From pull-apart basins to ultraslow spreading: Results from the western Barents Sea Margin

Libak, A., Hauk Eide, C., Mjelde, R., Keers, H. and Flueh, Ernst R. (2012) From pull-apart basins to ultraslow spreading: Results from the western Barents Sea Margin Tectonophysics, 514/517 . pp. 44-61. DOI 10.1016/j.tecto.2011.09.020.

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This paper describes results from a geophysical study in the area between the ultraslow Knipovich Ridge and
Bear Island, western Barents Sea. The objective was to map the crustal structure along a profile crossing
a pull-apart rifted continental margin and oceanic crust generated by ultraslow spreading. The results
are based on modeling of wide-angle seismic and gravity data, together with interpretation of multichannel
reflection data. Our results show a two layered oceanic crust in the western part of the profile. The thickness
of the oceanic crust is variable in the western 130 km, ranging from 3.5 to 5.5 km. East of km 130 the crustal
thickness is relatively constant, with values close to the global average for oceanic crust. The oceanic crust is
buried by a thick package of Cenozoic sedimentary rocks. The continent–ocean transition (COT) is placed in
the interval 207–255 km, between unequivocal oceanic crust and the foot of the westernmost fault in the
Hornsund Fault Zone. It is not possible to conclude whether this interval is oceanic crust or thinned and intruded
continental crust, but we favor the latter interpretation, at least for the eastern part of the COT.
Stretched continental crust is observed between Hornsund Fault Zone and the Knølegga Fault. Here the sedimentary
rocks have high velocities and are interpreted to be mainly of Mesozoic and Late Paleozoic age. In
this interval Moho depths increase abruptly from 15 km in the west to 27 km in the east. Crystalline basement
velocities are observed close to the seafloor east of the Knølegga Fault. We suggest that continental
breakup north of Greenland–Senja Fracture Zone occurred around 33 Ma, after a period of pull-apart tectonics.
The spreading rate of the earliest seafloor spreading may have been higher than the present day spreading,
creating thicker oceanic crust close to the COT.

Document Type: Article
Keywords: Seismology; Geodynamics; Geophysics; Ocean bottom seismometer ; Knipovich Ridge ; Hornsund Fault Zone ; Continent–ocean transition ; Magmatic centers
Research affiliation: OceanRep > GEOMAR > FB4 Dynamics of the Ocean Floor > FB4-GDY Marine Geodynamics
OceanRep > The Future Ocean - Cluster of Excellence
Refereed: Yes
DOI etc.: 10.1016/j.tecto.2011.09.020
ISSN: 0040-1951
Projects: Future Ocean
Date Deposited: 09 Jan 2012 09:44
Last Modified: 15 Jun 2016 11:59

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