Benthic foraminifera of surface sediments from the continental slope off Sierra Leone, North-West Africa
On "Meteor" cruise 30 (1973) 22 piston-cores were collected off Sierra Leone from water-depths between about 5000 m (Sierra Leone Basin) and 500 m (upper continental slope) with the objective to study the sediment composition and age as well as processes of sedimentation on the continental...
| Main Authors: | , |
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| Format: | Dataset |
| Language: | English |
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PANGAEA
1978
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| Subjects: | |
| Online Access: | https://doi.pangaea.de/10.1594/PANGAEA.548464 https://doi.org/10.1594/PANGAEA.548464 |
| Summary: | On "Meteor" cruise 30 (1973) 22 piston-cores were collected off Sierra Leone from water-depths between about 5000 m (Sierra Leone Basin) and 500 m (upper continental slope) with the objective to study the sediment composition and age as well as processes of sedimentation on the continental slope in a tropical humid region. Granulometric analysis and determinations of the carbonate contents of the sediment samples were carried out, as well as qualitative and quantitative analysis of the components of the grain size fractions > 63 µm and of the planktonic and benthonic foraminifera > 160 µm. Presently, the cold Canary Current influences the composition of the planktonic foraminifera within the northwestern area of investigation (profile A), whereas the planktonic fauna of the eastern area (profile C) seems to be truly tropical. In all Quaternary sediments from the continental slope off Sierra Leone, species of Globorotalia are less abundant than in truly pelagic sediments. For that reason, the zonation of the Pleistocene sediments based on the presence or absence of Globorotalia cultrata does not always agree with the climatic changes reflected in the sediments. Concerning past climates better results can be obtained by using the changes in percentage abundances of Globigerina sp. sp. and Globigerinoides sp. sp. as indicators for cool and warm temperatures. The Tertiary sediments contain a pelagic foraminiferal assemblage. In the Holocene sediments the benthonic foraminifera do not only serve as good paleodepth indicators, but their communities are also restricted to defined water masses, which change their positions in accordance with climatic changes. Thus, Cassidulina carinata in the area of investigation is an excellent indicator for sediments deposited during times, which were cooler than today; this is true for all cores from the continental slope off Sierra Leone independent of water-depth although this species presently abounds at water-depths around 600 m. The cores from the continental rise and ... |
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