According to a
new study of fossilized wood from the Kyffhäuser Mountains in northern
Germany’s Saale Basin:
“Among all organic hard tissues, wood has the strongest
chemical affinity to mineralize.”
The study looked at
Carboniferous-aged, fossilized wood that was buried in riverbeds in a tropical
region of the supercontinent Pangea. The study indicates that the
wood-containing sediments were buried and compressed into rock and underwent
four rounds of mineralization, after initial silicification into opal. Each
phase of mineralization produced a different form of quartz. The quartz types
also record the pressure and temperature ranges when each form of quartz was
formed. Pressure changed due to burial depth, which in the last phase was between 3 kilometers and 5.5 kilometers (1.9 miles to 3.3 miles).
The research confirms that
woody debris undergoes the same processes as the other sediments and the rock
as a whole. Each form of quartz reveals information about the basin when it was
formed. The quartz can preserve basinal and continental history. In this case,
the wood fossils are a now-extinct early conifer relative.
IFL Science summarizes the
four mineralization phases below, after opalization, or initial
permineralization:
“Conditions 304 million to 299 million years ago allowed
silicic acids to enter the buried wood and produce opal formations that
preserved the shape of the cell walls, the study reports.”
1) “Then,
between 299 and 290 million years ago, the fossils were buried beneath
sediments and heated to temperatures between 50°C and 70°C (122°F and 158°F),
which turned the opalized wood into crystals of fine quartz.”
2) “The
team found that, once enough layers of strata built up above the mineralized
wood, heat, pressure, and salinity caused most of the fine-crystalline quartz
to be replaced with coarser quartz-hematite crystals, erasing the
preservation of the anatomical structures where this occurred.”
3) “Another
long period of stasis followed, they write, before exposure to temperatures
between 170°C and 290°C (338°F and 554°F) created yet another form of
quartz: blocky euhedral crystals.
4) The
final transformation involved the production of quartz baryte,
which is recognizable by its production of blue light when it is bombarded with
electrons, a process known as cathodoluminescence.”
“In the silicified trunks from the Kyffhäuser, we
recognize five silica generations: the initial permineralization (P) of the
Kyffhäuser wood, followed by successive quartz stages (Q1–Q4) with discrete
paragenetic sequences of authigenic mineralization.”
Below is the stratigraphy,
paleogeography, depositional environments, fossils preserved, and volcanic ash
beds found in the section.
According to the paper:
“Successive burial–uplift cycles contributed to a
complex diagenetic history of the Kyffhäuser red beds with a latest Jurassic
maximum burial depth of c. 5,000 m, followed by late Cenozoic exhumation. The
burial diagenesis was punctuated by crust-scale fluid flow resulting in typical
vein mineralizations in the Kyffhäuser and nearby Harz basements and identical
paragenetic sequences in the Kyffhäuser red beds and wood.”
The figure below shows the basin subsidence history derived and relationships to the different mineralization phases.
The four mineralization phases are explained below:
Eogenetic opal-quartz transformation – Q1 (299–290 Ma;
between 30°C and 70°C and shallow depth/meteoric water zone)
The transformation of opal
into the first form of quartz (Q1) bears signatures of meteoric waters being
involved, which constrains the temperature and burial depth. Thus, the opal to
fine quartz recrystallization probably occurred at low temperature and at
shallow depths.
Quartz-hematite mineralization – Q2 (257–260 Ma; c. 100
°C and c. 1 km depth)
Basement-sourced saline
brines brought minerals that replaced Q1 with quartz-hematite (Q2). This
manifested as vein mineralization. It happened at higher temperatures,
pressures, and increasing burial depth. Pervasive replacement and cementation
are indicated in this phase.
Maximum-burial quartz mineralization – Q3 (c. 180–150 Ma;
between 170°C and 290°C)
Q2 was partially to entirely
replaced by large, blocky euhedral quartz crystals (Q3) occurring as
pore-filling in the Kyffhäuser wood and red beds. Highly saline basement brines
delivered the minerals for the replacement.
“These mineralizations are related to an Early–Late
Jurassic rift-related tectono-magmatic phases and fluid-driven authigenesis in
the Variscan basement and the Carboniferous–Permian strata.
Quartz-baryte mineralization – Q4 (c. 100 Ma; between 100
and 150 °C)
This last form of quartz
occurs as pore fillings and grain overgrowth in the Kyffhäuser red beds and as
vein mineralization cross-cutting the Kyffhäuser wood fossils. It exhibits
intense blue cathodoluminescence. Mineral replacement was gradual.
“The quartz-baryte mineralization (Q4) in the Kyffhäuser
wood corresponds to the baryte-fluorite vein mineralization of the Harz and
Kyffhäuser basements. In the latter, hydrothermal alteration, preceding vein
mineralization, is dated to an interval ranging from 116 ± 2.9 Ma
to 99 ± 2.2
Ma37, corresponding to an Early Cretaceous tectono-magmatic phase of
intra-basin magmatism and fluid-driven authigenesis.”
As shown below, the silica
source for the initial permineralization phase, which took place in the
meteoric water zone, was found to be soil, dissolved and conveyed by the
meteoric water. Phases Q2-Q4 destroyed much of the cell structures of the wood
trunks. Thus, local fossils of the same section that did not undergo those
phases have much better-preserved cell structures, better for fossil
collectors.
“The Kyffhäuser fossil trunks demonstrate that
fossilized wood can contribute to clarifying local to regional basin
development. However, not all silicified plant remains appear to be suitable
for this purpose. While the Kyffhäuser wood silica is polyphase and consists of
several SiO2 generations covering the eogenetic–telogenetic postdepositional
stages, there are also monophase silicifications that only record the
syndepositional to early eogenetic stages.”
Eureka Alert also provided a
nice summary of the mineralization phases interpreted by the researchers and the implications:
“Initially, dissolved silicic acid penetrates the dead
wood, templating the cell walls and thus preserving the finest anatomical
structures. Over millions of years, these initial siliceous deposits eventually
crystallised into quartz, replacing the original tissue bit by bit. The study
shows that the preservation of these fossils is far more nuanced than
previously thought in terms of structure, geochemistry and the age of the
quartz phases. The research team identified five successive generations of silicic
acid. Each of these generations contains information about the temperature,
pressure and composition of the solutions from which they formed. They document
five stages spanning a period of 200 million years from the late Carboniferous
to the Early Cretaceous. If the subsequent uplift to the Earth’s surface is
taken into account, this period extends to as much as 300 million years. This
is the longest documented sequence of successive wood mineralisation stages to
date.”
“They show that fossilised wood can record the history
of subsidence in a geological basin and reveal tectonic events on a timescale
of hundreds of millions of years.”
The researchers used several
techniques to study the rocks including quartz
cathodoluminescence, fluid inclusions, oxygen and silicon isotopes, Raman
thermometry, electron-probe microanalysis and scanning-electron microscopy, as
well as so-called in-situ U-Pb dating – a geochronological method for
determining the age of rocks and minerals.
Trumper noted the uniqueness
of the study and its limitations to suitable basins:
“A sequence of five stages of mineralisation has never
before been documented in fossilised wood. As fossilised wood occurs in many
rock formations worldwide, this opens up a valuable source of information. It
provides science with a new tool for tracing the evolution of continents.”
However, the analyses show that the suitability of fossilised wood for basin
analysis depends less on the tectonic setting and more on the climatic and
sedimentological conditions during its burial.
The authors also point to a
2025 paper in Scientific Reports that explored high-temperature silicification
of wood in China’s Qitai Silicified Forest in Xinjiang Province, in the Junggar
Basin. That paper provided the first quantitative P–T constraints on wood
fossilization, revisited thermal limits, and advanced the study of wood fossil
genesis in volcanic environments. The abstract is below:
References:
300-million-year-old
fossilized wood tells us more about geologic history than anyone imagined. Stephen
Luntz. IFL Science. July 30, 2026. 300-million-year-old
fossilized wood tells us more about geologic history than anyone imagined
New
geological archive discovered: Fossilised wood reveals 300 million years of
Earth’s history: Research team uses quartz from fossilised wood to trace
Europe’s development.Peer-Reviewed Publication. University of Münster. July 24,
2026. New geological
archive discovered: Fossilised wood reveals 300 million years of Earth’s
history | EurekAlert!
Fossil
wood cells recorded 300 million years of Europe’s tectonic history. Steffen
Trümper, Matthias Franz, Graciela Sosa, Alfons van den Kerkhof, Armin Zeh,
Michael Tatzel, Andreas Kronz, Kirsten Techmer, Tommaso Di Rocco, Andreas Pack
& Ronny Rößler. Scientific Reports. volume 16, Article number: 22068 (2026).
July 14, 2026. Fossil
wood cells recorded 300 million years of Europe’s tectonic history | Scientific
Reports
High-temperature
wood silicification: constraints from fluid and carbonaceous inclusions in quartz
from Qitai, NW China. Wenqing Liu, Guanghai Shi, Zhiguang Zhou, Linli Qin,
Xinling Li, Xiaoyun Quan, Ye Yuan, Tobias Häger, Anne Jantschke & Roman
Botcharnikov. Scientific Reports. (2025) 15:42961. High-temperature_wood_silicification_constraints_f.pdf
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