The steps and methods for the establishment of the global boundary stratotype section and point (GSSP) are summed up briefly as follows. (i) Select rock sequences of approximately the same age duration in a region, make a thorough study of their properties or attributes in order to establish the high-resolution stratigraphic units reflecting the natural rhythms in Earth’s history, and proceed by multidisciplinary comprehensive studies to reveal the relationship, including time-space relation and possible mutual causality, among the various stratigraphic units and the different natural rhythms established. (ii) Seek for the "natural break" that represents the "major natural changes in the historical development of the Earth" in shallow marine facies areas, which is frequently the third-order sequence boundaries. (iii) Trace from shallow marine facies areas toward the continental slope and bathyal areas to seek for a continuous depositional sequence that corresponds in time span to the "natural break" of shallow marine facies areas. (iv) Seek for a horizon within the continuous depositional sequence that approximately coincides with the maximum regressive point in the "natural break". This horizon is commonly within a lowerstand systems tract (LST) or a shelf margin systems tract (SMST) of the relevant third-order sequence. (v) Seek immediately above this horizon of maximum marine regression for an organic radiation or explosion event closely related to the natural boundary, which is generally the first flooding surface (FFS) of the relevant third-order sequence. (vi) Select within the organic event deposits closely related to the FFS the base boundary of a fossil taxon with widest geographical range as the Leading Group biozone for designation of the stratigraphic boundary. (vii) Select from among the sections with continuous depositional sequence formed under similar sedimentary palaeogeographic background (in general continental slope or bathyal environments) the section which possesses the shortest distance between the base boundary of the Leading Group biozone and the immediately underlying FFS of the relevant third-order sequence as the global stratotype section. The first appearance datum (FAD) of the Leading Group biozone species in the section may be regarded as the ideal GSSP. The steps suggested above are a supplement and improvement of the currently used procedures and methods for establishing GSSP. The GSSP established by using the steps and methods suggested here would make the stratigraphic boundaries better reflect the "major natural changes in the historical development of the Earth", more readily distinguishable and easily operable in recognition and correlation, and at the same time also make the designation of boundaries more objective.

A study on the relationship between biostratigraphy and sequence stratigraphy in several designated global boundary stratotypes shows that the best way may be to take the GSSP at a point coincident with the base of the first widespread Leading Group biozone above the first flooding surface (FFS) of the relevant third-order sequence. It is suggested that the first flooding surface of the sequence should be an important reference criterion for the selection of GSSP. As the base of the first widespread Leading Group biozone chosen for the definition of GSSP could not be lower than the first flooding surface of the referred sequence, the latter surface may be an important criterion for the recognition and correlation of the chronostratigraphic boundaries.

The aim of this study is to discuss the tectonic position of Baoshan in Yunnan Province, China, during the Late Paleozoic by comparison of the sedimentary facies, fauna and palaeomagnetic data from the Baoshan region with those from the Yangtze region and southern Tibet. The sedimentary facies change suggests that in the Late Palaeozoic the Baoshan region underwent a similar geological history to southern Tibet, but different from that of the Yangtze region. The rugose corals and brachiopods as well as vertebrates of Baoshan are different from those of the Yangtze region during the Late Palaeozoic. An evident segregation seems to exist between them. The Late Paleozoic fauna of Baoshan shows certain similarities to southern Tibet. The Devonian and Late Carboniferous faunas, especially, are very similar to those in southern Tibet. This indicates that there was no evident segregation between them in the Late Palaeozoic. The palaeomagnetic data reveal that in the Late Palaeozoic the Yangtze region was close to the equator, while the Baoshan region and southern Tibet were situated in the middle latitudes. On the basis of the palaeontological, sedimentological and palaeomagnetic data, it is inferred that Baoshan and southern Tibet were situated in the same continental margin, and both regions were far from the Yangtze region during the Late Paleozoic. The Baoshan region may be considered as a massif within the Gondwana tectonic domain which includes southern Tibet, while the Yangtze region was located in another tectonic domain--the South Asian domain, with a wide ocean, the Tethys between them. Copyright 0 1996 Published by Elsevier Science Ltd.