Electron Spin Resonance of Petrified Woods for Geological Age Assessment

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Abstract
Electron spin resonance (ESR) spectra of both organic and inorganic radicals in petrified woods have been studied for the assessment of age and burial condition. Young woods contain lignin radicals that produce a signal with a width of about 7 G at g=2.0036. Radical spectra of acetic acid (CH2COOH·) and of methyl (CH3·) with hyperfine structures were observed for petrified woods of the Miocene epoch. ESR signal at g=2.0025 similar to coal was observed for the black carbonated portion. The spectrum, similar to that of natural quartz, was observed for silicated petrified woods older than Miocene. It is concluded that a rough age estimation of petrified wood can be made with ESR.