THE LOWER BOUNDARY AND INTERMEDIATE BOUNDARY OF THE CARBONIFEROUS IN HUNAN

The Devonian and Carboniferous Systems in Hunan belongs to typical shallow-water coral-brachiopod facies deposits. The traditional Devonian-Carboniferous boundary is drawn at the base of the Shaodong on the basis of corals. According to the position of occurrence of the associated conodonts, foraminifers, spores and cyrtospirifers, the author considers that the coral Cystophrentis Zone should belong to the Devonian System and that the Devonian-Carboniferous boundary should lie between the Menggong’ao Formation and the Malanbian Formation aud passes through the interior of the Guiyang Formation in southern Hunan. The traditional boundary in Hunan is drawn at the top ofthe Zimenqiao Formation on the basis of large fossils. But the intermediate boundary recommended by the Subcommission on Carboniferous Stratigraphy is based on planktonic organisms, so this boundary in Hunan should be restudied. Through the analysis and correlation of four conodonts zones near the traditional boundary, the author considers that the intermediate boundary of the Carboniferous is not far from the traditionalone. As the top boundary of the Zimenqiao Formation is diachronous, the intermediate boundary fluctuates near its top boundary.