The lithosphere-asthenosphere boundary in the North-West Atlantic region

A detailed knowledge of the thickness of the lithosphere in the north Atlantic is an important parameter for understanding plate tectonics in that region. We achieve this goal with as yet unprecedented detail using the seismic technique of S-receiver functions. Clear positive signals from the crust-mantle boundary and negative signals from a mantle discontinuity beneath Greenland, Iceland and Jan Mayen are observed. According to seismological practice, we call the negative phase the lithosphere-asthenosphere boundary (LAB). The seismic lithosphere under most of the Iceland and large parts of central Greenland is about 80 km thick. This depth in Iceland is in disagreement with estimates of the thickness of the elastic lithosphere (10-20 km) found from postglacial rebound data. In the region of flood basalts in eastern Greenland, which overlies the proposed Iceland plume track, the lithosphere is only 70 km thick, about 10 km less than in Iceland which is located directly above the proposed plume. At the western Greenland coast, the lithosphere thickens to 100-120 km, with no indication of the Iceland plume track identified. Below Jan Mayen the lithospheric thickness varies between 40 and 60 km.