8th International Nannoplankton Association Conference


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Dimitris Frydas, Spyridon Bellas:
Dependence of Late Quaternary coccolith associations to the impact of climatic changes; Preliminary report from the Ionian Sea

The piston-core, M25/4-KL13, of 11.20m length, which comes from a water-depth of 2533m from the Ionian Sea, has been studied for its calcareous nannofossil content. Samples were taken an average of 10cm distances. Calibration was based on a stable isotopic curve for the planktonic foraminifer, Globigerina bulloides (Schmiedl et al., 1998). Furthermore, the sediment-core was stratigraphically compared through graphical correlation of the 18O curve with the SPECMAP-standard isotope curve (Imbrie et al., 1984). Accordingly, the investigated core reaches until isotope stage 9 (about 330ka) and covers the sapropel formations S1 to S10.

The impact of climatic fluctuations on the marine Mediterranean palaeoenvironment (palaeoproductivity, deep-water formations) during the Late Quaternary is herein quantified on the basis of coccolith associations consisting of the 'heavy' and 'light' groups (enriched or diminished in 18O, relative to equilibrium: Steinmetz, 1994). The former group includes the species Emiliania huxleyi, Gephyrocapsa caribbeanica, G. oceanica and small gephyrocapsids dominated by G. ericsonii and G. muellerae, while the latter group includes Calcidiscus leptoporus, Helicosphaera carteri var. carteri, H. carteri var. hyalina, H. carteri var. wallichii, Scyphosphaera pulchra and Umbilicosphaera sibogae.

According to our data, it was possible to subdivide the stratigraphic interval of the last 300ka into eight coccolith climatic zones. These zones were defined by a) dominance, b) first appearance, c) recurrence and d) change in dominance of two closely-related species. Their positions relative to Isotope Stages 1 to 9 follows: 1) dominance of Emiliania huxleyi with a participation of more than 20% until Isotope Stage 1.1, and 2) less than 20% of E. huxleyi from Isotope Stage 1.1 to 3.1; 3) increasing Calcidiscus leptoporus and helicosphaerids between Isotope Stages 3.1 and 3.3; 4) change in dominance ratio between E. huxleyi and G. muellerae below Isotope Stage 4.2; 5) recurrence of E. huxleyi between Isotope Stages 5.2 to 5.5; 6) dominance of small gephyrocapsids (mostly G. ericsonii and G. muellerae); 7) recurrence of G. oceanica from Isotope Stage 7.2 to the first appearance of E. huxleyi, located just above Isotope Stage 8.4, dated at about 266ka; 8) dominance of G. oceanica between Isotope Stages 8.4 to 9.


Imbrie, J., Hays, J.D., Martinson, D.G., McIntyre, A., Mix, A.C., Morley, J.J., Pisias, N.G., Prell, W.L. & Shackleton, N.J. 1984. The orbital theory of Pleistocene climate: Support from a revised chronology of the marine 18O record. In: A. Berger, J. Imbrie, J. Hays, G. Kugla & B. Satzmann (Eds). Milankovitch and climate. Reidel, Dordrecht: 269-305

Schmiedl, G., Hemleben, C., Keller, J. & Segl, M. 1998. Impact of climatic changes on the benthic foraminiferal fauna in the Ionian Sea during the last 330 000 years. Paleoceanography, 13(5): 447-458.

Steinmetz, J.C. 1994. Stable isotopes in modern coccolithophores. In: A. Winter & W.G. Siesser (Eds). Coccolithophores. Cambridge University Press: 219-229.


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