The Klastline Formation is a

stratigraphic unit A stratigraphic unit is a volume of rock of identifiable origin and relative age range that is defined by the distinctive and dominant, easily mapped and recognizable petrographic, lithologic or paleontologic features (facies) that characterize ...

Pleistocene The Pleistocene ( , often referred to as the '' Ice age'') is the geological epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was finally confirmed ...

age in northwestern

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

, Canada.

Description

The Klastline Formation is part of the

Mount Edziza volcanic complex The Mount Edziza volcanic complex is a large and potentially active north-south trending complex volcano in Stikine Country, northwestern British Columbia, Canada, located southeast of the small community of Telegraph Creek. It occupies the sout ...

. This is the second largest eruptive centre in the

Northern Cordilleran Volcanic Province The Northern Cordilleran Volcanic Province (NCVP), formerly known as the Stikine Volcanic Belt, is a geologic province defined by the occurrence of Miocene to Holocene volcanoes in the Pacific Northwest of North America. This belt of volcanoes e ...

, attaining a volume of and an area of . It consists of

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 ...

es,

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and p ...

es,

cinder cone A cinder cone (or scoria cone) is a steep conical hill A conical hill (also cone or conical mountain) is a landform with a distinctly conical shape. It is usually isolated or rises above other surrounding foothills, and is often of volcanic ...

s and

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruption ...

s that have formed in the last 12 million years. The Klastline Formation was emplaced during the fourth magmatic cycle of the Mount Edziza volcanic complex. It consists of

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcan ...

s that were issued from at least three eruptive centres on the northern and eastern sides of the Mount Edziza volcanic complex which produced minor

lava fountain Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

s and small pyroclastic cones. Lava of the Klastline Formation temporarily blocked streams adjacent to the volcanic complex which resulted in the creation of

lava dam A volcanic dam is a type of natural dam produced directly or indirectly by volcanism, which holds or temporarily restricts the flow of surface water in existing streams, like a man-made dam. There are two main types of volcanic dams, those crea ...

med lakes.

Lithology

The Klastline Formation consists primarily of

alkali basalt Alkali basalt or alkali olivine basalt is a dark-colored, porphyritic volcanic rock usually found in oceanic and continental areas associated with volcanic activity, such as oceanic islands, continental rifts and volcanic fields. Alkali basalt ...

flows

interbedded In geology, interbedding occurs when beds (layers of rock) of a particular lithology lie between or alternate with beds of a different lithology. For example, sedimentary rocks may be interbedded if there were sea level variations in their sedimen ...

with sand and gravel. It contains two named subunits; the Village Member which consists of regular

columnar basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of ...

jointing, and the Junction Member which is characterized by swirly jointed basalt. A sedimentary sequence referred to as the Days Ranch Member is preserved between various remnants of the Village Member. It consists of well-sorted sand and gravel.

Distribution

The Klastline Formation has a volume of , making it one of the least voluminous

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 expo ...

s of the Mount Edziza volcanic complex. It occurs along the valleys of Kakiddi Creek and the

Klastline River Klastline can refer to: * Klastline Cone, a volcanic cone in British Columbia, Canada * Klastline Plateau, a plateau in British Columbia, Canada {{geodis ...

where it forms isolated, usually flat-topped erosional remnants with high

escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. The terms ''scarp'' and ''scarp face'' are often used interchangeably with ''esca ...

s. Klastline Cone on the western side of Kakiddi Valley was the main source of the Klastline Valley flows. Remnants of Klastline Formation basalt flows south of Buckley Lake form scattered

outcrop An outcrop or rocky outcrop is a visible exposure of bedrock or ancient superficial deposits on the surface of the Earth. Features Outcrops do not cover the majority of the Earth's land surface because in most places the bedrock or superficia ...

s and likely issued from a low, grassy hill surrounded by younger

Big Raven Formation The Big Raven Formation is a stratigraphic unit of Quaternary age in northwestern British Columbia, Canada. It is the youngest and least voluminous geological formation of the Mount Edziza volcanic complex (MEVC); it overlies at least six older f ...

basalt flows. A sequence of Klastline Formation basalt flows is exposed along the

Stikine River The Stikine River is a major river in northern British Columbia (BC), Canada and southeastern Alaska in the United States. It drains a large, remote upland area known as the Stikine Country east of the Coast Mountains. Flowing west and south ...

downstream from the Klastline River confluence.

Age

The Klastline Formation was probably deposited over a long period of eruptive activity during the

Middle Middle or The Middle may refer to: * Centre (geometry), the point equally distant from the outer limits. Places * Middle (sheading), a subdivision of the Isle of Man * Middle Bay (disambiguation) * Middle Brook (disambiguation) * Middle Creek (d ...

Late Pleistocene The Late Pleistocene is an unofficial age in the international geologic timescale in chronostratigraphy, also known as Upper Pleistocene from a stratigraphic perspective. It is intended to be the fourth division of the Pleistocene Epoch within ...

K–Ar dating Potassium–argon dating, abbreviated K–Ar dating, is a radiometric dating method used in geochronology and archaeology. It is based on measurement of the product of the radioactive decay of an isotope of potassium (K) into argon (Ar). Potassium ...

of a large remnant of Klastline Formation basalt in Klastline Valley has yielded an age of 0.62 ± 0.04 million years. This age is consistent with its

stratigraphic Stratigraphy is a branch of geology concerned with the study of rock layers ( strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostr ...

position between the Edziza and Kakiddi formations, which have ages of 0.9 million years and 0.3 million years, respectively. A K–Ar date of 0.33 ± 0.03 million years has been obtained from the top of a Village Member basalt flow on the

Tahltan River The Tahltan River is a tributary of the Stikine River in northwest part of the province of British Columbia, Canada. It flows generally east and southeast about Length measured using Google Maps path tool, BCGNIS coordinates, topographic maps, anTo ...

, suggesting that Klastline

volcanism Volcanism, vulcanism or volcanicity is the phenomenon of eruption of molten rock (magma) onto the Earth#Surface, surface of the Earth or a solid-surface planet or moon, where lava, pyroclastics, and volcanic gases erupt through a break in the su ...

may have been coeval with that of the Kakiddi Formation. Village Member basalt about downstream from the mouth of the Tahltan River on the east bank of the Stikine River has yielded a similar Ar–Ar date of 0.30 ± 0.10 million years.

References

{{Mount Edziza volcanic complex Geologic formations of the Mount Edziza volcanic complex Pleistocene British Columbia Pleistocene volcanism Basalt formations Stikine River

Description

Lithology

Distribution

Age

See also

References