The investigation of acritarch and prasinophyte assemblages from the Tangchih Formation of Lower Ordovician outcrops from the eastern Yunnan Province reveals the presence of 39 genera and 54 species. The assemblages are dominated by the genera Coryphidium, Dactylofusa, Leiosphaeridia, Lophosphaeridium, Micrhystridium, Polygonium, Rhopaliophora, and the galeate acritarch plexus. The first occurrences of Aryballomorpha, Aureotesta clathrata simplex, Barakella, Coryphidium, C. bohemicum, Dactylofusa velifera, Dasydorus, Peteinosphaeridium, Rhopaliophora, Striatotheca and Vulcanisphaera indicate that the age of the Tangchih Formation corresponds to the latest Tremadocian to Floian. The microflora can be correlated to the messaoudensis-trifidum assemblage of western Europe and coeval assemblages worldwide. In terms of palaeoecology, the composition of the palynomorph assemblage, together with sedimentological and trace fossil evidence, indicates a shallow-water environment in the study area during the late Tremadocian to early Floian. In the context of palaeobiogeography, the palynomorph assemblage contains elements of both the 'warm water' Aryballomorpha-Athabas-caella-Lua assemblage and the 'cold water' diacromorph acritarchs, possibly showing a mixed microflora in South China during the Early Ordovician. (c) 2025 Elsevier B.V. and Nanjing Institute of Geology and Palaeontology, CAS. All rights are reserved, including those for text and data mining, AI training, and similar technologies.