Big Raven Formation

Big Raven Formation
Stratigraphic range: Quaternary
0.020–0 Ma
↓
A dark-coloured volcanic cone with a summit crater rising above a sparsely snow-covered rocky plateau.
Nahta Cone of the Big Raven Formation
TypeGeological formation[1]
Unit ofMount Edziza volcanic complex[2]
Sub-unitsSheep Track Member[1]
OverliesNido Formation, Spectrum Formation, Raspberry Formation, Armadillo Formation, Klastline Formation, Ice Peak Formation, Edziza Formation[3][4]
Lithology
PrimaryAlkali basalt, hawaiite[1]
OtherTrachyte[1]
Location
CoordinatesBig Raven Plateau[5]
57°42′59″N 130°45′06″W / 57.71639°N 130.75167°W / 57.71639; -130.75167[6]

Arctic Lake Plateau[5]
57°17′59″N 130°46′06″W / 57.29972°N 130.76833°W / 57.29972; -130.76833[7]

Kitsu Plateau[8]
57°27′59″N 130°45′06″W / 57.46639°N 130.75167°W / 57.46639; -130.75167[9]
RegionBritish Columbia[10]
CountryCanada[10]
Type section
Named bySouther et al., 1984[11]
Map
Location in Mount Edziza Provincial Park

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 formations of this volcanic complex. The main volcanic rocks of the Big Raven Formation are alkali basalts and hawaiites, although a small volume of trachyte comprises the Sheep Track Member. These rocks were deposited by volcanic eruptions in the last 20,000 years during the latest magmatic cycle of the MEVC. Alkali basalt and hawaiite are in the form of lava flows and small volcanic cones while trachyte of the Sheep Track Member is mainly in the form of volcanic ejecta which covers an area of about 40 square kilometres (15 square miles).

The Big Raven Formation is widespread throughout the MEVC, occurring on or adjacent to the Arctic Lake, Big Raven and Kitsu plateaus. Two lava fields of the Big Raven Formation occur on the Big Raven Plateau which in total contain at least 22 separate vents that issued lava flows. At least four isolated Big Raven vents occur on the eastern flank of Mount Edziza and on the extreme northern slope of the Big Raven Plateau. The Kitsu Plateau contains a much smaller Big Raven lava field near the edge of an escarpment; at least three separate vents are in this lava field. Two isolated Big Raven vents on and adjacent to the Arctic Lake Plateau produced lava flows, as did two isolated Big Raven vents in Walkout Creek valley. Most Big Raven vents are marked by a cone of pyroclastic rocks.

  1. ^ a b c d Souther 1992, p. 213.
  2. ^ Edwards, Benjamin Ralph (1997). Field, kinetic, and thermodynamic studies of magmatic assimilation in the Northern Cordilleran Volcanic Province, northwestern British Columbia (PhD thesis). University of British Columbia. pp. 3, 10, 11. ISBN 0-612-25005-9.
  3. ^ Souther 1992, p. 246.
  4. ^ Souther, J. G. (1988). "1623A" (Geologic map). Geology, Mount Edziza Volcanic Complex, British Columbia. 1:50,000. Cartography by M. Sigouin, Geological Survey of Canada. Energy, Mines and Resources Canada. doi:10.4095/133498.
  5. ^ a b Souther 1992, p. 235.
  6. ^ "Big Raven Plateau". BC Geographical Names. Archived from the original on 2021-09-30. Retrieved 2024-04-03.
  7. ^ "Arctic Lake Plateau". BC Geographical Names. Archived from the original on 2021-09-25. Retrieved 2024-04-03.
  8. ^ Souther 1992, p. 234.
  9. ^ "Kitsu Plateau". BC Geographical Names. Archived from the original on 2021-10-01. Retrieved 2024-04-03.
  10. ^ a b "Edziza: General Information". Global Volcanism Program. Smithsonian Institution. Archived from the original on 2021-08-10. Retrieved 2021-09-25.
  11. ^ "Big Raven Formation". Lexicon of Canadian Geologic Units. Government of Canada. Retrieved 2023-09-06.