Ichnofabrics From The Mantou Formation (Cambrian Series 2,3) In Western Henan Province

On basis of the detail observation and description of the 2, 3 series Cambrian Mantou Formation exposed in Dengfeng, Mianchi and Lushan areas of Western Henan, this project mainly deals with the composition of ichnofossil, morphologic feature and behaviour process of tracemakers, ichnofabrics and their genetic mechanism, classification of tiering and firm ground ichnofossil, five aspects of results are chiefly obtained as follows:(1) Based on the fossil composition and lithologic character of limestones of the Mantou Formation in study area, 19 ichnogenus and 29 ichnospecies were recognized and described according to ichnotaxonomy regulation, including 7 species indeterminata.(2) 10 types of ichnofabrics were recognized, 6 ichnofabrics of them in the carbonate rocks including Thalassinoides ichnofabric and ThalassinoidesThrombolites ichnofabric(formed in low energy subtidal restricted platform), Planolites ichnofabric and Planolites- Stromatolite ichnofabric(formed in high energy subtidal oolitic shoal), Skolithos- Stromatolite ichnofabric, Skolithos- Arenicolites ichnofabric(formed in high-energy coastal shoal shoal); 4 ichnofabrics of them in the siliciclastic rocks including Beaconites ichnofabric and Beaconichnus-Diplichnites ichnofabric(formed in high intertidal sand-mud flat), Cruziana-Rusophycus ichnofabric(formed in mid-intertidal flat), Scolicia ichnofabric(formed in low intertidal mud-sand flat).(3)Based on sedimentary environment, the bioturbation depth and nutritional types of the benthos, the trace fossils from Mantou Formation Cambrian, Western Henan, can be divided into shallow tier, middle tier and deep tier types. 11 ichnogenus and 17 ichnospecies were divided into shallow tier trace fossils, including Beaconites antarcticus, Gordia marina, Palaeophycus striatus,Beaconichnus ichnosp.,Cruziana rouaulti,Cruziana barbata,Diplichnites ichnosp.1,Diplichnites ichnosp.2, Dimorphichnus cf. obliquus, Diplichnites subtilis,Diplichnites robustus,Monomorphichnus bilinearis,Monomorphichnus linearis,Qipanshanichnus gyrus, Rusophycus ramellensis, Rusophycus yunnanensis and Palaeophycus striatus. 3 ichnogenus and 3 ichnospecies were divided into middle tier trace fossils, including Bergaueria aff. hemispherica, Thalassinoides horizontalis and Treptichnus ichnosp. 6 ichnogenus and 6 ichnospecies were divided into deep tier trace fossils, including Arenicolites yunnanensis, Diplocraterion ichnosp.,Monocraterion ichnosp., Skolithos linearis, Planolites montanus and Scolicia anningensis.(4) Large number of firm ground trace fossils were recognized from the carbonate rocks and clastic rocks of the 2, 3 series Cambrian Mantou Formation with perfect preservation details showing the good preservation potential. The firm ground trace fossils formed in siliciclastic rocks were consist of scratch trace fossils(including Beaconichnus, Cruziana barbata, Diplichnites ichnosp.1, Diplichnites ichnosp.2, Dimorphichnus cf. obliquus, Diplichnites subtilis, Diplichnites robustus, Monomorphichnus bilinearis, Monomorphichnus linearis, Qipanshanichnus, Rusophycus ramellensis, Rusophycus yunnanensis), vertical domichnia Treptichnid and Bergaueria aff. hemispherica with sharp clean edge, Palaeophycus striatus with longitudinal scratches, Beaconites antarcticus that developed on the mud crack, and Scolicia with clear meniscate fill. The firm ground trace fossils formed in carbonate rocks were consist of Skolithos linearis, Diplocraterion ichnosp., Monocraterion ichnosp. and Arenicolites yunnanensis from Skolithos ichnofabric.(5)On the basis of the analysis of the indentified ichnofossils from 2, 3 series Cambrian Mantou Formation, the trophic web of subtidal and intertidal zone of Cambrian Mantou Formation was established which can reflect the predatory relationship between the ichnocoenosis directly. The colonization of benthonic faunas in intertidal zone showing it is a comfortble environment for benthonic faunas to survive. In addition, the occurrence of a large number of deep tier trace fossils from high-energy oolicitc shoal and coastal shoal environment showing the exploration of more ecospace for the benthos during Mantou period of Cambrian.