Nechako River Map-Area
Early Jurassic Time

It is probable that in Early Jurassic time the marine basin covered much
the same area as it did in Triassic time except that the margin of the central
land area was farther south. Terrestrial red beds accumulated, probably on
marginal plains in the northwest part of Nechako River map-area, while marine
sedimentation and volcanism, similar to that of Upper Triassic time, occurred
in the remainder of the area. Apparently the land underwent successive uplifts
which extended the margins of the land area and caused the reworking of earlier
deposits. The intrusion of the Topley granites probably began during this period
and was closely related to these uplifts. Farther south, along the western boundary
of the map-area, volcanic islands apparently were formed near the close of Early
Jurassic time and were the forerunners of the land area that formed the southwest
margin of the Middle Jurassic basin.

a

Frangois Lake pa

Area of accumulation of a —<
Lower Jurassic Red beds

“+(| + MT. GREER

<7
™?

Ret

+ KUYAKUZ MTN.

Upper Triassic strand line.........

Lower Jurassic strand line........, __
ees

FIGURE 3. Suggested positions of Upper Triassic and Lower Jurassic
strand lines within Nechako River map-area.

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