Canadian Taconic Eriiptives. — Winchell. 361 
gone comparatively little subsequent disturbance. Its extent entitles it 
to be recognized as one of the most important geological features of 
North America. 
There is but one other Canadian locality where the Taconic 
eruptives may be identified. It is the region of Thunder bay 
on the northwest coast of lake Superior. By the Canadian 
geologists the rocks of the Animikie have been referred con- 
sistently and uniformly to the age of the Lower Cambrian, but 
they fail, for the most part, to apprehend their identity with 
the rocks of the original Huronian — a correlation to which 
American geology is first of all indebted to the late R. D. Ir- 
ving. The Animikie rocks extend into Minnesota and some of 
their structural and petrographic characters as they there ap- 
pear will be mentioned when we come to consider especially the 
Lake Superior basin as a structural unit. At the present it is 
only necessary to refer to some of the descriptions that have 
been published. Logan put them in the "lower volcanic 
group" of the Copper-bearing series, and later made them of 
"Quebec" age. Selwyn distinctl}' affirmed their Cambrian 
age. Irving showed that they are the horizontal and unmod- 
ified strata of the original Huronian, which, until the confu- 
sion and misconception introduced by the extension of that 
term downward to the Archean gneisses, had been classed as 
Cambrian by Canadian and English geologists. 
At the bottom is a great mass of chert or flint, replaced 
sometimes by an erosion-conglom erate, very siliceous, made 
up of pebbles from the underljdng gneisses and schists. Lime- 
stone appears in association with the basal beds, but this fea- 
ture is not greatly developed. In this limestone are masses of 
chert usually somewhat angular. Above this rises a great 
thickness of black slates, siliceous gray slates, very fine gray- 
wackes and quartzytes. These beds are nearly horizontal, 
and, according to Irving, they are non-conformably overlain by 
the sandstones and marls of the lower Keweenawan in the vi- 
cinity of Black baj'. That, however, which liere is to be spe- 
cially noted is their association with eruptives. These have 
been described by Bell, Ingall and Lawson,* and by others. 
*RoiJKRT Bki,l, Geol. Sur. Canada, Rep. for 18(59, pp. 313-303: ditto, 
1872, pp. 87-03. 
E. D. Ingai,!,, (Jeol. Sur. Can., Rep. for 1H87-8S, part 2. Report H, pp. 
1-131. 
A. C. Lawson, Geol. Sur. Miimcsdia. liulletin 8. The laccolitic sills 
of the northwest coast of lake Sui)frior, 18!)3. 
