This paper describes Mesozoic trace fossils collected by the Hebei Geological Survey during mapping of the Sage region in 2001 and by China University of Geosciences during mapping of Jiangzi and Yadong regions in 2002.These trace fossils occurred in the following locations and geological ages:Fossil site 1:Late Cretaceous rocks in Sage and Jilong,fore-arc basins in Gangdisi and flyschdepositsintheAngrenFormationShigatseGroup.Fossilsite2:LateTriassicNiejeiFormationinLaguigangri,Kangmaregion,northernHimalayas;EarlyMiddleJurassicTianbaGroup,Early Cretaceous Jiabula Formation, and Late Cretaceous Zongzhue Formation flysch deposits.Fossil site 3: (small amount) Late Cretaceous Gangbacunkou Formation in the southern part of northern Himalayas.12 ichnogenera and 14 inchnospecies are described.Mostofthesetracefossils5inchnogeneraand7inchnospecieshaveneverbeenreportedinChinapreviously includingtwonewinchnospeciesEthologicalcharacteristicsofthesetracefossils,including9commonMesozoicandCenozoicichnogenera,thatoccurredinflyschdeposits around the world, were analyzed. According to their taphonomic environment andpreservationalstyle,thesetracefossilscan be divided into two categories:thefirsttypeisknownaspost-turbiditetraceswhicharepredominatedbyfeedingandgrazingtrails in the deep sea,forexample,Gyrophyllites,Phymatoderma,HelminthoidaandPhycosiphon.Thesetracesarecharacterizedbyactivebackfills.Thisgroupalsoincludesanimalswithchemosymbiosisthathasadoptedlowsoxygenconditions,suchaschondritesandcladichnus.Thesecondtypeispre-turbiditegraphoglyptidawhicharecharacterizedbycomplextunnelingsystemthatwasfilmedbybacteriaandgardening(Agrichnia).RepresentativesofthistypeareMegagrapton,Rhabdoglyphus,andHelicorhaphe.ThesedescribedtracefossilsalsoincludedwellingandfeddingstructuressuchasSchaubcylindrichnus,Syringgomorpha, and Cubichnia that are aligned with water currents such as Sagittichnus.Except for Tibet,Mesozoicdeepseaflychstrata(especiallyLateTrassicandJurassicCretaceousrocksarerarelydevelopedinotherpartsofChina.Thus,thesetracefossilsprovideuniquevaluablematerialtowardbetterunderstandingofsedimentology,stratigraphy, and paleogeography in Tibet.
