Ounjougou (Mali): A History of Holocene Settlement at the Southern Edge of the Sahara
Huysecom, E., Ozainne, S., Raeli, F., Ballouche, A., Rasse, M., Stokes, S., Antiquity
In sub-Saharan West Africa traces of Early Holocene occupation are sparse, and more recent sites are generally restricted to a short chronological span. It is therefore rare to be able to examine a long sequence of climatic, environmental and cultural interactions for this period. The archaeological strata described here from the Bandiagara Plateau in Mali (Figure 1) provide a new basis from which these interactions may be examined.
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Previous archaeological and palaeoenvironmental descriptions of the Bandiagara Plateau consist of only a short note which mentions the existence of a Neolithic occupation (Szumowski 1956). We define here as Neolithic the populations producing ceramics and using grinding implements prior to the appearance of metallurgy, and who may or may not have practised agriculture and animal husbandry. Our exploration of this areas began in winter 1993-1994, when survey led to the discovery, of the Ounjougou site complex (Huysecom 1996). Situated around ten km east of the city of Bandiagara, this complex includes numerous archaeological sites within a zone of 10 [km.sup.2] on the sloping valley of the Yame, a tributary of the Niger (Figure 1). Currently located on the southern edge of the semi-arid Sahelian zone, it comprises a series of gullies cut into a complex succession of Quaternary aeolian, alluvial and colluvial deposits. The 16 m thick stratigraphic sequence has yielded archaeological material from the Lower Palaeolithic to modern times. The sediments also contain abundant palaeoecological remains (pollen, leaves, charcoal, wood, seeds, etc.) for which the state of preservation is exceptional for the sub-Saharan area. The value of the Ounjougou site complex for examining relationships between human occupation and environmental variation over a long chronological sequence motivated the development, in 1997, of an international interdisciplinary research program titled "Palaeoenvironment and human settlement in West Africa" (Huysecom 2002). Research undertaken to date has permitted the establishment of a preliminary sequence and occupations from the Pleistocene to the historic period to be identified (Robert et al. 2003; Mayor et al. forthcoming). The present article focuses on archaeological and palaeoenvironmental data for the Holocene, covering the period from the tenth to the second millennium BC.
The Holocene sequence of Ounjougou and the five occupation phases
The Holocene sites of Ounjougou are distributed around a confluence zone where four watercourses meet, and the main permanent water source for the region is found (Figure 1). From a hydrographical point of view, it appears that the confluence has undergone changes in riverine/lacustrine flow regime which are represented by the deposition of a complex suite of sedimentary facies ranging from imbricated gravel-dominated open channel facies, through to fine grained and organic-rich lacustrine and slackwater deposits. Archaeologically, these sites are either habitations in primary position on recent terraces, or on the valley floor covered by rapid colluvial deposits or overflow, or sites on the valley floor where the archaeological material, although discovered in stratified levels, is no longer in primary position, but is derived from nearby habitation sites.
The results of our research currently permit us to define five principal occupation phases on the basis of chronostratigraphic, archaeological and palaeoenvironmental data. These are discussed separately below.
Phase 1 (tenth--beginning of the ninth millennium BC)
After a favourable humid climatic period, characterised by relatively dense and diversified Palaeolithic occupations, the arid Ogolian begins locally around 23 000 BP and is represented at Ounjougou by a significant depositional and archaeological hiatus (Robert et al. 2003). It is not until the Holocene and the return of humid climatic conditions, beginning in the tenth millennium BC, that it is possible to again observe evidence of human occupation. …