Ivanova, Elena v.

Max, Lars

Nürnberg, Dirk

Ovsepyan, Ekaterina A.

Riethdorf, Jan-Rainer

Tiedemann, Ralf

English

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Reconstruction of bottom water ventilation and export production based on benthic foraminiferal assemblages from the Shirshov Ridge (Bering Sea) during MS1-2  Ekaterina A. Ovsepyan, Elena V. Ivanova, Shirshov Institute of Oceanology RAS, Moscow, Russia, Lars Max, AWI, Bremerhaven, Germany, Jan Riethdorf, IFM-GEOMAR, Kiel, Germany, Ralf Tiedemann, AWI, Bremerhaven, Germany, Dirk Nürnberg, IFM-GEOMAR, Kiel, Germany,  (e-mail: ameli_cat@mail.ru)  The 18m-long core SO201-2-85KL (57°30.30 N, 170°24.79 E, w.d. 968 m) was retrieved from the Shirshov Ridge, western Bering Sea. Benthic foraminiferal assemblages have been studied in the size fractions 63-100 µm and >100 µm through the upper 3 m of the core that recovered MIS 1-2 according to the oxygen isotope stratigraphy and AMS- 14C dates. Three foraminiferal assemblages are distinguished based on the faunal portions (%) and abundance (tests/g of dry sediment) of the relevant species. The oldest assemblage corresponding to the early MIS 2 consists of several common species including Islandiella norcrossi, Trifarina angulosa, Uvigerina peregrina, Alabaminella weddellensis and Cassidulina reniforme. It indicates relatively high seasonal bioproductivity and moderate bottom water hydrodynamics. The latter seems to increase prior to the LGM as follows from the very high percent of T. angulosa. The next assemblage characterizes low-productivity conditions of the LGM with decreased benthic and planktic foraminiferal abundance. Benthic and planktic assemblages are dominated by I. norcrossi, A. weddellensis and Neogloboquadrina pachyderma sin respectively. This fauna points to cold conditions with rather low productivity related to the seasonal phytoplankton bloom with a pulsed phytodetritus flux. Low values of T. angulosa and a lack of epifaunal species ascertain weak bottom currents and restricted ventilation. The youngest assemblage contains much more abundant fauna compared to two older ones. Along with the numerous I. norcrossi and A. weddellensis it consists of noticeable amount of T. angulosa, U. peregrina, Elphidium batialis and Epistominella exigua. Very high abundance of planktic and benthic foraminifera, enhanced faunal portion of phytodetritus feeding A. weddellensis and E. exigua, productivity-related U. peregrina, E. batialis and planktic species Globigerina bulloides collectively suggest a considerable increase in bioproductivity over the termination, most likely at the Bølling-Allerød warming. The Holocene interval of the core contains much more siliceous microfossils while planktic and benthic foraminifera are remarkably less abundant.   

Reconstruction of bottom water ventilation and export production based on benthic foraminiferal assemblages from the Shirshov Ridge (Bering Sea) during MS1-3

Ivanova, Elena V.

Reconstruction of bottom water ventilation and export production based on benthic foraminiferal assemblages from the Shirshov Ridge (Bering Sea) during MS1-3

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