DISCOVERY OF THE CAMBRIAN TRILOBITES IN KUNSHAN OF SOUTHEAST JIANGSU WITH REFERENCE TO THE FAUNAL PROVINCIALITY AND PALAEOGEOGRAPHY
Lin Tian-rui (Departmentof Geology, Nanjing University) Lin Huan-ling (Nanjing Institute of Geology and Palaeontology, Academia Sinica) Zhou Tian-yong (The Eighth Geologieal Surveying and Prospeeting Team, Guizhou Province)
The Middle and Upper Cambrian trilobites described in this paper were obtained from a drilling core in the Kunshan area (about 60km west to Shanghai), SE Jiangsu. They consist of 21 genera, 27 species and 2 indeterminable forms. Among them, 2 genus and 10 species are new. The Middle Cambrian species are Lisania paratungjenensis Yang, Solenoparia jiangsuensis Lin et Zhou (sp. nov.), Paranomocarella parallela Yang, P. parapolita Yang, Jiangsuia typica Lin et Zhou (gen. et sp. nov.), Triplagnostus sp., Peronopsis sp. Dorypyge sp., and the upper Cambrian forms are Dorypygella posterocosta Yang, D. (?) sp.,Liostracina bella Lin et Zhou (sp. nov.), Fenghuange magnispina T. R. Lin (sp. dot.), F. subtriangularis Lin et Zhou (sp. nov.), Monkaspis quadratics Yang, Bergeronites jiangsuensis Lin et Zhou (sp. nov.), B. yushanensis T. R. Lin (sp. nov.), B. kunshanensis T. R. Lin(sp.nov.), Jiangnania miranda Lin et Zhou (gen. et sp. nov.), Liaoningaspis sp. Eoshengia sp. Coosia(?) sp., Paracoosia sp., Homagnostus sp., Proceratopyge sp., Koptura temenus Lin et Zhou (sp. nov.), Lisania(?) sp., Cyclolorenzella caijiapingensis Yang, Damesellids and Gen. et sp. indet. Detailed lithological characters and fossil horizons of the drilling core are given in the Chinese text. The discovery of the trilobite fauna in SE Jiangsu is of importance to the faunal provinciality and the palaeogeography of the Cambrian geology in E China. First of all, the fauna bears strongly transitional characters between the Yangzi Subprovince of the North China Faunal Province and the Jiangnan Subprovince. of the Southeast China Faunal Province. Moreover, it shows a closer relationship to the former fauna rather than to the latter one. Many agnostid genera, Which are very abundant in W. Zhejiang, S. Anhwei, Central Hunan, N. Guangxi and in NW China of the Jiangnan Subprovince, are rare in Kunshan area; while the non-agnostid trilobites, such as Koptura, Lisania, Monkaspis, Liaoningaspis, Liostracina, Eoshengia, Cyclolorenzella, Solenoparia, Dorypygella, Dorypyge, Paranomocarella and Damesellids are closelyrelated to the fauna of the North China Faunal Province. Secondly, in the Lower Yangzi flood plain, only some limestone, dolomite and siliceous limestone outcrops and drilling cores are scatteringly distributed. The age of these calcareous rocks are usually regarded as the Sinian (dolomites and siliceous limestones) or the Permo-Carboniferous (limestones), and the "Stone-Coal" Series, occurring at the base of the Lower Cambrian, is considered to be the Permian or Carboniferous coal measures. The Cambrian trilobites discovered in the Kunshan area and some orthid brachiopods found in the suburbs of Shanghai reveal that many but not all the mentioned calcareous rocks in the Lower Yangzi belong to the Lower Palaeozoic. Thirdly, as suggested by H. Y. Liu and others, thereisan oldland mass——the so-called "Taihu Oldland", which occupied the present Taihu Lake region and extended eastward to the vicinity of Shanghai in the Cambro-Ordovician time. The trilobite fauna proves that the "Taihu Oldland" is not a landmass but an epeiric sea which was connected with the North China Sea in the north and the Southeast China Sea in the south during the Cambrian time. The characteristic features of the new genera are as follows: Family Proasaphiscidae Chang, 1963 Jiangsuia Lin and Zhou (gen. nov.) Type species: Jiangsuia typica Lin and Zhou (sp. nov.) The genus is similar to Manchuriella and Proasaphiscus. It differs from Manchuriella typa Resser et Endo and Proasaphiscus yabei Resser et Endo in the very large palpebral lobes, the short and convex eye ridges, the norrower (sag.) posterior lateral limb, the more divergent anterior sections of facial sutures, the narrower pygidial axis, the distinct border furrow and broader border. Family Aulocodigmetidae Opik, 1967 Jiangnania Lin and Zhou (gen. nov.) Type species: Jiangnania miranda Lin and Zhou(sp. nov.) Ajrikina Kroskov, 1963, is closely similar to the new genus, but differs in the shorter and less oblique forward-outward eye ridges, the narrower and flattened fixed cheek without 2 pairs of elevations and 1 pair of depressions, and the absence of a pair of al-like elevations. Besides the type species, this genus includes Ajrikina elongata Ergaliev (1980. p. 140, pl. 6, fig. 7).