58 Loughlin and Hechinger — Unconformity 



and green slates. Wood worth states- that " the prevailing 

 whitish and grayish lines of the basal arkose, and of the con- 

 glomerates immediately above them, are in strong contrast to 

 the often vivid reds of the overlying and occasionally inter- 

 calated Wamsutta series,'' and advances the supposition " that 

 the superficial products of weathering previous to their trans- 

 portation in Carboniferous time were leached of their iron 

 salts, which penetrated downward. The first transportation of 

 detritus affected the superficial leached layer, and thus the 

 basal beds became white. . . . When erosion had stripped away 

 the bleached materials at the surface, it reached the highly dis- 

 colored rock beneath, as yet very imperfectly disintegrated, 

 from which were produced the red beds of the Wamsutta 

 series." 



The granite pebbles from the Pondville conglomerate, as 

 well as from the Wamsutta formation, are of the same type, 

 both in megascopic and microscopic characters, as the under- 

 lying granite mass. The granite mass, though in an area 

 which is prevailingly of the Dedham type, has characters 

 strongly resembling variations of the Sterling granite-gneiss 

 in which gneissoid structure is absent or inconspicuous. 



The TT \unsutta formation. — The name Wamsutta group was 

 given by Woodworthf to designate the series of red conglom- 

 erates, sandstones, and shales which occupy the northern part 

 of the ^arragansett Basin and are continuous with the strata 

 of the Xorfolk County Basin. It passes downward into the 

 Pondville conglomerate, and in places is exposed resting 

 directly on granite. The writers studied this formation in the 

 northwest part, and along part of the northern border of the 

 ,Narragansett Basin, but in the limited time at their disposal 

 found no exposures where the relations of the Wamsutta to 

 the other sedimentary formations were clearly indicated. They 

 will, therefore, confine themselves to consideration of the com- 

 position of the Wamsutta formation, before attempting to dis- 

 cuss structural relations. 



The principal pebbles in the conglomerate beds are quartzite, 

 granite representing different variations of the Dedham (and 

 Milford X) types and locally felsite of the type which cuts 

 the Dedham granite in nearby areas, not the white-weathered 

 type so abundant in the u Coal measures." The presence of 

 Dedham granite pebbles points to a more intimate relation of 

 the Wamsutta formation to the Dighton conglomerate, contain- 

 ing Sterling (and Dedham X) granite pebbles, than to the " Coal 

 Measures " which contain neither. This relation can only be 

 suggested at present, as the relations between the Dedham, 

 Milford and Sterling granites must be proved before the 



*Op. cit., p. 138. fOp. cit.. p. 141. 



