Pylon Assemblage
Encyclopedia
The Pylon Assemblage is an accreted terrane
of igneous rock
s in southwestern British Columbia
, Canada
, located about north of Vancouver
. It is named after Pylon Peak
, a subsidiary summit of the Mount Meager
massif
. Two units make up the Pylon Assemblage, although the youngest unit comprises nearly 100% of the assemblage.
On the southern flank of Pylon Peak, the oldest unit consists of andesitic
lava flows. It locally overlies The Devastator Assemblage
and older basal breccia
. Porphyritic
plagioclase
andesite of the youngest unit underlies much of the southern and western portions of Meager. Devastator Peak
, a volcanic plug
at the southern end of the Meager massif, was the source for these lava flows between 1,000,000 and 500,000 years ago. The Pylon Assemblage represents the largest geological formation comprising Meager.
Terrane
A terrane in geology is short-hand term for a tectonostratigraphic terrane, which is a fragment of crustal material formed on, or broken off from, one tectonic plate and accreted or "sutured" to crust lying on another plate...
of igneous rock
Igneous rock
Igneous rock is one of the three main rock types, the others being sedimentary and metamorphic rock. Igneous rock is formed through the cooling and solidification of magma or lava...
s in southwestern British Columbia
British Columbia
British Columbia is the westernmost of Canada's provinces and is known for its natural beauty, as reflected in its Latin motto, Splendor sine occasu . Its name was chosen by Queen Victoria in 1858...
, Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, located about north of Vancouver
Vancouver
Vancouver is a coastal seaport city on the mainland of British Columbia, Canada. It is the hub of Greater Vancouver, which, with over 2.3 million residents, is the third most populous metropolitan area in the country,...
. It is named after Pylon Peak
Pylon Peak
Pylon Peak is the southernmost summit of the six named volcanic peaks of Mount Meager in British Columbia, Canada. Two pinnacled ridges extend out from Pylon and are named respectively the Pylons and the Marionettes. Pylon Peak overlooks the Meager Creek Hot Springs.Erosional remnants of flows from...
, a subsidiary summit of the Mount Meager
Mount Meager
Mount Meager, originally known as Meager Mountain, is a complex volcano in the Sea-to-Sky Corridor of southwestern British Columbia, Canada. It is located north of Vancouver at the northern end of the Pemberton Valley. Part of the Cascade Volcanic Arc of western North America, its summit is above...
massif
Massif
In geology, a massif is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole...
. Two units make up the Pylon Assemblage, although the youngest unit comprises nearly 100% of the assemblage.
On the southern flank of Pylon Peak, the oldest unit consists of andesitic
Andesite
Andesite is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and dacite. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende. Magnetite,...
lava flows. It locally overlies The Devastator Assemblage
The Devastator Assemblage
The Devastator Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Devastator Peak , the lowest and southernmost subsidiary peak of Meager...
and older basal breccia
Breccia
Breccia is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix, that can be either similar to or different from the composition of the fragments....
. Porphyritic
Porphyritic
Porphyritic is an adjective used in geology, specifically for igneous rocks, for a rock that has a distinct difference in the size of the crystals, with at least one group of crystals obviously larger than another group...
plagioclase
Plagioclase
Plagioclase is an important series of tectosilicate minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series...
andesite of the youngest unit underlies much of the southern and western portions of Meager. Devastator Peak
Devastator Peak
Devastator Peak, also known as The Devastator, is the lowest and southernmost of the six subsidiary peaks that form the Mount Meager massif in southwestern British Columbia, Canada. It is located west of Bralorne.-Geology:...
, a volcanic plug
Volcanic plug
A volcanic plug, also called a volcanic neck or lava neck, is a volcanic landform created when magma hardens within a vent on an active volcano. When forming, a plug can cause an extreme build-up of pressure if volatile-charged magma is trapped beneath it, and this can sometimes lead to an...
at the southern end of the Meager massif, was the source for these lava flows between 1,000,000 and 500,000 years ago. The Pylon Assemblage represents the largest geological formation comprising Meager.
See also
- Mosaic AssemblageMosaic AssemblageThe Mosaic Assemblage is a rock unit of the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It is the namesake of Mosaic Glacier, which is drained by Mosaic Creek. This geological formation formed 140,000 to less than 90,000 years ago when porphyritic...
- Job AssemblageJob AssemblageThe Job Assemblage is a geological formation comprising a portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Mount Job, a subsidiary peak of Meager. The rock unit was formed during a period of rhyodacite volcanism during the Pleistocene epoch.Around Mount...
- Capricorn AssemblageCapricorn AssemblageThe Capricorn Assemblage is a geological formation comprising the central portion of the Mount Meager massif in southwestern British Columbia, Canada. It is named after Capricorn Mountain, the third highest subsidiary peak of Meager...
- Plinth AssemblagePlinth AssemblageThe Plinth Assemblage, also known as the Plinth Formation, is an accreted terrane of igneous rocks in southwestern British Columbia, Canada, located just north of the Lillooet River and on the northern flank of the Mount Meager massif...
- Volcanism of Western CanadaVolcanism of Western CanadaVolcanism of Western Canada produces lava flows, lava plateaus, lava domes, cinder cones, stratovolcanoes, shield volcanoes, submarine volcanoes, calderas, diatremes and maars, along with examples of more less common volcanic forms such as tuyas and subglacial mounds.-Volcanic belts:*Anahim...
- List of Cascade volcanoes
- List of volcanoes in Canada