u Š- 
MANSFIELD: ROXBURY CONGLOMERATE. 280 
(5) The structure shows a system of folds of Appalachian type and 
dimensions — a broad syncline in the middle, with steeper synclines 
on either side, overturned toward the border. 
(6) The preserved thickness is at least 12,000 feet. 
(7) Igneous rocks as basic intrusives or acid effusives are associated 
with some of the lower members of the series. 
(8) Metamorphism has been intense in certain areas but in general 
its effects have been slight. 
Tur HARVARD CONGLOMERATE.— General Description. The only 
accounts of the conglomerate in this region found by the writer are 
- by L. S. Burbank (1876) and Crosby (1880). The rock has a limited 
area of wedge-like form, broadest at the north, where it is only 400 
or 500 feet in width, and tapering southward, where it dies out after 
two miles. According to Burbank the conglomerate is associated 
with soft argillite and chloritized slate and all are interstratified with 
the inclosing gneiss and coincide with the dip and strike of the latter. 
The pebbles of the conglomerate consist chiefly of a gray quartzite 
unlike any neighboring rock (Burbank, p. 224-225). 
Structure. The writer’s somewhat hasty observations in the field 
show that the conglomerate is interbedded with grit and sheared 
sandstone. The strike is north-northeast and the dip is steep westerly, 
nearly vertical. On the west the conglomerate is bordered by phyllite, 
while a short distance east the gneiss appears. In conversation with 
the writer, Professor Emerson, who has studied the Harvard section, 
expressed the opinion that the gneiss and phyllite there exposed form 
part of the northeast extension of the similar rocks at Worcester, 
which he regards as Carboniferous. The structure at Worcester, 
as made out by Perry and Emerson, is an eroded anticline with a 
symmetrical syncline on the east (Perry and Emerson, p. 49)... East 
of this syncline lies the great anticline of older rocks that extends 
northeast from Rhode Island into Massachusetts through Douglass, 
Uxbridge, Sutton, and Northbridge (ibid., p. 155-156). 
Possibly the Harvard Conglomerate may represent a portion of the 
eastern limb of the syncline, as made out by Perry and Emerson. ‘The 
tapering wedge-like form of the conglomerate mass is suggestive of 
faulting. Perhaps the conglomerate may be a lens in the phyllite 
formation, but if so the northern end of the lens is not ee to the 
writer’s knowledge. 
Thickness. Since the dips are very steep the combined thickness 
of the conglomerate, with its interbedded grits and sandstones may 
