163

Little is known of the stratigraphic position within the Takla group
of the beds from which these fossils were obtained. In the vicinity of
Vega Creek, faulting is so prevalent that any reconstruction of the
original stratigraphic sequence is impossible on the basis of present informa-
tion. The horizon from which the Upper Triassic fossils were obtained
near the Granite Basin claims lies at least 5,000 feet from the base of a
continuously exposed section more than 12,000 feet thick without any
recognized duplication of beds. Thus, the only conclusion based on
information gathered in Aiken Lake map-area that can be drawn regarding
the age of the Takla group is that it includes Upper Triassic and early
Lower Jurassic beds.

CoRRELATION

In its type area in Takla map-area, the Takla group has been defined
(Armstrong, 1946) as “an apparently conformable succession of interbedded
voleanic and lesser sedimentary rocks, ranging in age from Upper Triassic
to Upper Jurassic”. The group has been found to be widely exposed in
Manson Creek map-area (Armstrong and Thurber, 1945) to the east of
Takla map-area, and in McConnell Creek map-area (Lord, 1948) adjoining
Aiken Lake map-area on the west. In Takla map-area, rocks of the Takla
group have provided marine fossils of Upper Triassic and Lower and Middle
Jurassic age; in Manson Creek map-area, of Upper Triassic age; and in
McConnell Creek map-area, the group can be separated into two divisions,
of which the lower is unfossiliferous, and the upper contains fossils
indicating Lower, Middle, and mid-Upper Jurassic horizons. The belt of
Takla group rocks exposed in Aiken Lake map-area connects the exposures
in Takla and Manson Creek, and McConnell Creek map-areas.

OMINECA INTRUSIONS
GENERAL STATEMENT

The name Omineca instrusions has been applied to the numerous bodies
of intrusive rocks of Upper Jurassic or Lower Cretaceous age that are
exposed in the Omineca and Cassiar Mountains. These bodies range in
size from sills and dykes to batholiths, and in composition from pyroxenite
and hornblendite to granite and syenite. Granodiorite, quartz diorite, and
adamellite (quartz monzonite) are the most common rock types.

The largest known body of these rocks is the batholith that extends
from Nation Lakes northwest across Manson Creek, Takla, Aiken Lake,
and McConnell Creek map-areas. This body, generally known as the
Hogem batholith (Armstrong, 1949, p. 98), occupies about 400 square miles
in the southwest corner of Aiken Lake map-area. It is a composite body
comprising a wide range of rock types, and contains many minor intrusive
bodies within the main mass. It probably represents a prolonged period
of intrusion of a differentiating magma.

Stocks, dykes, and sills, satellitic to the Hogem batholith, are abundant
in the surrounding Takla group and late Paleozoic rocks. All are relatively
small.

The various kinds of intrusive rocks composing the Omineca intrusions
within Aiken Lake map-area fall, on the basis of their composition and

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