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| Titel |
Past environmental and climatic changes during the last 7200 cal yr BP in Adamawa plateau (Northern-Cameroun) based on fossil diatoms and sedimentary carbon isotopic records from Lake Mbalang |
| VerfasserIn |
V. F. Nguetsop, I. Bentaleb, C. Favier, C. Martin, S. Bietrix, P. Giresse, S. Servant-Vildary, M. Servant |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 7, no. 4 ; Nr. 7, no. 4 (2011-12-12), S.1371-1393 |
| Datensatznummer |
250004694
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| Publikation (Nr.) |
 copernicus.org/cp-7-1371-2011.pdf |
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| Zusammenfassung |
| Past limnological conditions of Lake Mbalang (7°19′ N, 13°44′ E,
altitude: 1130 m) and vegetation type were reconstructed from diatoms and
sedimentary stable carbon isotope records (δ13C) since 7200 cal yr BP.
The data showed that before 3600 cal yr BP, the water column was
dominantly stable except around 5000–5300 cal yr BP where diatoms
evidenced a mixed upper water layer and δ13C data suggest more
forested vegetation in the landscape. These stable conditions can be
explained by a strong monsoon flux and relatively northern position of the
ITCZ that entailed high or low rainfall well distributed over the year,
allowing the development of mountainous forest taxa. The decreasing trend of
the monsoon flux towards the mid-Holocene was affected by several abrupt
centennial to millennial-scale weakening at 6700, 5800–6000, 5000–5300, 4500
and 3600 cal yr BP. However, their impact on the vegetation is not visible,
probably because rainfall distribution was favourable to forest maintenance
or extension. After 3600 cal yr BP, the water column became very mixed as a
result of more intense NE trade winds (Harmattan) that led at ~3000 cal yr BP
to the establishment of savannah in the vegetation landscape. At
that time, rainfall was probably reduced following the southward shift of
the ITCZ, and the distribution of yearly rainfall was not favourable anymore
to forest development. A strong seasonality with a marked dry season was
established, conditions that maintained the savannah vegetation until today.
Diatom data suggest the lake did not dry up during the last 7200cal yr BP;
however, a low lake level observed at 2400–2100 cal yr BP is
contemporaneous to a climatic event evidenced in several areas of tropical
Africa and could correspond to the southernmost position of the ITCZ. Other
low lake levels are observed at 1800 and 1400 cal yr BP, after which the
lake rose to its present level. |
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