9 
occur abundantly in the underlying Precambrian series. The quartzite 
pebbles are identical with the quartzites of the underlying Phillips forma- 
tion. The occurrence of these pebbles already metamorphosed- before the 
deposition of the Burton indicates a time interval between the deposition 
of the Roosville and Burton formations. 
(3) The grit which overlies the conglomerate is characterized by the 
abundance of milky-white quartz pebbles evidently derived from the 
erosion of quartz veins which are known to be present in the Underlying 
Roosville formation and in other members of the Precambrian series. 
Green pebbles of the Roosville siliceous metargillites are also present, and 
since they are metamorphosed similarly to the metargillites of the under- 
lying Roosville, it supports the idea that the Roosville was metamorphosed 
before the Burton was laid down. Hence the idea of a time interval 
between the deposition of the Roosville and the Burton formations is 
strengthened. 
(4) The difference in degree of metamorphism of the Roosville and 
the Burton formations is very striking in the field. The laminae of the 
Roosville metargillites are so thoroughly cemented together that they 
always form steep cliffs, in fact the perpendicular walls of the Elk River 
canyon are carved in the Roosville formation. In contrast to this, the 
Burton formation weathers to a soft earth and is characterized by gentle 
slopes usually covered with vegetation. 
RELATIONSHIP OF THE PURCELL SERIES TO THE LOWER 
CAMBRIAN NEAR CRANBROOK, B.C. 
Six miles east of Cranbrook, B.C., on the Cranbrook-Fort Steele 
wagon road, an outcrop of shale containing Lower Cambrian fossils was 
exposed in an excavation made to obtain road material. In this area the 
basal member of the Lower Cambrian and its relationship to the Purcell 
series was discovered. This contact was traced northwards across the 
St. Mary river, at which point it disappears under the gravels which cover 
the floor of the Rocky Mountain trench. The accompanying map (Figure 
2) illustrates the areal distribution of the several formations. 
It is rather fortunate that in the vicinity of Cranbrook the section (an 
easterly dipping monocline) of the Purcell series which underlies the 
fossiliferous Lower Cambrian is complete down to and including its oldest 
known member, the Aldridge formation. It leaves no doubt whatever as 
to the horizon of the Purcell series, which is in contact with the Lower 
Cambrian. Also the Purcell lava, the best known horizon marker in the 
whole of the Purcell series, is exposed in the immediate vicinity of the 
Lower Cambrian-Precambrian contact. The geological column is expressed 
as follows : 
Erosion surface 
Feet 
Lower Cambrian Eager formation t 300 
Cranbrook formation 600 
Unconformity 
Precambrian Siyeh formation 
Purcell lava 
Siyeh formation 
Kitchener formation, 
Creston formation. . . 
Aldridge formation. . 
300- 
100 
4.000 
4,500 
5.000 
8.000 
