FxJj43: A window into a 1.5-million-year-old palaeolandscape in the Okote Member of the Koobi Fora Formation, northern Kenya

FxJj43 differs from most other archaeological sites preserved in the Okote Member of the Koobi Fora Formation in ways that make it especially suited to the problem of clarifying the behavioral information encapsulated in fine time-lines. At this site in northern Kenya, a continuous strip of outcrops, preserving a set of interlocking landforms, can be traced around the modern erosion front for more than half a kilometer. The characteristics and three-dimensional geometries of the beds making up these outcrops show that they have preserved the southern bank, levee, and floodplain of a westerly flowing sandy channel. Both stone tools and animal bones are strewn across the eroding surfaces of these outcrops, and excavations show that they are derived from a narrow stratigraphic horizon immediately overlying the volcanic ash at the base of the sequence. The blue tuff, and the archaeological horizon that overlies it, have been dated using the 40Ar-39Ar method on single crystals of alkali feldspar. Although there is no direct measure of how long it took the archaeological horizon to accumulate, it probably accumulated over a time span of 102-103 years. Thus the locality may be used to test the proposition that the analysis of archaeological debris from fine-time lines will help to resolve ambiguities in the interpretation of early Pleistocene archaeological assemblages.