60 Adams—Contribution to our knowledge of the Laurentian. 
tion of which only is embraced within the limits of the map. 
The rest of the crystalline area is occupied by the Grenville 
Series with the exception of a subordinate area about Tremb- 
ling Mountain and possibly another to the west of St. Jerome, 
which are to be referred to the Fundamental Gneiss. The 
erystalline limestones of the Grenville Series are represented on 
the map. The distribution of these in the extreme southwest 
corner has been taken from Logan’s map, as this portion of the 
area has not been personally examined in detail. It will be 
observed that these limestones are cut off by the anorthosite 
intrusions. The various gneisses, quartzites and pyroxenic 
rocks making up the rest of the Laurentian have in the map 
been classed together, as it would be impossible to represent 
them separately on so small ascale. In one portion of the 
area, however, the township of Brandon, they have been sepa- 
rated and will be so represented on a map accompanying the 
report above mentioned. | 
Desiring to maintain as objective an attitude as possible, the 
Grenville Series will not in the present paper be referred to as 
stratified or bedded; it may be safely stated however that the 
rocks composing it frequently alternate in well-defined bands, 
the whole series also exhibiting a well-defined foliation usually 
parallel to the banding. The series thus often has a decidedly 
stratified appearance similar to that presented by bedded sedi- 
mentary rocks. 
The direction of the strike where actually observed is, on 
the accompanying map, indicated by the short black dashes; 
these are connected up by interrupted lines which serve to 
bring out the structure more distinctly. 
It will be seen that the whole area was, at a time long ante- 
dating the Potsdam, but subsequent to the intrusion of the 
anorthosite and granite, subjected to great pressure which 
. Induced a foliation not only in the banded gneisses but in por- 
tions of these intrusions also, as is especially well seen in the 
eastern portion of the Morin anorthosite. It will also be 
noted that probably owing to a flattening of the eastern portion 
of this anorthosite mass in a north and south direction by this 
pressure, a certain movement of both gneiss and anorthosite 
along the line of contact has taken place, especially to the 
northeast of Lac Ouareau, where the gneiss is seen to undergo 
an abrupt change in strike amounting to nearly ninety degrees 
along its contact with the anorthosite, while there is every- 
where a tendency for the strike to follow the outline of the 
large intrusions, the small intrusions being squeezed flat and 
foliated with the surrounding rocks. 
We have here then a marked example of the structural 
effects of pressure acting on a large Archean area. 
