Palynoflora and palaeoclimate of the late Early Jurassic (Toarcian) in eastern Liaoning, China
2021
The late Early Jurassic (Toarcian) terrestrial succession exposed in the Tianshifu Basin, eastern Liaoning Province, northeastern China, was examined for palynomorphs. This sequence is part of the upper Changliangzi Formation and is mainly composed of shale and siltstone intercalated with several sandstone layers. The palynoflora in the upper part of the Changliangzi Formation is dominated by pteridophyte spores (average of 64.01%) and gymnosperm pollen grains (average of 34.99%), while the bryophyte spores are less than 1%. The dominant component of this palynoflora alternates between pteridophyte spores and gymnosperm pollen. The vegetation reconstructed from the palynoflora mainly comprises lowland ferns and cycads/ginkgophytes accompanied by upland conifers in low amounts, which is similar to the macroflora components of the Changliangzi Formation. The composition and evolution of this palynoflora indicates that eastern Liaoning was dominated by hot and subhumid climatic conditions with several warm and moderately humid intervals during the late Early Jurassic (Toarcian). Compared to the lower part of the Changliangzi Formation with coal-bearing strata, which is characterised by a rather moist climate, the upper part of this formation might represent a drier climate, although the inferred difference in temperature is small. Although there are several records of warming and drought in some inland regions in northern China during that time, which might be associated with the famous global geological event called the Toarcian oceanic anoxic event, most areas in northern China were dominated by a hot/warm and moist climate, especially in the eastern coastal region. The warm and wet flows from the Proto-Pacific Ocean may be responsible for this hot and humid climate.
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