Has the Western Greenland Continental Margin Experienced Depth-Dependent Stretching?
Alsulami, Sulaiman; Paton, Douglas A.; Cornwell, David; Stuart, Graham
The fundamental control on extensional basin formation is considered to be the thinning of the continental lithosphere that results in the breakup of continental passive margins. The aims of this study are to measure the magnitude of: 1) upper crustal; and 2) whole lithosphere extension to investigate whether depth-dependent stretching models can explain the west Greenland continental margin evolution.
Stretching factor (β) estimation from upper-crustal faulting as well as flexural backstripping, decompaction and reverse post-rift subsidence modelling methods were derived from three depth-converted seismic reflection profiles. The profiles sample three key locations that together define the western Greenland continental margin, from south to north they are: a 170 km-long profile in the Davis Strait; a 132 km-long profile across Baffin Bay; and a 295 km-long profile across the Labrador Sea margin.
The Davis Strait profile showed a gradual increase in β from ~1.5 to ~4.5 from NE to SW, with a higher beta value (to infinity) for the SW most 15 km of the section. We interpret this as evidence that the greatest lithospheric thinning occurred centrally beneath the rift axis. We also estimate 250-700 m of uplift towards the eastern end of the profile. The profile across the Labrador Sea margin requires a whole lithosphere β of ~1.6 to restore the platform to its paleobathymetry (the 5 km NE side of the section) then an abrupt increase to β=8 for the remainder of the margin. The Baffin Bay section required a β factor of (2.1 to 5) that is higher in both the NE and SW ends of the section respectively than in the centre (β=1.4).
Based on our analyses we find that the stretching factor (β) from the upper crust faulting (typically ~1.1 to 1.4) is less than the stretching factor (β) from the whole lithosphere (from ~1.5 to >10). Even accounting for extension that is accommodated on sub-seismic scale structures, we conclude that the whole lithosphere has extended more than the upper crust. Depth-dependent stretching model therefore may be valid when considering the break-up evolution of the west Greenland margin. Furthermore, our preliminary interpretations suggest that the Labrador Sea and Davis Strait margins display evidence of more symmetric stretching in contrast to the Baffin Bay area that appears to be more asymmetric.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013