A characterization of petrified and mummified wood from an Eocene deposit in Mississippi

Abstract

This study experimentally investigates pieces of fossilized wood that include both mummified and petrified portions within the same pieces collected from the Red Hills Lignite Mine in Mississippi, USA. To the authors' knowledge, having petrified and mummified regions within the same piece of wood has not been previously reported. Our study analyzes the chemical compositions, microstructures, and nanohardness to characterize the fossilized wood. The chemical analysis revealed that the composition of the mummified regions included mainly carbon, oxygen, and small amount of minerals indicating these regions were similar to currently growing wood, and the petrified regions included silicon and oxygen indicating these regions were petrified-in the same piece of wood! This chemical analysis verified the mummified/petrified wood regions in multiple pieces of wood. Micrographs showed that the mummified regions retained well-preserved wood cell structures, and the petrified regions retained recognizable plant structures. Based on the wood cell structures, we confirmed that the wood originated from a species of conifer. Nano-indentation results showed the nanohardness of the petrified region to be 4.57 ± 3.11 GPa and the mummified region to be 0.71 ± 0.39 GPa. These hardness results also confirm that the petrified regions and mummified regions were clearly different materials as the silicate region is known to be much harder than the carbon regions. With respect to the environmental condition that enabled petrification and mummification within the same pieces of wood, this evidence suggests that a heavy flood buried wood that was then covered by sediment resulting in anoxic conditions within a short time. Water from heavy rain receded to make xeric conditions while some remained causing petrification.

A New Opportunity for Research in Romania – Subfossil Wood

“…Generally, the fossilization process is associated with marine or volcanic hydrothermal water [20], [30].…”