RUI: Botanical and Geographical Sourcing of Pine Tar by Component Analysis: A Step Towards Documenting the Tar Trade

Vassar College, Poughkeepsie NY

Investigators

Abstract

With National Science Foundation support, Dr. Curt W. Beck and his group at Vassar College, including undergraduate students, will conduct a comprehensive chemical analysis of multiple samples of resins collected from each of the 13 species of pine endemic to Europe and North Africa, as well as of pine tars made from these resins at various temperatures. The species will be authenticated by an international team of botanists and foresters from all the countries concerned. The rapid growth of underwater archaeology has brought to light large numbers of specimens of resins and tars from shipwrecks, ranging in time over 3000 years. They are found in amphoras once containing resinated wine, in the caulking of the ships, in the lining of transport amphoras, and as cargo. Most of these resins and tars can be identified as derived from the pine genus, but the customary analysis for high-molecular-weight resin acids does not identify the species of pines and thus their geographical origin. Recent work at Vassar College, using gas chromatography (GC) to separate the components, mass spectrometry (MS) to identify them, and specific ion monitoring (SIM) to enhance the sensitivity, has shown that the resin of the Aleppo pine, which is the dominant pine species in the Mediterranean, contains traces of the low-molecular-weight compound methyl benzoate, and that this characteristic constituent survives in archaeological tars that have been exposed to high temperatures. This compound is not present in the resins and tars derived from the Scots pine of Central, Eastern, and Northern Europe. The work proposed will establish whether this biomarker is unique to the Aleppo pine, and what other trace constituents can permit the identification of individual pine species or of geographically specific groups of species, The intellectual merit of the chemical characterization of the European pines is to provide a fact-based method of distinguishing archaeological tars of Southern Europe that were made locally from those that were imported. The data obtained will also constitute a substantial contribution to the biochemical genetics of the genus pine. The broader impact of the work will be a better understanding of a central question in European archaeology, - the 'barbarian-civilized' relations between transalpine and Mediterranean cultures. These relations have long been evident in Mediterranean durable goods that were traded north, but our knowledge of what may have been traded in exchange has so far been limited to Baltic amber. Proof of tar trade will add significantly to our knowledge of commercial and cultural contacts throughout prehistory. Furthermore, the volume of tar trade in different prehistoric and early historic periods will test current views about the anthropogenic deforestation of the Mediterranean, since increases in the volume of imports would indicate shortfalls of local sources of tar. The work involves undergraduate students in research of archaeological and anthropological significance while introducing them to research methodologies and techniques that are used in all of the natural and social sciences.