360 GEOLOGY OF THE NARRAGANSETT BASIN. 



conglomerate series consist also chiefly of sandstone. Some of the sand- 

 stone layers contain scattered pebbles, or even thin streaks of conglomerate; 

 conglomerates with pebbles of moderate size also occur, but do not consti- 

 tute an important element of the Sakonnet sandstones. Shaly layers are 

 more common, and occasionally attain considerable thickness — for instance, 

 iii the case of the coaly shales along the shore directly west of Windmill 

 Hill. As a rule, however, the sandstones predominate very much at this 

 horizon. The sandstone exposures north of High Hill, and the sandstone, 

 shale, and fine conglomerate extending from the shore west of Windmill 

 Hill nearly to Browns Point, are characteristic exposures of this Sakonnet 

 sandstone on the east side of the river. The shales and sandstones south 

 of Corys Wharf may possibly represent some lower horizon in the Aquid- 

 neck shale series. 



ABSENCE OF THE SHALE SERIES BENEATH THE COARSE CONGLOM- 

 ERATES EAST OF THE SAKONNET RIVER. 



The upper Aquidneck shales are therefore believed to merge into 

 sandstones on approaching the present eastern border of the Carboniferous 

 basin. And this may be true also of the lower horizons of this series. If 

 the coarse conglomerates on the eastern side of the Sakonnet River be, 

 indeed, the equivalents of the coarse conglomerates on Aquidneck Island and 

 northwest of Taunton River, and if the sandstones just mentioned belong 

 to the Sakonnet series as interpreted west of the river, very little space 

 intervenes in most localities on the east side of the Sakonnet River between 

 these conglomerates and sandstones and the basal arkose layers and coaly 

 shales. The section east of the Sakonnet River must have had a somewhat 

 different history from that on the mainland west of the bay. An extensive 

 system of irregular faulting would seem to offer a possible explanation for 

 this sudden diminution of the Aquidneck shale and Kingstown sandstone 

 section. The irregularity of the dip and strike of the coarse conglomerate 

 exposures and their areal distribution would seem to favor the existence of 

 marked local faulting. But it is also possible that the basal arkose east of 

 the bay is not identical in age with that west of the bay. It may belong 

 to a higher horizon, possibly corresponding to part of the Aquidneck shale 

 series. In that case the failure of any equivalent of the Kingstown sand- 

 stone series to appear east of the bay is not so surprising. 



