332 COPPER-BEARING ROCKS OF LAKE SUPERIOR. 
series of quartzose sandstones, dolomitic sandstones and red marls, which 
plainly belong at the base of the Keweenaw Series. According to Logan,’ 
the whole thickness of these rocks is between 800 and 900 feet; Bell, how- 
ever, from later study, making it between 1,300 and 1,400 feet. The fol- 
lowing is the succession, as given by Bell:? 
Feet. 
Alternating red and white dolomitic sandstone, with a red conglomerate layer at 
the bottom, oceurring on Wood’s location, Thunder Cape*............-..--. 40 
Light-gray dolomitic sandstone, with occasional red layers and spots and patches 
of the same color. These sandstones occur along the southwest side of 
Thunder Bay and on Wood's location == Je. cam sem care steelers aie sine <eerereels ae 200 
Red sandstones and shales, interstratified with white or light-gray sandstone 
beds, frequently exhibiting ripple-marked surfaces, and also with conglom- 
erate layers composed of pebbles and bowlders of coarse red jasper in @ 
matrix of white, red, or ereenishisand 2 - tse eee eee ee 500 
Compact light-reddish limestones (some of them fit for burning into quicklime), 
interstratified with shales and sandstones of the same color ...-....-.-..-.---- 80 
Indurated red and yellowish-gray marl, usually containing a large proportion of 
the carbonates of lime and magnesia.® This division runs through the center 
of the peninsula between Thunder Bay and Black Bay, and may, in this re- 
gidn, have a thickness of 3b0Heet or more. = sane ae 8 eee yee eee 350 
Red and white sandstones, with conglomerate layers, the red sandstones being 
often very argillaceous and variegated with green spots and streaks, and hav- 
ing many of their surfaces ripple-marked. These rocks are found all along 
the northwest side of Black Bay as far up as the township of McTavish....-- 200 
This succession is of interest as presenting us with the only instance 
of a considerable accumulation of detrital matter at so low a horizon in the 
entire extent of the Keweenaw Series; and the only instance, also, so far as 
the immediate basin of Lake Superior is concerned—not taking local infil- 
trations of calcite into account—of the occurrence of calcareous and dolo- 
mitic matter in the sandstones of this series. The reference of these rocks 
to the Keweenaw Series has, in fact, been questioned by Macfarlane® and 
Hunt;’ the former regarding them, along with the underlying slates, as the 
?Geology of Canada, 1863, p. 70. 2 Op. cit., p. 319. 
SMacfarlane finds the red sandstone to contain 123 per cent. of carbonate of lime and 11 per cent. 
of carbonate of magnesia. 
4Macfarlane found them to contain 13 per cent. of carbonate of lime and 12 per cent. of carbonate 
of magnesia. 
5The amount varying, in the specimens analyzed by Macfarlane, from 21 to 343 per cent. of the 
carbonate of lime, and from 7} to 13} of the carbonate of magnesia. : 
®Canadian Naturalist; New Series, III, p. 252; IV, p.3s. 
7Second Geological Survey of Pennsylvania; Azoic Rocks; Part I, p. 241. 
