PLATE LIII. 



CROW WING AND MORRISON COUNTIES, 1888. WARREN UPHAM. 



Crow Wing county has no rock outcrops, but Morrison has many. The oldest 

 are the greenstones seen in the northwestern part of Morrison county, cut by the 

 railroad at Randall station (sec. 1; T. 130-30). It is a fragmental rock, appearing 

 somewhat conglomeratic (No. 1677). Between this and the granites of the eastern 

 part of the county are mica schists, as seen at Little Falls and at Pike Rapids, and 

 on the Mississippi below Pike Rapids. These mica schists are due to metamorphism 

 of rocks like the greenstone seen at Randall, or other fragmental strata associated 

 with them. These schists are garnetiferous wherever seen in Morrison county, and 

 at Pike Rapids they are conspicuously staurolitic. They are, in some places, quite 

 fitted for building stone, being fine grained, homogeneous and of a light-gray color. 



In the midst of the staurolitic mica schists, at a point a short distance below 

 the mouth of Swan river, and where the principal rock reef causing the principal 

 water-fall crosses the river, is a marble-like layer of limestone, standing several feet 

 above the water, rather poorly exposed, seen on the west bank. It is pinkish and 

 fine grained, and marked apparently with a sedimentary structure which coincides 

 in direction and dip with the principal structure of the staurolitic schists of the place. 



Accompanying the metamorphism of the clastic strata of the Archean much 

 granitic rock was formed. This is found in most of that part of Morrison county 

 east of the Mississippi river, extending in a belt eastward from Little Falls. It 

 extends from Belle Prairie to Buckmantown, in a north and south direction, and in 

 an east and west direction nearly to the eastern line of the county. It is also quite 

 certain that it is a part of the granite seen at Mille Lacs. This granite is of later 

 date than the schists, being intrusive in the schists. 



At about two miles west-northwest from Little Falls is a rock that may be 

 younger than the granite. It is gabbro (No. 1678) similar to that seen at Duluth, 

 but sometimes it is hornblendic, constituting a dioryte rather than gabbro. 



The youngest rock in the county is of the Cretaceous, seen at the mouth of Two 

 rivers, but probably extending under the drift over most of the southern part of the 

 county. In this Cretaceous have been found Margaritana and Unio, also a shark's 

 tooth. These shales are lignitic and are referred to the later part of the Cretaceous. 

 They contain evidently a large proportion of kaolinic clay derived from the pre- 

 glacial decay of the Archean. Analysis showed 19.81 per cent of silica and 52.43 

 per cent of alumina. This substance would probably make fire-brick. Its hardness 

 is but little less than that of limestone. 



