Birch-Bark Tar at Neolithic Makriyalos, Greece. (News & Notes)

Article excerpt

Introduction

The potential for organic analysis of Neolithic pottery from Greece is largely unexplored. The results of a pilot study conducted on vessels from the Late Neolithic settlement at Makriyalos, northern Greece are reported in part here. Gas chromatography-mass spectrometry (GC-MS) is used to study the lipid composition of 19 vessels representing the range of main vessel types. The lipids from visible residue and ceramic extracts of three of these vessels show the presence of molecular markers consistent with birch-bark tar. These results are the first evidence in Greece both for its use and for the use of natural products to affect the performance characteristics of pottery vessels.

The site

The site at Makriyalos is situated in the coastal area of Pieria, Northern Greece (FIGURE 1), less than 2 km from the sea. Fifteen km to the west lie the Pieria Mountains with Mt Olympus, the highest mountain in Greece, on the southern side. The settlement is located on the gentle slopes of a natural low hill. Two ravines pass near the site to the northeast and southwest. The prehistoric settlement covers about 50 ha and is one of the largest non-tell sites in prehistoric Macedonia. Two main phases of occupation, Makriyalos I and II, both dated to the Late Neolithic period, are clearly distinguished (Pappa & Besios 1999).

[FIGURE 1 OMITTED]

Samples

All 19 vessels analysed for organic residues come from Makriyalos I which is dated to the beginning of the Late Neolithic period (c. 5400-4900 BC; Pappa & Besios 1999). Samples of three of these vessels are discussed here. A black-topped carinated vessel has a visible black residue on the interior surface in the form of a narrow strip along a fracture. It is likely that the vessel was broken and subsequently repaired in antiquity at the point where two coils joined. A small sample (6.2 mg) of the residue was removed with a scalpel and dissolved in dichloromethane.

Two sherds from bases of 4-handled jugs have traces of black residues deposited on the bottom and lower part of the inner vessel walls. Two grams of the powdered potsherd with trace residue were taken from the interior and exterior surface of the sherds up to a depth of 2 mm using a Dremel drill fitted with an abrasive bit. The resulting sherd powders were then extracted with 10 ml of chloroform:methanol 2:1 (v/v) with ultrasonication for 5 minutes. After centrifugation, the solvent was transferred to a clean vial. A portion of each extract was decanted and evaporated under a stream of nitrogen. These were then derivatized with a few drops of BSTFA, with 1% TMCS. Combined gas chromatography-mass spectrometry (GC-MS) was carried out. The splitless injector and interface were maintained at 300[degrees]C and 340[degrees]C respectively. The temperature of the oven was programmed from 50[degrees]C (2 minutes) to 340[degrees]C (12 minutes) at 10[degrees]C/min. The GC was fitted with a CP-SIL 5 CB low bleed/MS (Chrompack) coated (0.1 [micro]m) fused silica column (15 m x 0.25 mm I.D.). The column was directly inserted into the ion source where electron ionization (EI) spectra were obtained at 70 eV with full scan from m/z 50 to 700.

The molecular identification of birch-bark tar

Partial reconstructed ion chromatograms of the visible residue and the sherd extracts are shown in FIGURE 2. The identified components are shown in TABLE 1, with references to an extensive body of published mass spectra. The GC elution orders were the same as reported in these published works. The presence of components 3 (lupa-2,20(29)-diene-28-ol), 5 (lupenone), 6 (lupeol) and 9 (betulin) identify all three residues as birch-bark tar. Components 1 ([C.sub.30][H.sub.48]) and 2 ([C.sub.30][H.sub.46]) are degradation products of triterpenoids resulting from the heating of birch bark (Regert et al. 1998). Nb peaks such as ([alpha]- or [beta]-amyrin, or [beta]-sitosterol have been identified. …