Environment and settlements in the Mid-Holocene palaeo-oasis of Wadi Tanezzuft (Libyan Sahara)

During the wet middle Holocene (7th-6th millennia BP), not only the ergs, but almost all the landscape units of the Wadi Tanezzuft were rich in water, which was provided by a rainy season connected to the northward movement of the central African monsoon. The whole desert around the Wadi Tanezzuft was suitable for intensive human occupation, constituted by semi-nomadic pastoral groups. The subsequent withdrawal of the monsoon to a more southerly position affected in different ways each of the landscape units in the area. At about 5000 BP, probably as a direct result of the monsoon shift, the most hydrologically fragile segments of the area (pediment, playas and dune field lakes) dried out, while the depletion of soil water reserves had been completed, at least locally, by about 3500 BP. Even so, fluvial activity along the course of Wadi Tanezzuft, notwithstanding the inactivation of the western branches, survived at least to 2700 BP. The reason for this seems to have been due to the immense amount of water stored in the catchment basin of the Tanezzuft during the wet Holocene. Three main phases of cultural adaptation to the changing landscape can be distinguished. An initial Middle Holocene phase, probably commencing around 6000 BP, with an 'anomalous' Middle Pastoral occupation, characterized by large settlements in the Titersin area, in the playa and along the dune fields, exploiting riverine resources, and with a specific socioeconomic organization. A second phase, roughly datable to the beginning of the Late Pastoral, associated with the first contraction and shift of the Tanezzuft system, which led to increasing site density in the region between Kaf Jinun and Tahala oasis. This region became the focal area for human communities, but dramatic site density, decreasing resources, and overexploitation of the landscape probably led to the emergence of social stratification, as suggested by the funerary rituals associated with this phase (di Lernia et al. 2001). Specifically, around this period cemeteries increase in size, with the co-existence of single and multiple burials, and there is much greater differentiation of grave goods, particularly along gender lines. Ovicaprine herding and soil management for plant exploitation appear to have provided the subsistence base. Ceramic containers underwent significant modifications in manufacture, shape, and decoration, highlighting a level of regional fragmentation and discontinuity with the surrounding areas, mostly the Acacus.