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    Crustal structure of the ocean-continent transition at Flemish Cap : seismic refraction results

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    2003JB002434.pdf (2.139Mb)
    Date
    2003-11-19
    Author
    Funck, Thomas  Concept link
    Hopper, John R.  Concept link
    Larsen, Hans Christian  Concept link
    Louden, Keith E.  Concept link
    Tucholke, Brian E.  Concept link
    Holbrook, W. Steven  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/3555
    As published
    https://doi.org/10.1029/2003JB002434
    DOI
    10.1029/2003JB002434
    Keyword
     Refraction seismics; Ocean-continent transition; Serpentinized mantle 
    Abstract
    We conducted a seismic refraction experiment across Flemish Cap and into the deep basin east of Newfoundland, Canada, and developed a velocity model for the crust and mantle from forward and inverse modeling of data from 25 ocean bottom seismometers and dense air gun shots. The continental crust at Flemish Cap is 30 km thick and is divided into three layers with P wave velocities of 6.0–6.7 km/s. Across the southeast Flemish Cap margin, the continental crust thins over a 90-km-wide zone to only 1.2 km. The ocean-continent boundary is near the base of Flemish Cap and is marked by a fault between thinned continental crust and 3-km-thick crust with velocities of 4.7–7.0 km/s interpreted as crust from magma-starved oceanic accretion. This thin crust continues seaward for 55 km and thins locally to ~1.5 km. Below a sediment cover (1.9–3.1 km/s), oceanic layer 2 (4.7–4.9 km/s) is ~1.5 km thick, while layer 3 (6.9 km/s) seems to disappear in the thinnest segment of the oceanic crust. At the seawardmost end of the line the crust thickens to ~6 km. Mantle with velocities of 7.6–8.0 km/s underlies both the thin continental and thin oceanic crust in an 80-km-wide zone. A gradual downward increase to normal mantle velocities is interpreted to reflect decreasing degree of serpentinization with depth. Normal mantle velocities of 8.0 km/s are observed ~6 km below basement. There are major differences compared to the conjugate Galicia Bank margin, which has a wide zone of extended continental crust, more faulting, and prominent detachment faults. Crust formed by seafloor spreading appears symmetric, however, with 30-km-wide zones of oceanic crust accreted on both margins beginning about 4.5 m.y. before formation of magnetic anomaly M0 (~118 Ma).
    Description
    Author Posting. © American Geophysical Union, 2003. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 108, B11 (2003): 2531, doi:10.1029/2003JB002434.
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    • Geology and Geophysics (G&G)
    Suggested Citation
    Journal of Geophysical Research 108, B11 (2003): 2531
     

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