REPRESENTATIVES OF PRE-WISCONSIN TILL 



323 



of sand and pebbles of foreign material, showing that it is to be 

 regarded as a true till in which, as in the two tills already 

 described, the material is almost entirely derived from the under- 

 lying rock. The color of the mass is a dirty, somewhat rusty 

 brown, there being no trace of the higher colors exhibited by 

 the tills previously considered. The line of demarcation between 

 the two tills is much less sharp than in the preceding instances 

 and is due to the predominance of the same granitic material in 

 both tills. The chief difference is that in the lower till the gran- 

 ite is present as a disintegrated arkose-like mass, while in the 



///Lx'/iv, ->|Cw-», 



/an~V/- 



Fig. 4. — Section showing general relations of granite, till, and drift terrace at 

 the Ames Pond exposure, Stoughton. Vertical scale, about 200 feet to an inch ; 

 horizontal scale, about 50 feet to an inch. 



upper till it occurs in a fresh condition and largely as glaciated 

 pebbles or bowlders. 



AMES POND EXPOSURE, STOUGHTON 



This exposure is in a gravel pit on the east side of the pond 

 north of the small bay which comes up to the highway (Fig. 2, 

 Exposure 4). The general section of the locality is shown in 

 Fig. 4. The till to be described is exposed on the east slope of 

 the rock and till ridge at d. 



The lower till is somewhat similar to that in the Pearl street 

 exposure at Brockton Heights, the material being a pink 

 granite. The chief point of difference, perhaps, lies in the fact 

 that the till of the Ames Pond exposure appears to have been 

 originally a bowldery till, the fragments of which in most cases 

 have subsequently completely disintegrated. The disintegrated 

 granitic material probably constitutes ninety or ninety-five per 

 cent, of the mass, and is apparently of local origin since a knob 

 of similar granite projects through the till a short distance to 



