The Little Iskut Formation is a
stratigraphic unit of
Miocene age in northwestern
British Columbia, Canada.
Naming
The Little Iskut Formation takes its name from the
Little Iskut River
The Little Iskut River is a tributary of the Iskut River in the northwest part of the Provinces and territories of Canada, province of British Columbia, Canada, in Cassiar Land District. From its source at Little Ball Lake in Mount Edziza Provincia ...
, a
tributary of the
Iskut River which flows southeast from the southern end of the
Mount Edziza volcanic complex.
Geology
The Little Iskut Formation has a volume of , making it the seventh most voluminous
geological formation comprising the Mount Edziza volcanic complex.
It occurs at the northeastern end of the
Spectrum Range
The Spectrum Range, formerly called the Spectrum Mountains and the Rainbow Mountains, is a subrange of the Tahltan Highland in the Stikine Country of northwestern British Columbia, 20 km west of the Stewart-Cassiar Highway, south of Moun ...
where it covers a roughly wide area. A small portion of the Little Iskut Formation is exposed in the
Mess Creek Escarpment The Mess Creek Escarpment is an escarpment in northwestern British Columbia, Canada, located on the east side of Mess Creek below Mess Lake and southeast of Telegraph Creek. It forms the central-western flank of the Mount Edziza volcanic complex, ex ...
to the west.
The Little Iskut Formation consists of
trachybasalt flows and
breccia. It ranges in thickness from on Stewpot Ridge to about near the middle of Artifact Ridge. The Little Iskut Formation originally formed a small symmetrical
shield volcano
A shield volcano is a type of volcano named for its low profile, resembling a warrior's shield lying on the ground. It is formed by the eruption of highly fluid (low viscosity) lava, which travels farther and forms thinner flows than the more v ...
during the Miocene.
The Little Iskut Formation conformably overlies the
Raspberry Formation
The Raspberry Formation is a stratigraphic unit of Miocene age in northwestern British Columbia, Canada.
Naming
The Raspberry Formation takes its name from Raspberry Pass, a mountain pass cutting through the central portion of the Mount Edziz ...
south of Bourgeaux Creek. Little Iskut trachybasalt is overlain by
rhyolite
Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral ...
of the
Armadillo Formation
The Armadillo Formation is a stratigraphic unit of Miocene age in northwestern British Columbia, Canada.
Naming
The Armadillo Formation takes its name from Armadillo Peak, a volcanic peak east of Raspberry Pass in the middle of the Mount Edziza v ...
and
basalt of the Nido Formation. Two subunits comprise the Little Iskut Formation. The upper unit consists entirely of trachybasalt lava flows while the lower unit consists of abundant breccia.
has yielded an age of 7.2 ± 0.3 million years for Little Iskut trachybasalt.
See also
*
Volcanism of Western Canada
References
{{Northern Cordilleran volcanoes
Geologic formations of British Columbia
Mount Edziza volcanic complex
Miocene Canada
Miocene shield volcanoes
Shield volcanoes of Canada