WEST OF CARBONATE FAULT. 263 



Western rim. — Oil the wcstem side, in the little canon at the mouth of the 

 east fork of the Arkansas, adjoining the west end of James Ridge, the Lower 

 Quartzite is exposed in considerable tliickness at the surface, dipping at an 

 angle of 8° to 10° to the southeast, and some workings to the east of this, 

 along the northern edge of James Ridge, are said to have disclosed the over- 

 lying White Limestone. The Peoria shaft, on James Ridge (not indicated on 

 the map), may be expected to afford further data as to the actual line of out- 

 crops of the formations and what portion of them have escaped erosion, 

 Avhen it reaches the rock surface. At the time of writing this shaft had a 

 depth of 375 feet and was still in the marl of the Lake beds. 



From these meager data and from the probable thickness of Lake beds 

 and the angle of dip of the underlying formations the line of outcrops of 

 the western rim of this basin have been constructed. While, therefore, the 

 fact that a synclinal basin exists beneath this area seems fairly well estab- 

 lished by the evidence just given, there is only a possibility that the line of 

 outcrops given on the map will be found by future exploration to be 

 strictly correct. They are dependent on two as yet unknown quantities : 

 fii'st, the angle of dip of the formations on either side of the basin, and, 

 secondly, the amount of erosion which had taken place before the Lake beds 

 had been deposited, or, what amounts practically to the same thing, the 

 thickness of the Lake bed deposits which now underlie Leadville. 



EXPLANATION OF TRANSVERSE SECTIONS. 



The detailed description given above of the geology of the Leadville 

 area can perhaps best be summarized in a consideration of the various sec- 

 tions which accompany the map, and in which this structure is graphically 

 delineated. For its better comprehension the reader is requested to place 

 these sections one above the other in the order indicated by their letters, 

 commencing at the top. The first nine sections (A to I) are on east and 

 west lines, approximately parallel with each other. These sections, being 

 in general across the sti-ike and more or less at right angles to the fault 

 planes, show not only the amount of displacement occasioned b}" these 

 fjiults, but the longitudinal folds into which strata have been compressed, 



