THE MORPHOMETRIC RESPONSE OF COCCOLITHUS PELAGICUS TO GLACIAL-INTERGLACIAL COUPLETS DURING THE LAST 4 MA.
Mário Cachão (1), Aurea Narciso (1), Alexandra Silva (2), CODENET team (3), Richard Jordan (4), Kozo Takahashi (4)
1 Centro e Departamento de Geologia, Faculdade de Ciências, University of Lisbon, Rua Escola Politécnica, No 58, P-1294 Lisboa CODEX, Portugal, mcachao@fc.ul.pt
2 Dep. Zoologia e Antropologia, Faculdade de Ciências, University of Lisbon, Ed. C2, 3¼ Piso, P-1749-016 Lisboa, Portugal, alexandra.ds@mail.telepac.pt
3 Coordinated at the Palaeontology Dept., The Natural History Museum, London, SW7 5BD, UK j.young@nhm.ac.uk
4 Dep. Earth & Environmental Sciences, Fac. Sc. Yamagata Univ., Yamagata 990 Japan, sh081@kdeve.kj.yamagata-u.ac.jp
Coccolithus pelagicus was defined as one of the key-species for the CODENET (European Comunity Training and Mobility of Researchers programme) research network. Included in CODENET's work area 3 (Coccolithophorid Ecology), subdivided in the research tasks RT13 (Holocene Sample Set) and 14 (Geological Sample Set), the morphometry of C. pelagicus was analysed with three main focus: (1) in cultures, (2) in Holocene samples worldwide and (3) during glacial and interglacial maxima, in the last 4 Ma.
Culture experiences, varying temperature and light conditions, performed at The Natural History Museum (London) provided specimens, which were subsequently measured by an automatic digitalized procedure. Due to the small number of specimens found in some of the Holocene and ODP samples, rippled smear slides were prepared and observed with optical petrographic microscopy to increase the probability of finding C. pelagicus coccoliths. Coccoliths were subsequently measured by eye estimation using an eyepiece graticule. 25 Holocene samples from Eastern Central Pacific, Western Central Pacific, Northern Pacific, Indian, North Atlantic, Central Atlantic and Southern Atlantic oceans were studied. From each ODP sites 81-522A (North Atlantic Ocean), 108-659A (Central Atlantic Ocean), 114-704A (South Atlantic Ocean), 115-709C (Indian Ocean), 130-806B (Western Central Pacific Ocean), 138-849B (Eastern Central Pacific Ocean), 10 samples were previously selected two (maximum glacial and maximum interglacial isotopic stage) for each 0-1Ma, 1-2Ma, 2-3Ma, 3-4Ma and 4-5Ma time intervals.
For each specimen maximum and minimum diameter was measured together with a simple characterization of the central area (with or without bridge). Measurements were tabulated and for each set of 100 measurements the mean, standard deviation, skewness and kurtosis of the curves were determined. The results were compared with available mean SST values for Holocene Samples and (18O values for ODP samples. Results were further compared with data from cultures.
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