Abstract:

The paper describes eight ichnospecies from the Middle Jurassic Mali Formation in Biru County, northern Tibet: Beaconites biruensis ichnosp. nov. is characterized by non-divarication aclinic burrow with slick, thinner pipe wall and crescent back-packing structure, Bifungites cf. hanyangesis Yang is characterized by dumbbell-shape burrow on bedding surface, Biruichnus maliensis ichnogen. et ichnosp. nov. is characterized by burrow with columned thick wall divarication showing reticulation, Cruziana ichnosp is long and narrow ichnofossils showing two leaf-shaped, Micatuba cf. verso Chamberlain is more divarication burrow  system formed into upright pipe with many actinomorphic and different diameters, Palaeophycus ichnosp.is crooked or slight cylindrical burrow paralleling bedding surface, Treptichnus cf. bifurcus Miller is three-dimensional burrow system showing flexuous and saw-shape, Rhizocorallium ichnosp is simple U-shaped burrow paralleling or showing small angle with bedding surface, web-shaped structure. Middle Jurassic Mali Formation from Biru County, Tibet  contains a variety of lenticular bedding, wave bedding and vein bedding which all called tidal bedding, also  can be seen erosion structure, main lithology of the upside is aubergine coarse sand and arkose which belong to littoral sedimentation. The ichnofossils from the Mali Formation have predominance of shallow repichina and pascichnia, also can be seen feeding burrow and crawling mark, besides, the position from ichnofossils can be seen small interference ripple,the makers of the trace fossils lived in the shore environment with low to middle energy.

Key words: trace fossils, sedimentary environment, Mali Formation, Middle Jurassic, Biru County, Tibet