Open AccessSeismic evidence for plume‐derived volcanism during formation of the continental margin in southern Davis Strait and northern Labrador Sea
Author(s) -
Gerlings Joanna,
Funck Thomas,
Jackson H. Ruth,
Louden Keith E.,
Klingelhöfer Frauke
Publication year - 2009
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.2008.04021.x
Subject(s) - geology , crust , oceanic crust , continental margin , transition zone , seismology , continental crust , plume , volcanism , seismic refraction , mantle plume , continental shelf , mantle (geology) , oceanic basin , geophysics , lithosphere , tectonics , oceanography , subduction , physics , thermodynamics
SUMMARY The crustal structure in the southern Davis Strait and the adjacent ocean–continent transition zone in NE Labrador Sea was determined along a 185‐km‐long refraction/wide‐angle reflection seismic transect to study the impact of the Iceland mantle plume to this region. A P ‐wave velocity model was developed from forward and inverse modelling of dense airgun shots recorded by ocean bottom seismographs. A coincident industry multichannel reflection seismic profile was used to guide the modelling as reflectivity could be identified down to Moho. The model displays a marked lateral change of velocity structure. The sedimentary cover (velocities 1.8–3.9 km s −1 ) is up to 4 km thick in the north and thins to 1 km in the south. The segment of the line within southern Davis Strait is interpreted to be of continental character with a two‐layered 13‐km‐thick crust with P ‐wave velocities of 5.6–5.8 and 6.4–6.7 km s −1 in the upper and lower crust, respectively. The crust is underlain by a 2‐ to 4‐km‐thick high‐velocity layer (7.5 km s −1 ). This layer we interpret as underplated material related to the Iceland plume. The southern segment of the line in Labrador Sea displays a 2‐km‐thick layer with a velocity of 4.5 km s −1 . This layer can be correlated to a well about 100 km to the west of the line, where Palaeocene basalts and interbedded sediments were drilled. Underneath is a 12‐km‐thick crust with a 2‐km‐thick upper layer (5.8–6.6 km s −1 ) and a 10‐km‐thick lower layer (6.8–7.2 km s −1 ). This crust is interpreted to be of oceanic character. S ‐wave modelling yields a Poisson's ratio of 0.28 for the lower crust, compatible with a gabbroic composition. The igneous crust is 5 km thicker than normal oceanic crust. We suggest that the increased magma production was created by buoyancy‐driving flow. We propose a model in which initial seafloor spreading occurred between Labrador and West Greenland, when the Iceland plume arrived in the area at ∼62 Ma and caused enhanced magma production. Shortly afterwards (chron 27–26), plume material was channelled southward underplating part of Davis Strait and forming basaltic flows interbedded with sediment.