LITHOFACIES AND PALAEOECOSYSTEM OF AN UPPER PERMIAN REEF AND ITS IMPLICATION IN PALAEOENVIRONMENT,IN GANTIAN’AO,LUODIAN,GUIZHOU PROVINCE,SOUTH CHINA
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Abstract:
In the late Permian there are plenty of radial fibrous cements (RFC)rich framestone developed in South China，and in Gantian’ao we found especially well preserved framestone reef outcrop．Base on the lithofacies and biological community analysis，we divided it to three stages：through all the history Peronidellais the dominant sponge in reef building，in stage 1 micrite framestone Peronidella and Imbricatocoelia are the dominant sponge，in stage 2 Peronidella and Guangxinella are the dominant sponge，however in stage 3 Polycystocoelia became the dominant sponge in reef building．In all three stages，the Sclerosponge is very rare here，compared to the reef in Longlin， Guangxi．The ecosystem is different to Ziyun’s reef even though it is so close．The encrustation in here is mainly Archaeolithoporella，the same as other reefs in South China at this time． By studying the history of the framestone here，especially the radial fibrous cements (RFC)．Per δ 13 C and δ 18 O isotope data we found that RFC’s contemporary temperature is as high as 37．86℃，we prefer to infer that RFC is an indication of high temperature marine water that incurred the accelerated process of calcite’s saturation and the RFC rich framestone is a symbol of hostile seawater，as well as the last phase of a reef ecosystem．
