Middle Triassic calcareous algae and microproblematica from south China

Abstract

The Yangtze carbonate platform (Southern China) recorded a long sedimentary evolution from Neoproterozoic to the basal Upper Triassic. During the Early and Middle Triassic, this platform was dominated by shallow-water carbonates. In various sectors of the platform, the Middle Triassic (Anisian-Ladinian) succession contain abundant assemblages of benthic foraminifera and calcareous algae. Following a previous paper about the Middle Triassic dasycladalean algae from SW Guizhou Province, the present study describes algae and microproblematic organisms from three sections: Honyan, Longtou and Guanling. Some dasycladalean algae are well known from the Alpine-Dinaric domain: Diplopora annulatissima, D. annulata, Euteutloporella triasina, Macroporella dinarica, Oligoporella minutula, O. pilosa pilosa, Poncetella hexaster and Pseudodiplopora proba. However, the dasycladalean association is dominated by species belonging to the genus Kantia, including K. cf. dolomitica and K. cf. comelicana. New Kantia species (K. intusannulata n. sp., K. granieri n. sp., K. muxinanii n. sp.) are characterized by the presence of intusannulation, a feature unknown from the Kantia species in the Alpine domain. The dasycladalean association also contains new species of the genus Mizzia and specimens belonging to the organo-genus Acicularia and/or Terquemella. Besides, rare specimens of "Solenopora" and Rivularia-type cyanobacteria are also present. The algal association is accompanied by microproblematic organisms including Tubiphytes sp., Zorniella obscura, Plexoramea cerebriformis, Ladinella porata, and Baccanella floriformis. Anisian-Ladinian foraminifera complete the micropaleontological spectrum of the sections studied. The most important are Meandrospira dinarica, Endotriadella wirzi, Paleolituonella meridionalis, and Turriglomina mesotriasica. The microfossils from the Middle Triassic Yangtze carbonate platform of south China belong to the Eastern Tethys province. Some of these species are also present in the Western Tethys (Alpine Domain). The new species presented in this study are absent from the Alpine Domain and probably represent endemic species for the Eastern Tethys.