546 ROLLIN T. CHAM BERLIN 



till which becomes somewhat clayey at its upper surface, the writer 

 found in 1907 small lumps of decayed vegetable matter and the remains 

 of several tiny twigs. These were all in the uppermost inch of the red 

 till. While there was no continuous layer of humus, these lumps 

 and fragments of former branches were a decided feature of the con- 

 tact. As this sort of material was found nowhere else in the red till 

 or the sand above, it would seem to mark a true interglacial horizon. 

 From the descriptions it appears to correspond closely with the humus 

 horizon reported by Dr. Atwood and his class in 1904,' but which 

 the writer has repeatedly sought but never been able to find, a fact 

 due no doubt to later concealment. 



Fifty pebbles from a calcareous portion of the lower red till were 

 classified as follows: 



Percentage 



Limestone 14 28 



Fine-grained greenstones 9 18 



Red Lake Superior sandstone 9 18 



Granite (i pink, 3 gray) 4 8 



Red aphanitic 3 6 



Jasper 2 4 



Quartz 2 4 



Chert 2 4 



Quartzite 2 4 



Red quartz porphyry i 2 



Gabbro-diorite i 2 



Mica schist i 2 



50 100 



The red rocks and the character of the greenstones show that this 

 is clearly a Lake Superior drift, but the presence of so much lime- 

 stone is surprising. Perhaps the ledges which furnished the lime- 

 stone were covered by drift at the time of the Wisconsin ice-advance, 

 so that the glacier failed to gather up much of this material. There 

 does not seem to be very much black drift below the red at this point, 

 since the rock appears quickly as one goes down the ravine. 



Several of the cuts along the Northern Pacific Railroad, between 

 Taylor's Falls and Franconia, show glacial deposits older than the 

 Wisconsin red drift. A cut in the middle of the east Hne, Section 35, 

 Shafer, exposes a rusty-looking gravelly deposit resting upon the 

 Franconia sandstone. Though much obscured by talus, this deposit 

 was seen to have a thickness of at least twenty feet. The upper part 



I See Jour, of GeoL, XIII, 248. 



