FxJj43: An Early Stone Age Locality in Northern Kenya. (News & Notes)
Stern, Nicola, Antiquity
FxJj43 is an Early Stone Age locality that lies towards the top of the Okote Member in the Koobi Fora Formation, in northwest Kenya, a geological formation famous for the extraordinary array of hominin remains it has yielded, together with abundant traces of their activities (Leakey & Leakey 1978; Wood 1991; Isaac 1997). The archaeological research conducted there during the 1970s helped to forge new approaches to the problem of generating behavioural information from the remote portions of the Palaeolithic record and established new expectations about the potential of the archaeological record for contributing to the narrative of hominin evolution. However, in the intervening decades only limited consensus has been achieved about the behaviours that can be reconstructed for the early stone-tool users. FxJj43 is the focus of a new generation of research that aims to come to a better Understanding of the empirical structure of the Early Stone Age record and hence, the behavioural and palaeoecological information it encapsulates.
It is the unusual geological setting of FxJj43 that lends this locality to this exercise: it comprises a 50-200-m wide strip of outcrops that can be traced around the edge of the modern erosion scarp for more than half a kilometre (FIGURE 1). Chipped stone artefacts and broken-up animal bones are strewn all the way along the eroding surfaces of these outcrops, all of them derived from a narrow stratigraphic horizon, immediately overlying a prominent layer of volcanic ash (FIGURE 2). An initial round of fieldwork aimed at documenting the depositional history of the locality, the palaeolandscape features represented there, the stratigraphic and palaeotopographic context of the archaeological debris and their age, has now been completed.
[FIGURES 1-2 OMITTED]
This work shows that the outcrops at FxJj43 are made up of approximately 8 m of flat-lying fluvial deposits, the oldest of which is a small body of unconsolidated channel sands laid down by a westerly flowing channel. In most parts of the site the base of the sequence is actually defined by a distinctive volcanic ash, known informally as the `blue' tuff, whose 3-dimensional geometry picks out the interlocking palaeolandscape features preserved: a sandy channel, its southern bank, a mid-channel bar, a levee and the adjacent floodplain (Stern et al. 2002: 370-78). In contrast to other Okote Member sites, this one preserves a related set of palaeotopographic features (FIGURE 2).
[sup.40]Ar-[sup.39]Ar age determinations on single crystals of alkali feldspar extracted from pumices found at the top of the blue tuff show that it was deposited 1,468,000[+ or -]16,000 years ago (Stern et al. 2002: 381-5). The blue tuff represents a massive flood event (probably the 1 in 500 year flood), caused when a viscous slurry of ash and water choked the channel, topped its banks and draped the surrounding landscape in up to 2 m of sediment. This destroyed the local vegetation cover and initiated an episode of bank erosion coeval with the infilling of the channel and with the accumulation of both chipped stone artefacts and broken-up animal bones in a variety of settings, but most conspicuously on the levee (Stern et al. …