Big Raven Formation

The Big Raven Formation is a stratigraphic unit of Holocene age in northwestern British Columbia, Canada.

Big Raven Formation
Stratigraphic range: Holocene
Nahta Cone of the Big Raven Formation
TypeGeological formation[1]
Unit ofMount Edziza volcanic complex[2]
Sub-unitsSheep Track Member[1]
OverliesRaspberry Formation, Armadillo Formation, Nido Formation, Ice Peak Formation, Klastline Formation[1]
Lithology
PrimaryAlkali basalt, hawaiite[1]
OtherTrachyte[1]
Location
Coordinates57.5°N 130.6°W / 57.5; -130.6[2]
RegionBritish Columbia[1]
CountryCanada[1]
Type section
Named forBig Raven Plateau[1]
Named bySouther et al., 1984[3]

Description

The Big Raven Formation is part of the Mount Edziza volcanic complex.[1] This is the second largest eruptive centre in the Northern Cordilleran Volcanic Province, attaining a volume of 670 cubic kilometres (160 cubic miles) and an area of 1,000 square kilometres (390 square miles).[4] It consists of shield volcanoes, stratovolcanoes, cinder cones and lava domes that have formed in the last 12 million years.[1][5]

Lithology

The Big Raven Formation consists primarily of alkali basalt and hawaiite. These rocks form lava flows and small volcanic cones throughout the Mount Edziza volcanic complex.[1] A small volume of comenditic trachyte pumice is assigned to the Sheep Track Member, the only formally named sub-unit of the Big Raven Formation.[3]

Distribution

The Big Raven Formation has a volume of 1.7 km3 (0.41 cu mi), making it the least voluminous geological formation of the Mount Edziza volcanic complex.[1][2] It includes the Desolation Lava Field on the northern slope of Mount Edziza, the Snowshoe Lava Field on the southwestern slope of Ice Peak, the Mess Lake Lava Field east of Mess Lake, Nahta Cone near the northern edge of the Arctic Lake Plateau, Kana Cone on the extreme northern flank of the Mount Edziza volcanic complex, two unnamed cinder cones and associated lava flows in Walkout Creek valley, and Cinder Cliff, Icefall Cone and Ridge Cone on the eastern slope of Mount Edziza.[1]

Age

The Big Raven Formation is the youngest geological formation of the Mount Edziza volcanic complex. It was deposited during the Holocene after Pleistocene glaciation had retreated from the area. As a result, the Big Raven Formation has not undergone glacial erosion. The young age of the Big Raven Formation is also indicated by its almost unchanged geomorphology.[1] A radiocarbon date of 610 CE ± 150 years has been obtained from charred willow twigs preserved beneath a thick layer of Big Raven basaltic tephra from Williams Cone in the Desolation Lava Field.[1][6]

See also

References
  1. Souther, J. G. (1992). The Late Cenozoic Mount Edziza Volcanic Complex, British Columbia. Geological Survey of Canada. pp. 23, 26, 28, 213, 214, 226, 228, 234, 235, 246, 253, 267. doi:10.4095/133497. ISBN 0-660-14407-7.
  2. Edwards, Benjamin Ralph (1997). Field, kinetic, and thermodynamic studies of magmatic assimilation in the Northern Cordilleran Volcanic Province, northwestern British Columbia (PhD). University of British Columbia. p. 10. ISBN 0-612-25005-9.
  3. "Big Raven Formation". Lexicon of Canadian Geologic Units. Government of Canada. Retrieved 2023-09-06.
  4. Edwards, Benjamin R.; Russell, James K. (2000). "Distribution, nature, and origin of Neogene–Quaternary magmatism in the northern Cordilleran volcanic province, Canada". Geological Society of America Bulletin. Geological Society of America. 112 (8): 1284. doi:10.1130/0016-7606(2000)112<1280:dnaoon>2.0.co;2. ISSN 0016-7606.
  5. "Edziza: Synonyms & Subfeatures". Global Volcanism Program. Smithsonian Institution. Archived from the original on 2021-08-10. Retrieved 2023-09-07.
  6. "Edziza: Eruptive History". Global Volcanism Program. Smithsonian Institution. Archived from the original on 2023-05-20. Retrieved 2023-09-18.
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