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TitleSea-level change and paleogeographics reconstructions, southern Vancouver Island, British Columbia, Canada
AuthorJames, T; Gowan, E J; Hutchinson, I; Clague, J J; Barrie, J V; Conway, K W
SourceQuaternary Science Reviews vol. 28, 2009 p. 1200-1216,
Alt SeriesEarth Sciences Sector, Contribution Series 20080257
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceBritish Columbia
NTS92B/05; 92B/06; 92B/11; 92B/12; 92B/13; 92B/14
AreaVancouver Island; Victoria; Strait of Georgia; O'Donnell Flats; Pike Lake; Maltby Lake; Gardner Pond; Blenkinsop Lake; Matheson Lake; Patricia Bay; Rithets Bog
Lat/Long WENS-123.6667 -123.3333 48.8333 48.3333
Subjectsgeochronology; marine geology; sea level changes; sea level fluctuations; paleo-sea levels; paleoenvironment; paleogeography; postglacial evolution; radiocarbon dates; radiocarbon dating; Cenozoic; Quaternary
Illustrationslocation maps; graphs; tables; plots
ProgramEnhancing resilience in a changing climate
AbstractForty-eight new and previously published radiocarbon ages constrain deglacial and postglacial sea levels on southern Vancouver Island, British Columbia. Sea level fell rapidly from its high stand of about +75 m elevation just before 14 000 cal BP (12 000 radiocarbon yrs BP) to below the present shoreline by 13 200 cal BP (11400 radiocarbon years BP). The sea fell below its present level 1000 years later in the central Strait of Georgia and 2000 years later in the northern Strait of Georgia, reflecting regional differences in ice sheet retreat and downwasting. Direct observations only constrain the low stand to be below -11 m and above -40 m. Analysis of the crustal isostatic depression with equations utilizing exponential decay functions appropriate to the Cascadia subduction zone, however, places the low stand at -30 ±5 m at about 11200 cal BP (9800 BP). The inferred low stand for southern Vancouver Island, when compared to the sea-level curve previously derived for the central Strait of Georgia to the northwest, generates differential isostatic depression that is consistent with the expected crustal response between the two regions. Morphologic and sub-bottom features previously interpreted to indicate a low stand of -50 to -65 m are re-evaluated and found to be consistent with a low stand of -30 ±5 m. Submarine banks in eastern Juan de Fuca Strait were emergent at the time of the low stand, but marine passages persisted between southern Vancouver Island and the mainland. The crustal uplift presently occurring in response to the Late Pleistocene collapse of the southwestern sector of the Cordilleran Ice Sheet amounts to about 0.1 mm/yr. The small glacial isostatic adjustment rate is a consequence of low-viscosity mantle in this tectonically active region.

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