Search

Sedimentary successions provide direct evidence of climate and tectonics, and these give clues about the causes of the mass extinction around the Permian–Triassic boundary. Terrestrial Permian–Triassic boundary strata in the eastern Ordos Basin, North China, include the Late Permian Sunjiagou, Early Triassic Liujiagou and late Early Triassic Heshanggou formations in ascending order. The Sunjiagou Formation comprises cross‐bedded sandstones overlaid by mudstones, indicating meandering rivers with channel, point bar and floodplain deposits. The Liujiagou Formation was formed in braided rivers of arid sand bars interacting with some aeolian dune deposits, distinguished by abundant sandstones where diverse trough and planar cross‐bedding and aeolian structures (for example, inverse climbing‐ripple, translatent‐ripple lamination, grainfall and grainflow laminations) interchange vertically and laterally. The Heshanggou Formation is a rhythmic succession of mudstones interbedded with thin medium‐grained sandstones mainly deposited in a shallow lacustrine environment. Overall, the sharp meandering to braided to shallow lake sedimentary transition documents palaeoenvironmental changes from semi‐arid to arid and then to semi‐humid conditions across the Permian–Triassic boundary. The die‐off of tetrapods and plants, decreased bioturbation levels in the uppermost Sunjiagou Formation, and the bloom of microbially‐induced sedimentary structures in the Liujiagou Formation marks the mass extinction around the Permian–Triassic boundary. The disappearance of microbially‐induced sedimentary structures, increasingly intense bioturbation from bottom to top and the reoccurrence of reptile footprints in the Heshanggou Formation reveal gradual recovery of the ecosystem after the Permian–Triassic boundary extinction. This study is the first to identify the intensification of aeolian activity following the end‐Permian mass extinction in North China. Moreover, while northern North China continued to be uplifted tectonically from the Late Palaeozoic to Late Mesozoic, the switch of sedimentary patterns across the Permian–Triassic boundary in Shanxi is largely linked to the development of an arid and subsequently semi‐humid climate condition, which probably directly affected the collapse and delayed recovery in palaeoecosystems. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Fluvial-eolian systems were identified in the Late Jurassic Tianchihe Formation. • The associations of eolian dune and eolian sandsheet indicate dry eolian system. • An evolving erg system occurred in the upper part of the Tianchihe Formation. • The vertical transition from fluvial to eolian systems suggest a drying trend. • The uplift of the East China Plateau resulted in the erg development. Abstract Eolian systems were widespread in China in the Cretaceous. However, the reports of pre-Cretaceous eolian and its related systems are scarce, which prohibits studying the construction, accumulation and preservation of eolian systems as well as its allogenic and autogenic controlling factors. In this paper, we report on fluvial–eolian successions from the Late Jurassic Tianchihe Formation in the Ningwu–Jingle Basin. These successions represent the oldest reported inland fluvial–eolian systems in China. Fourteen lithofacies types are recognized in the Tianchihe Formation and have been grouped into six facies associations, including meandering fluvial channel, levee and overbank in the lower part, and eolian sandsheet, eolian dune, ephemeral fluvial channel and floodplain in the upper part. The fluvial system comprises a series of wetting upward cycles, which indicate humid climate culminating in high precipitation and shallow water table level. Eolian dune deposits composed of grainflow, grainfall, wind ripple strata and pin stripe laminations currently implies that all deposits types are internally bounded by reactivation surface and superimposition surface, suggesting compound dunes or draas. Eolian sandsheet deposits consist dominantly of subcritical climbing translatent strata and pin stripe lamination. The association of eolian dune and eolian sandsheet is development of a dry eolian system. Twelve drying upward cycles mainly composed of eolian sandsheet–eolian dune successions and four wetting upward cycles consisting of eolian sandsheet/dune–ephemeral fluvial channel/floodplain successions occur in the eolian system. These repeated cycles likely reflect an evolving erg system directly controlled by sediment supply, sediment availability and relative water table. The vertical transition from fluvial to eolian systems indicate a local climatic oscillation from relatively humid to arid conditions, which may be related with the uplift of the East China Plateau in the Late Jurassic. [ABSTRACT FROM AUTHOR]

This paper presents the first report of sauropod tracks from the Upper Jurassic of Shanxi Province, China. Dinosaur tracks appear concentrated in five trackways, in different stratigraphic levels of the Late Jurassic Tianchihe Formation. Tracks are dominantly small and medium-size sauropod tracks and are tentatively assigned to Brontopodus based on preserved track morphology, trackway pattern and statistical analysis. The Tianchihe Formation in which the tracks appear shows a gradual change from meandering fluvial to sandy braided fluvial depositional systems developed in a seasonally arid environment. Comparisons of the evaluated speed of bipedal to quadruped trackways indicate that the slower walk more easily produces pes-dominated overprints. Trackways in the Guxian tracksite appear following different orientations, suggesting that these trackways were produced by different sauropods at different times. An unusual trackway following a curved pattern has been identified in the site and could represent a special locomotion character or a social behavior. The presence of eolian deposits in central Shanxi Province could have acted as a paleogeographic and paleoenvironmental barrier for the dispersion of the Yanliao Biota that survived in northern Hebei-western Liaoning and northestern Shanxi Province to the Ordos Basin during the Late Jurassic. [ABSTRACT FROM AUTHOR]