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TitleHistory and isostatic effects of the last ice sheet in southern British Columbia
AuthorClague, J J; James, T SORCID logo
SourceQuaternary Science Reviews 21, 2002 p. 71-87,
Alt SeriesGeological Survey of Canada, Contribution Series 2000305
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92; 102; 93A; 93B; 93C; 93D; 103A/01; 103A/02; 103A/07; 103A/08; 103A/09; 103A/10; 103A/15; 103A/16
AreaSouthern British Columbia; Puget Sound; Northern Washington State; Vancouver Island; Strait of Georgia; Coast Mountains; Selkirk Mountains; Columbia Mountains; Cascade Range; Olympic Mountains; British Columbia Interior; Juan de Fuca Strait; Seattle; Vancouver; Victoria; Howe Sound; Courtenay; Parksville; Canada; United States of America
Lat/Long WENS-129.0000 -120.0000 53.0000 47.0000
Subjectssurficial geology/geomorphology; Wisconsinian glacial stage; glacial history; glacial tectonics; crustal tilt; crustal uplift; marine sediments; proglacial lakes; glacial landforms; modelling; sea level changes; Holocene; shoreline changes; isostatic rebound; glaciation; deglaciation; Cordilleran ice sheet; Fraser Glaciation; Puget lobe; Juan de Fuca lobe; Coquitlam Stade; Evans Creek Stade; Port Moody Interstade; Vashon Stade; Puget Lowland; Interior Plateau; Cordillera; Pend Oreille lobe; Lake Russell-Hood; Lake Bretz; Seattle fault; Fraser Lowland; Juan de Fuca plate; Cascadia subduction zone; British Columbia continental shelf; Last Glacial Maximum; Late Pleistocene; Late Wisconsinan; ice divides; Quaternary; Cenozoic
Illustrationsphotographs; sketch maps; block diagrams; graphs
Released2002 01 01
AbstractThe Late Wisconsinan Cordilleran ice sheet covered British Columbia, southern Yukon Territory, and parts of Alaska, Washington, Idaho, and Montana. Its major source areas were the high mountain ranges of the Canadian Cordillera, and flow was strongly controlled by topography. The last ice sheet began to develop about 30,000-25,000 14C yr ago, but it did not achieve its maximum extent until 15,000-14,000 14C yr BP. Ice sheet growth was interrupted locally by stillstands and retreat. Ice sheet decay was rapid and was characterized by complex frontal retreat at the periphery, accompanied locally by brief readvances, and by downwasting and stagnation. By 10,000 14C yr BP, <5000 yr after the Last Glacial Maximum, ice cover in British Columbia was similar to that of today. The Cordilleran ice sheet depressed the crust over which it formed. Rapid isostatic rebound during deglaciation caused the sea to fall relative to the land along the southern British Columbia coast. A postglacial rebound model explains crustal tilting and rapid uplift in this region during retreat of the ice sheet in the late Pleistocene. Small values of modelled viscosity for the upper few hundred kilometers of the mantle deliver small present-day crustal tilt rates, consistent with mid- and late-Holocene sea-level observations. Rapid sea-level fall (land uplift) on eastern Vancouver Island during deglaciation requires, in addition to a low mantle viscosity, rapid unloading of the crust due to accelerated wastage of coastal portions of the southern Cordilleran ice sheet about 12,000 14C yr ago.

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