The Davis Strait crust—a transform margin between two oceanic basins

Abstract

The Davis Strait is located between Canada and Greenland and connects the Labrador Sea and the Baffin Bay basins. Both basins formed in Cretaceous to Eocene time and were connected by a transform fault system in the Davis Strait. Whether the crust in the central Davis Strait is oceanic or continental has been disputed. This information is needed to understand the evolution of this transform margin during the separation of the North American plate and Greenland. We here present a 315-km-long east-west-oriented profile that crosses the Davis Strait and two major transform fault systems-the Ungava Fault Complex and the Hudson Fracture Zone. By forward modelling of data from 12 ocean bottom seismographs, we develop a P-wave velocity model. We compare this model with a density model from ship-borne gravity data. Seismic reflection and magnetic anomaly data support and complement the interpretation. Most of the crust is covered by basalt flows that indicate extensive volcanism in the Davis Strait. While the upper crust is uniform, the middle and lower crust are characterized by higher P-wave velocities and densities at the location of the Ungava Fault Complex. Here, P-wave velocities of the middle crust are 6.6 km s −1 and of the lower crust are 7.1 km s −1 compared to 6.3 and 6.8 km s −1 outside this area; densities are 2850 and 3050 kg m −3 compared to 2800 and 2900 kg m −3. We here interpret a 45-km-long section as stretched and intruded crust or as new igneous crust that correlates with oceanic crust in the southern Davis Strait. A high-velocity lower crust (6.9-7.3 km s −1) indicates a high content of mafic material. This mantle-derived material gradually intruded the lower crust of the adjacent continental crust and can be related to the Iceland mantle plume. With plate kinematic modelling, we can demonstrate the importance of two transform fault systems in the Davis Strait: the Ungava Fault Complex with transpression and the Hudson Fracture Zone with pure strike-slip motion. We show that with recent poles of rotation, most of the relative motion between the North American plate and Greenland took place along the Hudson Fracture Zone.

Tectonic variation and structural evolution of the West Greenland continental margin

“…New COT boundaries have been interpreted based on multidisciplinary data integration of seismic reflection, refraction interpretation, gravity, magnetic 2D modelling and backstripping thermal subsidence modelling. ............... 48 , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013. Serpentinite zone from Nafe-Drake polynomial curve was interpreted in Baffin Bay, , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013.…”

“…............... 48 , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013. Serpentinite zone from Nafe-Drake polynomial curve was interpreted in Baffin Bay, , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013. Serpentinite zone from Nafe-Drake polynomial curve was interpreted in Baffin Densities were then calculated as a function of velocities using four different methods and in comparison with published data of , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013.…”

“…Serpentinite zone from Nafe-Drake polynomial curve was interpreted in Baffin Bay, , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013. Serpentinite zone from Nafe-Drake polynomial curve was interpreted in Baffin Densities were then calculated as a function of velocities using four different methods and in comparison with published data of , Funck et al (2007Funck et al ( , 2012, and Suckro et al (2012Suckro et al ( , 2013. Serpentinite zone from Nafe-Drake polynomial curve was interpreted in Baffin Bay, Figure 6.1: Regional tectonic framework of the west Greenland area generated by data integration of 2D seismic data (GEUS), structural provinces after Knutsen et al, (2012), seafloor data from Müller 2008, Global Seafloor Fabric and Magnetic chrons from Roest and Srivastava 1989;and Chalmers and Laursen (1995 shear-simple shear model (Lister et al, 1986), have described how crustal attenuation, followed by thermal subsidence and isostatic compensation have played the key roles in lithospheric and mantle geodynamics.…”

“…The structure of Baffin Bay province is characterised by two NW-SE trending implying that the area is underlain by Cretaceous strata Dam et al, 2009Suckro et al, 2013 and. …”

“…The evolution of West Greenland during continental breakup is controversial. Diverse opinions centre on the timing of uplift, on the number of phases of extrusive volcanism, on the initiation of rifting, sea-floor spreading and geotectonic development of the region during the continental breakup (Korstgärd and Nielsen, 1989;Storey et al, 1998;Larsen et al, 2009;Funck et al, 2012;Oakey and Chalmers 2012;Suckro et al, 2013).…”