18 



KEMPS ORE DEPOSITS. 



tions are brought to a standstill, the continuation is usually found 

 as follows, according to Schmidt's law. If the fault dips or hades- 

 away from the workings, the continuation is down the hade ; if it 

 dips toward the workings, it should be followed upward. Such a 

 fault is called a normal fault, and is illustrated in the figure 

 on p. IV, after A. A. Blow. This is a natural result of the draw- 

 ing apart of the two sides. The least supported mass would slip 

 down on the one which has the larger base. Less commonly the 

 opposite movement results. Thus when the fault is due to com- 

 pression, the beds pass each other in the reverse direction, and 

 what is called a reverse fault results. The accompanying cut il- 

 lustrates a very extended one in the southern Appalachians. 

 While we would naturally think of a reversed fault as resulting 



StCT/ON /. 



^^^^^^^V^-fr^^S-^^ Coiuiasauga Shales 



* Cohuttw Conytomei-alfr 



Ocoee State 

 Knox Dolomite 



FIG. 4. Reversed fault at Holly Creek, near Dalton, Ga. After C. W* 

 Hayes, Bull. G. S. A., Vol. II., PL 3, p. 152. 



from a compressive strain, in that in this case the lower wedged- 

 shaped portion would be forced under the upper one, yet normal 

 faults can likewise, in instances, be explained by compression. If 

 we consider the fault to be caused by the vertical thrust or com- 

 ponent, that would always be present in the compression of a 

 completely supported arch, this would tend to heave upward the 

 portion next the fissure, that had the larger base. Along an in- 

 clined fracture such portion is manifestly the under one. It is also 

 important to note whether the fault plane, both in normal and in 

 reversed faults, cuts inclined beds in the direction of the dip or 

 across it. (See Margerie and Heim, Dislocation der Erdrinde^ 

 Zurich, 1888.) 



1.02.09. The movement of the walls on each other produces 

 grooves and polished surfaces called slickensides, or slips. They 



