PLATE LVI. 



CARLTON COUNTY, 1899. N. H. WINCHELL. 



The. Archean (Keewatin) appears in the central and western portions of this 

 county. It is in a sub-crystalline condition, and is correctly denominated mica 

 schist throughout a large part of its area. In that condition it is accompanied by 

 numerous veins and lenticular masses of white quartz, and by pyrite which in some 

 cases has been somewhat exploited for gold, but with poor success. The crystalline 

 condition fades out more and more, and the usual lithology of the clastic greenstones 

 of the Lower Keewatin can be fully identified at points a few miles west from Mah- 

 towa; while from Barnum and Moose Lake westward to the Kettle river the under- 

 lying rocks are chiefly fine mica schists, with some indications of Cretaceous. There 

 is no known granite in Carlton county, but it can be at no great distance away toward 

 the west or southwest, judging from the prevalence of metamorphic rocks in that 

 part of the county. The Animikie overlies nonconformably the Archean, but owing 

 to the thickness of the drift and the similarity of the Keewatin to the tilted Animikie 

 the line of strike of the base of the Animikie has never been clearly defined. The 

 quartzyte and taconyte, which are at the bottom of the Animikie along the'Mesabi 

 range, have not been discovered in Carlton county, although the quartzyte has been 

 doubtfully identified in Aitkin county and probably exists in Carlton. The slates at 

 Carlton and along the St. Louis river to Cloquet and the slate seen at the railroad 

 cuts southeastward from Carlton are here classed as Animikie. They are much 

 broken and folded, but they are not crystalline. They are usually dark colored, 

 showing both slaty cleavage due to pressure and a slatiness due to sedimentary 

 structure. They are sometimes gritty with abundant quartz, but rarely become 

 graywackes. 



Overlying the Animikie is a coarse quartz-pebbly conglomerate, seen in the 

 valley of the St. Louis near the east county line. This is followed by red sandstones 

 and shales. The conglomerate is, at other places, followed by a great thickness of 

 quartzyte, and together these represent the true Potsdam of New York. In Carlton 

 county the quartzyte was never deposited, or was subsequently removed, and a later 

 sandstone, represented by the Fond du Lac sandstone, comes directly and apparently 

 conformably upon the conglomerate. But between the date of the conglomerate 

 and these sandstones there was more or less igneous eruption in the immediate 

 vicinity, and great lava sheets were spread over much of the country further east. 

 Some of this igneous action was also cotemporary with these sandstones, judging 



