Alpha-Mendeleev Rise, Arctic Ocean: A double volcanic passive margin

Abstract

Data collected by several expeditions to the Arctic Ocean have yielded a seismic stratigraphic framework and basin fill history for the Alpha-Mendeleev Rise (AMR) and adjacent Podvodnikov, Makarov, North Chukchi, Toll, Mendeleev, Nautilus and Stefansson basins. The AMR comprises a double-sided volcanic passive margin formed in Aptian-Albian time. The North Chukchi, Podvodnikov, Toll, Mendeleev, Nautilus, and Stefansson basins formed synchronously with the Alpha-Mendeleev Rise as failed micro-oceanic basins. Their formation started with rifting and volcanism at ∼ 125 Ma and ended at 100–90 Ma. Ages are constrained by new isotope magmatic rock ages. The region now comprising the Amerasia Basin was in an intraplate tectonic setting during Aptian-Albian times. On the Mendeleev Rise seismic units interpreted as seaward-dipping reflectors (SDRs) form wedges separated by highs. We propose an axial line along the Mendeleev Rise that separates probable half-grabens of different polarity. On the western slope of the Rise, all bright reflections have westward dips, while on the eastern slope they have eastward dips. SDR-like seismic units are common within the adjacent basins as well. Gravity/magnetic crustal modelling for two regional seismic lines demonstrate that the Mendeleev Rise and adjacent basins are associated with stretched continental crust.