The Pylon Assemblage is an accreted

terrane In geology, a terrane (; in full, a tectonostratigraphic terrane) is a crust fragment formed on a tectonic plate (or broken off from it) and accreted or " sutured" to crust lying on another plate. The crustal block or fragment preserves its own ...

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main The three types of rocks, rock types, the others being Sedimentary rock, sedimentary and metamorphic rock, metamorphic. Igneous rock ...

s in southwestern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...

, located about north of

Vancouver Vancouver ( ) is a major city in western Canada, located in the Lower Mainland region of British Columbia. As the List of cities in British Columbia, most populous city in the province, the 2021 Canadian census recorded 662,248 people in the ...

. It is named after Pylon Peak, a summit of the

Mount Meager massif The Mount Meager massif is a group of volcanic peaks in the of the Coast Mountains in southwestern British Columbia, Canada. Part of the Cascade Volcanic Arc of western North America, it is located north of Vancouver at the northern end of the ...

. 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 () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...

lava flows. It locally overlies

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 (also known as The Devastator), the lowest and southernmost subsidiary p ...

and older basal

breccia Breccia () is a rock composed of large angular broken fragments of minerals or rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of di ...

Porphyritic Porphyritic is an adjective used in geology to describe igneous rocks with a distinct difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all ...

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more prope ...

andesite of the youngest unit underlies much of the southern and western portions of Meager.

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 Devastator Peak is a d ...

, a

volcanic plug A volcanic plug, also called a volcanic neck or lava neck, is a volcanic object created when magma hardens within a vent on an active volcano. When present, a plug can cause an extreme build-up of high gas pressure if rising volatile-charged mag ...

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 A geological formation, or simply formation, is a body of rock having a consistent set of physical characteristics ( lithology) that distinguishes it from adjacent bodies of rock, and which occupies a particular position in the layers of rock exp ...

comprising Meager.

References

{{coord missing, British Columbia Mount Meager massif Volcanism of British Columbia Geologic formations of British Columbia Pleistocene volcanism

See also

References