CHAPTER V. 



DESCRIPTIVE GEOLOGY OF LEADVILLE AND VICINITY. 



GENEKAL STRUCTURE. 



The central region of the general map is, as has already been seen, 

 the region of the greatest dynamic as well as eruptive action. A section 

 across the range at Leadville shows, as the result of dynamic action, five 

 anticlinal folds and six principal faults. On the east side of the range, as 

 already seen, the structure is relatively simple. The beds sloping back to 

 the eastward are broken by one main anticlinal fold and its accompanying 

 fault, the London fault. On the west of the crest, however, instead of one 

 main fault, as in the regions north and south, the continuity of the beds is 

 broken up by six principal and several minor faults. 



The map of Leadville and vicinity (Atlas Sheets XIII and XIV) shows 

 the most important features of the geology of that region. Its eastern 

 border extends to within two or three miles of the main crest, which con- 

 sists of Archean rocks capped by easterly dipping Paleozoic beds and in- 

 trusive porphyries. For a better comprehension of the description which 

 follows, the reader is requested to refer constantly to this map and its ac- 

 companying sections. He will there see that its area is divided into a series 

 of irregular zones or blocks by the lines of six principal faults having a 

 general north and south direction. For purposes of description these have 

 received the following names, commencing on the east: 1, Mosquito fault; 

 2, Ball Mountain fault ; 3, Weston fault ; 4, Mike fault, with a branch called 

 Pilot fault ; 5, Iron fault ; 6, Carbonate fault, with a branch called Pendery 

 fault. Besides these there are the following minor and cross faults: 1 , on the 



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