and areas of stony surface, while the soil is 

 coarser and occasionally gravelly. They are both essentially and characteristically 

 prairie counties, with very little timber along the bluffs of the streams and lakes. 



The glacial water-course seen in Freeland and Garfield is probably of the same 

 date and origin as that noted in Yellow Medicine county, and probably served to 

 connect portions of the glacial lake that lay east from the Antelope moraine. The 

 great river, named river Warren by Mr. Upham, which a little later in glacial time 

 drained lake Agassiz, and which is perpetuated by its diminished descendant, the 

 Minnesota river, presents a similar instance of the practical abandonment of its 

 glacial bed. This abandoned gorge is that which connects Big Stone lake with lake 

 Traverse. The rest of the gorge, excavated by river Warren, is occupied by Big 

 Stone lake and by the Minnesota river below that lake.* 



The rocks that underlie these counties belong to the Archean, covered more or 

 less by a nonconformable later coating of Cretaceous. The former are exposed along 

 the Minnesota valley from Ortonville southeastwardly to Marsh lake, and on the 

 shores of Lac qui Parle. The latter is not known in the county, but outcrops in the 

 edge of Dakota, opposite the northwest corner of Big Stone county. 



Near Ortonville the granite has been considerably quarried, and furnishes a 

 coarse, even porphyritic, variety with a prevalent light-red color, resembling the 

 so-called Scotch granite. N. H. w. 



'The history of this episode in glacial geology is given by Mr. Upham in Monograph xxv of the I'nileil States Geological, 

 Survey. 



