FOLDS AND FAULTS. 287 



one niig-lit imagine the aionoclinal flexure under conditions of greater press- 

 ure, and with a general uptilting of the whole sedimentary series involved, 

 developing into one of these S-folds. As regards the position of the fault 

 plane, in the supposed case of the monocline "it actually cuts the steep side; 

 but here it cuts generally through the syncline on one side of it. It can 

 readily be seen by reference to the section that a comparatively slight lat- 

 eral displacement of the fault planes to one side or the other would produce 

 the above-quoted conditions of an opposite dip on either side of the foult, 

 or, to be more accurate, opposite as regards the fault plane, since the actual 

 dip is the same on both sides of the fault in the case of the raonoclinal fault 

 and reversed in the case described here. 



In connection with the shorter and less important faults which trav- 

 erse the region of the Leadville map, the folds are much more gentle and 

 less stron^gly marked than in the case of these larger faults ; but in almost 

 every case where it is possible to obtain data it is found that the same inter- 

 dependence of folding and faulting exists. 



Hade of faults. — In the fcw instances where it was possible to obtain act- 

 ual measurements of the hade of the foult planes, or their inclination from 

 the vertical, it was found to be towards the downthrow side, or that the 

 plane of the fault slopes away fi'om the side which has risen ; this is the 

 condition which generally prevails, and it is explained on the theory tliat the 

 uplifted side has thus a broader base than tbe downthrow side. In only a 

 few isolated cases was evidence found, and only indirect evidence at that, 

 of the opposite conditions, or of a reversed fault. The angle of hade 

 in the observed cases was almost equal to the angle of dip of the strata ; 

 in other words, the fracture was directly across the beds. In drawing the 

 faults where the angle could not be observed, as was the case in the major- 

 ity of instances, they were constructed to accord with this condition. The 

 objection has been made to the assumption that the normal hade of faults 

 should l)e in the direction of downthrow, that it is opposed to the theory 

 that faulting, like folding, is the result of contraction, inasmuch as hading in 

 this direction tends to lengthen the linear space occupied by a series of beds 

 on a given cross-section, rather tlian to contract it. This may be graphically 

 seen in the sections on Atlas Sheet VIII. In Section A, for instance, where 



