Biostratigraphy and palaeoenvironment of the Kulinda section (Transbaikalia,Russia) based on the Middle Jurassic palynology and macroflora

The palynological and macrofloral assemblages from the Lower Member of the Ukurey Formation have been studied based on the materials from a section exposed along the Kulinda Ravine (Olov Depression, Transbaikalia). This section is of special interest due to the occurrence of ornithischian dinosaurs. Based on palynological and palaeobotanical data, the studied deposits are dated as Middle Jurassic (Bathonian). Specific features of the palynological assemblages allow the correlation of the studied interval with Western Siberian palynozones calibrated by ammonite and foraminiferal successions. The resulting biostratigraphy suggests that the lower extent of the Ukurev Formation is not restricted to the Upper Jurassic as previously assumed. Lacustrine origin of the Lower Member of the Ukurev Formation is confirmed based on palaeoenvironmental analysis, showing changes of the terrestrial vegetation, associated with climatic conditions and fluctuations of the lake-level. Palaeobotanical and palynological data suggest that Middle Jurassic floras of eastern regions of Central Asia, southern regions of Siberia and Far East, as well as northern regions of China exhibit similar features.