CHAPTER III. 



CARBONATE HILL GROUP. 



GENERAL STRUCTURE. 



The geological structure of Carbonate Hill 1 is very similar to that 

 of Iron Hill in that it is formed by a series of easterly-dipping beds broken 

 on the west by a line of faulting or displacement. Outcrops are also exposed 

 on its southern face by the erosion of California gulch, but in a less com- 

 plete series, owing to its being shallower and proportionately wider, in con- 

 sequence of which the bounding slopes are less steep and more thickly cov- 

 ered by surface debris. The fault is nearly parallel to that of Iron Hill, 

 and, like it, merges into the axis of an anticlinal fold on the north. In the 

 southern half of the hill, however, the movement of displacement is dis- 

 tributed in part to a "second nearly parallel fault a short distance to the 

 west. Of the southern continuation of these faults less satisfactory data are 

 available, but they are supposed to merge together before crossing Califor- 

 nia gulch, and probably pass into an anticlinal fold under the Lake beds to 

 the southwest, like the Dome fault, the normal continuation of the Iron 

 fault. As on Iron Hill, there is also evidence of a basining-up of the beds 

 of the relatively down-thrown mass on the west as they approach the fault; 

 in other words, of a synclinal structure. Upon this evidence, which will be 

 given later in full, depends the solution of the important question whether 

 ore bodies exist under the present site of Leadville or not. 



Rock formations. The series of beds of which the hill is composed is essen- 

 tially the same as that given in the Iron Hill section, but the distribution of 

 the later intrusions of Gray or Mottled Porphyry differs somewhat in detail. 



1 See Atlas Sheets XXVIII, XXIX, and XXX. 



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