A. Romanova, N. Iurchenko
Table 2. Complexes of planktonic foraminifera in the Sea of Okhotsk in cores 936, LV 40 - 06, LV 40 - 18, LV 40 - 20.
Complex max F с, H, e Characteristics of paleoassemblage D Province
I 2749 0.4; 0.7-1; 0.4 Relative abundance of N. pachyderma sin down to 54%; G.
bulloides up to 40%, presence of N. pachyderma dex., G.
glutinata, T. quinqueloba, G. scitula, G. uvula +- Central
II 108 0.7; 0.3, 0.7 N. pachyderma sin. up to 100%; G. bulloides down to 5.6%,
presence of N. pachyderma dex - Northern
III 603 0.4; 0.8; 0.5
N. pachyderma sin 43% - 84%
G. bulloides up to 38%
N. pachyderma dex. (up to 6%), T. quinqueloba (up to 5%), G.
scitula (up to 1%), G. glutinata (up to 1%)
+- Central
IV 21 0.7; 0.5; 0.6 N. pachyderma sin. up to100%; in some intervals presence of
G. scitula, G. quinqueloba; G. bulloides up to 20% -
the central
V 346 0.7; 0.5; 0.6 N. pachyderma 60% - 78%; G. bulloides up to 28%;
T. quinqueloba up to 8%; presence of N. pachyderma dex., G.
scitula, G. glutinata +- Central
Note: Each complex corresponds to MIS 1-5. D—traces of dissolution; max F—maximum of foraminiferal number or total abundance of foraminifera
(shells/g of dry sediments); c, H, e—diversity indices.
4. Conclusion
Therefore, we conclude that diversity indices can be additional proxy for paleooceanologial changes that should
be used in comprehensive foraminiferal analysis in case with the Okhotsk foraminiferal fauna that has some
challenges in studying. Diversity indices show different aspect of changes in structure of foraminiferal assem-
blages: dominance of N. pachyderma sin., increasing role of another taxa, evenness with which individuals are
divided among the taxa present. A map of species diversity (number of species) shows a good defined region of
high diversity in the central part with slow accumulation rates, low terrigenous dilution and influence of warm
Pacific waters. Use of the Shannon diversity index enhances and clarifies this region of high diversity. We as-
sume that Shannon and Simpson indices are more representative and sensitive to changes in structure of assem-
blages that is caused by environmental changes. Equitability index is not so indicative because in case of small
number of species (1 - 2) and dominance of one species it repeats the Simpson index. Correlation the data ob-
tained from sediment station with cores data showed that borders of the biogeographical provinces were moved
from the northern part to the central during cold MIS 2, 4. Structure of assemblages during MIS 3, 5 was close
to the modern Central province but characterized by low total foraminiferal abundance in the sediments.
Acknowledgements
The authors would like to express their sincere appreciation to Dr. M. Cherepanova for fruitful suggestions and
comments, and to Dr. S. Gorbarenko, A. Derkachev for provided material. We also appreciate Prof. V. Pushkar,
Prof. M. Kuchera and N. Lubke for their help and constructive critics. This research was supported by grant
FEB RAS 14-III-В-08-186.
References
Barash, M. (1970). Planktonic Foraminifera in North Atlantic Sedimen ts . Moscow publ.
Dieckmann, G. , Spindler, M. , Lange, M. A. , Ackley, S. F. & Eicken, H. (1991): Antarctic Sea Ice: A Habitat for the Fo-
raminifer Neogloboquadrina Pachyd erma. Journal of Foraminiferal Research, 21, 182-189.
http://dx.doi.org/10.2113/gsjfr.21.2.182
Gorbarenko, S. A., Southon J. R., Keigwin L. D., Cherepanova M. V., & Gvozdeva I. G. (2004). Late Pleistocene-Holocene
Oceanographic Variability in The Okhotsk Sea: Geochemical, Lithological And Paleontological Evidence. Palaeogeo-
graphy Palaeoclimatology Palaeoecology, 209, 281-301. http:// dx.doi.org/10.1016/j.palaeo.2004.02.013
Harper, D. A. T. (Ed.) (1999). Numerical Palaeobiology. New York: John Wiley & Sons.
Loeblich, A. R., & Tappan, H. (1987). Foraminiferal Genera and Their Classification. New York: Van Nostrand Rienhold