36 CONNECTICUT GEOL. AND NAT, HIST. SURVEY. [Bull. 



4. EVIDENCE OF GLACIAL FILLING AND DEGRADING OF THE RIVER BED 



Hobbs has suggested that the waters of the Housatonic may 

 have 'been ponded at a point near West Redding until they rose 

 high enough to overflow into the " fault gorge " below Still River 

 Station, thus giving the streams of the Danbury region an outlet 

 to the Sound by this route. This hypothesis calls for a glacial 

 dam which has not been found. It is true there are glacial de- 

 posits in the Umpog valley south of Bethel. The Umpog flows 

 as it does, however, not because of a glacial " dam " but in spite 

 of it. The river heads on rock beyond and above the glacial 

 deposits and picks its way through them (fig. 7). Drift forms 

 the divide at the western end of Still River valley beyond Mill 

 Plain, but the ponded water which it caused did not extend as far 

 as Danbury (see discussion of Still-Croton valley). The Sugar 

 Hollow pass is also filled with a heavy mantle of drift, but the 

 valley is both too high and too narrow at the col to have been 

 th outlet of the Housatonic. 



It might be assumed that just previous to the advent of the 

 ice sheet Still River headed south of its present mouth and flowed 

 southward. In this case the Still, when reversed, should have 

 overflowed at the lowest point on the divide between it and the 

 Housatonic. It should have deepened its channel over the 

 former divide, and the result would have been a gorge if the 

 divide were high, or at least some evidence of river cutting even 

 if the divide were low. On the contrary, Still River joins the 

 Housatonic in a low, broad, and poorly drained plain. 



The existing relief is due to the uneven distribution of drift. 

 The river is now cutting a gorge at Lanesville, but the appearance 

 of the valley to the west indicates that glacial deposits forced the 

 river out of its former bed (fig. 6) and that no barrier lay 

 between the preglacial Still River valley and the Housatonic 

 Valley. 



5. GLACIAL SCOURING 



A reversal of Still River may be explained by glacial scouring 

 which caused the northern end of the valley to become lower than 

 the present divides at West Redding and Mill Plain. The 

 evidence of such scour should be an overdeepened, U-shaped 

 main valley and ungraded tributaries. 



