ai on

North and south of Nation Lakes the Takla group
strata trend nearly east and west, but north of Germansen
Lake and Omineca River the general trend is northwesterly.

The Takla group, as. exposed in the Takla map-area
to the west, has provided marine fossils of Upper Triassic
and Lower and Middle Jurassic age; in the McConnell Creek
map-area to the northwest it contains Middle and Upper
Jurassic faunas. In the Manson Creek map-area the diagnostic
Upper Triassic fossil Halobia was identified from argillite
outcropping south of Chuchi Lake. No other fossils were
found in this area. More than 3,000 square miles of Fort
Fraser, Takla, and Manson Creek map-areas is underlain by
rocks of the Takla group, and in this great area fossils have
been found in only nine localities. The formations in the
group, whether of Triassic or Jurassic age, are composed: of
lithologically similar types and, except “where fossils were
found, could not be mapped separately.

North of Germansen Lake the Takla and Cache Creek
groups are in contact along a fault. In the southeastern
part of,\the map-area the contact between the two groups is
obscured by drift, but they appear to be structurally
conformable, though . representing an erosional interval that
probably extended | from, Middle Permian to Upper Triassic time.

micas Intrusions .

The name Omineca intrusions has been applied to
numerous bodies of intrusive rocks of Upper’ Jurassic or Lower
Cretaceous age that are exposed in the Omineca mountain
system. They range in size from sills and dykes to batholiths,
and in composition from pyroxenite to granite, granodiorite
and einer diorite predominating.

The largest known body of these rocks is the
batholith that extends from Chuchi Lake northwest across the
Takla, Aiken Lake, and McConnell Creek map-areas. It
underlies an area of at least 1,200 square miles. Only the
southeastern part, 125 square miles, of this batholith
outcrops: in the Manson Creek area. Here it consists of
medium- to coarse-grained diorite composed of white and jade
green feldspar, dark green hornblende and pyroxene, and black
biotite. The contact of this diorite with the invaded green
andesites of the Takla group is gradational, probably as a
result of assimilation of the andesites by the diorite.

The batholith that outcrops between Tsaydaychi and
Germansen Lakes is about 300 square miles in area, and
consists mainly of medium-grained, pink and light green
granodiorite and quartz diorite grading in places into
granite and diorite.

The small stock of granodiorite near Klawli Lake
carries phenocrysts of pink orthoclase up to 2 inches long
in a matrix of white plagioclase, quartz, and biotite.

In addition to the intrusive rocks ane there
are many related dykes and sills up to 100 feet wide of
similar composition to the batholithic intrusions.

‘The Omineca intrusions cut formations of the Takla
group, which range in age from Upper Triassic to Upper