The concept of “Indosinian” was first introduced by Fromaget (1931, 1934) for folding in Indochina that took place during the Anthracolithic (a term, no longer commonly in use, for the Carboniferous and Permian together) and the Triassic. It is now just over 50 years since that concept was elaborated in an account of the work of the Service Géologique de l'Indochine (Fromaget, 1941).

The term “Indosinian” has been widely used, with many different meanings, for folding events in southern, central, southeastern, and eastern Asia that took place during the Permian and Triassic, or during various parts of that time interval. More recently it has been coupled (Dickins, 1985, 1988a, b) with the term “Hunter-Bowen” from eastern Australia to describe a period of worldwide folding and compression, beginning at the mid-Permian, involving a twofold division of the Permian in the Russian type sequence, and continuing to the end of the Triassic. There have been many recent studies of the geology of Indochina, with abundant new data. Within the framework of IGCP Project 272, and with related information from neighbouring countries, we here return to the issue of the Indosinian Tectogeny. This chapter describes some newly collected data related to the issue and presents a preliminary geological correlation for that noteworthy period on a fairly large scale in Southeast Asia.

Much attention has recently been given to the major biological changes in the Phanerozoic. The emphasis has been on extinctions, whereas the nature of the recoveries by faunas and floras after the times of major extinctions has not been so fully examined. In this chapter, attention is directed to that latter aspect. Emphasis is also placed on relating the biological developments to the geological changes and examining how those relationships interacted with the environment.

The term “mass extinction” is avoided, because it does not accurately describe most, if not all, of the examples of important extinctions during the Phanerozoic. In a detailed context of time and stratigraphy, it is not easy to say that any change was “abrupt” – see, for example, even the Permian–Triassic extinction (Dickins, 1983; Sweet et al., 1992), often rated as the largest within the Phanerozoic (regarding the Precambrian–Cambrian change as outside the Phanerozoic).

Until recently, correlations involving the mid-Permian (in the twofold Permian subdivision based on the Russian type area) have proved difficult, especially because of the worldwide regression and the associated strong tectonic changes (Dickins et al., 1989). The difficulty in making correlations has obscured both the geological and biological changes. A more nearly satisfactory resolution has become possible by considering the geological and biological aspects together, and that has led to the synthesis that is the subject of this chapter.

In so many features the Permian and Triassic periods differed from the present that if we could be transported back to that distant past, surely we would think that we were on another planet. The plants and animals would be largely unrecognizable – no mammals, and none of our modern trees or grasses. Although the nature and dispositions of the seas, lands, and mountains during that time are subject to different interpretations and conflicting views, who can doubt that the world's geography would be unrecognizable? The climate would have varied widely, from very cold at the beginning of the Permian (perhaps not unlike the glacial climate of the world a few thousand years ago) to a hot, dry climate during the Triassic, like nothing we see at present, followed by a warm climate continuing into the Jurassic.

Major changes in faunas were associated with the beginning of the Jurassic period, as reviewed by Boucot (1990), Dickins (1993a), and Hallam (1981). Boucot stated that “the modern marine … benthic fauna and communities really begin with the Jurassic.” In the latter part of the Permian and during the Triassic the earth was wracked by vast earthquakes, and great mountain chains were formed. There was magmatic-volcanic activity on an enormous scale. Some of those events are described in this volume, and some of the most interesting problems for future investigation are considered.

Project 272 of the International Geological Correlation Programme (IGCP-272), “Late Palaeozoic and Early Mesozoic Circum-Pacific Events and Their Global Correlation,” is a successor project to IGCP-203, “Permo-Triassio Events of East Tethys and Their Intercontinental Correlation,” and has been succeeded by IGCP-359, on Tethyan, circum-Pacific, and marginal Gondwanan late Palaeozoic and early Mesozoic correlations (biota, facies, formations, geochemistry, and events). The 25 reports that make up this volume represent the final report of IGCP-272. During the five years of the project (1988 to 1992) the participants met and carried out field work in Brazil (Sao Paulo), Australia and New Zealand (Newcastle, Hobart, and Dunedin), Argentina (Buenos Aires), the United States (Washington and Chicago), Russia (Perm), Japan (Kyoto), and the Russian Far East (Vladivostok).

The events reported here were diverse in nature and timing, and considerable attention has been devoted to improving the time scale. A special feature has been to emphasize the time relationships of different events that otherwise might seem to have been unrelated. The first chapter in this volume, by the coleaders of IGCP-272, provides an overview that describes a framework for location of those events that reflects the recognized worldwide standard stratigraphical and time scales for systems, series, and stages and emphasizes their real, physical basis.

Introduction

Although Upper Permian and Lower Triassic rocks are widespread, no sequences representing latest Permian and earliest Triassic marine deposition are known from Australia and no well-defined boundary sequence has been recognized in New Zealand. In the western part of Australia, where marine deposits are present, the uppermost Permian and the lowermost Triassic are represented by a hiatus. In central and eastern Australia only terrestrial deposits are known both in the Upper Permian and the Lower Triassic.

The floral changes associated with the boundary in Australia have been considered by Balme & Helby (1973) who concluded that a very marked change took place between the Permian and the Triassic. Dickins (1973) who summarized Australian boundary sequences, concluded that an important regression was apparent.

Western part of Australia

Considerable hiatus is present between the Permian and the Triassic (Fig. 16.1) with generally some, but not very distinct, angular structural discontinuity (Archbold & Dickins, 1991; Dickins, 1976; Banks, 1978).

In the Perth Basin, a gap is present between the Lower Permian marine Carynginia Formation of oldest Baigendzhinian (Upper Artinskian) age and the apparently nonmarine Wagina Sandstone, the age of which, on palynological grounds, is early Upper Permian (Lower and Upper here referring to a twofold subdivision of the Permian as used in the traditional type area in the Russian Platform-Ural Mountains region). A hiatus is then present beneath the Kockatea Shale, which contains a good open-sea marine fauna regarded as not older than Upper Griesbachian (Balme, 1963; McTavish & Dickins, 1974).

In the Carnarvon Basin no marine deposits are known that are younger than the Kungurian, the top stage of the Lower Permian.

Introduction

It has long been recognized that a major change in fauna and flora was associated with a major regression in the latest Permian and earliest Triassic (see Dickins, 1983). The nature of this regression (or eustatic change) and its relationship to orogenic and tectonic developments in the Upper Paleozoic and Lower Mesozoic are discussed in this paper, which also includes comparisons with the Cretaceous–Tertiary boundary sequence. The climate of the Permo-Triassic boundary interval is also considered and its nature and influence amplified.

Volcanic rocks are widespread in Permo-Triassic boundary sequences but, as indicated elsewhere in this volume, their importance has only recently been recognized. The volcanism indicated by these rocks was related to tectonic and magmatic developments, which, together with the eustatic change and climate, must have had a profound effect on the fauna and flora of the time. These factors and apparently associated changes in the composition of seawater, the atmosphere, and the nature of the land, seem more than adequate to explain changes in the flora and fauna. The latter, in turn, are important potential guides to understanding development of the earth below the crust.

Tectonic and magmatic development

The Permo-Triassic boundary interval includes evidence of a remarkable regression, which represents a large-scale eustatic fall in sea level. Newell (1962, 1967a, 1967b, 1973) advanced strong reasons for recognizing this worldwide regression, which he thought contributed importantly to the change in life that marks the difference between the Paleozoic and Mesozoic. In the decade in which Newell's papers appeared, however, coeval worldwide transgressions and regressions were not accepted in geology, as they are today.

Introduction

It has long been clear that waning stages of the Permian Period and initial phases of the Triassic make up an interval of time during which there were profound changes in the Earth's internal and surficial features, in its atmosphere and climate, and, conspicuously, in its biota. Unfortunately, however, rocks that record this fascinating segment of Earth history are greatly restricted in distribution by comparison with those from which we reconstruct events in earlier Paleozoic or later Mesozoic history. Furthermore, subsequent orogenic cycles have dismembered, effaced, and in other ways complicated the record. In combination, these factors make development of a stratigraphic scale for the Permo-Triassic boundary interval difficult, and this, in turn, serves to insure that the history of the latest Permian and earliest Triassic has been reconstructed thus far in only very general outline.

Project of 203 of the International Geological Correlation Programme (IGCP) was organized in 1984 with the aim of integrating modern studies of rocks and fossils in the Permo-Triassic boundary interval into an internally coherent and well-controlled body of information from which it might ultimately be possible to infer something meaningful about the history of late Paleozoic and early Mesozoic times. The attention of project participants naturally focused on Permian and Triassic strata in the eastern part of the Tethyan realm, in South China and India, for marine rock sequences of this age are most continuously developed there. However, close cooperation with students of the Permian and Triassic in Italy, Hungary, Yugoslavia, Israel, the Soviet Union, Australia, and New Zealand has enabled development of a data base that now includes information for essentially the entire length and breadth of the former Tethys seaway.

The 16 reports that make up this volume constitute the final report of Project 203 of the International Geological Correlation Programme, which dealt with Permo-Triassic events of the East Tethys and their intercontinental correlation. During the five-year life of Project 203, participants met twice in Beijing, and once each in Columbus, Ohio (USA) and Brescia (Italy), to exchange views, consider new data, and examine pertinent sections in the field. These conferences have provided new insight into the stratigraphy, classification, and relations of strata within the Permo-Triassic boundary interval, and a wider appreciation of the problems involved in the correlation and interpretation of these rocks, which document an unusually significant period in Earth history.

It will be clear to the reader that the 40 contributors to this volume are in substantial agreement in their interpretation of many features of the Permo-Triassic boundary interval, but disagree, at least by implication, in their evaluation of others. Although as editors we have strived to achieve readability and uniformity in basic terminology, we have also attempted to avoid interference with strongly held individual views, even though they run contrary to those of other contributors. In brief, it would be inappropriate to suggest that in five short years participants in Project 203 solved all problems with respect to the Permo-Triassic boundary interval – for many of these are likely to persist as long as vigorous study continues. We do suggest, however, that data and ideas gathered and expressed during the five-year life of Project 203 and summarized in this volume are important contributions toward understanding and interpreting the rock and fossil record of the late Permian and early Triassic.