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- Bornmalm, Lennart, 1956, et al.
(författare)
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COILING PATTERNS IN 4 BENTHIC FORAMINIFERAL SPECIES THROUGH THE TERMINAL MIOCENE AND PLIOCENE IN THE CARIBBEAN SEA
- 1993
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Ingår i: Journal of Foraminiferal Research. - 0096-1191. ; 23:2, s. 118-122
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Tidskriftsartikel (refereegranskat)abstract
- Coiling patterns in four epibenthic foraminiferal species, Nuttallides umbonifera, Oridorsalis umbonatus, Cibicidoides wuellerstorfi and Epistominella exigua have been analysed in Deep Sea Drilling Project (DSDP) Hole 502A, located in the Colombia Basin, western Caribbean Sea. The studied sequence represents the time interval between 5.47 and 1.72 Ma. Oridorsalis umbonatus is dominantly dextrally coiled in four intervals, 3.9, 3.6-3.4, 2.6, and 1.9 Ma; in all other samples the species is randomly coiled. Epistominella exigua is also randomly coiled in most of the samples where coiling ratios could be determined, except in one sample from 3.6 Ma, where coiling is predominantly dextral. Consequently, E. exigua exhibits dextral coiling in one of the samples, where also O. umbonatus is dextrally coiled. Because sufficiently large sample sizes of E. exigua and O. umbonatus could not be obtained for the intervals of increased deltaO-18 values between 3.2-3.0 Ma and between 2.3-2.2 Ma, the influence of cooling events on coiling ratios in these species could not be assessed. The other two species investigated, N. umbonifera and C. wuellerstorfi, are randomly coiled throughout the studied sequence.
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| 3. |
- Naidu, P. Divakar, et al.
(författare)
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Quaternary history of calcium carbonate fluctuations in the western equatorial Indian Ocean (Somali Basin)
- 1993
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Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - 0031-0182. ; 103:1-2, s. 21-30
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Tidskriftsartikel (refereegranskat)abstract
- A study of the Quaternary history of calcium carbonate fluctuations in the equatorial Indian Ocean, based on the Swedish Deep-Sea Expedition Core 154 demonstrates that the Calcite Compensation Depth (CCD) was shallower during interglacial periods than during glacials. Higher percentages of calcium carbonate, lower percentages of dissolution-resistant planktonic foraminifera and lower values of the Berger dissolution index, suggesting better calcium carbonate preservation, are recorded during glacial periods and/or at glacial/interglacial transitions. In contrast, interglacial periods are marked by stronger calcium carbonate dissolution. The data indicate that dissolution is the main controlling factor of calcium carbonate in the western equatorial Indian Ocean. Higher dissolution during interglacial periods and enriched δ13C are due to higher noncarbonate productivity and enhanced Antarctic Bottom Water (AABW) ventilation in the equatorial Indian Ocean.
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