Mendeleev Ridge Ambiguities and the Need for Drilling

Nina Lebedeva-Ivanova
Department of Earth Sciences, Uppsala University, Uppsala, Sweden.

The origin of the Mendeleev (and Alpha) Ridge is one of the most debated subjects in the Arctic Ocean. Not so much geological and geophysical data has been collected up to nowadays from the Ridge.

The wide angle seismic data, acquired on the Arctic-2000 profile across the Mendeleev Ridge, provided the base for a model of the crustal structure of the Ridge and adjacent Mendeleev and Podvodnikov basins. It shows the thick crust below the Ridge, composed of two layers with mean P-velocities of c.6.2 km/s and c.7.1 km/s; these have thicknesses up to 4 km and 20 km respectively. The crust is covered by up to c.4 km of well lithified deposits with P-velocities of c.5.2 km/s and various thicknesses (a few kilometres) of younger overlying sediments with lower velocities. The Moho discontinuity was observed to vary from 22 km bsl to 32 km bsl; at some places between the Moho and lower crust, a few kilometres of underplating, with P-velocities 7.4-7.8 km/s, have been distinguished.

Dredged samples from Arctic-2000 profile area are dominated by carbonate and terrigenous sedimentary rocks, with some igneous intercalations; they have a Palaeozoic and younger age (Kaban’kov et al., 2004). This line of evidence suggests that the Mendeleev Ridge may be composed of continental material that has been substantially altered during the development of the deep Arctic Basin and associated magmatism. However, the dredged samples may not be of local origin; on alternative theory cannot be rejected - that of spreading centre being fed by a hot spot forming a feature in the Cretaceous similar to the Iceland-Faeroe Plateau (Jackson et al., 1986).

The ambiguous origin of the Mendeleev Ridge cannot be uniquely resolved by new geophysical data. Only deep drilling of the bedrock at a few locations on the Ridge can give clear answers. Drilling of the northern part of the Mendeleev Ridge can be more efficacious because of thinner sediments; already collected seismic data can be very helpful for finding places where the basement is close to the seafloor.

AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia