DISCOVERY OF ACANTHOMORPHIC ACRITARCHS FROM THE BAICAOPING FORMATION IN YONGJI,SHANXI AND ITS GEOLOGICAL SIGNIFICANCE
Yan Yu-zhong;Zhu Shi-xing Tianjin Institute of Geology and Mineral Resources,Chinese Academy of Geological Sciences,Tiajin 300170
The Baicaoping Formation in Yongji, Shanxi, as one of the lithologic units in the upperPrecambrian Ruyang Group, is composed of siltstone and shale of near--shore facies. In the blackishgrey Shales have been discovered spinose and sphaeroid acritarchs as well as microfossil remains ofsupposed green and brown algae. This microfossil assemlage comprises 6 genera and 15 species,including 1 new genus (Shuiyousphaeridium Yan), 4 new species (Shuiyousphaeridium membraniferumYan, Dictyosphaera incrassata Yan, Foliomorpha stipulifera Yan, Manicosiphoninema shuiyouense Yan) and1 new combination (Shuiyousphaeridium macroreticulatum (Du) Yan). The most common elements of the spinose acritarchs are vesicles of Shuiyousphaeridiummacroreticulatum(Du) Yan gen et comb. nov., which are large in size, with numerous branchesfurcated and enveloped by peteinos processes. Due to the appearance of complicated spinose acritarchs,it may be inferred that the Baicaoping Formation belongs to the upper Proterozoic Sinian system. Thecomplicated spinose acritarchs may be the primitive forms of dinoflagellate. They are not only ofbiostratigraphical value, but also important for understunding the evolution of Precambrian algae.