478 A. O. Lawson—Geology of the Rainy Lake Region. 
holding water-worn pebbles; green volcanic breccias; finer 
textured clastic rocks or ‘graywackes’; sericitic schistose quartz- 
porphyries and regular porphyroids; and soft, fissile, nearly 
always much decomposed hydromicaceous schists with which 
are associated yellowish dolomitic segregations. 
The breccias, graywackes and hydromica schists are more 
commonly met with in the northern part of the Rainy Lake 
Region than on Rainy Lake itself. This group of rocks is the’ 
same as a large portion of the series described in my report on 
the Lake of the Woods Region as the Keewatin series, and in the 
northern part of the Rainy Lake Region can be traced in direct 
continuity with that series. They will therefore be referred to 
as the Keewatin series of rocks. Concerning the geological re- 
lations of the Coutchiching and Keewatin series it is not possi- 
ble to make any sweeping statement as to their conformity or 
unconformity. The-Coutchiching rocks do not appear to have 
been at all disturbed prior to the deposition of the Keewatin, 
and the parallelism of the strike and dip of the strata or beds 
of the two series is often seen to be perfect. But as Geikie 
points out the geological conformity or unconformity of two 
sets of strata implies a broader question than the mere relations 
in space of their contiguous portions. Strata which are in close 
contact and show at certain places perfect parallelism may 
sometimes be separated by ages. The appearance of parallel- 
ism is often simulated by pressure and folding so that it is not 
always a criterion of continuity’ of geological history. The 
very diverse character of the two series, the Coutchiching and 
the Keewatin, is proof of a profound alteration in the condi- 
tions of rock formation, which implies a geological break, 
though it does nct indicate its duration. ‘ke Coutchiching 
series is seen occasionally to be cut by intrusions of a certain 
character which have not been detected traversing the Kee- 
watin rocks. These may possibly be instances of vents from 
which the traps of the Keewatin series were extravasated. In 
the northern part of the Rainy Lake Region the Keewatin 
series comes into direct contact with the Laurentian without 
the intervention of the Coutchiching series, and the conditions 
of contact are those. which have been described as obtaining in 
the Lake of the Woods Region. The contact of the horn- 
blende schists and altered traps with the Laurentian rocks is of 
the same igneous or brecciated character as that observed on 
the Rainy Lake between the Coutchiching and the Laurentian, 
the direct inference being, of course, that the Laurentian rocks 
are of more recent age as such than either the Coutchiching or 
Keewatin, although stratigraphically they are inferior to both. 
Of later age than Laurentian, Keewatin or Coutchiching is a 
system of dykes and bosses of red granite, in which there has 
