Stratigraphic and spatial distribution of ochre and ochre processing tools at Porc-Epic Cave, Dire Dawa, Ethiopia

Reassessment of the archaeological assemblages recovered by Kenneth D. Williamson in 1975 and 1976 at Porc-Epic Cave, Dire Dawa, Ethiopia, demonstrates that the Middle Stone Age (MSA) levels of this site yielded one of the richest known collections of ochre and ochre processing tools from this period in terms of quantity. We analyze the vertical and horizontal distribution of all ochre fragments (n ¼ 4213) and ochre processing tools (n ¼ 23) of known provenance, and compare them with the distribution of other categories of archaeological remains. Our results suggest that no major post-depositional reworking occurred at the site. Virtually no ochre fragments and processing tools are recorded in the superficial levels of the site (0e60 cm below datum). Concomitant and statistically significant changes in the location of ochre and ochre processing tool concentrations are observed at various depth intervals in deeper levels, interpreted as changes in the location of the area devoted to ochre processing. Comparison of the vertical distributions of ochre fragments and lithics highlights that, in most cases, ochre and lithics covary. The vertical distribution of gastropod opercula (interpreted by other authors as ornaments) and of ochre fragments throughout the sequence also follows the same trends. However, concentrations of ochre and ochre processing tools do not coincide with that of the opercula, spatially. 14C determinations obtained at Porc-Epic indicate a relatively short chronology for the accumulation of the main archaeological deposits and date to ca. 40 ka cal BP the levels containing most of the ochre. This is consistent with the fact that no significant typo-technological variations in the lithics are observed throughout the sequence and argues in favour of the site reflecting a phase of the transition from the Middle Stone Age to the Later Stone Age (LSA) in this region of Africa.