ABSTRACT
This review focuses on Holocene swampy, estuarine and fluvial systems of the southern coast of Congo. These deposits can provide proxy data at various geographic and chronologic palaeoclimate scales. During the relative high stand of the MIS 3, about 45,000–35,000 years BP, an important thickness of peat deposited in mangrove swamp in the palaeo-valley of the Kouilou estuary. During MIS 2, the significant fall in the sea level led to the emersion of this site and to the important compaction of these peaty deposits. During MIS 1, the approach of the Holocene led new conditions favourable to the mangrove development. In the Bay of Pointe-Noire, the morpho-structural depression of the Upper Cretaceous between 9000 and 7000 years BP allowed the rapid deposition of more than 10 metres of not compacted peat. In Kouilou River palaeo-valley, it was only during the end of the Holocene that the bank deposition shows recurrent evidence of the mangrove proximity.
Holocene palaeoclimatic changes of central Africa are now well documented, but there is evidence that landscape evolution of the coastal plain has also been affected by approach and then arrival of the marine transgression and its influence on hydrological process. From 7000–6000 years BP, the construction of large beach barriers by the oceanic drift allowed the definition of long and narrow depressions where Monopetalanthus swampy forests developed, thus allowing accumulation of peat and organic muds. Water table oscillations favoured an active podzol process of the littoral sands and development of hydromorphic soils (gley). Indications of a marked renewal of erosion, probably of climatic origin, are present on the scale of the last centuries. Finally, a more recent generation of beach barriers came to bury these paralic deposits. Today, very dynamic oceanic erosion is exposing these Holocene deposits and providing new opportunities to obtain more and better palaeoclimate databases.
