Late-Holocene equatorial environments inferred from deposition processes,carbon isotopes of organic matter,and pollen in three shallow lakes of Gabon,west-central Africa |
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| Authors: | Pierre Giresse Makaya Mvoubou Jean Maley Alfred Ngomanda |
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| Institution: | (1) Laboratoire d’études des Géo-Environnements Marins, Université de Perpignan-Via Domitia, 52, Av. Paul Alduy, 66860 Perpignan, France;(2) Paléoenvironnement et Palynologie, CNRS/ISEM, Université Montpellier II, 34095 Montpellier, France |
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| Abstract: | Seven vibro-cores were collected from three shallow lakes of the Gabon (Kamalété, Nguène, Maridor) along a 300-km west–east
transect close to the Equator. These lakes are located in very distinct landscapes: coastal forest-savanna mosaic, rain forest
and savanna with colonising forest, respectively. Core chronologies were established by radiocarbon dating. Study of these
lacustrine archives (textural variables, clay minerals, organic matter components, δ13C, pollen) allowed comparison of late Holocene environmental changes recorded at each site and with results from other studies.
Lake Kamalété indicates minor climatic deterioration (increased drying and greater seasonality) between 1,410 and 500 cal.
years BP, which is also recognised in southern Cameroon and east-central Africa. Lake Nguène was surrounded by dense moist
forest throughout the last 4,110 years, but shows significant deterioration from ~2,800 cal. years BP, a phenomenon seen at
nearby sites. Lake Maridor shows a decline of forest initiated a little after 3,800 cal. years BP, which indicates timing
that is distinct from the two other sites. This was probably a response to local conditions (i.e. outlet damming). Although
the three lakes display generally parallel climatic trends perhaps linked to SST oscillations, there is not perfect coherence
between these three sites. Differences among the three basins may be attributable to local factors like groundwater hydrology
and slope instabilities of such shallow lake systems in this equatorial region. |
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| Keywords: | Gabon Holocene Lacustrine sediment Pollen δ 13Corg Climatic trend |
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