Palaeoecology in the Dogon Country (Mali)

Introduction

The site complex of Ounjougou – situated at the transition of the Sahelian and Sudanian zones – was the starting point of our palaeoecological research in the Dogon Country.  Here, the Yamé River and its tributaries have exposed thick stratified sediment deposits, unique archives of the region’s settlement and climate history and dating back up to 100,000 years before present.

Since 1995 the interdisciplinary project „Peuplement humain et paléoenvironnement en Afrique de l’Ouest“, directed by Eric Huysecom (University of Geneva), has studied the settlement and landscape history of the Ounjougou region. In 2005, archaeobotanists of Goethe University joined the team. In close cooperation with sedimentologists, archaeologists and dating specialists, the archaeobotanical samples are put into a precise chronological framework, facilitating their taphonomical interpretation (e.g. regional vs. local origin from the gallery forest).

Sampling at the site Ravin Sud (Ounjougou)

Holocene vegetation and landscape development

At Ounjougou, the sediments of the last 10,000 years are extremely rich in botanical micro- and macro-remains which allow for a reconstruction of the gallery forest and the surrounding savannas. They have been strongly altered during this period under the influence of climatic fluctuations and human impact, mainly burning and agriculture. The effects of climate and human impact on the vegetation interfere and are often hard to separate out. Investigations of micro-charcoal in seasonally laminated sediments provide clear evidence for intentional burning.

In the Early Holocene, the open savanna with Sahelian affinities and low species diversity was rarely subject to bush fires. After ca. 8000 BC, dense Sudano-Guinean savannas and open forests established and were regularly burned, as well as the gallery forest. A prominent element of the in the gallery forest was the African bamboo Oxytenanthera, represented by charcoal and burnt phytoliths. In the second millennium BC, Sahelian elements appeared again under the influence of increasing aridity.

Bamboo (Oxytenanthera) charcoal	Burnt bamboo (Oxytenanthera) phytolith

Agriculture at Ounjougou at least dates back to the first half of the second millennium BC, as evidenced by finds of charred pearl millet grains (Pennisetum glaucum) at the site Varves Ouest. But distinct vegetation changes in the course of the third millennium BC, confirmed by macro-charcoal and phytolith analyses, point to an earlier onset of plant cultivation.

In the Dogon Country’s younger history, at least after 1000 AD intensive iron metallurgy at the western margins of the plateau altered the woody vegetation and landscape due to rigorous wood-cutting for smelting. Contemporaneously, areas under cultivation were extended. We investigated these younger developments mainly at archaeological sites (settlement mounds in the Séno Plain, settlements at the Bandiagara cliff, and slag heaps at the western margins of the Dogon Plateau) because Ounjougou does not provide continuous palaeoecological sequences for this period.

Outlook: Phytolith Research

Currently, phytolith analyses are in the methodological focus of our research in the Dogon Country. Phytoliths are microscopic silica bodies in plants which may persist in soils for a very long time and are useful for palaeoecological reconstructions. We investigate phytoliths preserved in Holocene samples and conduct comparative studies on modern plants and surface soil samples.

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Selected publications

Eichhorn, B., Neumann, K. & A. Garnier (2010): Seed phytoliths in West African Commelinaceae and their potential for palaeoecological studies. - Palaeogeography, Palaeoclimatology, Palaeoecology 298: 300-310.

Eichhorn, B. & K. Neumann (in press): Holocene vegetation change and land use at Ounjougou (Mali). - In: Fuller, D. & M.A. Murray (eds.): Flora, Past Cultures and Archaeobotany in Africa. Walnut Creek (Left Coast Press).

Eichhorn, B., Robion-Brunner, C., Perret, S. & V. Serneels (in press): Fuel for iron – wood exploitation for metallurgy on the Dogon Plateau, Mali. Proceedings of the "World of Iron Conference", London 2009.

Huysecom, E., Rasse, M., Lespez, L., Neumann, K., Fahmy, A., Ballouche, A., Ozainne, S., Maggetti, M., Tribolo, C. & S. Soriano (2009): The emergence of pottery in Africa during the tenth millennium cal BC: new evidence from Ounjougou (Mali). - Antiquity 83: 905–917.

Huysecom, E., Ozainne, S., Robion-Brunner, C., Mayor, A., Ballouche, A., Chaix, L., Cissé, L., Eichhorn, B., Guindo, N., Le Drezen, Y., Lespez, L., Mezger, H., Neumann, K., Perret, S., Poudiougou, M., Rasse, M., Sanogo, K., Schneider, K., Serneels, V., Soriano, S., Soulignac, R., Traoré, B. D., & C. Tribolo (2009): Nouvelles données sur le peuplement du pays dogon: la onzième année de recherches du programme « Peuplement humain et évolution paléoclimatique en Afrique de l'Ouest ». - SLSA Jahresbericht 2008: 71-183.

Le Drézen, Y., Lespez, L., Rasse, M., Garnier, A., Coutard, S., Huysecom, E. & A. Ballouche (2010): Hydrosedimentary records and Holocene environmental dynamics in the Yamé Valley (Mali, Sudano-Sahelian West Africa). - Comptes Rendus Geoscience 342: 244-252.

Lespez, L., Le Drezen, Y., Garnier, A., Rasse, M., Eichhorn, B., Ozainne, S., Ballouche, A., Neumann, K. & E. Huysecom (2011): High-resolution fluvial records of Holocene environmental changes in the Sahel: the Yamé River at Ounjougou (Mali, West Africa). - Quaternary Science Reviews 30: 737-756.

Neumann, K., Fahmy, A., Lespez, L., Ballouche, A. & E. Huysecom (2009): The Early Holocene palaeoenvironment of Ounjougou (Mali): Phytoliths in a multiproxy context. - Palaeogeography, Palaeoclimatology, Palaeoecology 276: 87-106.

Ozainne. S., Lespez, L.,  Le Drezen, Y., Eichhorn, B., Huysecom, E. & K. Neumann (2009): Developing a chronology integrating archaeological and environmental data from different contexts: the Late Holocene sequence of Ounjougou (Mali). - Radiocarbon 51: 457–470.

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