ARCHEAN GRANITES. 259 



Topography. — The granite does not seem to affect the topography very 

 materially. One point noted is that the lakes in the area of the sediments 

 have, as a rule, a northeast-southwest trend, agreeing thus with the struc- 

 ture of the district, upon which they are largely dependent, whereas in the 

 granite area they are more likely to be of very irregular or more or less 

 rounded outline, owing to the more homogeneous character of the granites 

 by which they are surrounded. The hills in the granite area are usually 

 rounded as a result of river erosion and subsequent glacial action. In 

 detail the topography is very rough, as is that of all this portion of the 

 country, but there are no very great differences in elevation. The district 

 underlain by the granite does not in general seem to have been much more 

 strongly affected by erosion than the adjacent portions of the Vermilion 

 district. In the course of a reconnaissance it was observed that on the 

 southeast' side of Iron Lake, which is on the international boundary, just west 

 of Crooked Lake, there is an area of country that has been reduced almost 

 to a base-leveled plain, with Iron Lake as the plane of base-level. The 

 shores of the lake for a considerable distance back from the water's edge 

 possess all the features of such a base-leveled plain. The streams enter the 

 lake through broad marshes having wide estuaries and flow in meandering 

 courses through these marshes. An occasional hill (monadnock) of granite 

 projects above this level plain. Some of the islands in the lake and points 

 projecting into it are so low that in many places by rising in the canoe- one 

 can see over them. 



PETROGRAPHIC CHARACTERS. 



Macroscopic characters. — The granite of Trout, Burntside, and Basswood 

 lakes shows a considerable variation in character, as one might be led to 

 expect from its great areal distribution. In color it varies from very light 

 gray through pink and reddish facies to very dark gray. An equal variation 

 in grain may be seen. It ranges from very fine-grained to coarse-grained 

 forms and also to granite-porphyries. The structure of the rock is in gen- 

 eral massive, but with these massive forms occur gneissoid rocks varying 

 in color from light gray to very dark. Some of these gneissoid rocks pre- 

 sumably owe their sti-ucture to pressure applied subsequent to their consoli- 

 dation. In these the minerals show to a large degree the effects of pressure. 

 Other facies may be due to differentiation processes and to movements in 



