400 Review of the Progress of 
are followed by a great thickness of red and green shales, often 
magnesian, and overlaid by 2000 feet of green and red sandstone, 
known as the Sillery sandstone, the whole from the bese of the 
conglomerate, having a thickness about 7000 feet. These red 
and green shales resemble closely those at the top of the Hudson 
those of the Oneida and Medina formations, that the Quebec 
group was for a long time regarded as belonging to the summit 
of the Lower Silurian series, the more so by a great break and 
upthrow to the S.E., the rocks of this group are made to overlap 
the Hudson River formation. ‘Sometimes it may overlie the 
overturned Utica formation, and in Vermont, points of the over- 
turned Trenton appear occasionally to emerge from beneath the 
overlap.”* ‘This great dislocation is traceable in a gently curving 
line from near Lake Champlain to Quebee, passing just north 
of the fortress; thence it traverses the island of Orleans, leaving 
a band of higher strata on the northern part of the island, an 
after passing under the waters of the Gulf, again appears on the 
main land about eighty miles from the extremity of Gaspé, where 
on the north side of the break, we have asin the island of Or- 
eans, a band of Utica or Hudson River strata. To the south ‘ 
1 
and east of this line the rocks of the Quebec group are arranged 
in long, narrow, parallel, synclinal forms, with many overturn 
dips. These synclinals are separated by dark gray and black 
shales, with limestones, hitherto regarded as of the Hudson River 
age, res which are perhaps the deep-sea equivalent of the 
otsdam. 
* See Sir William Logan’s letter to Barrande, Canadian Naturalist for Jan, 1861+ 
and this volume, 261. oe 
