RHODE ISLAND COAL MEASURES. 173 



that all the red beds lying on the outskirts of the great Wamsutta mass 

 belong on the same horizon. In a red slate core there conld be seen 

 annelid casts, such as characterize the red slates on the south side of the 

 Attleboro syncline (see p. 178). It is to be noted also that about 1 mile 

 northeast of Perrins cut the red series is exposed in the northeast corner of 

 the town of Rehoboth. Red shales here also contain annelid tubes. 



The stratigraphic thickness of the boring, on the doubtful assumption 

 of the parallel dip of the beds to the bottom, is about 628 feet There are 

 upward of 1,800 feet of measures to the highest exposures just above the 

 Seekonk conglomerate, and there are upward of 2,000 feet of concealed 

 measures from this horizon upward to Great Rock, where coarse conglom- 

 erates, supposed to be of the Dighton horizon, come in. This calculation 

 gives the group of Coal Measures below th^ Dighton conglomerate in this 

 section a minimum thickness exceeding 5,000 feet. If 5,000 feet of strata 

 below the Dighton conglomerate are measured, in the typical area on either 

 side of the syncHnal axis in Dighton and Swansea, it will appear that the 

 bottom of the series is here by no means reached. I am therefore led to 

 place the beds just described relatively high up in the Coal Measures. 



SEEKONK BEDS. 



About a mile east of the Tenmile River beds, and about 1,000 feet 

 higher up stratigraphically, is a series of monoclinal ridges of sandstone 

 and conglomerate which afford the best natural exposition of the Carbon- 

 iferous strata that is found anywhere in the inland portion of the basin. 

 While sandstones form the dominant exposures and leading topographical 

 feature of this series, shales enter about equally into the thickness of the beds. 



West and south of the farm of Mr. Davis Carpenter these arenaceous 

 and gritty rocks rise from 20 to 30 feet in height, in an area of about 

 1 square mile, in five principal ridges, striking a few degrees E. of N. and 

 dipping E. from 20*^ to 30°. The aggregate thickness, including sandstone 

 and shale below a thick conglomerate bed, is somewhat less than 2,000 feet. 

 There is no evidence to show that the successive ridges are due to the repe- 

 tition of step faults bringing up a single bed. East of the stream on the 

 Woodard place, in the southeastern part of the area of exposures, a sand- 

 stone ridge has been quarried, the strata here affording rough, thick flags. 

 The large strike joints which occur here are very smooth and nearly par- 



