[ELLS] GEOLOGY OF THE OTTAWA PALÆOZOIC BASIN 111 
the Archean, and extend from the Ottawa river in the vicinity of 
Ottawa city to the St. Lawrence, where the western limit of these for- 
mations is seen in the township of Lansdowne. ‘Thence eastward they 
form the lowest members of the great Ottawa-St. Lawrence series and 
are displayed along the St. Lawrence river as far east as the junction 
of these two great rivers, about twenty miles south-west of Montreal. 
There is no well-defined break between the limestones of the Calciferous 
and the underlying Potsdam sandstone in Canada, in so far as yet 
observed. 
While the upper beds of the Calciferous are highly calcareous, the 
lower portion of the succeeding Chazy is largely sandy, consisting of 
sandstones and sandy shales, generally greenish or greenish-gray in 
colour. At the very base there are apparently a few feet of transition 
beds, which in their dolomitic character resemble the Calciferous, but 
these also contain fossils of the horizon of the Chazy. The lower part 
of the Chazy sandy beds is sometimes a conglomerate or very coarse 
grit. 
The Chazy formation is divisible into two portions, the upper being 
largely a limestone. As regards the thickness of the formation, this in 
places apparently approximates about 175 feet. Thus along the Ottawa 
river, between Grenville and Carillon, the thickness of the transition 
beds from the Calciferous is about ten feet, succeeded upward by about 
fifty feet of shales and sandstones. The thickness of the upper division 
west of Montreal, is placed at seventy feet. In a section roughly made 
near Aylmer the thickness of the lower division was estimated at not 
far from one hundred feet, and this rests upon the Calciferous along the 
shore of the Ottawa river. Inland the country rises and the limestones 
of the upper division present a further thickness of about seventy-five 
feet to the assumed base of the Black River formation. 
In the western part of the basin, north of Kingston, as at Storring- 
ton, the shales have an exposed volume of only twenty-three feet, and 
the overlying limestones of about fifty-nine feet, while at Marmora the 
total observed thickness is about forty-two feet, the lower fourteen feet 
representing the shaly portion. 
In the eastern area, at Mingan Island, it is estimated that the for- 
mation is somewhat thicker, reaching not far from 300 feet. 
About eight miles east of Ottawa city, near Green’s creek, three 
escarpments are seen on the south side of the river, the lowest of which 
represents about forty feet of the Chazy shales, the middle about thirty 
feet of the limestones of. the upper division, while the third shows about 
forty-eight feet of the overlying Black River formation. In some of 
