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  • 1
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    Structure of the SE Greenland margin from seismic reflection and refraction data: Implications for nascent spreading center subsidence and asymmetric crustal accretion during N Atlantic opening (2003)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 108 (B5). p. 2269.
    Details
    Publication Date: 2020-07-23
    Description: Seismic reflection and refraction data from the SE Greenland margin provide a detailed view of a volcanic rifted margin from Archean continental crust to near-to-average oceanic crust over a spatial scale of 400 km. The SIGMA III transect, located ∼600 km south of the Greenland-Iceland Ridge and the presumed track of the Iceland hot spot, shows that the continent-ocean transition is abrupt and only a small amount of crustal thinning occurred prior to final breakup. Initially, 18.3 km thick crust accreted to the margin and the productivity decreased through time until a steady state ridge system was established that produced 8–10 km thick crust. Changes in the morphology of the basaltic extrusives provide evidence for vertical motions of the ridge system, which was close to sea level for at least 1 m.y. of subaerial spreading despite a reduction in productivity from 17 to 13.5 km thick crust over this time interval. This could be explained if a small component of active upwelling associated with thermal buoyancy from a modest thermal anomaly provided dynamic support to the rift system. The thermal anomaly must be exhaustible, consistent with recent suggestions that plume material was emplaced into a preexisting lithospheric thin spot as a thin sheet. Exhaustion of the thin sheet led to rapid subsidence of the spreading system and a change from subaerial, to shallow marine, and finally to deep marine extrusion in ∼2 m.y. is shown by the morphological changes. In addition, comparison to the conjugate Hatton Bank shows a clear asymmetry in the early accretion history of North Atlantic oceanic crust. Nearly double the volume of material was emplaced on the Greenland margin compared to Hatton Bank and may indicate east directed ridge migration during initial opening.
    Type: Article , PeerReviewed
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  • 2
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    Plate Boundary Zones (2002)
    AGU
    In:  Washington, D.C., vii + 425 pp., AGU, vol. 30, no. Publ. No. 12, pp. 95-104, (ISBN 0-87590-532-3, AGU Code: GD0305323)
    Details
    Publication Date: 2002
    Keywords: Textbook of geophysics ; Plate tectonics ; Seismicity ; Seismology
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    BIBLIOGRAPHY SEISMOLOGY
  • 3
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    The global moment rate distribution within plate boundary zones (2002)
    AGU
    In:  Bull., Polar Proj. OP-O3A4, Plate Boundary Zones, Washington, D.C., AGU, vol. 30, no. 2, pp. 173-190, (ISBN 0-87590-532-3, AGU Code: GD0305323)
    Details
    Publication Date: 2002
    Keywords: Crustal deformation (cf. Earthquake precursor: deformation or strain) ; Strain ; GSRM ; map ; Paleomagnetism ; Plate tectonics ; Seismicity
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    BIBLIOGRAPHY SEISMOLOGY
  • 4
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    Crustal Structure of the Ocean-Continent Transition at Flemish Cap: Seismic Refraction Results (2003)
    AGU
    In:  Journal of Geophysical Research: Solid Earth, 108 (B11). p. 2531.
    Details
    Publication Date: 2020-07-23
    Description: 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).
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