An international team of paleontologists has discovered a tropical forest preserved in ash when a volcano erupted 300 million years ago in what is today northern China.
Reconstruction of a 300-million-year-old peat forest in northern China (Ren Yugao / J. Wang et al / PNAS)
A new study, published today in the Early Edition of the Proceedings of the National Academy of Sciences, presents a reconstruction of this fossilized forest, lending insight into the ecology and climate of its time.
At the discovered site, located near Wuda in Inner Mongolia, China, the plants were preserved as they fell, in many cases in the exact locations where they grew, because volcanic ash covered them over the course of only a few days.
“It’s marvelously preserved,” said Hermann Pfefferkorn, a Professor at the University of Pennsylvania and a co-author on the study. “We can stand there and find a branch with the leaves attached, and then we find the next branch and the next branch and the next branch. And then we find the stump from the same tree. That’s really exciting.”
The researchers date the ash layer to approximately 298 million years ago that falls at the beginning of Permian, during which Earth’s continental plates were still moving toward each other to form the supercontinent Pangea.
The researchers also found some smaller trees with leaves, branches, trunk and cones intact, preserved in their entirety. They were able to examine a total of 1,000 m2 of the ash layer in three different sites located near one another.
In each of the three study sites, Prof. Pfefferkorn and collaborators counted and mapped the fossilized plants they encountered. They identified six groups of trees. Tree ferns formed a lower canopy while much taller trees – Sigillaria and Cordaites – soared up to 80 feet above the ground.
The researchers also found nearly complete specimens of a group of trees called Noeggerathiales. These extinct spore-bearing trees, relatives of ferns, had been identified from sites in North America and Europe, but appeared to be much more common in these Asian sites.
Reconstruction of the flora on the three sites (Ren Yugao / J. Wang et al / PNAS)
They also observed that the three sites were somewhat different from one another in plant composition. In one site, for example, Noeggerathiales were fairly uncommon, while they made up the dominant plant type in another site.
“This is the first such forest reconstruction in Asia for any time interval, it’s the first of a peat forest for this time interval and it’s the first with Noeggerathiales as a dominant group,” Prof. Pfefferkorn said.
He also noted that the discovery cannot alone explain how climate changes affected life on Earth, but it helps provide valuable context.
“It’s like Pompeii. Pompeii gives us deep insight into Roman culture, but it doesn’t say anything about Roman history in and of itself,” said Prof. Pfefferkorn. “But on the other hand, it elucidates the time before and the time after. This finding is similar. It’s a time capsule and therefore it allows us now to interpret what happened before or after much better.”
