Investigations on plant remnants in a prehistoric Saharan highland rock shelter

The 6.035 and 3.700 B. P. layers in Uan-Muhuggiag rock shelter, Tadrart Acacus (Libya), have yielded a few plant macro-remains. Wood belonging to Cupressaceae, Leguminosae, Oleaceae, Tamaricaceae has been possible to determine. Some fruit-stones of Balanites aegyptiaca and fruit of Zilla spinosa have also been found. The Mediterranean element Olea can be regarded as a relict of milder periods during Pleistocene when the Mediterranean flora spread out into the Sahara. In the neolithic site of Amekni charcoal of Olea was among remnants; at present this taxon grows in the Hoggar Mountains. Analysis carried on charcoal remnants from different sites helps to suggest a shift to the north of tropical climate and vegetation belts in the Holocene. At Fachi-Dogonboulo in Niger the 7000 B.P. sudanian flora points to a simultaneous shift of the vegetation zones in the Eastern and in Central Sahara. Nevertheless the coexistence of vegetational formations both Sahelian and Sudanian in the ca.7000 B.P.layers in central Sahara looks to be probable. At Fachi the samples contain sudanian taxa which today grow 400 km further south. With increasing aridity from 5200 onwards, the savanna formations retreated to the south until their present position was reached by 3300 B.P. Pollen analysis in the Tibesti 14000-6000 bears out this climatic trend showing both tropical sahaelian elements together with typical oro-mediterranean ones. The Mediterranean element Olea can be regarded as a relict of milder periods during Pleistocene when the Mediterranean flora espanded into the Sahara.