二叠系－三叠系研究的进展

介绍了近年来二叠系、三叠系年代地层学的研究趋势及最新的年代地层表与磁性地层表。在二叠系、三叠系界线方面报道了新的底界方案及四个层型候选剖面，以及与之有关的生物地层学进展。界线事件地层学的，总趋势是球外事件研究趋于沉静而缺氧事件、海侵事件及火山事件的综合作用导致生物大绝灭的观点已占主导地位，其中界线缺氧事件的确立以及海侵始于二叠纪末的新观点是引人注目的发展。在层序地层学方面对于二叠系的全球海平面变化一般趋向于分四个旋回，但对于三叠纪则尚未统一。早二叠世的全球冰期－海平面升降旋回及三叠纪的米兰柯维奇旋回在我国均有可能发现和研究。文章最后提出了层序地层界线与年代地层界线不一致所产生的理论问题并探讨了解决方法。

ADVANCEMENTS OF PERMIAN AND TKIASSIC RESEARCH

Advancements of Permian-Triassic chronostratigraphy , magnetostratigraphy and sequencestratigraphy as well as Permo-Triassic boundary are indicated and commented.Newly establishedtime scale and magnetostratigraphic column of Permian and Triassic are presented.Recent discoveriesof P/T boundary which lead to enhancement of the status of Hindeodus parvus as the boundary indexfossil as proposed by the Chinese Working Group(1993 ) are reported. The paper calls to attentionthe probably world-wide distribution of anoxic event right at the Permo-Triassic transition whichcould have caused the P/T mass extinction, and also the accumulating facts showing that the trans-gression following the great end-Permian regression commenced not in earliest Triassic , but in latestPermian already.The last part of this paper summarizes general tendencies of sequence stratigraphicsubdivision of Permian and Triassic , proposes application of glacio-eustatic cycles in South China'sQixian Stage(Lower Permian) as well as Milankovich rhythms and cycles in Triassic strata of SouthChina.After a discussion on the discordance of sequence stratigraphic and chronortratigrahic bound-aries ,this paper raises the theoretic problem of whether it is appropriate to shift the sequence bound-ary , especially that of the II type sequence, from base of the lowstand tract to the base of transgres-sive tract.