330 THE VERMILION IRON-BEARING DISTRICT. 



glomerate and between it and the overlying- Knife Lake slates, into which 

 at other places the conglomerate grades. While this formation is not found 

 everywhere between the conglomerates and slates, in those places where it 

 does occur it always occupies that position. It is clearly, then, an inter- 

 mediate horizon of comparatively local origin, and our studies have shown 

 that in the Vermilion district it is unimportant from an economic standpoint. 



In age it is therefore younger than the Ogishke conglomerate, and older 

 than the great mass of Knife Lake slates, and forms a part of the Lower 

 Huronian series. 



THICKNESS. 



The thickness of the formation varies considerably. On the Wind 

 Lake-Moose Lake portage it has a thickness of about 6 feet. At other 

 places on the United States side of the boundary the exposures are so poor 

 that no correct determinations could be made of its thickness, but at all of 

 these places it appears to be considerably thicker than at the locality just 

 mentioned. The best opportunity for determining its thickness was afforded 

 by the exposures in Canadian territory, where very accurate determination 

 could be made. The best exposures seen in this area are those on the range 

 of hills crossed by the portage from Agawa Lake into This Mans Lake. 

 The rocks are here exposed in a syncline, and on each side of the center 

 of this syncline, which is occupied by a belt of slates, there was found the 

 alternating series of belts of jasper and slates forming the iron-formation 

 complex and having a total thickness of about 50 feet. 



INTERESTING LOCALITIES. 



The best place at which to study the characters of the Agawa forma- 

 tion is on the string of lakes known as That Mans, Agawa, This Mans, 

 and The Other Mans lakes, which lies at an average distance of about 

 1^ miles north of the international boundary on Knife Lake, and trends 

 about N. 45° E. Exposures of the formation may be seen at intervals 

 along the south shore of the string of lakes, on the islands near the 

 center, and on the necks of land which separate the lakes and across 

 which the portages run. Ou the point north of the north end of the 

 portage that comes from Emerald Lake on the south to That Mans Lake 



