Sea-level change and paleogeographic reconstructions,southern Vancouver Island,British Columbia,Canada |
| |
| Authors: | Thomas James Evan J Gowan Ian Hutchinson John J Clague J Vaughn Barrie Kim W Conway |
| |
| Institution: | 1. British Antarctic Survey, High Cross, Madingley Road, Cambridge CB3 0ET, UK;2. Department of Geology, University of Leicester, University Road, Leicester LE1 7RH, UK;3. Aon Benfield UCL Hazard Research Centre, Department of Earth Sciences, University College London, 136 Gower Street, London WC1E 6BT, UK;4. CSIRO National Marine Facility, Castray Esplanade, Hobart, Tasmania, Australia;5. Department of Geography, University College London, 136 Gower Street, London WC1E 6BT, UK;6. British Geological Survey, Keyworth, Nottingham NG12 5GG, UK;1. Institut de Radioprotection et de Sûreté Nucléaire, P.O. Box 17, 92262 Fontenay-aux-Roses Cedex, France;2. ISTerre, IRD-CNRS-OSUG, Université de Grenoble, 1381 rue de la piscine, 38400 Saint Martin d''Hères, France;3. Bureau de Recherche Géologiques et Minières, Service Risques Naturels, P.O. Box 36009, 45060 Orléans Cedex 2, France;4. Escuela Politécnica Nacional, Instituto de Geofísica, Ladrón de Guevara E11-253 y Andalucia, P.O. Box 2759, Quito, Ecuador;5. Instituto Nacional de Investigación Geológico Minero Metalúrgico-INIGEMM, Sector Monteserrin, De Las Malvas E15-142 y Los Perales, Quito, Ecuador |
| |
| Abstract: | Forty-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 (11 400 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 11 200 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. |
| |
| Keywords: | |
| 本文献已被 ScienceDirect 等数据库收录！ |
|
