Whitesail Lake Map-Area

and tuffs, now mainly greenstones and amphibolites, cut by granitic dykes
and cupolas; and an upper layered series consisting of quartzite, andesite
tuff, schist, and limestone (see Figure 3). These greenstones are intruded,
near Tahtsa Lake, by dyke swarms and cupolas of coarse red granite. This
granite contains many inclusions of the older rocks and is itself cut by many
dark green to black basaltic dykes. The actual boundaries of this type of

7
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COAST RANGE INTRUSIONS OLDER ROCKS

Quartz diorite, granodiorite Layered group
WS Diorite eed Granite
7] “Complex” with numerous
small granite masses
LL] “Complex”

Fault (defined, approximate)... nn...‘ wr

Scale of Miles
0

Figure 3. Map showing surface geology along the line of the Alcan Tunnel, B.C. (After R. A. Stuart, 1955.)

rock is difficult to determine. Occupying Horetzky Creek below timber-line
and underlying Siffleur Lake and its immediate vicinity is a tongue of grey
quartz diorite and granodiorite that is younger than the red granite dykes.

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