MANSFIELD: ROXBURY CONGLOMERATE. 281. 
southwest part of the Norfolk Basin and the folds and faults of the 
corresponding portion of the Narragansett Basin are prevailingly 
north-northeast. 
Thickness. The thickness of the sedimentary series in the Boston 
Fic. 10.— Deformed pebbles of the Harvard Conglomerate. 
Basin may be as great as 5,300 feet. In the Norfolk Basin it is cer- 
tainly equal to that figure and is probably considerably greater, per- 
haps nearly 10,000 feet. In the Narragansett Basin the structure 
requires a preserved thickness of 12,000 feet. In all these areas an 
unknown thickness of sediments has been removed by erosion, so 
that the original depth of the Carboniferous deposits in this region 
may have greatly exceeded even the largest of the figures given. The 
