NEW ENGLAND APPALACHIAN SYSTEMS 



183 



Purgatory conglomerate of the southern field. The basin beds become 

 metamorphosed to slates and quartzites to the south and the pebbles of 

 the conglomerates are elongated and indented. They are regarded as 

 Carboniferous in age and probably Pennsylvanian. 



Recent detailed work by Richmond (1952) Quinn et al. (1949), Quinn 

 (1951, 1952), Nichols (1956), Quinn and Springer (1954), and Chute 

 (1950) is responsible for the correlation chart (Fig. 11.29), and the 

 following generalizations. The succession of formations given by Emer- 

 son is not found in any one quadrangle. The unconformity at the base of 

 the Pennsylvanian beds in the Narragansett basin is striking, and is 

 shown by the near right angle discordance of the contacts of older forma- 

 tions with the Pennsylvanian, and by the discordance in outcrop of bed- 

 ding and schistosity. Three episodes of metamorphism may be detected 

 (Quinn, 1952). The beds of the Blackstone series were first moderately 

 affected — sandstone to quartzite, mudstones to amphibolite schist. The 

 later Esmond granite is mildly metamorphosed as are the volcanics of 

 the East Greenwich group. Since the East Greenwich beds contain peb- 



Fig. 11.28. Carboniferous basins of Rhode Island and Massachusetts. 





NARRAGANSETT DASIN 



W00NS0CKET BASINS 



BOSTON BASIN 



Sedimentary 



Igneous 



Sedimentary 



Igneous 



Sed lmentary 



Igneous 



TRIASSIC 





Diabase d ikes 





Diorite and 

 diabase dikes 







PERMIAN*? 

 PENNSYLVANIAN 



Dighton congl. 

 Rhode Island fm. 

 Wamsutta gr. 

 Pondville congl. 



Narragansett Pier 

 granite b peg. 





Pegmatite and 

 aplite 









Bell ingham 

 congl . 





Cambridge 



slate 

 J fSquantun 

 u tillite 



Dorchester 

 £ . slate 

 a Brook line 

 X cgl. & 



£ I vols. 



MISSISSIPPI.** 





East Greenwich 



group 

 (granite ff vols . ) 









tiuincy granite 



DEVONIAN 



OR 

 EARLIER 





Esmond granite 

 ?Scituate granite 





Fine grained 



gran . 

 Esmond granite 

 Metadiabase 



dikes 

 Scituate gr. gn. 



Fossil iferous 

 Lower CaAbnan 



Dedhaa 



granodionte 

 Salem gabbro- 



d lorite 

 Volcanic rocks 



PRECAMBRIAN 



Amp 







JL IT 



■a 



hibolite 

 hist 

 Sneech Pond 



schist 

 Westboro 



qtz. 

 Mussey Brook 

 . schist 





Blackstone 



ser, 



Woonasqua- 

 tucket fm. 



Absalona fm. 



Sipsachuck 

 gneiss 



Porphyritic 

 metadiorite 







Fig. 11.29. Some sedimentary and igneous rocks of Rhode Island and Massachusetts. 



