The crustal structure in Baffin Bay and Davis Strait

Baffin Bay is the northwest extension of the Labrador Sea spreading system. The transition zone between these two areas is characterized by the sinistral Ungava transform-fault system across Davis Strait. The crustal type within Baffin Bay is considered to be oceanic based on a few refraction seismic experiments of older vintage. However, the velocity-depth profiles obtained from these experiments also indicate deviations from normal oceanic crust. A refraction profile in northern Baffin Bay indicates that spreading there was amagmatic and that serpentinized mantle is encountered beneath the sedimentary sequence. In addition, no magnetic anomalies related to seafloor spreading could be detected in Baffin Bay so far. This leaves a relative uncertainty about the geodynamic evolution of the Davis Strait and Baffin Bay region. For this reason, a geophysical study was carried out onboard the research vessel Maria S. Merian in 2008, collecting wide-angle reflection/refraction seismic data, supplemented by coincident and additional deep reflection seismic profiles, potential field measurement, swath bathymetry and high-resolution sediment profiling (Parasound). The refraction seismic data set comprises three lines running across the centre part of Davis Strait and southern Baffin Bay extending from Greenland to Baffin Island. The seismic source was an airgun array with a total volume of 7006 cubic inches and the shots were recorded by up to 25 ocean bottom seismometers (OBS) deployed along each line. Initial velocity models will be presented for line AWI-20080600 extending from the Sisimiut Basin off Greenland across the Hellefisk well, farther towards the NW and parallel to the assumed extinct spreading axis (based on gravity data) up to the Baffin Island continental margin some 60 km to the south of ODP site 645. The record sections indicate considerable lateral variations of the crustal structure and character along the line