73 

 Underlying Surface. 



In the vicinity of Cobalt, the Cobalt series rests, char- 

 acteristically, on a weathered surface of one or other of the 

 older series of rocks. Most commonly the underlying series 

 is the Keewatin, as rocks of this age are more widespread 

 in the productive part of the area than are the other pre- 

 Cobalt series. No surface that has the appearance of 

 having been produced by glaciation is known beneath the 

 Cobalt series in the vicinity of Cobalt. 



Where the rocks of the Cobalt series rest on the green- 

 stones or other easily decomposed members of the 

 Keewatin there is a gradual transition from the non-dis- 

 integrated rock upward into the distinctly fragmental 

 member of the Cobalt series. The disintegrated material 

 on the surface of the Keewatin has been recemented and 

 consolidated, or, in other words, recomposed. It is im- 

 possible at certain contacts, without the examination of thin 

 sections under the microscope, to distinguish the recom- 

 posed material from the underlying massive igneous rock. 



Something the same may be said of the contact between 

 the upper members of the Cobalt series, the Lorrain arkose, 

 and the Lorrain granite. In the township from which 

 the name of these rocks is derived, arkose lies on the 

 weathered surface of the granite, there being a gradual 

 passage from the undecomposed rock upward into the 

 arkose. 



At the base of the Cobalt series there is the recomposed 

 material described in the preceding paragraphs with, 

 typically, conglomerate or breccia, many of the frag- 

 ments of which can be seen to have originated in place. A 

 striking example of the origination in situ of such material 

 is to be seen on the shore of lake Temiskaming, on the 

 extreme north end of lot 15 in the first concession of the 

 township of Bucke, a couple of miles south of Haileyburv. 

 Here, as the geological map, scale 1 mile to 1 inch, shows, 

 the Cobalt series forms a contact with the Keewatin. At 

 the contact the Keewatin consists of greenstone, or basalt, 

 and a dike of feldspar-porphyry. That the conglomerate 

 and breccia of the Cobalt series, here resting on the 

 Keewatin, has, for the most part at least, originated in situ 

 is shown bv the fact that it contains fragments of various 



