Aridity in Equatorial Africa During the Last 225,000 Years: A Record of Opal Phytoliths/Freshwater Diatoms From the Zaire (Congo) Deep-Sea Fan (Northeast Angola Basin)
| Autor: | J H F Jansen, C Alderliesten, C M Houston, A F M de Jong, K Van Der Borg, J M Van Iperen |
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| Rok vydání: | 1989 |
| Předmět: |
010506 paleontology
Archeology 060102 archaeology 06 humanities and the arts 01 natural sciences Deep sea Arid law.invention Paleontology Angola Basin Oceanography law General Earth and Planetary Sciences 0601 history and archaeology Radiocarbon dating Quaternary Cenozoic Geology 0105 earth and related environmental sciences |
| Zdroj: | Radiocarbon. 31:557-569 |
| ISSN: | 1945-5755 0033-8222 |
| DOI: | 10.1017/s0033822200012145 |
| Popis: | Maps of accumulation rates of freshwater diatoms and opal phytoliths in the surface sediments of the Zaire fan show that both types of microfossils were supplied to the ocean floor by the Zaire River, and that opal phytoliths also have a southern source, probably the region of the Namibian desert. The PhFD ratio, of opal phytoliths to freshwater diatoms, can be regarded as an aridity index for equatorial Africa, and probably for large parts of the central and southern Atlantic. In two cores, the record of the PhFD ratio indicates humidity ca 225–190 ka BP, aridity 190–135 ka BP with maxima ca 170 and 140 ka BP and a humid excursion 150 ka BP, an increase in humidity 115 ka BP, a less humid period 90–30 ka BP, more humidity ca 30–17 ka BP with possibly more arid intervals ca 22.5 and 20 ka bp. In general, glacial (sub) stages were more arid and interglacial (sub) stages more humid. For the last 20 ka, the PhFD ratio corresponds closely with the known climatic events in tropical Africa. |
| Databáze: | OpenAIRE |
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