376 THE VERMILION IRON-BEARING DISTRICT. 



Exposures. — The exposures in the areas outlined are very good. In 

 all instances thej^ are sufficient to enable one to study the rocks in consid- 

 erable detail and trace out their continuation without greater difficulty 

 than is offered by the very rough and thickly timbered character of the 

 country. 



Topography. — Where the Gunflint formation occurs in sufficient quantity 

 to affect the topography to a noticeable extent, the forms produced in it are 

 faii'ly characteristic. As the result of the monoclinal southward dip and 

 the differential erosion of the harder and softer layers, a series of ridges ai-e 

 produced which trend about east-west and have very steep northward-facing 

 escarpments with gentle southei'ly slopes corresponding aj)proximately to 

 the dip of the beds. It may be well to mention here that sills of dolerite 

 lying ajDproximately parallel to the bedding frequently form the top of the 

 larger ridges. This same kind of topography, but in a more marked form, 

 is also developed in the area underlain by the Rove slates, which is adjacent 

 to that in which the Gunflint formation occurs, and will be found described 

 in greater detail elsewhere (pp. 391-392). 



About a mile east of Paulson's mine there is one very noticeable topo- 

 graphic feature which is not in agreement with the general topography — 

 a large cross valley, running about north and south, which appears to rep- 

 resent an old pre-Glacial valley formerly occupied, perhaps, by a fore- 

 runner of the present Cross River, which flowed through it on its way north 

 into Boundary River and Saganaga Lake. 



STRUCTURE. 



The structure of the Grunflint formation in that portion which is 

 exposed in the Vermilion district is not very complicated. There is a 

 small northeast-southwest trending area of Grunflint formation rocks exposed 

 on the southeast shore of Disappointment Lake. Here the sediments have 

 a strike corresponding very closely to the trend of the area itself — that 

 is, northeast-southwest — and they dip to the south. In rocks of similar 

 age on Gobbemichigamma Lake the structure is a little bit more compli- 

 cated. In this case the sediments have been folded, and as a result we 

 now ^find them forming in the main a syncline plunging toward the 

 northwest, but with a subordinate anticline near the center which has 

 an axis plunging to the southeast. In the narrow belt extending- from 



