BASAL BEDS. 135 



FOKMATIOKS BELOW THE COAL MEASURES. 



PONDVILLE GROUP. 



BASAL ABKOSE BEDS. 



Along the northern border where observations can be made, the red 

 rocks of the Wamsutta series either rest directly on the granitite or are 

 separated from that basement rock by a sheet of grayish arkoses and quartz 

 pebble and quartzite conglomerates. It is evident that the first appearance 

 of red sediments was not simultaneous all along the border, but that it 

 depended upon local conditions, such as the debouchure of streams, the 

 position of headlands or bays controlling the nature of local shore-line 

 deposits. With the exception of the few places where the red sediments 

 designated as members of the Wamsutta series come in at the base, there 

 may be said to exist a horizon of sediments not of red color underlying the 

 Wamsutta and bearing in the nature of their particles, independently of 

 their position, every evidence of being a basal series. These rocks appear 

 not only beneath the red strata in the Narragansett Basin, but also in a 

 characteristic section in the western part of the Norfolk County Basin. I 

 shall refer to the exposures of these basement strata in the few localities 

 where they may be studied to advantage. 



Foolish Hill exposures. — ^At the baso of the Carboniferous, on the southern 

 face of Foolish Hill, between Mansfield and Foxboro, basal arkoses are well 

 exposed; but here thin bands of red slate begin to make their appearance, 

 a few feet above the base. 



North Attieboro exposures. — In tho to wu of North Attloboro, on Division street, 

 and at points near the railroad station on High street, there are broad 

 exposures of a gray arkose derived from the disintegration of the horn- 

 blendic granitite. Similar exposures occur east of the town, where by 

 folding the basal series are^ brought up in close-pressed folds. 



Pierces Pasture in PondviUe, Norfolk County Basin. The clcarest exhlbitlOU Of the baSal 



beds of the Carboniferous is to be found in the Norfolk County Basin near 

 Pondville Station, on the Walpole and Wrentham Railroad. The small 

 area known as 'Tierces Pasture" exhibits in its topography much of the 

 ruggedness of an unglaciated region, insomuch that the nearly vertical beds 

 stand out in ridges where hard and resisting, or sink into depressions where 

 soft and yielding. The almost entire absence of glacial drift from the area 



