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University of California Publications in Geology [Vol. 13 



The validity of this evidence is borne out by the fact of general 

 shearing on the contact, accompanied usually by the development in 

 the overlying sediments of large and small dip-slip reverse faults 

 parallelling the contact in a rough way. Finally, further confirmation 

 is found in the relations of certain other joints, particularly those 

 which constitute the vein fissures. 



The origin of the flat surface of the Keewatin upon which the 

 Cobalt Series was deposited is still obscure. The hypothesis of glacia- 

 tion was tentatively discarded in view of the weight of evidence that 



Fig. 1. Idealized plan showing relation of veins to folds. The contours rep- 

 resent the Keewatin-Cobalt contact and the Keewatin-diabase contact respectively, 

 the dotted lines veins, and the solid lines strike-slip faults. Scale 1" to 5000'. 



accumulated in favor of normal secular delay and stream erosion. 

 All the evidence on this point offered by Miller has been corroborated 

 by myself. A particularly convincing example in support of the idea 

 of secular decay is found on the third level of the Buffalo Mine, where 

 the old Keewatin bedrock can be seen with jagged serrations protrud- 

 ing up into the ancient soil, in which angular fragments detached 

 from the bedrock were mingled with rounded granite and other foreign 

 pebbles, which had worked their way down through the soil. If the 

 surface had been produced by the glacier assumed to have deposited 

 the Cobalt Series, it must have been pared down sufficiently to remove 

 the preexisting topographic features or to have considerably modified 

 them. But had that occurred, then none of the residual soil of the 

 older surface could have remained. The fossil soil found by Miller 

 and myself must be regarded as a proof that the surface was not 



