BLACK HILLS GEOLOGY. 189 



In the latter state and toward the northwest are the Bear Lodge 

 mountains, the highest point of which is Warren's Peak. These 

 constitute an upHft which is distinct both topographically and 

 geologically from the Hills proper, and although the igneous 

 rocks there exposed will probably prove to be genetically re- 

 lated to the eruptives of the northern hills, the district will not 

 be included in this paper. 



For a description of the general geological character of the 

 hills we can scarcely do better than quote from Newton's in- 

 troductory chapter : 



" Around a nucleal area of metamorphic slates and schists 

 containing masses of granite, the various members of the sedi- 

 mentary series of rocks, the Potsdam, Carboniferous, Trias or 

 Red Beds, Jura, Cretaceous and Tertiary lie in rudely concen- 

 tric belts or zones of varying width, dipping on all sides away 

 from the elevatory axis or region of the hills. From the hills 

 outward the inclination of the beds gradually diminishes until 

 all evidence of the elevation is lost in the usual rolling config- 

 uration of the plains. At numerous points also within the 

 hills are centres of volcanic eruption." As Newton further goes 

 on to describe, the Archean (Algonkian) area, which is some 

 thirty miles in length by twenty- five in breadth, is situated very 

 much nearer to the eastern than to the western border of the 

 hills and forms fully one-half of the entire area. The nucleal 

 area of schists and slates is not, however, as simple as would at 

 first appear, for at some distance out in the western covering of 

 sediments and between the main Algonkian nucleus and the 

 western border of the ellipse is situated the additional uplift of 

 Nigger Hill. We have here exposed an area of schists with 

 associated granites just as in the Harney Peak region of the 

 southern hills. Around the small Algonkian area is present 

 the same Cambrian escarpment as that which characterizes the 

 main nucleus. The Carboniferous rests upon it and dips away 

 from the centre so as to quickly conform to the gradual slopes 

 of the main ellipse. The uplift is of extremely local character 

 and has exercised so small an influence on the general topog- 

 raphy and drainage of the Carboniferous plateau, that, were 



