As an important part of the Central Asian Orogenic Belt, Mongolia has a complex geotectonic history. Unlike several cratonal block in central Mongolia, the Lake Zone in western Mongolia formed part of the magmatic-arc systems in the Cambrian period, characterized by the extensive distribution of subduction complexes and magmatic rock. This makes the biological features of the Lake Zone very important for understanding the evolution and paleogeography of the Palaeo-Asian Ocean in the Cambrian. However, no detailed study has been done in this remote area except a small amount of preliminary investigation of Cambrian fossils in the last century.
Recently, leading by Research Prof. ZHAO Fangchen and PhD student SUN Zhixin from the Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences (NIGPAS), Prof. YANG Aihua from Nanjing University and other colleagues, discovered a new lower Cambrian trilobite assemblage from the Lake Zone. This diverse trilobite assemblage provides new insights into trilobite evolution and early Cambrian biogeographic affinity of the Lake Zone. The study was published in Journal of Paleontology.
The new assemblage is exposed in the Seer section, on the eastern side of Khovd, western Mongolia. Trilobite fossils were collected from uppermost Burgasutay Formation and corresponding to the earliest Cambrian Stage 4. This assemblage is dominated by dorypygids and consists of 13 trilobite genera belonging to 9 families including Catinouyia heyunensis sp. nov. These fossils comprise the youngest and richest lower Cambrian trilobite assemblage in Mongolia.
“The composition of the Lake Zone fauna suggests its biogeographic affinity with the Siberian Platform and Altay-Sayan Foldbelt, but the presence of inouyiids also implies a connection of this region with East Gondwana”, says SUN.
This study was supported by the National Key Research and Development Program of China and the National Natural Science Foundation of China.
Reference: Sun, Z., Yang, A., Zhao, F., Zhuravlev, A., Pan, B., Hu, C., Feng, Q., Chen, X., Zhu, M. (2023). New trilobite assemblage from the lower Cambrian (upper Stage 4) of the Lake Zone, western Mongolia. Journal of Paleontology, 1-14. https://doi.org/10.1017/jpa.2023.23.
Figure 1. Location and geological setting of the Seer Ridge section and correlation of lower Cambrian sections in Mongolia.
Figure 2. The most abundant trilobite in Lake Zone assemblage, Kootenia spp.
Figure 3. Representative genus in the Lake Zone assemblage:1-3, Pagetides; 4, Eoptychoparia; 5, Amecephalus; 6, Chondragraulos; 7, Catinouyia.
Contact:
LIU Yun, Propagandist
Email: yunliu@nigpas.ac.cn
Nanjing Institute of Geology and Palaeontology, Chinese Academy of Sciences
Nanjing, Jiangsu 210008, China
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