PRE-CAMBRIAN OF NORTHERN ONTARIO AND QUEBEC 317 



obtained by mapping. Thus in McGarry Township porphyry 

 masses are seen (Fig. 2) to cut across the*^ bedding of the Timiskam- 

 ing near its base, into the underlying Keewatin. The same thing 

 on a smaller scale may be observed to the north of the Harris- 

 Maxwell mine, where masses of porphyry cut across the bedding 

 of the sediments, from the conglomerates into the overlying 

 greywackes and slates. 



Relations to the Cobalt series. — The Cobalt series overHes the 

 Timiskaming with very great unconformity. The relations of the 

 two series are seen in two places. In Grenville Township, near 

 Kenogami station, the fiat-lying Cobalt series outcrops a quarter 

 of a mile northeast of the Timiskaming, which dips 60 to 70 degrees. 

 The Cobalt series outcrops again near the Timiskaming series at 

 Larder Lake. As mentioned previously, a small outcrop of the 

 Cobalt basal conglomerate north of the Harris-Maxwell mine was 

 observed to lie on a peneplaned surface beveling the Timiskaming 

 series and th& porphyries and lamprophyres which intrude it. 

 The Cobalt conglomerate here lies in turn on Timiskaming con- 

 glomerate, greywacke, and slate, which are tilted into vertical 

 attitudes, as well as on the intrusives. The unconformity is thus 

 clearly proved. The Cobalt conglomerate on Pearl Point (Fig. 

 2) contains numerous fragments of the greywackes, slates, and 

 porphyries of the Timiskaming series. The Timiskaming there- 

 fore suffered intense folding, intrusion, and peneplanation before 

 the Cobalt was laid down on it. 



The thickness of strata eroded during the peneplanation which 

 took place before the Cobalt series was deposited has never been 

 estimated, but some data obtained in Boston Township permit of 

 the calculation of a minimum figure. Careful observations made 

 on the structure of the Keewatin in this district and elsewhere 

 throughout northern Ontario and Quebec, show, wherever studied, 

 that it has been thrown into close isoclinal folds, usually upright 

 or slightly inclined, but occasionally overturned. Such a fold is 

 illustrated in Figure 4. Erosion has cut so deeply into these folds 

 as to remove the crests entirely, so that only the steeply inclined 

 limbs may now be observed. In three or four places the writer 

 has found good outcrops directly across the axis of such a fold, 



