Role of a Labile Terpene Compound in the Assessment of the Age of a Fossil Wood from Siena (Tuscany, Italy)

Abstract

Summary Fossil samples of Pinus sylvestris found near Siena (Tuscany, Italy) in geological formations 2–3 million years old were chemically examined in order to solve the problem of the contrast between the age of geological formations and their good degree of preservation. Comparison with a living Pinus sylvestris was carried out on standard wood component analyses, cation exchange capacity and residual terpene content. The analyses of wood components were close to those of the reference pine, whilst the cation exchange capacity values showed remarkable changes. The increase of salt carboxyls suggested the hydrolysis of ester carboxyls originally present, whilst the reduction of total carboxyls revealed a partial loss of hemicelluloses. Both changes were attributed to the percolation of salt-bearing water through the wood, thus causing ester hydrolysis, carboxyl salification and hemicellulose solubilisation. Residual terpene analysis showed, for the first time in a terrestrial fossil, tetrahydroabietic acid which forms by disproportion of the abietic acid. The 14C dating assigned the fossil to an age of about 18,000 years and suggested a landslide of Wurmian interglacial age occurred inside the geological formations of 2–3 million years old. Transient terpene compounds, formed in incipient diagenesis, are proposed as tracers for the assessment of particular ranges of fossil age, as previously suggested by the analyses of both a Larix decidua 14,500 years old and a Picea abies 100,000 years