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TitleKitasu Hill: a Late-Pleistocene volcano, Swindle Island, British Columbia
LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorBednarski, J M; Hamilton, T S
SourceGeological Survey of Canada, Open File 8593, 2019, 57 pages, Open Access logo Open Access
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
File formatpdf (Adobe® Reader®)
ProvinceBritish Columbia
NTS103A/01; 103A/02; 103A/06; 103A/07; 103A/08; 103A/09; 103A/10; 103A/11
AreaKitasu Hill; Swindle Island; Milbanke Sound; Helmet Peak; Mathieson Channel; Kitasoo/Xai'Xais First Nation territory; Laredo Channel; Price Island
Lat/Long WENS-129.0000 -128.0833 52.6667 52.1333
Subjectsgeochemistry; geophysics; structural geology; stratigraphy; surficial geology/geomorphology; tectonics; Nature and Environment; Science and Technology; Pleistocene; volcanoes; cinder cones; bedrock geology; structural features; lineaments; fault zones; faults; faults, strike-slip; lithology; basalts; pillow lavas; lavas; volcaniclastics; hyaloclastites; pyroclastics; volcanic ash; agglomerates; pillow breccias; glacial deposits; glacial landforms; glacial features; erratics; gravels; moraines; meltwater channels; landforms; scarps; strandlines; deltas; source areas; geophysical surveys; paleomagnetism; petrographic analyses; geochemical analyses; brecciation; stratigraphic analyses; relative ages; topography; morphometry; geological history; tectonic history; volcanism; glacial history; glaciation; Wisconsinian glacial stage; ice flow; deglaciation; glacial erosion; stress analyses; tectonic setting; Milbanke Strandflat; Principe-Laredo Fault; Lake Island Formation; Milbanke Sound Cones; Cordilleran Ice Sheet; Alexander Terrane; ice-flow directions; limit of submergence, marine; glaciofluvial sediments; Phanerozoic; Cenozoic; Quaternary
Illustrationslocation maps; digital elevation models; geoscientific sketch maps; rose diagrams; profiles; tables; photographs; cartoons; photomicrographs; plots; stereograms; ternary diagrams; geochemical plots
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2019 12 03
AbstractKitasu Hill is a small volcano on an outer island of coastal of British Columbia and is one of a group of the four late Quaternary-aged cinder cones peripheral to Milbanke Sound. The cones coincide with major structural lineaments in the area, but their relationship with these fault zones is unknown. Kitasu volcano was examined in detail by high resolution lidar topography and by paleomagnetic, geochemical and petrographic analyses on a limited number of field samples. An elevated platform of brecciated alkaline basalt and pillow lava forms the base of Kitasu volcano. The platform is straight-edged, abruptly terminating at ~80 m above sea level (asl) and is partially overlain by a well-preserved cinder cone reaching 233 m asl with two smaller cones nested within the main crater. Stratigraphy shows that parts of the volcanic platform is underlain by hyaloclastite containing a mixture of locally sourced basaltic material and ~20% mineral grains and glacial erratic cobbles from Coast Mountain sources. The sediment characteristics and overall morphology of the volcanic platform intimates that Kitasu volcano is a tuya with the initial eruption taking place in a subglacial setting during the waning stage of the last glaciation between 14.5 and 12.5 ka BP (radiocarbon years ago). Geomorphology and petrography, showing the preservation of glass and olivine in volcanic sediment, suggest that Kitasu Hill is predominantly a monogenetic depositional feature with little or no reworking or redeposition. The final pyroclastic eruptions took place sometime after 12.3 ka BP, based on the postglacial relative sea level history of the region. It is concluded that the Milbanke cones likely erupted near the end of the last glaciation rather than during postglacial time like previously thought. Coincidentally, during Late Pleistocene deglaciation the four cones were positioned similarly with respect to the retreating ice sheet and thus may have undergone similar glacially induced crustal stresses and erosion. We propose that the ice sheet mostly eroded two of the four Milbanke cones previously reported as erosional remnants, whereas Helmet Peak, the second best preserved cone, was partly eroded by south-flowing ice in Mathieson Channel. Kitasu Hill lies within the unceded territory of the Kitasoo/Xai'Xais First Nation.
Summary(Plain Language Summary, not published)
Kitasu Hill is a small volcano on the outer coast of central British Columbia. It is comprised of a cinder cone sitting on a terrace of basalt. The eruption was thought to have been recent, at least since after the last glaciation, because of the cone¿s fresh appearance. The volcano lies on a major fault zone but its relationship to this bedrock structure and risk of future eruptions is unknown. This open file describes the geomorphology and stratigraphy of the edifice and the petrography and geochemistry of the basalts comprising it. The results indicate that the volcanic eruption likely took place subglacially during the waning stages of the last glaciation, perhaps during a time of increased crustal stress caused by retreat of the ice sheet.

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