L. Hatch — Marine Terraces in S.E. Connecticut. 327 



Altliougli there is no distinct evidence of the Cretaceous 

 peneplain, there is a suggestion that the region was at one 

 time reduced to a plane of no relief and covered with coastal 

 plain material. This is apparent from superposition of some 

 of the streams on very hard rock, such as the Shunock-Pawca- 

 tuck river, which probably would not have crossed the Red- 

 stone Kidge at Westerly unless let down upon it. But the 

 date of the superposition was long after Cretaceous time, as 

 can be worked out from the larger rivers of Connecticut. 



The southeast courses of the rivers in Connecticut are 

 believed to be due to the southeastward tilting of the Cretace- 

 ous peneplain. This course is shown in the lower Connecticut 

 and Housatonic rivers, but also in the upper tributaries of the 

 Thames River (four miles west of the Stonington quadrangle). 

 The lower course of the Thames, and practically all the smaller 

 rivers in the shoreward parts of Connecticut, show a decidedly 

 nortli-south arrangement, as in the Stonington region. This 

 seems to call for another advance of the sea at a later date, 

 with a coating of marine sediments to obliterate the southeast 

 trending valleys near the sea. After this advance the land rose 

 uniformly, causing the streams (except the Connecticut, whose 

 deeper valley was not quite obliterated) to take a southerly, as 

 contrasted to their southeasterly, course to the sea. 



The change from a southeasterly to a southerly course is 

 most clearly shown in the lower Housatonic river, while the 

 Thames, the only large river near the Stonington quadrangle, 

 shows the same thing near Norwich. In both cases the higher 

 hills reach the 500-foot level near the places where the rivers 

 change in direction. 



It is thus believed that there was an incursion of the sea at 

 the 600-foot level, like that postulated for the Cretaceous, and 

 that the topography of the Stonington quadrangle dates only 

 from this incursion, whatever its date. 



Whether the 500-foot level was a peneplain of subaerial 

 erosion which was covered by marine sediments as the sea 

 advanced, or whether it was carved out primarily by the sea, 

 can not be told. The writer believes that at least the iinishing 

 touches were probably given to it by the sea, because of its 

 similarity to the terraces at lower elevations which so strongly 

 suggest a marine origin. 



The lower terraces, then, were probably carved out of what 

 remained of this 500-foot plain, after extensive subaerial ero- 

 sion had taken place. The subparallel bending inward of the 

 shorelines along river valleys, shows that at no later date, how- 

 ever, did the sea obliterate all marks of the previous river ero- 

 sion. 



