Abstract
Trees of the fossil gymnosperm Phyllocladus trichomanoides were buried by a volcanic eruption at Taupo, New Zealand about 2000 years ago. Three samples of fossil heartwood and fossil sapwood from this tree have been studied by 13C solid-state nuclear magnetic resonance (NMR) techniques including dipolar dephasing. The spectra of sapwood contain more resonances from carbohydrates at 66 and 75 ppm whereas the spectra of heartwood contain significantly more signal from methoxyl and other lignin derived carbons. Values obtained for the fraction of aromatic carbon that is protonated in the samples (ƒ a a,H ) are of the order of 0.50, in good agreement with that expected for a lignin-based, mainly guaiacyl structure. In addition to estimating z. hfl; a a,H, dipolar dephasing appears to be useful in accentuating differences in methoxyl content between heartwood and sapwood.
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