HOW EVOLVING HOLOCENE LANDSCAPES ARE FILLING IN THE VALLEY BOTTOMS OF GABON’S LOPÉ NATIONAL PARK IN THE MID OGOOUÉ VALLEY

Abstract

Sedimentological and geochemical ana- lyses and 14C dating were performed for a sedimentary core sample from the Lope 2 marsh in the northern zone of Gabon’s Lope National Park. The results produced a division of the core sample into three main units. The basal part of the core sample was dated to 2,320 years cal BP. At this time, the Lope 2 marsh was a topo- graphic hollow that flooded sporadically during the rainy season. This unit corres- ponds to a soil formation of clay, quartz and highly decomposed organic matter. The upper boundary of this unit corres- ponds to the end of the climatic deterio- ration that affected central Africa around 2,500 years BP. The second unit represents the period from 2,320 to 585 years cal BP. This shows a gradual decrease in the flow of quartz that reflects the increasing rela- tive density of the marsh vegetation as the climate became more humid. The organic matter in this unit is of mixed origin, rela- tively abundant and with a high content of refractory material. The third unit, repre- senting the period from 585 years cal BP to the present, shows plant cover asso- ciated with developing marshland (which began in unit 2) that was sustained by the humid climate. The organic matter here is rich in biological material.