22 



of carbon, as shown by Prof. Ellis, must have been 

 fluid in the beginning, probably bitumen driven from the 

 carbonaceous shale by the heat of the eruptive beneath. As 

 the black slate is the softest rock in the region, it has suf- 

 fered from erosion more than the rest, and is mostly covered 

 by old lake deposits. 



The Chelmsford sandstone is dark gray and might almost 

 be called graywacke. It encloses numerous large oval con- 

 cretions of impure limestone. When the Animikie beds 

 were bent into the synclinal form the uppermost layers, 

 especially the sandstones, were thrown into compression and 

 rose as dome-shaped anticlinal ridges a few hundred feet 

 high. There must have been a dozen or more of these 

 elongated domes in the beginning, all stretching parallel to 

 one another and to the longest axis of the basin. Now the 

 domes are all more or less ruined, and some scarcely show 

 above the drift deposits. One of the largest, at Chelmsford, 

 is two miles long by a third of a mile wide, and rises about 

 150 feet above the plain. Several thick layers of sandstone 

 have been removed from the top, and buttresslike remnants 

 of beds rise from the fields on each side, so that its height 

 must have been much greater in the beginning. A good 

 example of a smaller anticline is crossed by the railway at 

 Larchwood, six miles west, where the dip of the beds on 

 each side is about 45 deg. 



This sedimentary series, resting upon the nickel eruptive, 

 has an average dip inwards of 30 deg., and has been meas- 

 ured up with the following results : 



r Chelmsford Sandstone .. 800 to 1,500 



Upper Huronian (Animikie' \ Onwatiti Slate 3,800 



- j Onapmg Tuft 3,7°° 



\ Trout Lake conglomerate 20 to 400 



9,400 

 The black slate resembles the Animikie slate at Thunder 

 Bay, but the remarkable tuff of glass fragments has no 

 equivalent in the western Animikie. It appears that these 

 relatively soft sedimentary rocks, if they ever existed in 

 other parts of the eastern pre-Cambrian, have been com- 

 pletely destroyed. Their preservation here is due to the 

 protection of the upturned edges of the nickel eruptive 

 basin, aided by the strengthening of the Trout lake con- 

 glomerate and of the lower part of the Onaping tuff by 

 metamorphic action due to the eruptive sheet. 



