Physiography and Glaciation

Table I
SUBDIVISIONS
SysTEMS AREAS =
Primary Secondary Tertiary Quaternary
Columbia |
Mountains |
Fraser Plateau |
Nechako Plain |
Nechako Francois Lake Nulki Hills
Plateau Highlands ee
Interior System |Southern Plateau) Interior Plateau | | Cheslatta Hills
and Mountain fee een ee Sk
area Tetachuck Hills

| Plateaux and

Entiako Plateau

| | Valleys —
| Chedakuz Valley

Euchiniko Plateau

Interior Ranges | Fawnie Range

| Nechako Range

\— - - — —

Central Plateau |
and Mountain |
area |

graphically. Fraser Plateau is underlain mainly by Tertiary volcanic rocks whereas
the Nechako Plateau is underlain mainly by pre-Tertiary volcanic, sedimentary,
and granitic rocks. Nechako Plateau is more dissected than Fraser Plateau
and is rougher in detail, with greater local relief.

The Nechako Plain, although extensively underlain by flat-lying volcanic
rocks, more probably takes its relatively even surface from extensive erosion
which truncated rocks of several ages, and from a deep covering of glacial
till or silt and glacial lake clay (Armstrong, 1949, p. 8).

Francois Lake Highlands (see Pl. Il) is a good descriptive name and its
further subdivision into groups of hills is topographically correct. These hills
are in no way oriented into ranges of mountains although some are referred
to as mountains. Most of these hills are less than 5,000 feet in elevation with
less than 1,500 feet relief, and although some may rise abruptly, most rise

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