Mummified wood is a rare form of fossil preservation where ancient plant material remains largely intact, retaining much of its original chemical structure and physical appearance rather than being converted into stone. This preservation offers scientists a direct look into the ancient world, allowing for detailed study of prehistoric plant anatomy and chemistry. The wood is considered “mummified” because the natural processes of decay and mineralization were halted, leaving the original organic material preserved over vast timescales.
Physical Properties and Composition
Mummified wood often looks strikingly similar to modern wood, sometimes retaining its original brown color and texture despite being millions of years old. The material still possesses the primary organic components that define wood, including the complex polymers cellulose and lignin, which form the plant’s cell walls and structural framework.
Chemical analysis shows that while some degradation has occurred, a significant portion of the original organic material, including the stable polymer lignin, is still present. Some specimens retain up to 17% of their original cellulose. The retention of these organic structures means the wood is relatively light and can be cut and examined using the same techniques applied to contemporary timber. However, the wood may appear compressed or fractured due to the pressure of the overlying sediment where it was buried.
The Unique Preservation Process
The formation of mummified wood depends on a specific set of environmental conditions that prevent both biological decay and chemical alteration. Wood normally decomposes rapidly through the actions of aerobic bacteria and fungi, which require oxygen to break down cellulose and lignin. Therefore, the first condition for mummification is the exclusion of oxygen, creating an anoxic environment immediately following the tree’s death.
This anoxic condition is often achieved through rapid burial in fine-grained, impermeable sediment, such as clay or silt, or by submergence in deep, stagnant water bodies. Rapid sealing is particularly effective when the wood is buried in waterlogged or peat-rich sediments.
The preservation process is often enhanced by low temperatures, particularly in environments like permafrost, such as the ancient forests discovered in the Canadian Arctic. Cold temperatures dramatically slow the rate of chemical reactions and enzymatic activity that contribute to the breakdown of the wood’s organic structure. The burial environment must also exclude mineral-rich groundwater that would initiate mineralization, ensuring the original organic structure is maintained and not replaced by stone.
Comparing Mummified and Petrified Wood
Mummified wood is fundamentally different from the more commonly known petrified wood, with the distinction lying in their chemical composition. Mummified wood involves the retention of the original organic, carbon-based material, meaning it remains wood. This material is prized in paleobotany because it allows for the study of the ancient plant’s molecular structure and cellular anatomy.
In contrast, petrified wood forms through a process called permineralization, where the organic material is entirely replaced by inorganic minerals, typically silica. During this process, mineral-rich water flows through the wood’s porous structure. As the original cellulose and lignin decay, the minerals precipitate and solidify in their place. This results in the formation of stone, which precisely replicates the structure of the original wood but contains no carbonaceous material from the ancient tree.