This paper reports a Lower Triassic inorganic carbon isotope profile from the North Pingdingshan Section in Chaohu, Anhui Province, China, which was situated in a deep part of the Lower Yangtze carbonate ramp. The δ(¹³C)excursion shows two periods from the Permian-Triassic boundary to the lower Spathian substage, corresponding to the ecosystem undergoing evolution and recovery after the end-Permian mass extinction and related events. The first period starts at the δ(¹³C)depletion caused by the mass extinction and evolves with a gradual δ(¹³C)increase resulting from the development of some disaster taxa during the Induan. The strong Smithian δ(¹³C)depletion in the second period might be formed by the collapse of the disaster ecosystem and the biotic recovery occurred with the explosive increase of bioproductivity in the Spathian. Thus the δ(¹³C)excursion in the Lower Triassic expresses patterns of biotic evolution and recovery during the erratic ecosystem that followed the great end-Permian mass extinction. KEY WORDS: Lower Triassic, inorganic carbon isotope, extinction and recovery, Chaohu, Anhui Province.

The presence of a single Otoceras species (O. boreale),morphologically very variable,at the base of the Nekuchan Formation in Verkhoyansk,we believe,is to be obvious. Some morphological evidence leaves no doubt that two described morphs of O. boreale are a strictly corresponding sexual dimorphic pair. It is very likely that Kummel's idea that Canadian O. concavum Tozer is an invalid species is truthful,considering the range of variability seen in larger Siberian and Himalayan Otoceras fauna. Just above the upper Tatarian Imtachan Formation,the six stages of ammonoid succession can be recognized within the lower part of the Nekuchan Formation in the Setorym River Section: (a) Otoceras boreale; (b) Otoceras boreale-Tompophiceras pascoei; (c) Otoceras boreale-Tompophiceras pascoei-Aldanoceras; (d) Tompophiceras pascoei-Otoceras boreale-Aldanoceras; (e) Tompophiceras morpheous-T. pascoei-Aldanoceras; (f) Tompophiceras morpheous-T. pascoei-Wordieoceras domokhotovi-Ophiceras transitorium; (g) Tompophiceras morpheous-T. pascoei,corresponding to the Otoceras boreale and Tompophiceras morpheous zones. In spite of the domination of Otocerataceae or Xenodiscaceae in both of these zones and the presence of some Permian type conodonts in the lower part of the Otoceras boreale Zone,they seem to be early Induan in age on the basis of the following arguments: (1) in contrast to the underlying regressive type sediments of the Upper Tatarian Imtachan Formation,both the Otoceras boreale and the Tompophiceras morpheous zones of the lowermost part of the Nekuchan Formation correspond to the single transgressive cycle; (2) typical early Induan ammonoids (Ophiceras and Wordieoceras) have been recognized in the Tompophiceras morpheous zone; (3) all described ammonoid succession stages (a-g) are characterized by very gradual changes and therefore correspond to the different parts of the single zone or to the different zones of the same stage,but not to the different systems (Permian and Triassic); (4) elsewhere in the Boreal realm (Arctic Canada),the conodont index species for the base of the Triassic,Hindeodus parvus,has been reported from the Otoceras boreale Zone. A new scheme of the phylogeny for the Otocerataceae and its Induan Olenekian offspring (Araxceratidae-Otoceratidae- Vavilovitidae n.fam.-Proptychitidae-Arctoceratidae) and Xenodiscaceae is offered.

Late Olenekian assemblages in the western Panthalassa have been recovered from bedded radiolarian chert sequences of an accretionary complex,the Ashio belt. These faunas are documented and considered in terms of radiolarian diversity and faunal turnover during the latest Permian to Middle Triassic time. The fauna includes 30 radiolarians belonging to Spumellaria or Entactinaria,with two relicts from the Late Permian. This late Olenekian fauna is markedly different from Permian and Anisian faunas,respectively,and is herein named the Minowa fauna. Study of the literature indicates that radiolarian provinces were significantly disconnected between the western Panthalassa and eastern Tethys during late Olenekian time. Furthermore,121 of 143 species disappeared during late Olenekian time,and in turn 118 new species appeared in the western Panthalassa around the Olenekian Anisian boundary. It is concluded that faunal turnover occurred at least three times between the latest Permian and Middle Triassic. The first turnover is the Paleozoic type radiolarian extinction at the Permian Triassic boundary,the second is the diversification of spheroidal Spumellaria and Entactinaria between early and late Olenekian time,and the third is a faunal turnover from the Minowa fauna to the true Mesozoic type radiolarian faunas that are characterized by multi segmented Nassellaria.

This paper proposes a scheme for the definition of the Lower Triassic Induan Olenekian boundary (IOB) based on investigation of sections in Chaohu,Anhui Province,China as well as data accumulated from other studies elsewhere. The conodont Neospathodus waageni is suggested as the index fossil of the boundary. According to the FAD of N. waageni,the IOB is at the base of bed 25 2 of the West Pingdingshan Section in Chaohu,42.19 m above the Permian Triassic boundary,and it is slightly higher than the base of the Flemingites-Euflemingites Ammonoid Zone at the section.

A selection of evidence,including a carbon isotopic excursion,iridium anomaly,fullerenes (C₆₀ and C₇₀) with trapped noble gases,microspherules and shocked quartz,is discussed in this paper. All the evidence in hand favors the hypothesis that the PTB event was probably related to an extraterrestrial cause,and the impact would lead to great physical change,including large volcanic eruptions on the earth's surface. The ET markers for the CTB event could be considered only as an example,and cannot be taken as a unique standard of an ET event.

After the establishment of the global stratotype section and point (GSSP) of the Permian Triassic boundary (PTB), the definition of the accessory section and point (ASP) of the terrestrial Permian Triassic boundary (TPTB) is now on the agenda. However, all good TPTB sections so far known have the following shortcomings: (1) the exact TPTB horizon is difficult to define paleontologically with high resolution, and (2) accurate correlation between marine and terrestrial PTBs is hard to attain. In order to enhance the understanding of the nature of the global life crisis in both the marine and terrestrial environments across the Paleozoic Mesozoic transition, these shortcomings need to be addressed. In western Guizhou and eastern Yunnan, Southwest China, some fossiliferous PTB sections which include marine, paralic and terrestrial are well developed, allowing bed to bed correlation of the PTB sequences. Fortunately, the marine PTB sequence in this area is almost the same as found at the Meishan Section, where the GSSP of the PTB is located, which may provide a reliable auxiliary marker for high resolution demarcation of the TPTB. These features found in western Guizhou and eastern Yunnan make this area a good place to study the ASP of the TPTB, so we propose to study the ASP of the TPTB in this area.

The Zhejue Section is an excellent terrestrial Permian Triassic boundary (TPTB) section not only for its convenient accessibility and good outcrop, but also for its abundant fossils. In addition, there are two claystone beds that were formed by events across the Permian Triassic boundary (PTB) at this section. The claystones provide a bridge for high resolution correlation between marine and terrestrial PTBs. Another advantage is that the PTB at the Zhejue Section can be correlated with that of littoral and neritic facies by tracing westwards. Synthesized stratigraphic studies, including biostratigraphy, eventostratigraphy (susceptibilities and carbon isotopes across the TPTB, and microspherules found in the boundary claystones) and sequence stratigraphy, are carried out at this section.

Abundant ichthyoid remains, conodonts and holothurians sclerites were recovered near the Permian/Triassic boundary from a section south of Isfahan. Recovered ichthyoid remains include shark micro teeth and scales. The ichthyolith material is similar to a Fasanian ichthyolith from the Zakazane area in the Slovak karst of the Western Carpathians, which represents a subspecies of Acodina triassica. Conodont species are mostly neogondolellids. This fauna indicates that the sedimentary environment was marine, while to the north of localities near Isfahan and Zagross, terrestrial deposition was dominant at that time. Aluminasilicate and kaolin are present in a continental unit in Dopolan refractory main (Shahid Nilchian mine) and a section south of Chahriseh Village, north of Isfahan. Pisolitie, ironstone facies and bauxite clay are common near the Permian/Triassic boundary in the Chahriseh region.

Meishan Section D in Changxing County, Zhejiang Province, China has been selected as the global stratotype of the Permian Triassic boundary and various studies have been done at the boundary, but the gas chromatographic mass spectrographic analysis of alkane biomarkers has not been investigated. This paper presents the results of a study of the biomarkers analyzed in a series of samples across the Permian Triassic boundary at both Meishan Section A and Section D. The results show that the overall concentration of alkane biomarkers in the Permian Triassic boundary strata is high in Bed 26 while it is low in Bed 27. A variety of biomarker parameters demonstrate that the main sources of organic matter in the sediment are algae and bacteria and that the depositional environment varied from weakly oxidizing to reducing during the studied interval.

On the basis of researches over several years on biostratigraphy of Changhsingian at Meishan Section D in Changxing County, the abundant materials were accumulated. This paper studies the ecostratigraphy and establishes 7 community zones (CZ), in ascending order, Sinoplatysomus-Geinitzina-Clarkina subcarinata, Tapashanites-Nodosaria-Clarkina subcarinata, Crurithyris-Geinitzina-Clarkina subcarinata, Glomospira-Clarkina changxingensis, Colaniella-Clarkina changxingensis, Rotodiscoceras-Palaeofusulina-Hindeodus typicalis, Clarkina meishanensis-Hypophiceras.The habitat type (HT) is different from upper shallow sea to the lower part of the lower shallow sea.

Based on the study of lithology, sedimentology and paleontology at the Permian Triassic boundary in Liaotian, Northwestern Jiangxi Province, the sequence stratigraphy and depositional environments across the boundary are reconstructed. The top part of the Upper Permian Changxing Formation is composed of very thick bedded light colored dolomitic limestone formed in high deposition rate on carbonate ramp, which indacates a transgression systems tract (TST). The Lower Triassic Qinglong Formation shows continuous deposition with the underlying Upper Permian. The lower member of Qinglong Formation consists of calcareous shale, shelly limestome and dolomitic limestone with abundant bivalves (Claraia sp.)and trace fossils (Chondrites). The calcareous shale at the bottom of Lower Triassic indicates a calm deep water environment to form the condensed section (CS). The shelly limestome and dolomitic limestone with shell fossils, intraclast, algal ooide show clean but turbulent environment of carbonate ramp, which produce the deposition of highstand systems tract (TST).

According to the latest International Chronostratigraphic Scheme (ICS, 2000), the Permian in the Middle Lower Yangtze region of South China can be divided into three series and nine stages relevant to the traditional six stages of South China. From Assellian to Changxingian of Permian, 44 Ma in age range, the strata are composed of 14 third order sequences, each of which is 3.14 Ma in average age range. There is one third order sequence of Zisongian, equivalent to middle and upper Chuanshan Formation or equal to Asselian and two thirds of Sakmarian. There are two third order sequences, corresponding to Liang shan Formation or Zhenjiang Formation and upper Chuanshan Formation, which are assigned to Longlingian, coinciding with Artinskian and one third of Sakmarian. In addition, three third order sequences, equal to Qixia Formation, are attributed to Chihsian, corresponding to Kubergandian and one third of Roadian. Four third order sequences, comprising Gufeng, Maokou, Yanqiao, Yinping and Wuxue formations, are assigned to Maokouan, equivalent to two thirds of Roadian, Wordian and Capitanian. Two third order sequences, equal to Longtan Formation or Wujiaping Formation, are included in Wuchiapingian. Other two third order sequences, corresponding to Changxing Formation or Dalong Formation, are assigned to Changhsingian. In brief, these above third order sequences can be incorporated into 4 sequences sets.