Trace fossils in Silurian Yimugantaw Formation in Kalpin area, Tarim Basin

Based on the analysis of trace fossils collected from the typical outcrop of the Silurian Yimugantaw Formation in the Kalpin area, the authors identified seven ichnospecies of six ichnogenus in Yimugantawu Formation. The ichnospecies mainly consist of such common trace fossils, i.e., Chondrites isp., Gordia.isp., Helminthopsis aff. abeli, Ophiomorpha nodosa, Planolites beverleyensis, Planolites montanus and Thalassinoides isp.. The trace fossils are of high diversity and low abundance. According to their palaeoecological, behavioral and ethological features, these trace fossils belong to three ethological categories: ①Domichnia:Ophiomorpha nodosa, Thalassinoides isp.;②Fodinichnia:Planolites beverleyensis, Planolites montanus, Chondrites isp.;③Repichnia:Gordia isp., Helminthopsis aff. abeli. These trace fossils can be assigned to Planolites-Chondrites ichnoassemblags and can be diagnosed as the Cruziana ichnofacies. According to the composition and distribution characteristics of these fossils in the sedimentary sequences and the characteristics of country rocks, these trace fossils might have formed in a mudflat sedimentary environment.