Paleogene–Quaternary Polyfacies Sedimentary System of the Southern Nansen Basin

A summary seismostratigraphic description of the Nansen Basin sedimentary cover was compiled using data from the Norwegian sector of the Eurasian Basin and data interpretation from the Russian Arktika-2011 project. It was found that sea level fluctuations had a significant impact on sedimentation processes in the Arctic basin. Erosion processes on the shelf and slope were developed during regression phases. In the deep-water part, these processes were accompanied by the formation of fan systems, contourites, and slump bodies in both Neogene–Quaternary and older seismic sequences in the Nansen Basin. They are confined to the modern outer fan distinguished in the bottom topography in both young and older seismic sequences. The sedimentary infill was transported through the Franz Victoria and St. Anna troughs, which already existed at the beginning of the Eurasian Basin opening. The distal parts of the fans form extended sedimentary bodies in the basin with a loss of coherence and acoustic blanking of the seismic record. The contourites are distinguished in all sections near the continental foothill, and slump bodies occur on the slope near the shelf edge. Miocene–Pliocene sequences contain gravity flow sediments located more than 100 km away from the modern fan boundary. The sedimentary infill of the Nansen Basin was regulated both by the intensity of sediment influx and by changes in the hydrological regime of the basin associated with the periods of its isolation from the World Ocean and transition to a single water circulation system. The accumulation of contourite sediments began in the Miocene. They are developed near continental foothills together with fan lobes, and it is not possible to separate these sedimentary body types. The sharpest sea level fall at the Pliocene–Quaternary boundary resulted in the intense sediment input and the formation of spacious zones of coherence loss in the distal fan parts of the basin. The occurrence and spatial distribution of contourite and gravity flow deposits in the basin correlate with sea level fluctuations in antiphase with intense erosion on the Barents Sea shelf, which also depend on vertical movements in the basin surrounding (Svalbard and Franz-Joseph Land archipelagos). Seismic profiles without superimposed interpretation are given in the electronic supplementary materials.