188 



KEMP'S ORE DEPOSITS, 



lead-silver ores, largely oxidized, occurring with much barite, 

 chiefly along the contact between extensively faulted, Lower Car- 

 boniferous, blue limestone and a brown, dolomitized, underlying 

 portion of the same; but also in fissures and less regular deposits 

 in these and older limestones and quartzite. Aspen is on the west- 

 ern slope of the Continental Divide, in the valley of the Roaring 

 Fork, just at the point where it crosses the contact of crystal- 

 line Archsean gneisses and Paleozoic sediments. The stream cuts 

 them at right angles to the strike. Aspen Mountain lies on the 

 south side and Smuggler Mountain on the north. The limestone 

 belt continues north and south, and is prospected over a stretch of 

 nearly forty miles. At Aspen there is evidence of a faulted, syn- 



ARCHXEAN 



Canon of Roaring Fork 



CAMBRIAN SILURIAN CARBONIFEROUS 



CARBONIFEROUS AND SILURIAN 



MIDDLE AND LOWER CARBONIFS. 



FIG. 48. Geological section at Aspen, Colo. After A. Lakes, Ann. Rep. 

 Colo. School of Mines, 1886. 



clinal fold, with many minor disturbances. The westerly dipping 

 rocks by the faulting are repeated to the west and are pierced by 

 a great granite intrusion and much porphyry. Still farther west 

 the Red Jura-Trias sandstones are in great force. The faulted 

 repetitions of the Paleozoic rocks are eroded into a narrow ridge, 

 between Castle Creek and the Roaring Fork, just below the town. 

 Over beyond Aspen Mountain, and to the south, lies Tourtelotte 

 Park, in a small synclinal basin of the limestones, and eight or 

 ten miles farther is Ashcroft. The dips in Tourtelotte Park are 

 low, but they increase going down the mountain toward Aspen, 

 and are steepest of all at its foot, where the strata at 60 run un- 

 der the stream gravels and glacial deposits. The geology when 

 closely viewed is very complicated, and involves the following 

 sections according to D. W. Brunton. (See papers of W. E. New- 

 berry and S. F. Emmons, cited on p. 191.) 



