Cenozoic deposition in the Nansen Basin, a first-order estimate based on present-day bathymetry

Abstract

Considering the age of the underlying oceanic crust, the Eurasia Basin in anomalously shallow, especially the southern Nansen sub-Basin. Particularly large bathymetric anomalies are found outside major erosional troughs on the Barents Sea Shelf, indicating sediment infill from the adjacent shelf as a major cause of the shallowing. To obtain a first order estimate of the sediment isopachs in the Eurasia Basin, the standard age-depth curve for oceanic crust in the North-Atlantic was used as a reference to define a bathymetric anomaly which was then inverted, assuming local isostatic equilibrium. The isopachs reveal a huge delta outside the St. Anna and Voronin troughs. Conservatively estimated this “twin delta” covers ≈ 75,000 km 2 and has a maximum sediment thickness ≈ 7 km. Similar, but smaller, deltas are found both east and west of this delta. The deltas in the Nansen Basin appear analogous to the Bjørnøyrenna and Storfjordrenna deltas, which are located off major submarine troughs in the Western Barents Sea and are comparable to the St. Anna/Voronin Delta in size. The latter deltas contains huge amounts of young, glacigenic sediments, and this is also likely to be the case for the deltas in the Nansen Basin. The huge sediment accumulations off the northeastern Barents Sea, the anomalously large depth of the Barents Shelf, and its trough dominated morphology, suggest that extensive erosion similar to that documented in the Western Barents Sea (0.5–1.5 km) affected the entire Barents Shelf.