Middle Palaeolithic Bitumen Use at Umm El Tlel around 70 000 BP

Article excerpt

The authors identify natural bitumen on stone implements dating to 70 000 BP. Ir u proposed that this represents residue from hafting, taking the practice back a further 30 000 years from the date previously noted and published in Nature. The bitumen was tracked to a source 40km away, using gas chromatography-mass spectrometry and carbon isotopes.

Keywords: Near East, Djebel Bichri, Mousterian, bitumen, micro-traces, hafting, microscopic techniques, geochemical analysis, stable isotope, absolute dating, gas chromatography-mass spectrometry

Introduction

In 1992 bitumen was discovered on convergent sidescrapers and Levallois flakes in Mousterian leveis dating to 40 000 BP ar Umm el Tlel (el Kowm Basin, Central Syria, Figure 1) (Borda & Muhesen 1993; Borda et al. 1996; 1998). This led to a reconsideration of the commonly accepted idea that bitumen on artefacts appeared in the Near East (near the Dead Sea at Netiv Hagdud) only in the eighth millennium BC. Since the year 2000, eight archaeological levels in Mousterian complex VI 3 at Umm el Tlel have been excavated over an area of 50[m.sup.2], yielding an impressive amount of lithic and faunal material (between 150 and 300 objects per [m.sup.2]). There is considerable uniformity between the assemblages from these levels, showing successive occupations by human groups sharing the same knowledge (Boeda et al. 2002). Seven burnt flints from layers VI 3c and d were dated by thermoluminescence (Aitken 1985), and yielded statistically compatible results anda weighted mean of 71 [+ or -] 4ka, which places the deposition of these two layers (Martinson et al. 1987) at the transition between MIS 4 and 3 (Table 1).

[FIGURE 1 OMITTED]

Among more than 1000 artefacts from the eight layers in complex VI 3, 200 lithic artefacts carried a black residue. Some of them had impregnated the underlying sediment with a very clear and well-preserved imprint. These black macro-residues are logically located, always corresponding to those parts of the tool which were grasped or handled as shown by two of the artefacts presented in this paper: a flake (no. 1780, Figure 2) anda Levallois point (no. 2023, Figure 3). While it is impossible to know the precise use of such material, we infer that it could have been used as adhesive to attach a handle composed of animal or vegetal material or as a sleeve to provide protection for the user's hand. It is also probable that the treatment or preparation of this material, as well as the amount applied to the surface of tools, would vary depending on its ultimate purpose.

Geochemical analysis of bitumen: identification of source

Geochemical analyses were carried out on samples of macro-residues of bitumen taken from the artefact surface or from imprints of three Levallois artefacts (nos. 1780, 1781 and 2023, Table 2), a fragment of black pebble (no. 1782, Table 2), and bitumen samples collected from Bichri tar sands (nos. 170 and 430, Table 2).

A crust of black organic matter, located on both faces of the Levallois artefacts (Figures 2 and 3), was scraped from the surface. Initial Rock-Eval pyrolysis (Espitalie & Bordenave 1993) was fully consistent with archaeological bituminous mixtures previously excavated from various sites from the Near East and the Gulf (Connan & Deschesne 1996; Connan et al. 1998). Samples extracted with dichloromethane exhibited a gross composition (Table 2) of archaeological bitumen, i.e. crude oil which has been severely altered by weathering (photo-oxidation, biodegradation, oxidation, water washing, evaporation, etc.).

The source of the bitumen was tracked using the carbon 13 isotope, since it has been shown that the [delta][sup.13]C values of asphaltenes can correlate archaeological bitumen to parent oil seeps (e.g. Connan et al. 2006; Connan & Carter 2007; Stern et al. 2007). In the present study, [delta][sup. …