The “double-edged sword” of volcanic activity
298 million years ago, the western margin of the North China Plate had frequent volcanic activities due to plate subduction, and a large number of volcanic materials spewed out in the air, heading for different distances. Wuda District, Wuhai City, Inner Mongolia Autonomous Region of China, is more than 100 kilometers away from the western edge of the North China Plate. On the contrary, the volcanic ash falling and accumulating in the sky has become a source of nutrients for plants, which makes the forests and vegetation flourish here. However, the good times did not last long, and a larger-scale volcanic activity broke the tranquility. This time, the thickness of the volcanic ash deposition and accumulation was a full 1.5 meters. The shorter ground cover plants are directly cut off due to the isolation of the air. The taller trees, due to the heavy load of the volcanic ash, were scattered all over the place, leaving only the stump that was still standing, and the entire swamp forest was sealed in the thick volcanic ash.
Open the gates of “Plant Pompeii”
After nearly 300 million years of geological compaction (under the heavy load of overlying sediments, the water is continuously discharged, the porosity is continuously reduced, and the volume is continuously reduced to become consolidated rocks), this swamp forest has long been buried deep underground. . However, thanks to people’s mining of coal resources, this layer of volcanic ash is often exposed to various corners of the Uda coalfield. In geological investigations that come and go, it has always been regarded as lacustrine mudstone, and no one has uncovered its mysterious veil. In 1999, Dr. Wang Jun from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences, came to the Wuda Coalfield in the process of tracing the fossil footprints of the Lapinnae. He was amazed at the exquisite preservation of the plant fossils of the caladium, but he had no idea that he was in a special buried ancient forest. It was not until 2003 that Dr. Wang Jun discovered the stubborn and straight upright tree stumps and realized that this was the direct evidence of the in situ burial of plant fossils. Because its preservation method is quite similar to the ancient city of Pompeii in Italy, Dr. Wang Jun named this treasure trove of fossil forests “Plant Pompeii”.
home of plant fossils
In most cases, the burial of plant fossils has to go through the steps of littering, transportation, and accumulation. In the first step, the plant body is mostly preserved in the form of fragmented organs, such as leaves, stems, reproductive organs, etc., and it is difficult to obtain the overall information of the plant. In the second step, the plant debris is generally transported to the deposition area by water flow. This process will not only further damage the plant debris, but also cause sorting due to the difference in buoyancy. the farther. Thus, plant fossils from the same habitat are transported to different downstream depositional areas. In contrast, in the third step, plant fragments from different habitats are also likely to be transported to the same depositional area for preservation, and are easily mixed with the plant groups originally grown in the depositional area. Under the influence of these uncertain factors, it is almost impossible to truly restore the community appearance of a certain habitat during its growth period. However, when some extreme geological events occur (eg, volcanic activity, earthquakes), regional vegetation is likely to be buried with sediments within a very short period of time (hours to months). This way of burying and preserving in situ allows paleobotanists to more accurately restore the true appearance of ancient forests.
The Preciousness of “Plant Pompeii”
Think carefully about the plant fossils you can see in museums, are they basically single organs of plants, and the overall appearance is unknown? However, in the “plant Pompeii” fossil forest treasure trove, the entire plant was quickly buried by volcanic ash. Preservation of plants as organ fragments is common due to mechanical damage during volcanic ash deposition, but they are generally distributed around the trunk of the parent plant. In addition, the fine-textured volcanic ash also creates conditions for the fine preservation of the internal structure of the plant. Therefore, the fossil material of “Plant Pompeii” can not only clearly show the overall morphological appearance of the plant, but also provide information on the anatomical features and reproductive organs inside the plant – this is the fossil material that paleobotanists dream of!
The Mystery of the Life Experience of the Syringae
The exact phylogenetic location of the scoliosis plant fossils has been a mystery since it was first reported in 1833. Since its reproductive cones are sporulated, it has been speculated that it may belong to the Cuneiformes, Eustachians, Progymnosperms, or some separate group of spore plants. The source of all these doubts is the lack of anatomical information. In the treasure house of the fossil forest of “Plant Pompeii”, there are a large number of complete tree-shaped fossils of Laconidaceae, which provides an opportunity to solve this century-old mystery. After more than ten years of specimen accumulation and in-depth research, the researchers finally found that the stems of the scourium have the wood anatomical characteristics of gymnosperms (reproducing with seeds instead of spores). Combined with the characteristics of spore reproduction, they finally confirmed that the Leaf plants belong to the category of pre-gymnosperms, which belong to the intermediate form of the transition from spore plants to seed plants. At the same time, it is shown that the pre-gymnosperms did not gradually die out with the rise of seed plants in the Carboniferous period (359 million to 299 million years ago), but flourished all the way in the Permian period (299 million to 252 million years ago) and eventually died out. During the mass extinction event at the turn of the Permian-Triassic.
In the “Plant Pompeii” fossil forest treasure trove, in addition to the scoliosis, researchers also found early cycads, early cypresses, and a large number of stone pine, knotted, true ferns and seed ferns. It is believed that there will be more paleobotanical mysteries to be solved in “Plant Pompeii” in the future.