Page 51 - Annuaire Statistique Québec - 1918

GEOLOGY 25

rocks of Pre-Cambl'ian ba~ement, more particularly along the axes of
folding. Moreover, this region having been the scene of great igneous
and volcanic activity, we find the sedimentary rocks penetrated and
invaded by bodies of acid and basic igneous rocks, often batholitic
in t'heir dimensions, the nature of which ranges from very acid granites
to peridotites and serpentines.
The Appalaehian Region is characterized by valuable economic
minerais. The chief ones at pl'esent being worked in the Province of
Quebec are the Asbestos deposits, which are the largest known in the
worId, and the Coppel' deposits of the Sherbrooke district. Of less
importance are, deposits of Gold, Chromite, Iron, Lead.

The highest rock formations known in the Province of Quebec
~onsist of a rim of Devono-Carboniferous ':oeks in the Gaspé peninsula.

The St. LRwrence Lowlands.

The region of the St. LavvTence Lowlands is bounded on the north
by the southern edge of the Laurentian Plateau, whieh approximately
follows a Ene joining the cities of Dttawa and Q,uebec. '1'0 the south-
east, it ab'uts against the great Champlain-St. Lawrence fault, which
follows a hne from the foot of Lake Champlain to Qllebec city. This
fa'ult separates the nearly horizontal Paleozoic strata of the Lowlands,
from the highly disturbed Appalachian region.
The St. Lawrence Low"lands are underiain by gently dipping beds
of sandstone, shale and limestone of Paleozoic age (Ordovician, Silurian
and Devonian) which succeed one another without break or unconfor-
mity. Over certain areas, they lie in lo\v, broad, dome-like folds, and
at times are travel'sed by faults, sorne \Jf which are of considerable throw,
but nevertheJess compared \vith the highly folded and faulted measures
of the Appalachian, they may be said to be undisturbed.

The district in question is ahnost whoIl}' occupied by strata of
Ordovician age. In a general way, it may be said that the various divi-
sions of these rocks occW' in bands, of successively younger formations,
roughly paralleling the edge of the ancient crystalline rocks on the north;
the oldest members occur to the north, and the youngest generally
border the St. Lawrence and Champlain fauIt. Owing to the level
character of the lowlands and the undisturbed character of the rocks,
the superficial deposits are thick, and outcrops are very unfrequent.
The t.otal voh-me of the Ordovician system is very great; in the neigh-
bourhood of the city of Montreal, there are 4,350 feet of strata, from
the base of the Potsdam to the highest members of the Lorraine there
exposed. .
The plain of the St. Lawrence Lowlands is characterized by a
uniformity of leveJ, and it may be called quite fiat. But this uniforrpity