Reflection mapping across the convergent margin of western Canada |
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Authors: | R M Clowes CJ Yorath RD Hyndman |
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Institution: | Department of Geophysics and Astronomy, 2219 Main Mall, University of British Columbia, Vancouver, Canada V6T 1W5;Pacific Geoscience Centre, Geological Survey of Canada, P. O. Box 6000, Sidney, B.C., Canada V8L 4B2 |
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Abstract: | Summary. Five marine multichannel seismic reflection profiles totalling 520 km were recorded across the western Canada convergent margin where the Juan de Fuca plate is subducting beneath North America. The data extend the results of LITHOPROBE on Vancouver Island. The primary objectives are definition of the offshore accretionary structures and clarification of the convergent interaction between the two plates. The main features of this preliminary interpretation are: (1) the subduction deformation front is complex with evidence of sediments being accreted and subducted; (2) the top of the oceanic crust and the Mono are imaged below the deep water sedimentary basin; (3) the top of the subducting plate is clearly imaged below the shelf; (4) beneath the inner shelf, one band of high reflectivity underlain by a zone of lesser reflectivity lies above the plate; (5) alternative interpretations place the present zone of decoupling at the base of the reflective band or the top of the plate; (6) the San Juan and Leech River faults that bound small accreted terranes are imaged as thrusts that merge at depth. |
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