ULVS XXVI: Sedimentological and Palynological Studies of Holocene Environmental Changes from a Plateau Basin Infill Sequence at Grerat D'nar Salem, near Beni Ulid, in the Tripolitanian Pre-desert

Abstract

AbstractThis paper describes an integrated series of sedimentological and palynological studies of the arenaceous deposits which infill the large alluvial basin of Grerat D'nar Salem, which is located on a limestone plateau in the semi-arid pre-desert of Tripolitania north-west of the town of Beni Ulid. This research shows that in the early and middle Holocene this depression was occupied by a large semi-permanent or permanent water body which was surrounded by a grass-steppe vegetation with some tree and shrub species, perhaps growing in wetter stream- and wadi-beds. Sometime in the mid-Holocene the region became much more arid, the lake disappeared, matching the pattern of environmental change observed elsewhere in northern Africa. The geomor-phic environment became dominated by aeolian processes, interrupted by occasional winter floods, in a landscape dominated by grass steppe — essentially the situation that has continued to the present day. It is clear from general biogeographical and geomorphic considerations that Romano-Libyan floodwater farming in the region must have brought about significant changes in the character of wadi floors. Field survey indicates that it has also left a legacy in the contemporary distribution of plants, animals and runoff in the modern landscape. Nevertheless, no clear evidence has emerged from this study that the widespread and intensive flood-water farming, evidenced by the archaeological remains in the area, was associated with either a climate or a landscape notably different from that of today. The new palynological evidence suggests that the nature of the related ancient cultivation at Grerat is better viewed as a monoculture, rather than the mixed farming deduced previously for wadi-floor areas. There is no evidence that any naturally-occurring environmental change was associated with the introduction or loss of floodwater farming in the region. There is some sedimentological evidence that such activity might have led to problems of soil salinity in this basin.