3i8 



MYRON L. FULLER 



rock are usually represented. The buff till is without visible 

 structure, while the lower oxidized till is characterized by a dis- 

 tinct, but rude and highly irregular lamination. 



Fig. 2. — Map 1 showing location of exposures of tills of probable Pre-Wisconsin 

 age. I. Center street exposure, Brockton; 2. Intervale Park exposure, Brockton; 

 3. Pearl street exposure, Brockton ; 4. Ames pond exposure, Stoughton ; 5. Pine 

 street exposure, Stoughton. 



The derivation of the lower till from the underlying decom- 

 posed conglomerate is plainly indicated by its color and compo- 

 sition. This conglomerate is composed largely of pebbles of 

 granite, black slate, quartzite, and some quartz, 2 embedded in a 



'Reproduced from special edition of the Dedham quadrangle of the U. S. Geo- 

 logical Survey. Presented through the courtesy of Professor W. O. Crosby and the 

 Boston Society of Natural History. 



2 Quartz also occurs in considerable amounts in the numerous small veins cutting 

 the conglomerate. 



