Permian-Triassic boundary in middle and eastern Tethys

The recent investigation on the conformable Permian-Triassic transition beds in South China revealed the existence of the mixed-fauna beds immediately above the Changhsing Formation or its equivalent, wh ich contain the Permian-type brachiopods and the Triassic-type ammonoids and bivalves. Three successive mixed-fauna beds, numbered I to 3, can be distinguished a t many places. The first two are referred as the Otoceras Zone and the last one as the Ophiceras Zone based on the new discovery of Otoceras sp. from the mixed-fauna bed no. I and a common occurrence of Ophiceras and Claraia in bed no. 3. The correlation of the Chinese sections with Permian-Triassic sequences in other parts of the Tethys province, such as Iran, Pakistan, and India, shows some time gap between the Upper Permian and Lower Triassic in those regions with the exception of Kashmir region. The Chinese sequences contain abundant ammonoids, brachiopods and conodonts that are usefu l for international correlation. Thus, the Chinese section, especially of the Changxing area, is considered to be a candidate of the stratotype of the Upper Permian and the Permian-Triassic boundary. Introduction and acknowledgements The transition between the Permian and Triassic Periods has been traditionally interpreted to represent the greatest biologic revolution in the history of the earth. Many scientists have successively given an outline of this event for many years. About a dozen years ago, an International Permian-Triassic Conference was held to discuss these subjects at the University of Calgary in Canada, and then was published the volume as to the boundary problems including the biostratigraphic as well as palaeontologie evidences on the world-wide basis. Some important problems are, however, still left in doubt even to the present day. The problems are, for instance, the cause of the biologic revolution and the biostratigraphic relationship between the Permian and Triassic sequences in the world . The successive sequences from the latest Permian to the earliest Triassic accompanied with a good exposure are limited in distribution, but certain favourable areas are expected to be found in South China, Kashmir, the Salt Range, Contribution from the Department of Geology and Mineralogy, Faculty of Science. Hokkaido University, No. 1832. * 1 Nanj ing Inst itute of Geology and Palaeontology, Academia Sinica. *2 Department of Earth Science, Kagaw.a University. Takamatsu. *3 Department of Earth Science, Himeji Inst itute o f Technology, Himeji. *4 Department of Geology and Mineralogy, Kyoto University, Kyoto. *5 Department of Geology and Mineralogy, Hokkaido University. Sapporo. 134 Sheng J.Z. ct al. the Julfa region of Soviet Armenia and Iranian Julfa in the northwestern part of Iran, the Abadeh region of central Iran, and the region of Kap Stosch in East Greenland, as already mentioned by Teichert et al. (1973). In South China, Zhao and his colleagues of Nanjing Institute of Geology and Palaeontology have contributed much to the Permian and Triassic stratigraphy and palaeontology and described the details of the Permian-Triassic boundary in South China. On the other hand, the Japanese members and their colleagues have engaged in the stratigraphic and palaeontologic examinations of the Permian-Triassic boundary in Kashmir (Nakazawa et aI., 1970, 1975), Afghanistan (Ishii et aI., 1971), Iran (IranianJapanese Research Group, 1981) and the Salt and Surghar Ranges (Pakistani-Japanese Research Group, 1981, and in preparation). In those contributions, the classification of the stages of the Upper Permian and the characteristic faunal assemblages in Late Permian were discussed in detail. Some questions, however, have remained unsettled, especially those regarding the correlation of the Upper Permian of the world. During the course of the study on the Permian and Triassic sequences in the Central and Eastern Tethys, all members of the Japanese team noticed the importance of the investigation of the Chinese sections in order to work out a solution to the boundary problems, and they wished to organize a cooperative study with Chinese team. On the other hand, Chinese specialists have desired to correlate reasonably the Chinese Permian and Triassic sections with other reference sections of the Tethyan realm. The present study has been performed by the specialists of the Permian and Triassic of the Nanjing Institute of Geology and Palaeontology of Academia Sinica and of Japanese universities. The research group of this study consists of the following members: from the People's Republic of China: Professor Sheng Jin-zhang, Professor Chen Chu-zhen, Dr. Wang Vi-gang, Dr. Rui Lin and Dr. Liao Zhuo-ting of the Nanjing Institute of Geology and Palaeontology, Academia Sinica; from Japan: Professor Yuji Bando, Kagawa University, Professor Ken-ichi Ishii, Himeji Institute of Technology, Professor Keiji Nakazawa, Kyoto University and Dr. Koji Nakamura, Hokkaido University. First joint work was proceeded by all members in November to December, 1981 at the Nanjing Institute of Geology and Palaeontology in Nanjing. They spent a half month in the field to examine the outcrops at Changxing, Longtan, Hushan and Mashishan in Xidongtingshan Island. After the field survey, they actively discussed the problems of the Permian-Triassic boundary in the Tethyan realm at the Nanjing Institute. The following year (1982) they met again for the preparation of joint paper at the Nanjing Institute in September. This paper is the result of these cooperative works by the Chinese and Japanese scientists. The present cooperative works were made possible by financial and material aids of the Academia Sinica of the Government of People's Republic of China and the International Cooperative Research Project promoted by the Japan Society of Promotion of Science of the Japanese Government. All the members wish to express their cordial appreciation to both the governments for their kind supports. The Chinese members are most grateful to Professor Zhao Jin-ke, the director of