12 CONNECTICUT GEOL. AND NAT. HIST. SURVEY. [Bull. 



peculiarities in the drainage have led to the inference that the 

 Cretaceous cover extended over the southern part of Connecticut. 



A general uplift of the region brought this period of deposition 

 to a close. As the peneplain, probably with a mantle of Cre- 

 taceous deposits, was raised to its present elevation, the larger 

 streams kept pace with the uplift 'by incising their valleys. The 

 position of the smaller streams, however, was greatly modified 

 in the development of the new drainage system stimulated by 

 the uplift. The modern drainage system may be assumed to 

 have been at first consequent, that is, dependent for its direction 

 on the slope of the uplifted plain, but it was not long before the 

 effect of geologic structure began to make itself felt. In the 

 time when all the region was near baselevel, the harder rocks 

 had no advantage over the softer ones, and streams wandered 

 where they pleased. But after uplift, the streams began to cut 

 into the plain, and those flowing over limestone or schist deep- 

 ened, then widened their valleys much faster than could the 

 streams which flowed over the resistant granite and gneiss. 

 By a system of stream piracy and shifting, similar to that which 

 has taken place throughout the Newer Appalachians, the smaller 

 streams in time became well adjusted to the structure. They 

 are of the class called subsequents ; on the other hand, the 

 Housatonic, which dates at least from the beginning of the up- 

 lift if not from the earlier period of peneplanation, is an ante- 

 cedent stream. 



The complex rock surface of western Connecticut had reached 

 a stage of mature dissection when the region was invaded by 

 glaciers. 1 The ice sheet scraped off and redistributed the mantle 

 of decayed rock which covered the surface and in places gouged 

 out the bedrock. The resulting changes were of a minor order, 

 for the main features of the landscape and the principal drainage 

 lines were the same in preglacial time as they are today. It is 

 thus seen that the history of the smaller streams like those 

 considered in this report involves three factors: (i) the normal 

 tendencies of stream development, (2) the influence of geologic 

 structure, and (3) the effect of glaciation. 



The cover of glacial deposits is generally thin, but marked 

 variations exist. The fields are overspread with coarse till con- 

 taining pebbles 6 inches in diameter to huge boulders of 12 



1 This stage of glaciation is presumably Wisconsin. No definite indication of 

 any older glacial deposits was found. 



