Fossilized wood study traces 300 million years of German basin history
A German-led study finds quartz in ancient wood tracked burial and tectonic events in the Saale Basin over up to 300 million years.
By Lucas Ferreira · Science & Environment Writer
3 min read
A fossilized wood study led by University of Münster geologist Steffen Trümper has found that ancient tree trunks can preserve a long record of a region’s geological past. The work matters because it points to a new way to reconstruct how sedimentary basins sank, heated, shifted and later returned toward the surface.
The research, published in Scientific Reports, examined silicified wood from the Kyffhäuser Mountains in northern Thuringia, Germany. According to the University of Münster, the fossils come from the Saale Basin, which formed about 300 million years ago in what is now central Germany and is part of the wider Central European Basin System.
How can fossilized wood record Earth history?
Fossilized wood can record geological history when minerals fill and replace its tissues during burial. In this case, quartz that formed inside the wood preserved chemical and physical evidence of the conditions under which the crystals grew, according to the research team.
The Kyffhäuser fossils include trunks up to 20 meters long embedded in reddish river deposits known as fluvial redbeds, the University of Münster said. The red color comes from iron oxides linked to a warm climate with seasonal dryness.
The trees grew in tropical dry forests on Pangaea, the supercontinent that existed when the region sat near the equator, according to the researchers. They were relatives of conifers that are now extinct, and floods later buried the trunks in river sediments.
Quartz showed five stages of mineral growth
The study focused on quartz that entered the dead wood as dissolved silicic acid and helped preserve fine cellular structures. Over time, those silica deposits crystallized and replaced the original plant material, the researchers reported.
Trümper’s team identified five separate generations of silicic acid and quartz formation. According to the study, those stages span about 200 million years from the late Carboniferous to the Early Cretaceous; when later uplift back toward Earth’s surface is included, the record reaches as much as 300 million years.
The University of Münster said this is the longest documented sequence of successive mineralization stages in fossilized wood. The scientists used several methods, including quartz cathodoluminescence, analysis of fluid inclusions, oxygen and silicon isotopes, Raman thermometry, electron-probe microanalysis, scanning-electron microscopy and in situ U-Pb dating.
Trümper said the small fluid inclusions inside the quartz were especially useful because they kept evidence of the conditions during crystal growth. The team found that some of the wood had been buried 3 to 5.5 kilometers deep and exposed to temperatures of 160 to 240 degrees Celsius.
What the finding could change
The findings suggest fossilized wood may help scientists trace the development of continents where the right burial conditions existed. Trümper said it was “astonishing” that a fossil sometimes no larger than a hand can contain evidence of a region’s geological history over hundreds of millions of years.
The researchers also cautioned that fossilized wood will not be equally useful everywhere. According to the study, its value for basin analysis depends less on the tectonic setting than on the climate and sediment conditions present when the wood was buried.
The study involved researchers from the University of Münster, the University of Göttingen, the Karlsruhe Institute of Technology, the Museum für Naturkunde Chemnitz and TU Bergakademie Freiberg. The publication identifies the paper as “Fossil wood cells recorded 300 million years of Europe's tectonic history.”
This story draws on original reporting from Phys.org.