No. 3O.] REGIONAL RELATIONS. II 



DRAINAGE MODIFICATIONS AND GLACIATION IN 

 THE DANBURY REGION, CONNECTICUT 



By Ruth S. Harvey 



REGIONAL RELATIONS 



The region discussed in this bulletin is situated in western 

 Connecticut and is approximately 8 miles wide and 18 miles long- 

 in a north-south direction, as shown on fig. i. 1 Throughout, the 

 rocks are crystalline and include gneiss, schist, and marble the 

 metamorphosed equivalents of a large variety of ancient 

 sedimentary and igneous rocks. 



For the purposes of this report, the geologic history may be 

 said to begin with the regional uplift which marked the close of 

 the Mesozoic. By that time the mountains formed by Triassic 

 and Jurassic folding and faulting had been worn down to a 

 peneplain, now much dissected but still recognizable in the 

 accordant level of the mountain tops. 



Erosion during Cretaceous time resulted in the construction 

 of a piedmont plain extending from an undetermined line 30 to 

 55 miles north of the present Connecticut shore to a point south 

 of Long Island. 2 This plain is thought to have been built up of 

 unconsolidated sands, clays, and gravels, the debris of the Jurassic 

 mountains. Inland the material consisted of river-made or land 

 deposits ; outwardly it merged into coastal plain deposits. When 

 the plain was uplifted, these loose gravels were swept away. In 

 New York, Pennsylvania, and New Jersey, however, portions 

 of the Cretaceous deposits are still to be found. Such deposits 

 are present, also, on the north shore of Long Island, and a well 

 drilled at Barren Island on the south shore revealed not less 

 than 500 feet of Cretaceous strata. 3 The existence of such thick 

 deposits within 30 miles of the Connecticut shore and certain 



lf The streams and other topographic features of the Danbury region are shown in 

 detail on the Danbury and the New Milford sheets of the United States Topographic 

 Atlas. These sheets may be obtained from the Director of the United States 

 Geological Survey, Washington, D. C. 



2 It was probably not less than 30 miles, for that is the distance from the mouth 

 of Still River, where the Housatonic enters a gorge in the crystallines, to the sea. 

 Fifty-five miles is the distance to the sea from the probable old head of Housatonic 

 River on Wassaic Creek, near Amenia, New York. 



3 Veatch, A. C., Slichter, C. S., Bowman, Isaiah, Crosby, W. O., and Horton. R. 

 E., Underground water resources of Long Island: U. S. G. S., PP. 44, p. 188 and 

 fig. 24, 1906. 



