Evidence of oceanic crust in the southern Baffin Bay from a seismic refraction experiment

The Baffin Bay is located north of the Labrador Sea and Davis Strait, separating Canada and Greenland. The nature of the Baffin Bay crust is still enigmatic due to the lack of clearly identified oceanic crust and its spreading centers. The position of an extinct spreading axis has been proposed from gravity data, but magnetic spreading anomalies were not yet identified. Alternative models have suggested thinned continental crust. New geophysical data were acquired from RV Maria S. Merian in 2008 in the southern Baffin Bay and Davis Strait. Multichannel seismic and wide-angle reflection and refraction profiling as well as magnetic and gravity surveying reveal characteristics of the southern Baffin Bay crust which points to an oceanic and transitional stage. One of three seismic refraction lines with 24 deployed ocean-bottom seismometers (OBS) will be presented here. The line is 470 km long and runs from Baffin Island in the SSW to the West Greenland margin in the NNE across the assumed position of an extinct north-south trending spreading center (based on gravity data). Forward modelling shows thick sedimentary sequences of 5-6 km thickness in the basin, underlain by basement of oceanic character. The crystalline crust is 7 km thick on average and shows a two layered architecture with a velocity structure typical for oceanic crust. A spreading center can be identified close to the formerly proposed spreading axis, derived from gravity data. An irregular Moho topography and velocity variations in the lower crust are interpreted to relate to major fracture zones and a variable magma production.