부산대학교 도서관

The Upper Ordovician Xiazhen Formation in the Jiangshan-Changshan-Yushan (JCY) triangle area at the Zhejiang-Jiangxi provincial border, South China, is composed of a mixed carbonate-siliciclastic sequence representing various shallow-water platform environments. The formation exposed at Zhuzhai, Yushan, is about 190 m thick and has recently been divided into three members: the Lower Member dominated by carbonate beds (75 m), Middle Member characterized by a mixture of carbonates-siliciclastic beds (90-95 m), and Upper Member dominated by siliciclastic beds (15-20 m). Highly diversified and abundant heliolitid faunas consisting of Acdalopora, Plasmoporella, Heliolites, Propora and Taeniolites are recognized from seven stratigraphic horizons in the three members in the formation. At Zhuzhai, heliolitid corals occur over time and space in certain stratigraphic horizons and various lithofacies. Acdalopora is the only heliolitid in the lower unit in ZU2 and the other four genera are found from mid- and upper units (ZU1 and ZU3) of the formation. The broad association of tabulate corals, agetolitid corals and stromatoporoids in many lithofacies probably indicates broadly similar ecologic tolerances.Heliolites and Plasmoporella are selected for morphometric study. Multivariate morphometric analysis is applied for differentiation of species and evaluation of intraspecific and interspecific variations of Heliolites and Plasmoporella respectively. Several morphological characters are quantified by examining and measuring them from transverse and longitudinal thin sections and statistically tested for selecting effective characters in discriminating species. Results of frequency histograms, correlation analysis and principle component analysis indicate that certain characters would be suitable for cluster analysis. The cluster analysis is performed on principle component score matrices obtained from the raw data set coordinated with coralla by all those characters. Five major clusters at a relative distance on the resulting dendrogram of Heliolites and Plasmoporella are regarded as morphospecies. The discrimination of those morphospecies of Heliolites and Plasmoporella by the cluster analysis is verified by discriminant analyses and descriptive statistics. Keywords: Heliolitid corals, Morphometircs, Heliolites, Plasmoporella, Xiazhen Formation, Zhuzhai, South China