The mineralogy and provenance of deep-sea sediments recovered by gravity corer off Sierra Leone,West Africa |
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| Authors: | Hakuyu Okada Katsutoshi Tomita E J W Jones |
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| Institution: | (1) Institute of Geosciences, Faculty of Science, Shizuoka University, 422 Shizuoka, Japan;(2) Institute of Earth Sciences, Faculty of Science, Kagoshima University, 890 Kagoshima, Japan;(3) Department of Geology, University College London, Gower Street, WC1E 6BT London, U.K. |
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| Abstract: | The mineralogy of eight gravity cores recovered between Sierra Leone and 25°W longitude has been examined in an investigation
of the provenance of the recent sediments in the eastern Equatorial Atlantic. X-ray analyses show that the principal mineral
components are calcite, quartz, feldspar, kaolinite, illite and montmorillonite. One core taken from the upper continental
slope off Freetown also contains gibbsite, a product of intense tropical weathering. Biogenic material forms the dominant
component of most sections of the cores but it is clear from the abundance of quartz, kaolinite and freshwater diatoms that
an aeolian supply of continental detritus has been important in the formation of the recent sediment cover. A significant
contribution from volcanic sources can be recognised to the west of the Sierra Leone Rise. The occurrence of calcareous turbidites
in two cores from the St. Paul's Fracture Zone and from the basin west of the Sierra Leone Rise appears to be a reflection
of recent tectonic activity. |
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