| Title | Seismic structure of the northern Cascadia accretionary prism: evidence from new multichannel seismic reflection data |
| Author | Spence, G D; Hyndman, R D; Davis, E E; Yorath, C J |
| Source | Continental Lithosphere: Deep Seismic Reflections; by Meissner, R (ed.); Brown, L (ed.); Dürbaum, H -J (ed.); Franke, W (ed.); Fuchs, K (ed.); Seifert, F (ed.); Geodynamics Series vol. 22, 1991 p.
257-263, https://doi.org/10.1029/gd022p0257 |
| Year | 1991 |
| Alt Series | Geological Survey of Canada, Contribution Series 57290 |
| Publisher | American Geophysical Union |
| Meeting | 4th International Symposium on Deep Reflection Profiling of the Continental Lithosphere; Bayreuth; DE; September 4-7, 1990 |
| Document | serial |
| Lang. | English |
| Media | paper; on-line; digital |
| File format | pdf |
| Province | Western offshore region |
| Subjects | seismic profiles, marine; seismic reflection surveys; continental margins; oceanic crust; pore pressures; subduction zones; sedimentary wedges; terranes; faults; plate tectonics; plate margins; plate
boundaries; Crescent Terrane; accretionary prism |
| Abstract | Within the Cascadia accretionary prism west of Vancouver Island, new marine seismic reflection profiles totalling 722 km provide improved images which enable the three-dimensional variation of
structures along the margin to be determined. At the deformation front, landward dipping thrusts spaced roughly 5 km apart are commonly observed which may penetrate to near the top of the subducting oceanic crust. Along lines separated by 3 km, the
amount of displacement on a given fault is seen to vary significantly along the margin. Seaward dipping faults occasionally develop, propagating upward from the frontal thrust. In one region above gently-dipping oceanic crust, a shallow taper
sediment wedge has formed, implying high pore fluid pressures along the detachment surface at the top of the oceanic crust. The detachment exhibits a strong reflection probably indicative of high fluid pressure. The accretionary prism is bounded by a
landward dipping continental backstop, formed by the marine volcanic Crescent Terrane. The base of this terrane is imaged extending down to near the top of the subducting oceanic crust, so that little sediment is available for deeper subduction or
underplating. The seaward part of the Crescent Terrane appears to have been uplifted, probably as a response to the accretion of prism sediments. |
| GEOSCAN ID | 203887 |
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