CARBONIFEROUS CONODONTS FROM THE CHANGJIANG AREA, HAINAN ISLAND,SOUTH CHINA

The Carboniferous rocks crop out quite well at Changjiang area, Hainan Island, South China. They include the Nanhao Formation and Sanlengshan Formation of Lower Carboniferous, and Qingtianxia Formation of Upper Carboniferous. The lithological features of those formations are shown in text figure 2. Of them, the Nanhao Formation has a wide distribution, and was previousely subdivided into 4 members, in descending order as Member 1 to Member 4. Such corals as Cystophrentis kalaohoensis, Pseudouralinia irregularis, Zaphrentis sp., Amplex sp., Syringopora gracilis, Kweichowpora baijinensis, K. panxianensis have been found in the top part of Member 4. Accordingly, the Nanhao Formation (about 2 100m thick) has been formerly placed in the Lower Carboniferous, and the Member 3 to Member 1 have been referred to the Middle to Upper Devonian. The above mentioned stratigraphic sequence of Nanhao Formation was accepted and followed by all of the geologists who worked in Hainan Island in the past. Fairly abundant and well preserved conodonts including two assemblages:the Siphonodella isosticha S. cooperi assemblage and Mesogondella clarki assemblage have been found for the first time in Member 4 and Member 3 of Nanhao Formation from Jishi and Jixin villages, Shilu Town, Changjiang County, Hainan Island respectively (Figs.1 and 2). The former assemblage indicates that the top part of Member 4 of Nanhao Formation refers to the early Early Carboniferous. While the latter assemblage shows that Member 3 of Nanhao Formation is of middle early Late Carboniferous. Obviously, the stratigraphic position of Member 3 is much higher than that of Member 4. So that the previous stratigraphic sequence of Nanhao Formation at the area is clearly an upside down sequence, and has to be rejected. A new stratigraphic succession for the Carboniferous at Changjiang area is set up in the present paper.