58 



the Laurentian Keewatin contract. The exposures are 

 not good, but the two formations may be observed within 

 five feet (1.5 m) of each other, and fine-grained dykes 

 may be seen traversing the felsite. Near the contact 

 the granite is characterized by a comparatively fine- 

 grained texture. On the main road from Mine Centre 

 to Shoal lake, the granite holds angular inclusions of 

 the nearby Keewatin rocks. 



Unconformable Superposition of the Seine Series 

 upon the Laurentian. — A few yards farther along the 

 white flag route, the contact of the Seine and older rocks 

 crosses the road. To the right (southeast) the contact of 

 the basal conglomerate with the granite is marked by 

 brown flags. The lower 15 feet (4.6 m) of the conglo- 

 merate is composed of a yellowish grit, or arkose, formed 

 by the disintegration and re-cementing of the granite. The 

 two rocks are notably similar. At a short distance from 

 the contact the granite assumes its normal pale pink 

 colour and granitic texture. By walking 200 feet (61 m) 

 southeast along the unconformity the relations and cha- 

 racters of the two formations may be observed more fully. 



A few quotations from Dr. Lawson's report (6) will 

 serve to draw attention to some of the salient features: — 

 "The bottom portion of the conglomerate formation, 

 while very clearly detrital, is neither water- worn nor far 

 transported. The fragments which compose it are regular 

 detritus of a desert alluvial slope. Where it rests upon 

 the granite, the detritus is nearly all derived from the 

 underlying granite, blocks of granite being enclosed in 

 a coarse quartzitic arkose matrix; and where it rests 

 upon the nearby Keewatin, it is nearly all derived from 

 the underlying rocks of that series, but with considerable 

 quartz in some parts of the matrix. This facies of the 

 accumulation is very evidently the same as that described 

 elsewhere under the name of fanglomerate. 



"Since the fanglomerate is without doubt a subaerial 

 formation it grades up into a conglomerate in which the 

 boulders and pebbles are well water-worn, it seems a 

 fair inference that the conglomerate represents a gravelly 

 flood-plain rather than the beach of a trangressing sea. 

 If this be true, then in a general way the distribution of 

 the conglomerate as outlined on a general geological map 

 of the region indicates the course of a river." 



