THE ASSEMBLAGE SEOUENCES AND BIOGEOGRAPHIC PROVINCES OF THE EIFELIAN RUGOSE CORALS IN NEAR-SHORE FACIES FROM SOUTH CHINA
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Abstract:
The Eifelian Stage has been divided from bottom to top into four conodont zones: partitus, costatus, australis and kocklianus by SDS. However, we have rarely found the above-mentioned standard zonation conodonts in the near-shore deposits from South China though we have found some important Devonian organism groups such as conodonts, ammonoids, tentaculites and others in the pelagic deposits of South China. Up to now, we have only found some long-term conodonts such as Eognathodus bipennatus bipennatus, Eognathodus bipennatus montensis and Icriodus corniger corniger in the Eifelian shallow water environments from South China.Devonian near-shore deposits are widespread in South China and rich in benthic brachiopods and corals. Based on a revised taxonomy and biostratigraphic range of rugose coral assemblages in South China, a coral biostratigraphy has been established, which indicates a subdivision of Eifelian into two discrete coral assemblages.Their correlation with the standard conodont zonation allows age determination of coral-bearing sequences. Lower-Middle Eifelian and Upper Eifelian rugose coral assemblage sequences in South China are shown as follows (in descending order): Upper Eifelian(2) Columnaria spinosa-Dendrostella praerhenana Assemblage (australis and kocklianus zones)Lower-Middle Eifelian(1) Utaratuia sinensis-Sociophyllum minor Assemblage (partitus and costatus zones).The Upper Eifelian coral assemblage is quite different from the Lower-Middle ones. Favositids, heliolitids and some rugose coral genera were extinct at the Mid-Eifelian bioevent. Some older elements of corals which lasted from Silurian and Lower Devonian survived in the Lower-Middle Eifelian. While the Upper Eifelian contained some advanced taxa of Rugosa.Biogeographic provincialism increased in late Lochkovian and Pragian time and reached a maximum during the early Emsian fauna. Lower Emsian rugose corals of South China are relatively endemic. However, after this time they became gradually cosmopolitan. The Eifelian rugose corals of South China are close to those of West Canada, Russia, West Europe and Australia. They all belong to the same Old World Realm.
