300 THE VEEMILION IRON-BEARING DISTRICT. 



of the district where the sediments have a considerable width their conti- 

 nuity is interrupted by numerous antichnes of older rocks. Here and there 

 a boss of granite which has been intruded through these sediments is found, 

 the sediments wrapping around it. These areas also are anticlinal in 

 structure. For the most part the various anticlinal areas are commonly 

 outlined by conglomerates which lie on the flanks of anticlinal hills whose 

 centers are occupied by an older rock. Where the sediments alone occur the 

 conglomerates occupy the centers of the anticlinal areas. The bedding is 

 so poorly preserved in the conglomerates as a rule that one can not get 

 many strike and dip determinations to assist in interpreting the structure. 

 Unquestionably these conglomerates must have been folded with the other 

 sediments, although such folding can not be traced in detail on their 

 exposures. It is shown, however, by the distribution of the slates, which 

 dip away from such anticlinal areas of conglomerate. The slates invariably 

 occur within the synclines, forming depressions as a result of their initial 

 position at the bottom of the syncline and as a result of the relative ease 

 with which they are eroded. This is shown, for example, in the broad area 

 of slate surrounding Knife Lake. Exceedingly fine-grained, very cherty 

 slates, breaking with conchoidal fracture, lie about in the axis of Knife Lake. 

 As we go farther south from this point the sediments get coarser, graywackes 

 gradually becoming associated with the slates, and finally the sediments 

 grade into conglomerates. This same condition exists north of the lake, 

 although there the conglomerates are not so greatly developed as to the south 

 of it. Within this and other broad slate areas small slate anticlines very 

 probably occur, for although no such anticlines have been clearly demon- 

 strated to exist, indications of them have been found. 



As is shown on the map, this broad area, underlain by the Lower 

 Huronian sediments, is separated from several detached areas to the south 

 by intervening highlands, occupied by the Ely greenstone and the Snow- 

 bank and Cacaquabic granites, named in order of age. In the area south 

 of these highlands, formed of the older rocks, the structure of the sediments 

 is totally different from that seen in the large area to the north. South of 

 these anticlinal highlands the sediments occur in a southward-dipping mono- 

 cline which extends with few interruptions from the vicinity of Snowbank 

 Lake to the eastern end of the slate area on Paul Lake. There is a contin- 



