The Lomonosov Ridge, central Arctic Ocean - the world's longest submarine ridge of continental origin: outline of the history of exploration, morphology, sediment deposition, and exhumation of the North American and Central ridge segments

We have accessed the North American segment of the Lomonosov Ridge in the central Arctic Ocean by a 12-month hovercraft expedition on drifting sea ice and revisit legacy seismic data to explore the geological history of the ridge. Seismic reflection images on the North American segment resemble the acoustic reflection sequence calibrated by scientific drilling at the ACEX site on the Central ridge segment, although the thickness of the Cenozoic sediment section is reduced to 70%. A base-Cenozoic unconformity is present north of about 88 ^o 30’ N and older sediments dip towards the Makarov Basin along the entire ridge segment. During the Eocene, sediment drifts were deposited along the flanks on top of the North American segment north of 87 ^o N as well as next to the ACEX drill site on the Central segment of the ridge. Two local sediment lenses deposited at the Canadian end of the Lomonosov Ridge document local ridge-uplift events at about 56 Ma and 48 Ma during the Eurekan Orogeny. Compressional velocity gradients derived from published seismic reflection/refraction measurements are consistent with 1-3 km of Cretaceous/early Cenozoic exhumation of an up to 500 km wide swath of continental crust along the polar continental margin including the Lomonosov Ridge, Svalbard and Franz Josef Land .