Breaks in the sedimentary and environmental equilibrium in the Congo Basin and incidences on the Oceanic sedimentation during quaternary

Abstract

Four climatic successions in the Congo region were observed for about 70 000 years B.P.: the first half of the Würmian or Wisconsinian (Maleukian, the most arid hypothermal phase), middle of AWürmian (Njilien, wetter hyperthermal), Late Würmian (Leopoldvillian, dryer hypthermal) and Holocene (Kibangian, wetter hyperthermal). The strongest podzolisations were located turing Njilian and Kibangian episodes. Clayey and impermeable slopes were eroded mostly during seasonal contrast phases, sandy slopes were incised during more regularly humid climate where the water table was near the surface. Stone-line accumulations correspond to loss balance during climatic changes. The transition from a slightly arid period toward a most humid one is correlated with an increase of precipitation on slopes tending to stay with savannah environments; the oceanic signal corresponds in the speeding-up of rates of sedimentation (x6 to x10) and in the flushing of quartzose sands. Iron content in marine deposits is higher during hyperthermal episodes.