362 J. F. KEMP — GRANITES OF ATLANTIC COAST 



Page 



Virginia '. 381 



North Carolina 381 



Sontli Carolina 381 



Georgia -. 381 



Resume 382 



Outline of the Geoloc4yof the Area discussed 



The area of ciystalline rocks which stretches along the north sliore of 

 Long Ishxnd sound from Narragansett bay to the New Haven Triassic em- 

 ba3anent has received ahnost no geological study since the state survey 

 of C. T. Jackson,* in 1840, in Rhode Island, and that of J. G. Percival,t 

 in 1842, in Connecticut. To the eastward, the region of Carboniferous 

 and Cambrian strata around Narragansett bay has been quite full}'' de- 

 scribed; to the northward, the central portion of Massachusetts has 

 been shown to consist largely of altered Cambrian sediments, now in the 

 form of gneisses, and to the northwest and west, the Triassic and meta- 

 morphosed Cambro-Silurian strata have received detailed attention, but 

 the triangular area forming central Connecticut, with its base on Long 

 Island sound, remains almost entirely for the future. The rocks are 

 prevailingly granitoid gneisses, presumably of Archean age. The}'' are 

 penetrated by intrusions of granite, of unknown age, which, with their 

 atteudant pegmatites in the shore district, are the subject of the present 

 contribution. 



The western shore of Narragansett bay is formed of Paleozoic schists 

 and granite where the rocks are not concealed by glacial deposits, but a 

 mile or two to the west, in the ridge of Tower and McSparren hills, the 

 gneisses appear and continue without a break, except for the intruded 

 granites, until the red sliales and sandstones of the Triassic are met, a few 

 miles east of New Haven. The east and west distance is about 100 miles. 

 'Jlie toj^ography is of a pronounced glaciated type. Low, rounded ridges 

 and knobs of rock project through the mantle of drift, and afford the 

 exposures on which one must base the study of the hard geology. Along 

 the shore, the drift often 'conceals all outcrops of rock for miles at a time, 

 but especially in Rhode Island it gives some compensation for this b}" 

 presenting some of the finest examples of morainal hillocks and glacial 

 dumping grounds in the east. Between the hillocks are the usual small 

 l)onds. In Connecticut the morainal hillocks are much less pronounced 

 and abundant, but, on the contrar\', narrow rocky points run out into 



*C. T. .Jacksou : Report on tho fteol. ami Agric. Survey of Rhode Island. Providence, lS4(i. 

 f.J. G. Pereiviil : Report on the geology of the state of Connecticut. New Haven. 1842. 



