In this study, fossil (Sequoioxylon) wood from the Oligocene-Miocene transition in istanbul, Turkey was examined using non-destructive test methods to evaluate changes in anatomical and chemical structure. Molecular changes in the cell wall structure of the wood were determined using Fourier transform infrared (MR) and FT-Raman spectroscopy, along with the comparison to recent wood [Sequoiadendron giganteum (Lindl.)]. We found that the cell wall carbohydrates of the fossil wood were significantly more degraded compared with lignin; FT-Raman spectroscopy revealed the degradation in more detail compared with FTIR spectroscopy. FT-Raman spectra also demonstrated that hemicellulose and holocellulose were decreased in the fossil wood. Laser-induced breakdown spectroscopy (LIBS) analysis confirmed that the mass loss was due to the decreased H and O content of the fossil wood sample and was caused by decomposition. Light microscopy also showed that fossil and recent woods have similar anatomic structures, and that the micro-morphological structure of the fossil wood was well-preserved. Published by Elsevier B.V.