Chinese fossils created by ancient volcanic eruptions have been the topic of close study since the 1950’s, but until now it was unknown why so many varied species were all buried in the same area, known as the Jehol Biota. The area is famous for its fossil density and has yielded near complete skeletons of insects, plants, lizards, frogs, early mammals and birds, pterosuars, turtles, and dinosaurs. The rock dates back roughly 120 million years, to when the entire region was dense coniferous forest.
Researchers at Nanjing University have concluded that a series of pyroclastic eruptions were the cause of the dense fossil layers after a study led by Jiang Baoyu. During the eruptions massive clouds of dust and ash bore down with tremendous speed upon all living creatures, be they fish, birds, or land walking dinosaurs. After being trapped and suffocated by the toxic cloud, the force of subsequent volcanic blasts of air is believed to have pushed the bodies into lakes, where they were buried in oxygen deprived environments, leading to the high number of varied and fantastically preserved fossils.
The Nanjing researchers reached this conclusion when it was noticed that many fossils found in the Jehol Biota featured spiderweb cracks along the edges of breaks in their bones, an effect of heat stress found in the remains of those buried in the ash of the eruption of Pompeii. As well, fossils of leaves featured streaks of carbon, indicating sudden scorching temperatures as well as high winds, both seen in pyroclastic eruptions. Animals with hollow or porous bones were found with the hollows filled with fine quartz dust. Many of the animals pulled from the rock seam are preserved enough to still feature recognizable scales, skin, and feathers. Now that it has been conclusively shown that the Chinese fossils were created by ancient volcanic eruptions, archeologists armed with the knowledge of how widespread an area the creatures preserved came from are eager to find out if any new species will be discovered.
As well as the bone and leaf fossils, researchers investigated layers of ashy sediment that are strewn across China’s north and support the theory of widespread eruptions. Due to the wide range of bird and sea life found in the Jehol Biota seam, researchers have conceded that eruptions would have lasted for lasted for a period of around 10 million years in order to throw up enough dust and soot to suffocate birds and drive them from the sky. This portion of the theory is supported by the uniform findings of creatures covered in layers of fine volcanic dust rather than the mud that would be expected by simply falling into a lake and drowning to be later preserved at the bottom. The new research has led to many searching for new fossil recovery sites to begin hunting for areas that were one volcanically active but have settled down in recent centuries in the hopes that the unique preservation situation found in Jehol Biota was replicated elsewhere.
By Daniel O’Brien