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Seismic profiles across the Lomonosov Ridge, Marvin Spur and adjacent basins, acquired near the North Pole by the drifting ice-station NP-28, provide a reflection image of the upper parts of the Ridge that is readily correlatable with those acquired by the Alfred Wegner Institute closer to the Siberian margin. A prominent flat-lying composite reflection package is seen in most parts of the Ridge at a few hundred meters below the sea bottom. Underlying reflections are variable in intensity and also in dip. The base of this reflection package is often accompanied by a sharp increase in P-velocity and defines a major angular discontinuity, referred to here as the Lomonosov Unconformity. The Arctic Coring Expedition (ACEX) cored the first c. 430 m section on the Lomonosov Ridge near the North Pole, in 2004 defining the deeper water character of the Neogene and the shallower water Paleogene sediments. These boreholes penetrated the composite reflection package towards the base of the hole and identified sediments (our Unit III) of late Paleocene and early Eocene age. Campanian beds at the very base of the hole were thought to be representative of the units below the Lomonosov Unconformity, but the P-velocity data suggest that this is unlikely. Correlation of the lithologies along the top of the Lomonosov Ridge and to the Marvin Spur indicates that the Marvin Spur is a sliver of continental crust closely related to, and rifted off the Ridge. This narrow (50 km wide) linear basement high can be followed into, beneath and across the Makarov Basin, supporting the interpretation that this Basin is partly resting on thinned continental crust. In the Makarov Basin, the Paleogene succession is much thicker than on the Ridge. Thus, the condensed, shallow water succession (with hiati) was deposited on the Ridge during rapid Eocene to Miocene subsidence of the Basin. In the Amundsen Basin, adjacent to the Lomonosov Ridge, the sedimentary successions thicken towards the Canadian margin and the reflections on the Ridge are not readily identifiable. The approximate ages of the sedimentary units are inferred from their relationships to the linear magnetic anomalies in the Basin. Lomonosov acoustic basement dips gently into the Basin over a distance of about 100 km and the linear negative anomaly, previously thought to be chron 25, is probably related to a rift-related mafic intrusive complex.

The c. 1500 km long refraction and shallow reflection seismic profile, TransArctic 1989–1991 from the East Siberian shelf northwards across the Podvodnikov and Makarov basins, provide a four layer model of the crust: Layer I (Vp=1.7–3.8 km/s) of sedimentary formations of late Mesozoic and Cenozoic age; Layer II (Vp=5.0–5.4 km/s) of older sedimentary rocks on the shelf and possibly also mafic volcanics in the basins; Layer III (Vp=5.9–6.5 km/s) and Layer IV (Vp=6.7–7.3 km/s) of crystalline crust. The East Siberian margin has c. 40 km thick continental crust, mainly composed of layers III and IV, both c.15 km thick. Beneath the Podvodnikov Basin, the Moho depth varies from c. 20 km bsl at southern and northern ends to c. 30 km bsl at the centre beneath the Arlis Gap; it probably was formed by longitudinal extension of continental crust during the late Mesozoic. The edge of the Alpha-Mendeleev Ridge, separating the Podvodnikov and Makarov basins, has a crustal thickness of c. 25 km, mainly composed of layers III and IV. The deep Makarov Basin is probably composed of oceanic crust, 8–12 km thick, but includes spurs of continental crust, rifted off the Lomonosov Ridge.