The early Viséan Rugose Coral Communities in China

by Wang Xunlian**, Kato Makoto and Wang Hongzhen** (With 4 text-figures and 3 tables) Within China six Early Visean rugose coral communities are recognized, they are : 1) the Siphonophyllia community, 2) the cool water Gangamophyllum community, 3) the Thysanophyllum community, 4) the Bothrophyllum Zaphrentites community, 5) the island Humboldtia community and 6) the cold water Hapsiphyllum-Rhopalolasma community. In northwest China, the Siphonophyllia community is distributed along the northern margin of the Tarim-Qaidam Oldland. The Gangamophyllum community was widespread north of the region occupied by the Siphonophyllia community, including north Tianshan, central Tianshan and east Junggar. In South China there were three rugose coral communities. The Thysanophyllum community occurs on the margin of the Upper Yangtze Oldland. The Bothrophyllum Zaphrentites community was confined to the southern and western part of the region occupied by the Thysanophyllum community. These two communities merge into each other without a distinct boundary. The Humboldtia community is found only in the Baoshan area. The Hapsiphyllum-Rhopalolasma community is found in Xainza and Himalaya of Tibet. The distribution of the six Early Visean rugose coral communities was controlled by the palaeogeographical background. The Gangamophyllum community occurs along the southern margin of the Siberia Oldland, while the Siphonophyllia community is distributed along the northern margin of Tarim-Qaidam Oldland. The Hapsiphyllum Rhopalolasma community is confined to the northern margin of the Gondwana Oldland. In the wide southern and western margin of Yangtze Oldland the distribution of the Thysanophyllum and the Bothrophyllum-Zaphrentites communities was controlled by the bathymetry. The Humboldtia community probably lived in island seas far from the Yangtze Oldland. The concept of commmunity has been applied to the study of fossils for near 100 years_ Although opinion is widely held on the definition of the community, many workers consider the community as a natural combination of various organisms, all living together in the same area and the same environment (Chen, 1984; Rong, 1986; Wu and Zhao, 1989) . Boucot (1975) established six benthic assemblages on the basis of the five Silurian marine brachiopod communities recognized by Ziegler (1965) between the shoreline and the pelagic facies in Wales and the Welsh Borderland_ The study of Palaeozoic benthic communities shows that Boucot's benthic assemblages are very useful in showing the distribution of level-bottom benthic community in a open marine where the distribution of communities are mainly controlled by depth of sea Contribution from the Department of Geology and Mineralogy, Faculty of Science, Hokkaido University, No. 2075 • This paper was read at the 29th IGC in Kyoto in 1992 • • China University of Geosciences (Beijing) , Beijing, China 330 Wang Xunlian, Kato Makoto and Wang Hongzhen water. It has to be pointed out that beside water depth, a lot of other factors, including temperature, sediments, tectonic as well as organic revolution, can affect the distribution of benthic community, and similar communities may occur in different environment. For instance, the community composed of small, solitary, nondissepimented corals, which was common in Palaeozoic period, may represent at least five different environments: 1. the lower part of continental slope in normal, warm open marine, which is represented by deep water forms described by Sando (1980) ; 2. deep water of faulted basins formed within the continental margin, this can be demonstrated by the forms known from the Middle Devonian N andan type deposits of South China; 3: cold, shallow water, so far reported in Early Permian rugose corals from southern Tibet are all small solitary forms without dissepiments (Wu, 1975 ; Wu et aI., 1982; Lin, 1983) ; 4. shallow water with abundant clastic sediments; and 5: normal shallow water on declining stage, exemplified by the Famennian corals in the Holy Cross Mountain of Poland (Rozkowska, 1969) . Moreover, coral communities of same depth may occur in the form of reef, non-reef or only small solitary nondissepimented corals depending on the variations of the temperature. In addition, barrier seas were also present, and the massifs between adjacent continents were common during geologic history. On islands there were certain communities, which sometime look like those developed on the continental margin of the open marine. These represent a special type of environment. Therefore in the course of studying palaeoecology, palaeogeography, palaeobiogeography, tectono-palaeogeography, palaeoclimatology and others affecting the distribution of organism, should receive more attention. All ecologists and palaeontologists agree that communities should be named, but there are divergent views on how to name a community. Environment, locality, stratigraphic unit and geologic time have been used to name communities. Recently most authors tend to name a community according to organic classification units, although no agreement exists on the level of classification units. We prefer to select dominant genera with high diversity and choose characteristic genera to designate the name of a community, which may best characterize environments in which they lived. Pedder and McLean (1982), Liao (1984) and Wu and Zhao (1989) all accepted Boucot's (1975) benthic assemblage in rugose coral paleoecology. According to Pedder and McLean (1982) , almost all Devonian, open marine, coral-bearing, levelbottom communities fall within the range of 3 through 5 in Boucot benthic assemblage scale, and some of the so-called Cyathaxonia facies community may include benthic assemblage 6 in this scale. The Lower Visean, widespread in China, is rich in rugose corals (Table 1) and provides an ideal basis for the study of rugose coral communities. So far within China, only two Early Visean communities, the Empachyphyllum-Clisiophyllum community and the PugilisMichelinia community, have been recognized from western Guizhou (Wu and Zhao, 1989) . In the present paper, the Early Visean rugose corals, namely those forms occurring within the range between the Pseudouralinia EARLY VISEAN RUGOSE CORAL COMMUNITIES 331 Table 1 The distribution of Early Visean rugose coral genera in different parts of China (see below) l' 2 3 4 5 6 7 8 9 10 11 Amplexiidae Amplexus X X Laccophyllidae Amplexicarinia X Barrandeophyllum X X Cyathaxoniidae Cyathaxonia X X Hapsiphyllidae A mplexizaphrentis X Hapsiphyllum X X X Longiclava X Zaphrentites X X X X X Zaphrentoididae Cumminsia X Zaphrentoides X Bradyphyllidae Bradyphyllum X X X Fasciculophyllum X Rotiphyllum X X Plerophyllidae Plerophyllum X Endothecium X Rhopalolasma X X Lophophyllidae Lophophyllidium X Lophophyllum X X X X X Caniniidae Caninia X X X X X X X X Bothrophyllidae Bothrophyllum X X X Calmiussiphyllum X Caninophyllum X X X X Characophyllum X Enygmophyllum X X X Heterocaninia X X X X X Kueichouphyllum X X X X X X X X Kusbassophyllum X X Parazaphriphyllum X Uralinidae Humboldtia X X Keyserlingophyllum X X Siphonophyllia X X X X X X Palaeosmil iidae Faberophyllum X Palaeosmilia X X X X X X Qinghaiphyllum X Koninckophyllidae Arachnolasma X X X X X X X Eostrotion X Koninckophyllum X Amygdalophyllidae Amygdalophyllum X