Analysis of composite structure and primordial wood remains in petrified wood

Among all the fossils, petrified wood belongs to the most impressive and most common of materials. Still, its study has not exceeded the purely phenomenological level. The recognition of the conserved structure of petrified wood seems to be of meaning for understanding the geological past, the complete carbon cycle inside the Earth, and the structure of potential new materials. The first ever published spatial distributions of the remains of the primordial organic material (lignin, cellulose, pectins) in the cells of permineralized wood, from Dunarobba (Central Italy), are presented here. They were collected using micro-Raman spectrometry. The composite nature of the petrified material (calcite located in the lumena of cells and goethite located in the cell walls) was confirmed by electron, proton, and X-ray microprobes. The structure of the cell walls was well preserved. The mineralization process was induced by the tracheidal water flow and was stopped after formation of pipe-like goethite shielding of the cell walls on the cellulose scaffolds. The chemical (Eh and pH ranges) and probable microbial conditions for such a pattern of mineralization were determined. We estimate that substantial amounts of the primordial organic matter were preserved in bodies of petrified wood on a global scale. The wood petrifaction process, if well understood, can be a basis for the production of "everlasting" organic-inorganic composite compounds.