It is a common sense that most of benthic metazoan fauna, except some cyanomicrobes, unlikely survive in dolomitic flats. The Cambrian （Stage 2） Wusonger Formation is dolostone-dominated with less limestone beds at the Xiaoerbulak section, Aksu of northern Tarim block in Xinjiang, NW China. Dolostones were largely formed in a wide shallow and strong evaporate tidal belt where was unfavorable for inhabitation of metazoan fauna including both benthic and nektonic communities. A low diverse ichnofauna is reported here for the first time, of which the taxa are all yielded from thin-bedded micritic limestones and identified as Chondrites, Helminthopsis, Skolithos, Stelloglyphu, Taenidium, Thalassinoides with descending order in abundance. Their morphological features are small burrows with simple structures and commonly occurred from shallow marine settings in Paleozoic time. Sparse trilobites and hyolithes shelly concentrations are also specially yielded from thin-bedded limestones. Therefore, palaeosalinity condition played an essential role in constraining of metazoan fauna. Both trace-makers without mineralization bodies and shelly fauna could migrated herein instantly once resurgences of normal salinity and turbulence environments coinciding to the deposition of thin-bedded limestones. The present case illustrates an evolutionary pattern that dolomitic flat hasn??t been idealized setting for metazoan fauna thriving since their Early Cambrian Explosion of the Phanerozoic.
Yu Shenyang Liu Lijing Yang Zhilin Ding Yi Li Yue. Monotony of the trace-making behavior from the Cambrian Wusonger Formation in Aksu, southern Xinjiang[J]. Chinese Journal of Geology, 2018, 53(2): 765-773.