QUANDARY PEAK. 99 



pectors this line seems to have had especial attraction, and not without 

 reason, since along it are the best exposures of the lower Paleozoic rocks, 

 in which on this side of the range there has been a considerable concentra- 

 tion of ore. 



The sketch given in Plate X is a view of the region adjoining the upper 

 Blue River Valley, as seen from Mount Lincoln. To the left or west of 

 this valley the hills are almost entirely Archean, with a few later sediment- 

 ary beds resting against their eastern spurs. On Quandary Peak alone do 

 they still extend up to the very summit. On the east of the valley are the 

 hills surrounding the town of Breckinridge, made up of Mesozoic beds and 

 numerous porphyry sheets, in which valuable ore deposits have been dis- 

 covered and from the debris of which rich gold placers have been accumu- 

 lated in the valleys. 



The Quandary Peak ridge is here described, although it does not come 

 within the limits of the map, since it was the only point at which the search 

 for fossils in the Cambrian quartzite was successful. On its eastern end, a 

 short distance above timber-line and perhaps half a mile above the Monte 

 Cristo mine, about fifteen feet of -greenish argillaceous slates, belonging to 

 the upper part of this formation, are exposed by a prospector's tunnel which 

 was run in on the north face of the spur. From these shales, after a dili- 

 gent search, good impressions of the Potsdam species Dicellocephalus were 

 obtained. Unfortunately the ground is too much covered by. soil and forest 

 to afford a continuous section ; but, unless a fault intervenes, this shale bed 

 should be below the quartzite and limestone in which the Monte Cristo 

 deposit occurs, and not many feet from it. Lithologically it resembles the 

 greenish shale beds observed in very many points throughout the region 

 below the calcareous shales and sandy limestones of the upper portion of the 

 Lower Quartzite series, but nowhere were any further traces of these fossils 

 found. 



The exposures of the Cambrian or Lower Quartzite formation are never- 

 theless those of the Paleozoic series which can be most clearly and con- 

 tinuously traced, as they slope up in a U-shaped curve on either side of the 

 valleys below the canon gorges of this portion of the range. In general 

 the outcrops in the valley bottoms and along the lower slopes are concealed 



