168 



Subsurface Geologic Methods 



imposed normal to the a, b, and c fold axes are the types one may expect 

 from the statistical study of the muscovite books. 



Figure 65. Lineation on west or upper limb of fold shown in figure 64. The hori- 

 zontal lineation is due to intersection of bedding (dipping 45° out of the picture) 

 and schistosity (dipping 50° out of picture). The lineation almost normal to it is 

 caused by quartz filling tension joints normal to the b axis and opened by 

 stretching along that axis. The fold shown in figure 64 was discovered by careful 

 mapping of the lineation and schistosity. 



Possible Applications 



Detailed structural studies to be complete should make thorough 

 use of petrofabrics. The individual techniques of petrofabrics, however, 

 may be used separately on special problems. 



Ingerson ^^ gives a list of possible applications of petrofabrics. There 



*" Ingerson, Earl, Why Petrofabrics? : Am. Geophys. Union Trans., vol. 25, pp. 636-652, 1944. 



