GEOSCAN Search Results: Fastlink


TitleDipping shear zones and the base of the crust in the Appalachians, offshore Canada
AuthorHall, J; Quinlan, G; Marillier, F; Keen, C
SourceSeismic probing of continents and their margins; Tectonophysics vol 173, no 1-4, test, 1990 p. 581-593,
Alt SeriesGeological Survey of Canada, Contribution Series 24089
Alt SeriesLithoprobe Publication 96
Alt SeriesInternational Lithosphere Program Contribution 154
PublisherElsevier BV
MeetingInternational Meeting on Seismic Probing of Continents and their Margins; Canberra; AU; 19880701; July 1-8, 1988
Mediapaper; on-line; digital
File formatpdf
ProvinceEastern offshore region
AreaGulf of St. Lawrence; Bay of Islands; Atlantic Ocean
Subjectsstructural geology; geophysics; geophysical surveys; seismic surveys, marine; continental margins; faults; shear zones; mobile belts; oceanography; tectonophysics; lithosphere; Appalachians
Illustrationssketch maps; seismic profiles
AbstractThe Seismological character of the Appalachian mobile belt offshore from eastern Canada includes an unusual concentration of northwest-dipping reflectors which appear to dip through sub-horizontal reflectors at the base of the crust. The geometry of these structures has been characterised by ray-trace migration. They are not point diffractors. They appear to dip at between 25 and 45°, but flatten upwards towards a mid-crustal "bright" band and disappear downwards into the mantle. We interpret the reflectors as shear zones which ramp through the lower crust from a mid-crustal detachment to a diffuse and less reflective set of shears in the mantle. It is suggested that the reflectors were caused by the collision of continental blocks at the final closure of the Iapetus Ocean, but may have been subject to later reactivation, especially during late Carboniferous strike-slip.