DISTRIBUTION OF AQUIDNECK SHALES. 361 



WEDGE-SHAPED AEEAL DISTRIBUTION OF THE AQUIDNECK SHAEE 



SERIES. 



If the Kingstown series may be compared with a wedge tapering- 

 southward, the Aquidneck shales may be said to form a wedge-shaped area 

 tapering northward, at least as far as Bristol Neck. From the northern end 

 of this wedge-shaped mass a narrower area extends northeastward toward 

 Taunton River. This wedge-shaped areal distribution suggests a general 

 inclination of the southern part of the Carboniferous formation toward the 

 south-southeast, a feature possibly to be studied in correlation with the south- 

 ward pitch of the rocks involved in the various coarse conglomerate synclines 

 and anticlines found in the southern third of Aquidneck Island. The pecu- 

 liar combination of northeast with more northerly boundary lines between 

 the sandstone and the shale series finds expression elsewhere in the sudden 

 changes in the direction of the shore line on the various islands, in the strikes 

 of the chief cleavag-e planes, and, to a certain extent, in the trends of the 

 hills. These facts suggest that the Carboniferous series has been subjected 

 to two systems of folding, making moderate angles with each other, the one 

 causing folds trending more nearly north-south and the other east of north. 



EQUIVALENCE OF THE KINGSTOWN SANDSTONES AND THE AQUID- 

 NECK SHALES. 



A reference to the map will show that the identifiable Kingstown 

 sandstones are confined to the western side of the Narragansett Basin, while 

 the Aquidneck shales belong to the middle area, so that the Kingstown 

 sandstones border in a general way the Western Passage of the bay, while 

 the Aquidneck shales border the Eastern Passage and a part of the Sakon- 

 net River. It has therefore several times been a serious question whether 

 these two formations may not be equivalent, the western Kingstown sand- 

 stone and shale series passing toward the east into a typically more shaly 

 Aquidneck phase. An interpretation of this kind would much simplify the 

 conception of the geology of the southern part of the Narragansett Basin. 

 Unfortunately there are insiiperable difficulties of observation at the very 

 point where the transition between these two formations should be traced. 

 The exposures along the Bonnet, those on Dutch Island, which do not lie 

 far above the same, and the rocks along the western shore of northern 

 Conanicut, along Slocums and Great ledges, all evidently belong to the 

 Kingstown series, while the shales on southern Conanicut, from Beaver 



