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The amazing power of volcanic ash: How did it create the perfect fossil preservation of the Erho biota?
In northeastern China, during the Lower Cretaceous period about 133 million to 120 million years ago, an amazing ecosystem was formed called the "Erho Biota." Fossils of this ecosystem are mainly found in the Yisun Formation and Jiufotang Formation, which are sediments composed of layers of volcanic ash and silt. Driven by seasonal rainfall, the ecosystem consists primarily of wetlands and lakes, and this unique geography has resulted in countless well-preserved fossils, giving scientists a glimpse into past life.
The origin of Erho biota
Regarding the evolution of the Erho Biota, some studies believe that it originated directly from the early Daohugou Biota. However, there is still disagreement on the absolute dating of Daohugou sediments. Scientists tried to solve this mystery through U-Pb dating of cassiterite in volcanic rocks, pointing out that the Daohu Trench sediments were formed earlier than the Biho Biota.
"The deposition and rapid coverage of volcanic ash is the key to maintaining the preservation of fossils."
Preservation of fossils
The Yisun Formation and Jiufotang Formation are considered to be typical Lagerstätte, that is, they have extremely superior conditions for fossil preservation. A large number of fossils are not only numerous, but also quite well preserved, often including complete bones, soft tissues, color patterns, and stomach contents. This perfect state of preservation has attracted a great deal of attention and research.
“The interlacing of volcanic ash layers and lake sediments is a perfect way to preserve fossils.”
Shelters and Laboratories
During the Early Cretaceous, the Erho biota was characterized by a mixture of advanced and ancient species, some found only in the Erho region, while others were globally distributed. For example, the Erho biota includes what are thought to be the earliest birds and dinosaurs. Research suggests Northeast Asia may have been the center of diversification of these dinosaur groups.
Diversity
The Erho Biota is known for its remarkable fossil diversity, which has allowed scientists to obtain a large number of plant and animal fossils during archaeological excavations. In the forests surrounding the lake, there are various types of plants, including early angiosperms, conifers, and many types of ferns. This biota displays not only a variety of dinosaurs but also insects, fish and mammals.
In-depth research
In 1959, the scientific community began to use the term "Ilho biota" to replace the earlier "Ilho fauna". After many definitions and studies, the term covers multiple geological mixed groups including Erhe coal seams, oil shale layers and volcanic rock layers. Combined with these in-depth studies, scientists are still revealing the earlier fossil beds of the Erho biota. The discovery of these early stages will undoubtedly play an important role in our understanding of the evolution of ancient ecosystems. Volcanic ash, a seemingly ordinary substance, plays a crucial role in this process.
As we study these fossils, can we imagine what the world was like millions of years ago?
