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TitleGeology of the Monmouth Creek volcanic complex, Garibaldi volcanic belt, British Columbia
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorWilson, A M; Russell, J K; Kelman, M C; Hickson, C J
SourceGeological Survey of Canada, Current Research (Online) 2016-2, 2016, 16 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Mediaon-line; digital
File formatpdf
ProvinceBritish Columbia
Lat/Long WENS-123.2500 -123.1667 49.7500 49.6667
Subjectsigneous and metamorphic petrology; geochemistry; petrography; igneous rocks; volcanic rocks; andesites; alluvial deposits; volcanic features; x-ray fluorescence; x-ray fluorescence analyses; geochemical analyses; geochemical interpretations; sedimentary rocks; Monmouth Creek Volcanic Complex; Garibaldi Volcanic Belt; Mount Cayley Volcanic Field; Quaternary; Tertiary
Illustrationslocation maps; cross-sections; photographs; photomicrographs; tables; diagrams
ProgramPublic Safety Geoscience National Hazard assessment
Released2016 11 14
AbstractQuaternary intermediate volcanic rocks of the Monmouth Creek volcanic complex, located west of Squamish, British Columbia were mapped to determine their extent and origin. The deposits are distributed within a deep embayment in the granite wall of the Howe Sound, and have a present day thickness of about 200 m. They comprise a sequence of andesite lavas, domes, and lobes, and associated monolithological andesitic breccia units. Cogenetic, en echelon andesite dykes intrude the entire complex, and their erosional remnants outcrop as a series of steep-sided, enigmatic pinnacles and spires. On the basis of petrographic and geochemical criteria the authors identify two distinct magma types expressed as aphyric andesite and hornblende andesite. On the basis of field relationships and the properties of the volcanic deposits and their distributions, the Monmouth Creek volcanic complex is shown to have a glaciovolcanic origin. A model is presented for the emplacement of the volcanic deposit that indicates the presence of a major fjord-filling glacier, likely greater than 1 km thick and occupying Howe Sound to an elevation of about 800 m above present-day sea level at the time of eruption.
Summary(Plain Language Summary, not published)
We mapped the geology of the Monmouth Creek volcanic complex (MCVC), located on the western shore of Howe Sound due west of Squamish, British Columbia in southwest BC's Garibaldi Volcanic Belt. The MCVC is a series of lava flows, breccia (broken rock), and dikes (vertical lava intrusions), cropping out as steep rock pinnacles. Studies of the chemistry and microscopic textures of the rocks indicate two different lava types. The largest and best-known pinnacle (known locally as the 'Castle'), has a contentious origin but our mapping suggests it is a deeply eroded dike. Textures and other features of the rocks (such as fracture patterns) indicate eruption under and against glacier ice that was likely more than 1 km thick.

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