The interpretation of seismic refraction and gravity data acquired in 2010 gives new insights into the crustal structure of the West Greenland coast and the adjacent deep central Baffin Bay basin. Underneath Melville Bay, the depth of the Moho varies between 26 and 17 km. Stretched continental crust with a thickness of 25 to 14 km and deep sedimentary basins are present in this area. The deep Melville Bay Graben contains an up to~11 km thick infill of consolidated and unconsolidated sediments with velocities of 1.6 to 4.9 km/s. Seaward, at the~60 km wide transition between oceanic and stretched continental crust, a mount-shaped magmatic structure is observed, which most likely formed prior to the initial formation of oceanic crust. The up to 4 km high magmatic structure is underlain by a~2 km thick and~50 km wide high velocity lower crust. More to the west, in the oceanic part of the Baffin Bay basin, we identify a two-layered, 3.5 to 6 km thin igneous oceanic crust with increasing thickness toward the shelf. Beneath the oceanic crust, the depth of the Moho ranges between 11.5 and 13.5 km. In the western part of the profile, oceanic layer 3 is unusually thin (~1.5 km) A possible explanation for the thin crust is accretion due to slow spreading, although the basement is notably smooth compared to the basement of other regions formed by ultra-slow spreading. The oceanic crust is underlain by partly serpentinized upper mantle with velocities of 7.6 to 7.8 km/s.

Plate kinematic models propose that India and Sri Lanka (INDSRI) separated from Antarctica by extremely slow seafloor spreading that started in early Cretaceous times, and that a long-distance ridge jump left a continental fragment stranded off the Antarctic margin under the Southern Kerguelen Plateau 1-3. Here, we present newly acquired magnetic and deep wide-angle seismic data that require a fundamental re-evaluation of these concepts. The new data clearly define the onset of oceanic crust in the Enderby Basin and off southern Sri Lanka, and date its formation with unprecedented confidence. The revised timing indicates that India and Sri Lanka detached from Antarctica earlier in the east than in the west. Furthermore, no compelling evidence for an extinct spreading axis is found in the Enderby Basin. A refined plate motion model indicates that India and Sri Lanka departed from Antarctica without major rift jumps, but by the action of three spreading ridges with different timings and velocities that must have been accommodated by significant intracontinental deformation.

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Investigating the crust of northern Baffin Bay provides valuable indications for the still debated evolution of this area. The crust of the southern Melville Bay is examined based on wide‐angle seismic and gravity data. The resulting P wave velocity, density, and geological models give insights into the crustal structure. A stretched and rifted continental crust underneath southern Melville Bay is up to 30 km thick, with crustal velocities ranging between 5.5 and 6.9 km/s. The deep Melville Bay Graben contains a 9 km thick infill with velocities of 4 to 5.2 km/s in its lowermost part. West of the Melville Bay Ridge, a ~80 km wide and partly only 5 km thick Continent‐Ocean Transition (COT) is present. West of the COT, up to 5 km thick sedimentary layers cover a 4.3 to 7 km thick, two‐layered oceanic crust. The upper oceanic layer 2 has velocities of 5.2 to 6.0 km/s; the oceanic layer 3 has been modeled with rather low velocities of 6.3 to 6.9 km/s. Low velocities of 7.8 km/s characterize the probably serpentinized upper mantle underneath the thin crust. The serpentinized upper mantle and low thickness of the oceanic crust are another indication for slow or ultraslow spreading during the formation of the oceanic part of the Baffin Bay. By comparing our results on the crustal structure with other wide‐angle seismic profiles recently published, differences in the geometry and structure of the crust and the overlying sedimentary cover are revealed. Moreover, the type of margin and the extent of crustal types in the Melville Bay area are discussed.

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