While fossil hunters often focus on animal bones and teeth, a new study published in Technology Networks demonstrates that plants are equally indispensable in revealing the planet’s prehistory. Researchers have discovered that fossilized wood can act as a natural archive, recording the geological history of an entire region over hundreds of millions of years.
Unlocking Millions of Years of Geological History Through Fossilized Wood
The research investigated fossilized wood from the Kyffhäuser Mountains in northern Germany’s Iflscience, a sedimentary basin formed around 300 million years ago. At that time, the region sat close to the equator on the supercontinent Pangaea, featuring tropical forests populated by now-extinct relatives of conifers. These trees were buried in riverbeds in an environment that alternated between dry seasons and floods.
Five Stages of Mineralization and Deep Burial
Following burial, water containing dissolved silica entered the wood. Over millions of years, the silica hardened into quartz while preserving the detailed structure of the tree cell walls. According to the study, this mineralization process did not happen just once. Instead, the wood underwent a sequence of five distinct mineralization stages over an extraordinarily long period.
A sequence of five stages of mineralisation has never before been documented in fossilised wood,
noted Dr. Steffen Trümper, a geologist from the University of Münster who led the research team.
Each generation of quartz formed under specific temperatures, pressures, and chemical conditions corresponding to how far underground the wood lay at the time. To reconstruct these stages, the scientists utilized multiple advanced laboratory methods, including quartz cathodoluminescence, fluid inclusions, oxygen and silicon isotopes, Raman thermometry, electron-probe microanalysis, scanning-electron microscopy, and in situ uranium-lead dating.
Microscopic fluid inclusions trapped inside the quartz crystals proved especially revealing because they preserved information about the exact conditions during crystal growth. Analysis of these fluid bubbles showed that parts of the fossilized wood were eventually buried between 3 kilometers and 5.5 kilometers (1.9 miles to 3.3 miles) beneath the Earth’s surface, encountering temperatures ranging from 160 to 240 degrees Celsius.
Timeline of Transformations and Continental Evolution
By determining the age of crystals surviving from each stage, Trümper and his colleagues established a timeline of transformations spanning from the late Carboniferous Period to the Early Cretaceous:
- Carboniferous Period (304 million to 299 million years ago): Silicic acids entered the buried wood, producing opal formations that preserved cell wall shapes.
- Late Carboniferous to 290 million years ago: Burial beneath sediments and heating to temperatures between 50°C and 70°C turned the opalized wood into fine quartz crystals.
- 257 million to 260 million years ago: Quartz-hematite formed.
- 150 million to 180 million years ago: Euhedral quartz developed.
- Around 100 million years ago: Quartz baryte formed at depths reaching up to 5.5 kilometers.
Today, this fossilized wood rests at the Earth’s surface directly in front of the Kyffhäuser Monument, indicating an immense tectonic uplift in the more recent past. Combined with the deep burial phases, the complete history preserved within the samples spans approximately 300 million years.
Implications for Future Geological Research
It is astonishing that a fossil, often no bigger than the palm of a hand, encapsulates the geological history of an entire region spanning hundreds of millions of years,
Trümper stated.
Because fossilized wood appears in numerous rock formations across the globe, the findings establish a valuable source of information that provides science with a new tool for tracing continental evolution, sedimentary basin formation, and changes in the Earth’s crust. However, the researchers noted that the suitability of fossilized wood for basin analysis depends primarily on the climatic and sedimentological conditions during its burial rather than the broader tectonic setting.
