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University of California Fublioaiions in Geology [Vol. 13 



to be parallel to, lines of faulting or folding, or of foliation and meta- 

 morphisni. In some areas these lines are known to be of great age, 

 and are believed to have persisted by continual renewal from the 

 earliest geological times. My belief is that most of them are earth- 

 joint systems or deep-seated complementary fractures resulting from 

 the deformation of the earth, dividing the crust into blocks, and con- 

 stituting surfaces of variable adjustment, sometimes serving thrusts 

 in one direction, and sometimes in another, the chief component of 

 displacement being horizontal. 



In the district about Cobalt these systems are represented, respec- 

 tively, by the west shore of Lake Timiskaming, the Montreal River, the 

 line of valleys including Cross, Kirk, Crown, and Goodwin lakes, and 

 other parallel features, and by the axes of Kerr, Peterson, and Cobalt 

 lakes, and the northwest arm of Lake Timiskaming. The exact nature 

 of some of these local lines is not definitely known, but it seems highly 

 probable that the west shore of Lake Timiskaming is determined by a 

 fault which existed in pre-Cambrian time, and was renewed after the 

 Silurian limestone was laid down, as indicated by the displacement 

 and local tilting of the limestone. The evidence of pre-limestone fault- 

 ing consists in the fact that the system of structures to which this fault 

 belongs originated before the cobalt-silver veins, whose age is approx- 

 imately Keewenawan. 



So far as exploration has gone, there has been no proof developed 

 of the character of the Cross-Lake structure, but jointing seems to 

 indicate an axial fault. Such a fault has been found on Cobalt Lake, 

 and this fault is believed by Miller and myself to extend southwest- 

 erly many miles, and northeasterly across Lake Timiskaming into the 

 Province of Quebec. 



In the Meyer workings of the Nipissing Mine along "490 Vein" 

 an abrupt slope occurs on the old Keewatin surface. It proved to be 

 30 feet or more in height, and several hundred feet in length, dying 

 out to the southwestward, and reappearing in the northeast end of the 

 Townsite Mine. A higher but shorter rise of similar kind was dis- 

 covered in the Chambers-Ferland Mine adjacent and parallel to that 

 on the "490 Vein." Still another similar and parallel feature was 

 found on Nipissing Hill north of the low-grade mill. The unconform- 

 able lapping of the overlying beds of the Cobalt Series against these 

 small ridges would seem to indicate that they represent pre-Cobalt 

 relief ; and their parallelism with each other and the axis of the Cobalt 

 Lake syncline, which is postdiabase in age, would seem to indicate 



