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The Qaidam Basin is one of the major coal‐bearing basins in northeastern China with the coal seams mainly preserved in the Lower–Middle Jurassic. The Middle Jurassic sedimentary environment, sequence stratigraphy, paleoclimate, and coal accumulation in the Qaidam Basin have been extensively studied, while the sedimentary characteristics and depositional evolution of the Lower Jurassic coal‐bearing series are less well known. We systematically analysed the facies association, depositional system, basin evolution, and coal accumulation of the Early Jurassic Pliensbachian‐aged coal‐bearing series from the Dameigou section in the northern Qaidam Basin. Five lithological types have been identified, ranging from conglomerates, sandstones, siltstones, and mudstones to combustible organic rocks, which were further subdivided into 12 lithofacies. These lithofacies were grouped into four facies associations, representing the braided fluvial, meandering fluvial, lacustrine, and meandering fluvial‐lacustrine transition deposits, respectively. The Pliensbachian Stage mainly developed as a fluvial‐lacustrine depositional system and an evolution history from braided fluvial to meandering fluvial, then to lacustrine, and finally back to meandering fluvial was reconstructed. We suggest that climate change is the major controlling factor for depositional evolution during the Pliensbachian. The transition of the depositional environment from fluvial to lacustrine in the study area can be attributed to the rapid climatic change induced by volcanism at this interval. [ABSTRACT FROM AUTHOR]

The breakup of Pangaea and the rapid opening of the Ligurian and Central Atlantic oceans during the Middle Jurassic resulted in widespread volcanism accompanied by significant shifts in global environments, climates, and floras. Although major volcanism is a plausible driver of such global changes, linking these phenomena in the Middle Jurassic is hindered by a lack of detailed sedimentary records from which to evaluate cause and effect. Here, we link Middle Jurassic environmental, climatic, and floral changes with volcanism using records from the Dameigou section of the Qaidam Basin on the Qinghai-Tibet Plateau. High-resolution chemostratigraphic (δ13C org patterns) and biostratigraphic (palynological fossils) data reveal three negative organic carbon isotope excursions (NCIE) at the Aalenian-Bajocian boundary, the Bajocian-Bathonian boundary, and in the middle of the Callovian, respectively. The first two NCIEs (NCIE-I and NCIE-II) were accompanied by relatively warm and humid climatic conditions and coal accumulation. In contrast, the third NCIE (NCIE-III) was accompanied by warm but dry climatic conditions, a decrease in coal accumulation, a decline in plant diversity, the significant decline in fern spore diversity and abundance, and a rapid increase in the abundance of Classopolli s pollen (based on petrological, palynological, PCA, Hydrophyte/Xerophyte ratio, and nMDS data). Four sedimentary mercury anomalies (Hg/Al 2 O 3 spikes) have temporal coincidence with the three NCIEs and climate warming events, suggesting a volcanic origin for these. We suggest that volcanism was a key driver of Middle Jurassic change, with major pulses releasing large amounts of CO 2 and Hg into the atmosphere, resulting in Hg loading, NCIEs, climatic warming, and floral changes in terrestrial strata. Our multi-proxy study provides new insights into the links between volcanism and terrestrial environmental, climatic, and floral changes during the Middle Jurassic. • Middle Juarssic terrestrial environmental and floral record from Qaidam Basin. • Negative δ13C org excursions and Hg peaks identify middle Jurassic volcanism. • Negative δ13C org excursions, climatic warming, and floral changes correspond to volcanism. • Volcanism important driver for changes in terrestrial environment, climate and flora. [ABSTRACT FROM AUTHOR]