Davis Strait and Ungava Fault Zone: First results from a recent geophysical survey

The Davis Strait is a bathymetric high that separates the southern Baffin Bay and the northern Labrador Sea. These basins are the result of Cretaceous and Paleogene rifting and seafloor spreading between the North American plate and Greenland. Being one of the main tectonic features of the Davis Strait, the Ungava Fault Zone is associated with transform motion related to a northward movement of Greenland relative to North America during rifting and seafloor spreading in Baffin Bay and Labrador Sea. The plate tectonic reconstruction of the Davis Strait contributes significantly to the understanding of the geodynamic history of the North-American - Greenland plates, not only the Davis Strait area but also the area of Lancaster Sound and Nares Strait, where it could shed light into the so-called Nares Strait Conflict. It is still under debate whether the spreading between Greenland and Baffin Island was compensated by sinistral transform motion along the proposed Wegener-Fault. Thus Nares Strait (trace of the Wegener Fault) and Lancaster Sound (failed arm rift) are relicts of this scenario. The lack of evidence for transform motion between Greenland and Ellesmere Island contradicts this model and provokes the conflict. As major compression along the Eurekan Fold Belt overprinted the proposed transform motion along the Wegener Fault, the Ungava Fault Zone in the Davis Strait could give the missing information for the plate tectonic reconstruction. The onshore-offshore geology and structural setting of Baffin Island is analysed by recent publications that show an essentially non-volcanic continental margin at Baffin Island that is interrupted by a volcanic-style margin around Cape Dyer. Intensive magmatic activity during the initial opening phase is indicated by widespread seaward-dipping-reflector sequences (SDRS) north of Cape Dyer. On the other hand, the structural setting of the Greenland margin side is unclear. The identification of the corresponding conjugate pattern on Greenland side provides fundamental information for the historic motion along the Ungava Fault Zone. The geophysical data of the DAVIS GATE cruise in 2008 provide new data to determine structure and type of conjugate margin segments of Greenland and Baffin Island. As part of the DAVIS GATE project, a set of multichannel seismic, refraction seismic, magnetic and gravity profiles across the Davis Strait was acquired with RV Maria S. Merian in 2008. In detail, three crossing refraction lines with up to 25 ocean-bottom seismographs, and 1500 nm multichannel seismic lines (3000 m streamer length, 240 channels and 50 litres airgun-array) build the framework of the DAVIS GATE project. This presentation illustrates first results from the multichannel seismic survey in addition with first results from magnetic and gravity profiling.

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