Discussion of the East-Siberian margin, Podvodnikov and Makarov basins and the Mendeleev Ridge origin based on geophysical data. (Invited)

The deep troughs and ridges of the Arctic Basin are some of the least known features of the Earth's crust. Seismic research in combination with potential field data over the East-Siberian margin, Podvodnikov and Makarov basins and the Mendeleev Ridge, provides a framework for understanding this enigmatic part of the Earth. The constrained models of the crust illustrate their structure. The crust beneath the East Siberian margin is up to 40 km thick; it thins to about 20 km towards to the Podvodnikov Basin. The models over the Arlis Gap, in the middle of the Podvodnikov Basin, and the Mendeleev Ridge have shown that the crust beneath both these features is anomalously thick (up to 28-32 km) and has a velocity structure that suggests the presence of highly attenuated continental crust. The crustal thickness over the Makarov Basin varies from 8 km to 15 km. Reflection seismic profiles provide evidence of the character and thickness of the sedimentary cover (mostly Cenozoic and late Mesozoic), both on the ridges and beneath the troughs. Presented here is evidence that some of the ridges (eg. Marvin Spur) appear to be fragments of continental crust rifted off the Lomonosov Ridge (with a similar, unconformable Cenozoic cover); however, they gently plunge into and beneath troughs (eg. Makarov Basin).