Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada
[ 1] We present a compressional seismic velocity profile of the crust of the eastern margin of the Grand Banks of Newfoundland, Canada. This velocity model was obtained by a tomographic inversion of wide-angle data recorded on a linear array of 24 ocean bottom seismometers (OBSs). At the landward si...
Published in: | Journal of Geophysical Research: Solid Earth |
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Online Access: | https://doi.org/10.1029/2005JB004156 http://hdl.handle.net/10222/26922 |
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ftdalhouse:oai:DalSpace.library.dal.ca:10222/26922 2023-05-15T15:42:08+02:00 Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada Van Avendonk, Harm J. A. Holbrook, W. Steven Nunes, Gregory T. Shillington, Donna J. Tucholke, Brian E. Louden, Keith E. Larsen, Hans Christian Hopper, John R. 2013-06-19T18:01:11Z https://doi.org/10.1029/2005JB004156 http://hdl.handle.net/10222/26922 unknown Journal of Geophysical Research-Solid Earth Van Avendonk, Harm J. A., W. Steven Holbrook, Gregory T. Nunes, Donna J. Shillington, et al. 2006. "Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada." Journal of Geophysical Research-Solid Earth 111(B11): 11404-B11404. DOI:10.1029/2005JB004156 0148-0227 http://dx.doi.org/10.1029/2005JB004156 http://hdl.handle.net/10222/26922 111 11 11404 This paper was published by AGU. Copyright 2006 American Geophysical Union article 2013 ftdalhouse https://doi.org/10.1029/2005JB004156 2021-12-29T18:08:42Z [ 1] We present a compressional seismic velocity profile of the crust of the eastern margin of the Grand Banks of Newfoundland, Canada. This velocity model was obtained by a tomographic inversion of wide-angle data recorded on a linear array of 24 ocean bottom seismometers (OBSs). At the landward side, we imaged a crustal thickness of 27 km in Flemish Pass and beneath Beothuk Knoll, which is thinner than the 35-km-thick crust of the central Grand Banks. We therefore assume that the eastern rim of the Grand Banks stretched uniformly by 25%. Farther seaward, the continental crust tapers rapidly beneath the continental slope to similar to 6 km thickness. In the distal margin we find a 60-km-wide zone with seismic velocities between 5.0 and 6.5 km s(-1) that thins to the southeast from 6 to 2 km, which we interpret as highly extended continental crust. Contrary to other seismic studies of the margins of the Grand Banks, we find seismic velocities of 8 km s(-1) and higher beneath this thin crustal layer in the continent-ocean transition. We conclude that mantle was locally emplaced at shallow levels without significant hydration from seawater or serpentinized mantle was removed along a decollement in the final stages of continental rifting. The outer edge of highly extended continental crust borders a 25-km-wide zone where seismic velocities increase gradually from 6.3 km s(-1) just below the top of acoustic basement to 7.7 km s(-1) at 5 km below basement. We interpret this area as a relatively narrow zone of exhumed and serpentinized continental mantle. Seaward, we imaged a thin and laterally heterogeneous layer with a seismic velocity that increases sharply from 5.0 km s(-1) in basement ridges to 7.0 km s(-1) at its base, overlying mantle velocities between 7.8 and 8.2 km s(-1). We interpret this area as unroofed mantle and very thin oceanic crust that formed at an incipient, magma-starved, ultraslow spreading ridge. A comparison of the conjugate rifted margins of the eastern Grand Banks and the Iberia Abyssal Plain show that they exhibit a similar seaward progression from continental crust to mantle to oceanic crust. This indicates that before continental breakup, rifting exhumed progressively deeper sections of the continental lithosphere on both conjugate margins. A comparison between the continent-ocean transition of the Grand Banks and Flemish Cap shows that the final phase of continental rifting and the formation of the first oceanic crust required more time at the Grand Banks margin than at the southeastern margin of Flemish Cap. Article in Journal/Newspaper Beothuk Newfoundland Dalhousie University: DalSpace Institutional Repository Canada Journal of Geophysical Research: Solid Earth 111 B11 n/a n/a |
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Dalhousie University: DalSpace Institutional Repository |
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ftdalhouse |
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description |
[ 1] We present a compressional seismic velocity profile of the crust of the eastern margin of the Grand Banks of Newfoundland, Canada. This velocity model was obtained by a tomographic inversion of wide-angle data recorded on a linear array of 24 ocean bottom seismometers (OBSs). At the landward side, we imaged a crustal thickness of 27 km in Flemish Pass and beneath Beothuk Knoll, which is thinner than the 35-km-thick crust of the central Grand Banks. We therefore assume that the eastern rim of the Grand Banks stretched uniformly by 25%. Farther seaward, the continental crust tapers rapidly beneath the continental slope to similar to 6 km thickness. In the distal margin we find a 60-km-wide zone with seismic velocities between 5.0 and 6.5 km s(-1) that thins to the southeast from 6 to 2 km, which we interpret as highly extended continental crust. Contrary to other seismic studies of the margins of the Grand Banks, we find seismic velocities of 8 km s(-1) and higher beneath this thin crustal layer in the continent-ocean transition. We conclude that mantle was locally emplaced at shallow levels without significant hydration from seawater or serpentinized mantle was removed along a decollement in the final stages of continental rifting. The outer edge of highly extended continental crust borders a 25-km-wide zone where seismic velocities increase gradually from 6.3 km s(-1) just below the top of acoustic basement to 7.7 km s(-1) at 5 km below basement. We interpret this area as a relatively narrow zone of exhumed and serpentinized continental mantle. Seaward, we imaged a thin and laterally heterogeneous layer with a seismic velocity that increases sharply from 5.0 km s(-1) in basement ridges to 7.0 km s(-1) at its base, overlying mantle velocities between 7.8 and 8.2 km s(-1). We interpret this area as unroofed mantle and very thin oceanic crust that formed at an incipient, magma-starved, ultraslow spreading ridge. A comparison of the conjugate rifted margins of the eastern Grand Banks and the Iberia Abyssal Plain show that they exhibit a similar seaward progression from continental crust to mantle to oceanic crust. This indicates that before continental breakup, rifting exhumed progressively deeper sections of the continental lithosphere on both conjugate margins. A comparison between the continent-ocean transition of the Grand Banks and Flemish Cap shows that the final phase of continental rifting and the formation of the first oceanic crust required more time at the Grand Banks margin than at the southeastern margin of Flemish Cap. |
format |
Article in Journal/Newspaper |
author |
Van Avendonk, Harm J. A. Holbrook, W. Steven Nunes, Gregory T. Shillington, Donna J. Tucholke, Brian E. Louden, Keith E. Larsen, Hans Christian Hopper, John R. |
spellingShingle |
Van Avendonk, Harm J. A. Holbrook, W. Steven Nunes, Gregory T. Shillington, Donna J. Tucholke, Brian E. Louden, Keith E. Larsen, Hans Christian Hopper, John R. Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada |
author_facet |
Van Avendonk, Harm J. A. Holbrook, W. Steven Nunes, Gregory T. Shillington, Donna J. Tucholke, Brian E. Louden, Keith E. Larsen, Hans Christian Hopper, John R. |
author_sort |
Van Avendonk, Harm J. A. |
title |
Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada |
title_short |
Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada |
title_full |
Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada |
title_fullStr |
Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada |
title_full_unstemmed |
Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada |
title_sort |
seismic velocity structure of the rifted margin of the eastern grand banks of newfoundland, canada |
publishDate |
2013 |
url |
https://doi.org/10.1029/2005JB004156 http://hdl.handle.net/10222/26922 |
geographic |
Canada |
geographic_facet |
Canada |
genre |
Beothuk Newfoundland |
genre_facet |
Beothuk Newfoundland |
op_relation |
Journal of Geophysical Research-Solid Earth Van Avendonk, Harm J. A., W. Steven Holbrook, Gregory T. Nunes, Donna J. Shillington, et al. 2006. "Seismic velocity structure of the rifted margin of the eastern Grand Banks of Newfoundland, Canada." Journal of Geophysical Research-Solid Earth 111(B11): 11404-B11404. DOI:10.1029/2005JB004156 0148-0227 http://dx.doi.org/10.1029/2005JB004156 http://hdl.handle.net/10222/26922 111 11 11404 |
op_rights |
This paper was published by AGU. Copyright 2006 American Geophysical Union |
op_doi |
https://doi.org/10.1029/2005JB004156 |
container_title |
Journal of Geophysical Research: Solid Earth |
container_volume |
111 |
container_issue |
B11 |
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n/a |
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1766374970012729344 |