贵州黄花冲下奥陶统湄潭组疑源类

ORDOVICIAN ACRITARCHS FROM MEITAN FORMATION OF HUANGHUACHONG, GUIZHOU, SOUTH CHINA

对贵州黄花冲奥陶系湄潭组Azygograptussuecicus带疑源类组合研究表明 ,该组合可以与扬子区陕南、川东南、黔北、黔南、湘西、鄂西等地同期组合对比 ,并根据特征分子产出判别该组合应划归环冈瓦纳疑源类生物地理区。

A well preserved acritarch assemblage is herein reported from the Azygograptus suecicus Biozone (“Arenigian”) of Meitan Formation at Huanghuachong section, Guizhou Province, South China. The following taxa have been identified: Acanthodiacrodium sp. Adorfia hoffmannensis Cramer, Allam et al. , 1974 Arbusculidium bicuspidatum (Burmann, 1968) Eisenack et al. , 1976 A.destrombesii Deunff,1968 A.filamentosum (Vavrdova,1965) Vavrdova,1972 Baltisphaeridium granosum Kjellstrom,1971 B. hirsutoides (Eisenack, 1951) Eisenack,1958 Coryphidium bohemicum Vavrdova,1972 Cymatiogalea granulata Vavrdova,1966 Leiofusa tumida Downie, 1959 Leiosphaeridia sp. Micrhystridium inconspicuum aremoricanum Paris et Deunff,1970 M.parinconspicuum Deflandre,1945 Peteinosphaeridium trifurcatum breviradiatum (Eisenack, 1959) Eisenack,1965 P.trifurcatum intermedium Eisenack,1976 P.trifurcatum trifurcatum (Eisenack,1959) Staplin et al. , 1965 Pirea ornata (Burmann, 1970) Eisenack et al. , 1973 Polygonium gracile Vavrdova,1966 Rhopaliophora impexa Tappan et Loeblich, 1971 R.membrana Li,1987 Stellechinatum brachyscolum Turner,1984 Striatotheca principalis parva Burmann,1970 Veryhachium trispinosum (Eisenack, 1938) Deunff,1954, ex Downie, 1959 Polygonium gracile it the commonest species among the assemblage, making up 55% of the total taxa. Cymatiogalea granulata is the second commnonest taxon, making up 12%, the other common genera are Peteinosphaeridium (8%), Rhopaliophora (6%), Arbusculidium and Baltisphaeridium (both 4%), Striatotheca (3%). The Huanghuachong assemblage is correlated with the assemblages from the equivalent strata of other localities from the Yangtze Platform, e.g. Tongzi of northern Guizhou, Sandu of southern Guizhou, Ningqiang of southern Shaanxi, Qijiang of southeastern Sichuan, Jishou of western Hunan, Yichang of western Hubei and Yushan of eastern Jiangxi. All of these assemblages are, to a certain extent, similar in composition and in the occurrence of diagnostic acritarch taxa. They are included in the Perigandwana acritarch Province. The assemblage of Yichang, however, yields many endemic and Baltic elements thought it shows a prevalent Perigondwana character. The difference of Yichang assemblage with those from other localities of the upper Yangtze region is rather environmental control than the provincial influence. Yushan is the only published acritarch locality of the lower Yangtze region. More data are needed for better understanding of acritarch flora from the lower Yangtze region. Stellechinatum is reported from Huanghuachong. That is not common in the Yangtze localities. The previous occurrence of this genus is from Yichang, Ningqiang and Xiushan. That extends the range of this genus from “Caradocian” downward to “Arenigian”. Acknowledgements This study is part of the PICS jointly sponsored by the Chinese Academy of Sciences and CNRS, and supported by NSFC(No.49972007) and MST (No.G2000077700).