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Continent‐Ocean Transition Across the Northeastern Nova Scotian Margin From a Dense Wide‐Angle Seismic Profile
Author(s) -
Lau K. W. H.,
Nedimović Mladen R.,
Louden Keith E.
Publication year - 2018
Publication title -
journal of geophysical research: solid earth
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.983
H-Index - 232
eISSN - 2169-9356
pISSN - 2169-9313
DOI - 10.1029/2017jb015282
Subject(s) - geology , continental margin , oceanic crust , crust , transition zone , seismology , continental crust , seafloor spreading , continental shelf , mantle (geology) , rift , subduction , tectonics , paleontology , geophysics , oceanography
To improve constraints on rifting processes resulting in the formation of the southeastern Canadian margin, we interpret the most detailed regional 2‐D velocity model from offshore Nova Scotia constructed using wide‐angle OETR‐2009 data. This 405‐km‐long profile was collected with 78 ocean bottom seismometers. The presented data analysis and interpretation are supported by a reflection image from the coincident long streamer GXT‐2000 profile. We identify a continental zone where the full‐thickness (~30 km), three‐layered continental crust beneath the inner shelf thins sharply seaward by a listric fault that forms a 12‐km‐deep Huron Subbasin beneath a high‐velocity carbonate bank (~5.8 km/s), creating a shadow zone above tilted crustal blocks. Depth‐dependent and variable initial thinning is evidenced in all three modeled crustal layers, which, nevertheless, pinch out together at their seaward ends. More gradual and regional thinning and a local amagmatic thickening are modeled seaward beneath the slope until 70 km from the shelf break, beyond which a deepwater amagmatic continent‐ocean transition shows velocity characteristics not typical of either continental or oceanic crust. The 100‐km‐wide continent‐ocean transition is characterized by a low‐velocity (5.3–5.4 km/s), low gradient, <2‐km thick upper crust, above a high‐velocity (6.3–7.5 km/s), high gradient, <5‐km‐thick lower crust, which can be interpreted as moderately serpentinized mantle. Underneath this layer is a <5‐km‐thick low‐velocity (7.1–8.0 km/s) partially serpentinized mantle layer. A ~5‐km‐thick oceanic crust is modeled seaward. Our results suggest that amagmatic processes dominated the continental breakup in this area.