SACHUEST ARKOSE. 379 



south of Nannaquacket Pond. — The steep escarpment southeast of Nannaquacket 

 Pond locates approximately the line along 1 which the arkose beds may 

 occur farther southward. 



Equivalence of the Tiverton arkoses to Jthose near Natick. The COai'Se Conglomerates 



assigned to the top of the Carboniferous series on the eastern side of the 

 basin overlie these arkoses within such a limited distance that it seems 

 hardly credible to suppose that if the coarse conglomerates along the 

 Sakonnet River correspond to the Purgatory conglomerates the arkoses on 

 the eastern side of the basin may correspond to the Natick arkoses and 

 conglomerates. Yet something of this relationship must be assumed, with 

 the jjossibility, however, of considering the Tiverton arkoses perhaps not 

 so old as those occurring on the western side of the bay, their basal posi- 

 tion not certifying to absolute equality of age with the Natick exposures, 

 but only to their early deposition as compared with other deposits on the 

 eastern side of the Carboniferous field. For the present, faulting is assumed 

 to account, in part, for the remarkably short distance intervening between 

 the coarse so-called Purgatory conglomerate in these regions and the basal 

 Tiverton arkoses, but the absence of the Kingstown series would also partly 

 explain the facts. The escarpment from Steep Brook to Tiverton and 

 thence east of Nannaquacket Pond indicates that the eastern floor of the 

 basin, upon which the Carboniferous rocks were deposited, consisted largely 

 of granitic rocks. Subsequent folding has placed them upon the eastern 

 side of a great synclinal fold, and subsequent denudation has left behind the 

 present escarpment. The original contours of the Carboniferous basin are 

 unknown. 



SACHUEST ARKOSE. 



The western and southern shores of Sachuest Neck, the northern shore 

 at Flint Point, and a small exposure offshore at a headland a quarter of a 

 mile south of Flint Point consist of arkose with which more or less coaly 

 shale is interbedded. Lithologically it strongly resembles the exposures 

 east of Nannaquacket Pond, and it contains ferns in the shale beds, as was 

 also the case at Fall River and Steep Brook. If the writer's view -as to the 

 geology of this region is coi'rect, the arkose of Sachuest Neck rests upon 

 Cambrian conglomerate and shale, and derived its materials from pre- 

 Carboniferous granite. The total thickness of these arkose beds may 

 amount to 20<) feet. 



