184 GEOLOGY OF THE NARRAGANSETT BASIF. 



line with offsets in the Attleboro sandstone which bounds the block on the 

 south. Goat Rock itself is the highest of these monoclinal ridges. (2) An 

 earlier fault has brought the gray Carboniferous rocks down into a right- 

 angled contact with the massive Attleboro sandstones. West of the Goat 

 Rock section the red series is met with in a few outcrops and in a well on 

 the northwest. There is reason to believe, therefore, that a fault bounds 

 this block on the west so "as to bring the red Wamsutta rocks up to the 

 surface. (See fig. 16, p. 157.) 



THE DIGHTON CONGLOMERATE GROUP. 

 Koxbury conglomerate Edward Hitchcock: Final Report on Geology of Massachusetts, 1841, p. 538. 



Reference has already been made to a coarse conglomerate bed 

 believed to form the upper limit of the Coal Measures. The name Dighton 

 conglomerate is here given to a group of coarse conglomerates, with alter- 

 nations to sandstone, found as the highest members of the Carboniferous in 

 Dighton, Somerset, and Swansea, in Massachusetts. The coarsest conglom- 

 erate bed is at the base of the formation. The rocks are better shown in 

 Swansea than in Dighton, but the latter place being better known and more 

 accessible for the purpose of examining these rocks, the latter name has 

 been chosen. A few areas of coarse conglomerates elsewhere are referred 

 to this horizon. 



The Dighton conglomerate group attains where most developed a thick- 

 ness of about 2,000 feet. Its Carboniferous age is not definitely proved, 

 but it is assumed on the following grounds: The Dighton conglomerate 

 directly overlies the Coal Measures. It is not derived from the erosion of 

 underlying Carboniferous beds, but it contains larger pebbles of upper 

 Cambrian quartzites than are known elsewhere in this field lower down in 

 the Carboniferous section. It differs from other Carboniferous conglomer- 

 ates only in that the fragments, being of larger size, demand for their trans- 

 portation more vigorous processes than those previously active. The beds 

 participated in the folding which closed the Carboniferous, and there is no 

 known unconformity between the Dighton conglomerate and the subjacent 

 strata. A typical outcrop of the coarse quartzite conglomerates of this 

 Dighton group may be seen in the crossroads nearest the southwest base 

 of Great Meadow Hill. One quartzite pebble, 8 inches long, contains the 

 brachiopods of the upper Cambrian fauna. 



