Margin segmentation of Baffin Bay/Davis Strait, eastern Canada based on seismic reflection and potential field data

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Abstract

The continental margin of Baffin Island was interpreted from a compilation of seismic reflection and potential field data. Based on these data, it was divided into volcanic and non-volcanic segments. In the northernmost area, coast-parallel grabens and continental basement highs are superseded beneath the slope by irregular basement topography. In combination with the velocities from refraction data and the lack of a magnetic slope anomaly, we propose a non-volcanic margin. In the central region, the seismic data show a limited region with a seaward dipping reflector sequence that may be intercalated with a sedimentary section. Both north and south of Cape Dyer extensive volcanic rocks are interpreted at and below seabed consistent with a volcanic margin. In the southern region, the depth to basement drops rapidly offshore. A thick prograding sedimentary wedge produces a high-amplitude long-wavelength free-air gravity anomaly that was previously confused with the continent–ocean boundary. Although some volcanic rocks are mapped in the region, this area is adjacent to the non-volcanic Labrador Sea margin and is interpreted to be of similar structure. Segmentation of the margin by major faults can explain the abrupt transitions from volcanic to non-volcanic margin segments. The continent–ocean boundary for the region is determined based on the potential field and seismic data. Along the Greenland plate in Davis Strait the continent–ocean boundary coincides with the Ungava Fault Zone. The continent–ocean boundary is used in conjunction with published poles of rotation to evaluate plate reconstructions at chrons 33n and 27n. The earlier reconstruction produces an extensive overlap of boundaries in the north. The later reconstruction shows a gap in the southern region. Thus, additional information is required to refine the reconstructions.

Section snippets

Geological and geophysical background

Baffin Bay and Davis Strait are located between Baffin Island and Greenland, to the north of the Labrador Sea (Fig. 1). Baffin Bay is believed to have been created by the northward extension of seafloor spreading from the Atlantic Ocean through the Labrador Sea. A review by Balkwill et al. (1990) discussed the debate on the development of Baffin Bay: one group suggests that the region formed by seafloor spreading, and another that continental crust is present. Available refraction profiles are

Description of data, distribution and processing

A regional interpretation of seismic reflection profiles on the Baffin Island margin in the area between 60 and 72°N was undertaken (Fig. 2). Three industry wells, one ODP well and 73 bedrock cores were available to control the seismic analysis. New compilations of magnetic and gravity data (Fig. 3, Fig. 4) from the Baffin Bay and Davis Strait were used to constrain the sub-seabed as well.

The 30,000 km of industry seismic reflection data (Fig. 1) were assembled from 13 different surveys acquired

Regional setting

The Baffin Island margin (60–72°N) can be divided into three areas based on the seismic reflection data (Fig. 1, Fig. 2). Areas 1 and 3 are dominated by extensional features produced during rifting separated by Area 2 created by translation and affected by volcanism. The potential field anomalies vary along the Baffin Island margin (Fig. 3, Fig. 4) consistent with the divisions made on the basis of the seismic data.

Area 1

The fault pattern in Area 1 (69–72°N), is elongate northwest–southeast striking

Discussion

We combine our interpretation of the margin of Baffin Island with that off of Greenland (Fig. 10) based on Chalmers, 1997, Chalmers and Pulvertaft, 2001, Chalmers et al., 1995, Chalmers et al., 1993, Louden and Chian, 1999. For the northern Labrador Sea, we incorporate the results of Roest and Srivastava, 1989, Chalmers, 1991, Chalmers and Laursen, 1995, Chian and Louden, 1992, Chian et al., 1995a, Chian et al., 1995b, Louden and Chian, 1999, Funck and Louden, 1999.

Conclusion

The two major results of this paper are the separation of the Baffin Island margin into non-volcanic and volcanic regions, and a reinterpretation of the COB. The data presented here, in particular the SDRs, the ages of the samples of volcanic rock and the high-frequency magnetic anomalies associated with positive gravity signatures, indicate extensive magmatism associated with the central part of the margin. In contrast, the margin segments to the north and south of the central areas show no to

Acknowledgements

The GEUS and GSC are thanked for providing the means for the principal author to spent 6 months at the GSCA. We thank Brian MacLean for access to the bedrock samples he collected on several cruises to the area. They were a significant constraint for the geology of the region. Jim Chalmers, GEUS and two reviewers Brian MacLean and Hans Wielens from GSCA reviewed the manuscript and made many helpful comments.

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