国际三叠纪年代地层研究进展

简要概述了近年来国际三叠纪年代地层等方面所取得的一些重要进展:国际地层委员会三叠系分会已于上世纪90年代确定将三叠系划分为3统7阶,但至今仅确定了三叠系底界一个“金钉子”,安尼阶-拉丁阶界线层型有望在近期内被最后确认,而其他5条界线仍在加紧工作中;随着同位素测年技术和手段的不断改进,三叠纪一些重要的年代地层界线的地质年龄也在不断更新;亚阶虽然不是国际三叠系研究的重点,但亚阶的划分也是三叠纪年代地层研究的重要方面,尤其在下、中三叠统研究中已有较好的基础;以脊椎动物为基础的陆相三叠纪年代地层划分方案有待在推广应用中得以完善。全国地层委员会于2 0 0 0年提出了3统6阶的中国海相三叠系划分方案和3统7阶的中国陆相三叠系划分方案,为启动中国三叠纪年代地层学奠定了基础。

RECENT ADVANCE IN THE TRIASSIC CHRONOSTRATIGRAPHIC STUDY

This paper presents a brief review of the recent advances in the Triassic chronostratigraphic study and its related aspects. The Subcommission on Triassic Stratigraphy (STS), ICS has formally voted through the scheme that the Triassic is divided into three series and seven stages in 1990's. So far only the Global Stratotype Section and Point (GSSP) for the base of the Triassic, however, has been formally defined. The GSSP for the Anisian-Ladinian boundary will be hopefully clarified soon. But the other five boundaries still need much work for the GSSP definition. With the improvement of the isotope dating techniques and methods, the Triassic timetable has been updated considerably and all the boundary ages between the stages have been redefined recently. The substage is not a main work of the STS, but the subdivision of the stages into substages is an important aspect in the Triassic chronostratigraphy, and the Lower and Middle Triassic especially have a good basis for substages. A terrestrial Triassic chronostratigraphical system based upon tetrapods has been suggested and to be improved in application. A scheme of three series and six stages for the marine Triassic of China and a scheme of three series and seven stages for the terrestrial Triassic of China have been proposed by the Chinese Committee of Stratigraphy in 2000, providing a proper basis for the chronostratigraphic study in China.