Late Neogene vegetation, climate, and lake evolution in the Taiyuan Basin of China based on palynological analysis

We report palynological data from a late Neogene drilling core (ZK03) in the Taiyuan Basin of China, together with the magnetic stratigraphic age determinations, to reconstruct the evolution of vegetation, climate change, and lacustrine environments in this region of East Asia. Our findings identify four pollen zones, from base to top, as follows: Zone I of terminal Miocene to the middle Early Pliocene age (∼4.0–5.5 Ma), characterized by a mixed forest-meadow vegetation consisting of coniferous and broad-leaved trees representing alternating colder and warmer climates that were generally mild and semi-humid; Zone II of Early to Late Pliocene age (∼2.6–4.0 Ma), dominated mostly by arboreal pollen representing a generally humid climate; Zone III of Early Pleistocene age (∼1.6–2.6 Ma), characterized by a significant increase in terrestrial herbaceous and shrub pollen types, notably Poaceae, Ephedraceae, Artemisia, and Chenopodiaceae, reflecting a climate trend towards dryness and cold; and Zone IV of late Early Pleistocene to present (∼0–1.6 Ma), characterized by the alternate dominance of arboreal and herbaceous pollen types, indicating fluctuating periods of warm-wet and cold-dry climates. These pollen assemblages are consistent with the global climate transition from warm Late Miocene to Pliocene conditions to the glacial-interglacial cycles of the latest Pliocene and Pleistocene. Pollen analysis shows that the ratio of arboreal and herbaceous pollen types gradually changed, after ∼3 Ma, with a decline in arboreal pollen and an increase in herbaceous pollen. This trend is consistent with the evolution of C₃-C₄ vegetation types, as revealed by black carbon δ¹³C values in the southwestern Japan Sea. We also show that the lakes of the Taiyuan Basin, which likely originated during the Early Pliocene and achieved their maximum extent at ∼4 Ma, subsequently, underwent shrinkage, in response to Pleistocene climate drying.