There are "young" and "ancient" stratigraphical models of bottom sediments in the Arctic Ocean . The "ancient" one is based on paleomagnetic analysis and revealing of certain index-species. The "young" one based on the ¹⁴C dating and oxygen stable isotope composition.

The piston core from 26 cruise of r/v "Akademik Fedorov" from the western flank of the Mendeleev Ridge ( 2280 m water depth, total core length ~ 350 cm ) has been treated. Size fraction > 125 µm in all samples was used for total planktonic and benthic foraminiferal abundance counts, and benthic species identification. Foraminiferal analysis reveals five abundance maxima of benthic foraminifera throughout the core, corresponding to brown sediment beds. The same intervals characterized by planktonic abundance maxima as well. The 0-15 and 20- 50 cm core intervals contain abundant assemblage of benthic foraminifera and are characterized by high biodiversity. The benthic foraminifera species composition probably reflects alternating inflow of Pacific and Atlantic waters in the time interval 34-183 kyrs. Oridorsalis tener are numerous in 190- 210 cm interval. It is known they become dominant in oligotrophic environment. 61- 112 cm interval separates two foraminifera abundance peaks from horizons that are almost barren of benthic and planktonic fauna. The fauna absence could possibly be explained with dissolution or other destruction processes. In some samples of the interval there are black colored particles. Some of them appeared to be foraminifer shells which are completely replaced with ferric compounds. The foraminiferal assemblages generally correspond with the faunas from the Mendeleev Ridge.

The age control was provided by three ^23OTh/²³⁴U dates. If the sediment age is determined correctly then benthic foraminifera-rich units corresponds with the Mikulinian and Likhvinian inerglaciations - MIS 5 (Marine Isotope Stages) and MIS 11. Similar age dates were obtained earlier for northern Mendeleev Ridge. At the same time the ¹⁴C and aminoacide dates were obtained. They indicate the younger age of same sediments. Benthic foraminifera-rich units in this case correspond to the Middle Valdaian (MIS 3) and Mikulinian (MIS 5) interglaciations. The problem of different dating methods could be considered as unsolved yet.

Ссылка на статью:

Khomenko E., Gusev E., Maksimov F., Levchenko S. Benthic foraminifers from Central Arctic ocean bottom sediments. Forams-2010. International Symposium on Foraminifera. Bonn . Sept. 5-10, 2010. Abstract Vol. with Program, P. 120-121.