Trace Fossils and Their Depositional Environments of the Early Triassic  Daye Formation in Huaxi Area, Guiyang

Key words: 
• Daye Formation

Abstract: There are lots of trace fossils preserved in the Lower Triassic Daye Formation in Huaxi area of Guiyang. Eighteen ichnogenera have been found in this region: Beaconichnus，Circulichnis, Cosmorhaphe, Dendrohaphe, Glockerichnus, Gyrochorte, Gordia, Maeandropolydora, Micatuba, Mammillichnis, Megagrapton, Planolites, Palaeophycus, Phycodes, Phycosiphon, Rhizocorallium, Thalassinoides and Undichna. Some trace fossils have been found for the first time, and they are Circulichnis, Glockerichnus, Maeandropolydora. Three ichnofabrics have been found in Daye Formation, including: Phycodes ichnofabric, PhycosiphonMammillichnis ichnofabric and Thalassinoides ichnofabric. Based on the relative abundance of the ichnogenera in Daye Formation, four ichnofacies have been distinguished: Cruziana ichnofacies of the first and third member, Zoophycos ichnofacies and Nereites ichnofacies of the second member. Combined with the analysis on ichnofabrics, the ichnofacies research shows that the study area located the front line of carbonate platform slope margin, and reflected less energy and anoxia environment. Phycodes ichnofabric and Thalassinoides ichnofabric can be assigned to Cruziana ichnofacies, PhycosiphonMammillichnis ichnofabric can be assigned to Zoophycos ichnofaciesNereites ichnofacies.