35 
large mass of granite; he mentions the quartz-porphyry on the railway 
west of Agassiz, which he regarded as of Lower Cretaceous (?) age, and 
with an unconformable relation toward the Agassiz series. The age of 
the Agassiz series is Upper Jurassic. The quartz porphyry flows, mentioned 
by Bowen, are part of the Porphyrite series, and are of Middle Jurassic age. 
Harrison Lake valley has been produced by erosion of disordered 
sedimentary series of great thickness accompanied by several masses of 
plu tonic rocks. The long axis of the lake is located mainly on what is 
believed to be the site of a great overthrust. This fault dips steeply to the 
east; Carboniferous and Triassic rocks to the east of it are thrust over 
Jurassic and Cretaceous rocks to the west. This great fault, which extends 
beyond the limits of the area, is single throughout most of its length, but 
in the middle part of Harrison lake it is divided into several subparallel 
and oblique faults between which are wedges of rock of the nature of 
schuppen. These are well illustrated by the structure of the peninsula, 
and that of Long island. In these two areas the surface is composed of 
narrow selvages of Jurassic and Cretaceous sediments, bearing their char- 
acteristic fossils, and all dipping to the east yet alternating with one 
another in a perfectly bewildering fashion. Such an arrangement could 
not possibly be the result of peculiarities of deposition, and could have been 
formed only by a succession of thrust faults. Throughout most of the 
zone the rocks have been considerably crushed. 
The oldest rocks lying to the east of the thrust fault are dark grey 
argillites with massive limestone lenses bearing Pennsylvanian fossils. 
These crop out over the west flank of Bear mountain, at the south end of 
the area. They dip steeply to the east, being bounded on the west by the 
thrust fault, and to the east by an overlying thick accumulation of sedi- 
ments, mostly argillites but with some beds of pyroclastics. This series 
borders the thrust fault on the east from Trout Lake creek to Fifteenmile 
creek and makes up all the mountains between these creeks. The sedi- 
ments dip uniformly steeply to the east (or a few degrees north of east). 
They are considerably crushed, in some places even to the state of foliation. 
So far they have yielded no fossils, but it is suspected that they are of 
Triassic age. The total thickness has not been determined, but is esti- 
mated at 14,000 or 15,000 feet. 
Overlying the supposedly Triassic series and, therefore, succeeding 
them to the north and east, is a thick formation of crushed greenstones of 
volcanic origin. This formation occupies most of the country east of 
Harrison lake. These rocks have been considerably crushed and are more 
or less schistose throughout, but apart from this there is a great resemblance 
as regards thicknesses and details of lithology and succession between these 
rocks and Jurassic rocks lying to the west of Harrison lake, but no fossils 
have been obtained from the greenstones lying east of the lake. 
The oldest rocks west of the great thrust occur in a small patch on the 
west shore of the lake immediately south of Camp cove. They consist of 
some 3,000 feet of sediments, mostly argillites with some tuffs and a con- 
glomerate bed. The conglomerate contains besides other things, pebbles 
of the fossiliferous Pennsylvanian limestones. The series has yielded no 
fossils of its own date; it belongs betw'een the top of the Pennsylvanian and 
the base of the Middle Jurassic. These rocks lie in the centre of a short 
