ARENIGIAN ACRITARCHS FROM THE DAPING SECTION (YANGTZE GORGES AREA, HUBEI PROVINCE, SOUTHERN CHINA) AND THEIR PALEOGEOGRAPHIC SIGNIFICANCE

A rich acritarch assemblage (called HD2) from the Arenigian Dawan Form ation of the Daping section (Yangtze Gorges area, Hubei Province, Sout hern China) is described. The new data supplied by the study of this a ssemblage support the previous opinion that the Upper Yangtze Region s hould be included within the Mediterranean (PeriGondwana) acritarch Pa leoprovince. But, compared with this scenario, the picture resulting f rom the above data seems to be more complicated. Actually, the HD2 ass emblages have a mixed composition, even if they show a prevalent Medit erranean character. Some Australian and Baltic affinities were also ob served. The extension of the Mediterranean acritarch biofacies up to t he Yangtze Platform during Arenigian times is attributed to a cool per iantarctic (that is peri-Gondwana) oceanic current first flowing along the subpolar margin of Gondwana and after rising northwards up to Sou th China. The proposed scenario implies that the above mentioned peri- Gondwana current branched northwest of Southern China, giving also ori gin to a progressively warmer current, then descending up to Baltica. The palaeobiogeographical implications of this oceanic current pattern are discussed. Nine new species are described: Baltisphaeridium fragi le, Ordovicium yangtzeense, Peteinosphaeridium armatum, P. exornatum, P. robustiramosum, P. tenuifilosum, Pirea baculifera, P. levigata, and Striatotheca rugosa. Six previously described species are revised: Am pullula? erchunensis (Fang Xiaosi, 1986) Tongiorgi, Yin and Di Milia, comb. nov., emend., Barakella I ara (Lu Li-chang, 1987) Tongiorgi, Yin and Di Milia, comb. nov., emend., Costatilobus? rhabdocladius (Lu Li- chang, 1987) Tongiorgi, Yin and Di Milia, comb. nov., emend., Costatil obus? striatum (Lu Li-chang, 1987) Tongiorgi, Yin and Di Milia, comb. nov., emend., Rhopaliophara mamilliformis Lu Li-chang, 1987, emend., a nd Veryhachium symmetricum Lu Li-chang, 1987, emend.