ELECTEIC PEAK. 



53 



The intrusive sheets extend, in diminishing numbers, northward in the 

 north ridge of Electric Peak. The}' resemble the sheets intruded in the 

 Jurassic shales of Cinnabar Mountain, though it is possible that the latter 

 intrusive rocks were derived from other sources more directly connected 

 with the synclinal folding and faixlting of Cinnabar Mountain. 



The north ridge of Electric Peak terminates in the low knob called 

 Cinnabar Mountain. This elevation is formed of upturned sedimentary 

 beds, presenting a most excellent and complete section of the stratigraphic 

 series from the Paleozoic to the summit of the Laramie, a section which is 

 here given, as it is typical for the Gallatin region. 1 



Section of the Mesozoic sedimentary rocks exposed in Cinnabar Mountain and 



Electric Peal;. 



S I Sandstones alternating with shales and carrying coal seams, many of -which are 



workable. 



r White, massive, and cross-bedded sandstone, easily disintegrated and crumbling readily 

 under pressure 



Impure sandstone, gray in color, carrying argillaceous material and often calcareous. 

 The outcrops frequently weather into flagstones a few inches thick, forming broken 

 reefs that project above the smoother slopes 



Alternating fissile sandstones and impure argillaceous shales which frequently carry 

 lenses of purer sandstone, and near the base contain much bituminous shale, which is 

 soft and crumbly upon weathering 



Arenaceous shales and shaly sandstones, generally greenish gray in color, and weathering 



into fine brown debris 



' Sandstones, generally forming ledges projecting above the slopes of shale 



Gray shales and shaly sandstones 



Soft, bituminous, black shale, weathering readily and forming a smooth slope covered 

 with the fine fragments of the leafy shale 



Calcareous beds, varying from impure arenaceous limestones to calcareous shale 



Black shales, alternating with thin arenaceous beds, aud containing strata of blue 

 splintery limestones which are argillaceous, dense in structure, and do not form per- 

 sistent horizons 



zz j Quartzite, forming a reef that projects as a wall above the slopes of shale 



Black and dark-blue shales, varying from arenaceous, light-gray, impure sandstones to 

 black, laminated, bituminous shales, and carrying the same impure dark-bine lime- 

 stones found above 



Sandstone, generally massive, gray. in color, weathering with a rusty surface; fissile, 

 granular in texture, and forming a wall projecting above the slope 



Sandstone, very fissile, and grading into an arenaceous shale 



Impure limestone, passing into argillaceous black shales and arenaceous shales 



Dark-colored, bluish-black, finely laminated shales with occasional interbeddod saud- 

 I stones J 



Feet. 



800 

 125 



240 



450 



226 



38 



164 



500 

 40 



400 

 5 



350 



25 

 15 

 50 



265 



1 See Cinnabar aud Bozeman coal fields, by W. H. Weed: Bull. Geol. Soc. Am., Vol. II, 1891, p. 352. 



