Stable carbon isotopes of wood: a clue to palaeoclimate?

Abstract

Detailed stable carbon isotope and molecular investigations were undertaken on a number of archaeological and fossil wood specimens to provide insights into their use as rigorous independent palaeoclimatic and palaeoenvironmental parameters. The isotope data revealed large differences amongst the material with the oldest specimens being least depleted in 13C. Although natural variation could account for some of the observed differences, the isotope values of the archaeological and Tertiary specimens are most probably related to the absolute abundance of polysaccharides present and the degree of lignin alteration. The molecular data, based on pyrolysis, of the Antarctic Cretaceous conifer specimens revealed only transformed lignin, with virtually no intact lignin building blocks (2- methoxyphenols) preserved, and no evidence of polysaccharides. This degree of chemical alteration is suggested here to be one of the main causes for the 13C enriched values of these conifer specimens. These results show the importance of combining detailed molecular information on individual wood components with stable carbon isotope data for palaeoclimatic and palaeoenvironmental studies.