204 GEOLOGY AND MINING INDUSTRY OF LEADVILLE. 



block of ground included between the principal fault-lines, will be described 

 in detail. The three cross-sections of the general map wliich cross the area 

 of the Leadville map will serve perhaps best to sliow the general outlines 

 of structure. 



In Section E, Atlas Sheet IX, which is drawn approximately through 

 the middle of the map, and which may, therefore, be considered as a type- 

 section, the effect of displacement is more prominent than that of folding. 

 Its line runs through the southern edge of the town of Leadville itself, 

 across Carbonate, Iron, and Breece Hills, passing just north of the crests of 

 Ball Mountain and of East Ball Mountain to the summit of West Dyer 

 Mountain. Along this line, going from west eastward, the following are tlie 

 main features of folding: In the region under Leadville, or from the western 

 edge of the map to the Carbonate fault, a shallow syncline; under Carbon- 

 ate Flill, or from Carbonate to the Iron fault, a second shallow syncline; 

 and from Iron Hill eastward, a third ; in all of which the prevailing dip is 

 eastward, only a small portion of the easterly edge of the basin having a 

 westerly dip. In the region between Iron Hill and Ball Mountain, or, in 

 other words, on the western slope of Ball Mountain, the surface is so uni- 

 formly covered with Pyritiferous Porphyry that tliere is no direct evidence 

 of any folding, although a slight anticlinal fold might be expected near the 

 line of the Pilot fault, from the fact tliat one exists on its strike both north 

 and south. At Ball j\Iountain is a sharp anticlinal fold, and east of that the 

 beds slope back in a monocline to the eastward. The effect of displace- 

 ment produced by the faults has been to lift each successive block of ground 

 up to the east of the fault, except in the case of a wedge-shaped portion 

 included between the Mike and Pilot faults, in which there has been a slight 

 downward movement. 



On an east and west line south of this (Section I I, Atlas Sheets XIX 

 and XX), the beds of Blue Limestone would be first met about due south 

 of the summit of Carbonate Hill, sloping east in a shallow synclinal basin 

 and rising again in an anticline whose axis corresponds to the southern 

 continuation of the Dome fault. The crest of this fold having been planed 

 off by erosion, the contact would be wanting for something over half a mile, 

 and be found at the head of Thompson gulch dipping to the eastward, but 



