Crustal structure across the Grand Banks–Newfoundland Basin Continental Margin – II. Results from a seismic reflection profile

• Main Authors: Lau, K. W. Helen, Louden, Keith E, Deemer, Sharon, Hall, Jeremy, Hopper, John R, Tucholke, Brian E, Holbrook, W. Steven, Larsen, Hans Christian
• Format: Publication
• Language: English
• Published: 03.03.2006
• Subjects: Continental margins; Crustal structures; Reflection seismology; Rifted margins; Seismic structures

Author Posting. © Blackwell, 2006. This is the author's version of the work. It is posted here by permission of Blackwell for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 167 (2006): 157-170, doi:10.1111/j.1365-246X.2006.02989.x. This work was funded by NSF grants OCE-9819053 and OCE-0326714 toWoods Hole Oceanographic Institution, NSERC (Canada) and the Danish Research Council.B. Tucholke also acknowledges support from the Henry Bryant Bigelow Chair inOceanography at Woods Hole Oceanographic Institution. New multi-channel seismic (MCS) reflection data were collected over a 565kmtransect covering the non-volcanic rifted margin of the central eastern Grand Banks and the Newfoundland Basin in the northwestern Atlantic. Three major crustal zones are interpreted from west to east over the seaward 350-km of the profile: (1) continental crust; (2) transitional basement; (3) oceanic crust. Continental crust thins over a wide zone (~160 km) by forming a large rift basin (Carson Basin) and seaward fault block, together with a series of smaller fault blocks eastward beneath the Salar and Newfoundland basins. Analysis of selected previous reflection profiles (Lithoprobe 85-4, 85-2 and Conrad NB-1) indicates that prominent landward-dipping reflections observed under the continental slope are a regional phenomenon. They define the landward edge of a deep serpentinized mantle layer, which underlies both extended continental crust and transitional basement. The 80-km-wide transitional basement is defined landward by a basement high that may consist of serpentinized peridotite and seaward by a pair of basement highs of unknown crustal origin. Flat and unreflective transitional basement most likely is exhumed, serpentinized mantle,although our results do not exclude the possibility of anomalously thinned oceanic crust. A Moho reflection below interpreted oceanic crust is first observed landward of magneticanomaly M4, 230 km from the shelf break. Extrapolation of ages from chron M0 to the edge of interpreted oceanic crust suggests that the onset of seafloor spreading was ~138Ma (Valanginian) in the south (southern Newfoundland Basin) to ~125Ma (Barremian-Aptian boundary) in the north (Flemish Cap), comparable to those proposed for the conjugate margins.