Évolution géomorphologique, enregistrements sédimentaires et dynamiques paléoenvironnementales holocènes à Ounjougou (Plateau Dogon, Mali, Afrique de l’Ouest)

Les enregistrements sédimentaires de la séquence holocène d’Ounjougou sont riches en informations. Plusieurs missions de terrain, les analyses de laboratoire et les nombreuses datations absolues permettent de proposer une reconstitution des grandes étapes de l’évolution hydrosédimentaire et paléoenvironnementale de la vallée du Yamé depuis le tout début de l’Holocène. L’analyse géomorphologique, l’étude stratigraphique des formations et les datations 14C, montrent que l’Holocène se caractérise par plusieurs phases d’incision et d’accumulation et par l’élaboration de deux niveaux de substitution en contrebas d’un glacis principal. Riches en pollens, en phytolithes, en feuilles et en bois fossiles, notamment à partir de l’Holocène moyen, les formations permettent également de se faire une première idée de l’impact des principales modifications climatiques et anthropiques sur les écosystèmes. Tout indique que l’Homme accroît son action sans doute à partir de l’Holocène moyen, mais surtout durant l’Holocène récent et final. Sa responsabilité est directement suggérée dans l’explication de la mise en place de la terrasse protohistorique durant le premier millénaire après J.-C.The sedimentary records of the holocene sequence of Ounjougou are rich in informations. Many onsite missions, laboratory analyses and numerous absolute datings make it possible to propose a reconstitution of the major stages of the hydrosedimentary and paleoenvironmental evolution of the Yamé valley from the start of the Holocene. The geomorphological analysis, the stratigraphic study of formations and 14C datings show the Holocene is characterised by various phases of incision and accumulation and by the elaboration of two levels of substitution downstream from a main glacis. Rich in pollens, in phytoliths, in fossils leaves and wood, in particular from the Middle Holocene, the formations also make it possible to have an initial idea of the main climatic and anthropic modifications on the ecosystems. Everything indicates that man increased his action, probably as of the Middle Holocene, but above all during the Recent and Final Holocene. Its responsibility is directly suggested in the explanation of the protohistoric terrace during the 1st millenium AD

Histoire des sciences au Moyen Âge

Programme de l’année 2010-2011 : I. Les intérêts scientifiques dans les commentaires bibliques (suite). — II. Les transformations de la matière et leurs théories médiévales (suite)

The First Emergence of Ceramic Production in Africa

The discoveries at Ounjougou (Mali), an open-air site in the Dogon Country, shed new light on the “early Neolithic” in Africa. The stratigraphic sequence and a cluster of absolute dates established a terminus ante quem of 9400 cal bc for ceramic sherds associated with a small bifacial lithic industry. The emergence of this typo-technical complex corresponds to one of the wet phases of the Pleistocene–Holocene transition in West Africa, most probably that of the climatic upturn at the beginning of the Holocene, between 10,200 and 9,400 cal bc. Paleoenvironmental results, particularly archaeobotanical ones, indicate that the landscape was in a state of change and that, for several millennia, the surfaces covered by desert overlapped an open steppe with grasses, some of which were edible. This environmental situation allowed the dispersion of prehistoric groups over the continent and probably encouraged a new behavior: the practice of intensive selective gathering (i.e., the targeted and rational harvesting of wild grasses for their seeds). However, not only must seeds be kept dry and protected from rodents, they must also be processed through cooking or fermentation. This process helps the human body to assimilate the starch, as the digestive enzymes necessary for its digestion are not naturally present. Ceramics would have been particularly useful in this process. Ceramics emerged in sub-Saharan Africa and seem to have spread toward the central Sahara during the early Holocene at the end of the 10th and the beginning of the 9th millennium cal bc, while the desert zone became increasingly greener. It has yet to be understood whether the Nile Valley was an important corridor for the diffusion of this technology or if ceramics appeared as the result of a second independent process of innovation