摘要
综合评述了5年来对二叠系—三叠系界线(PTB)全球层型剖面——煤山D剖面的研究进展。简要介绍剖面的研究历史、地理和地质背景,叙述了世界上最完整的二叠纪长兴期至三叠纪格里斯巴赫期的牙形石和菊石带,并简短讨论了Otoceras的年代。叙述了煤山与其他剖面长兴期至格里斯巴赫期磁性地层学的对比。介绍了δ13C和δ34S的化学地层学最新研究进展,特别是在PTB附近多个δ13C负漂移的发现。两项重要的分子地层学研究显示了基础生态系统的深刻变化——微生物生态系的灾变和在二叠纪—三叠纪生态系之交严重缺氧事件期间透光带的静海相环境。文章报道了自2001年以来PTB年代测定的进展。PTB之下14cm处火山成因的粘土层25层的年代,现在定为(252·4±0·3)Ma(Mundil等,2004)。文章还讨论了事件地层学,认为尽管在25-26层有一个主事件,煤山PTB附近的事件是多幕式的,并且开始于事件层25-26层之前。因此,PTB大绝灭主因是外星撞击导致的可能性是不大的。
This paper provides a synthesis of the research conducted on the Meishan section D, the Global Stratotype Section and Point of the Permian-Triassic Boundary （PTB）, East China. The historical, geographic and geological setting of the section are briefly introduced. Changhsingian to ＂Griesbachian＂ conodont and ammonoid zonations, one of the best Permo-Triassic zonations in the world, are presented, with a short discussion on the age of Otoceras. The paper presents a correlation of the Changhsingian to ＂Griesbachian＂ magnetostratigraphy along the Meishan section. Recent developments on the chemostratigraphy of δ^13C and δ^34S are introduced, especially the discovery of more than one negative δ^13C excursions across the PTB. Two important molecular findings reveal profound changes at the base of ecosystem-the microbial catastrophe, and the euxinic conditions in the photic zone during the Permian-Triassic superanoxic event. The paper reports changes in the determination of the age of PTB since 2001. According to Mundil et al. （2004） the age of volcanogenic clay bed 25, 14 cm below the PTB, is now set at （252.4±0.3） Ma. A discussion on the event-stratigraphy concludes that, although there is a major event episode at beds 25-26, the events across the PTB at Meishan mountain are multi-episodic and commenced prior to the Event Beds 25-26. Therefore , the possibility that the mass extinction was mainly induced by an extraterrestrial impact is excluded.
出处
《地学前缘》
EI
CAS
CSCD
北大核心
2006年第6期257-267,共11页
Earth Science Frontiers
基金
国家自然科学基金资助项目(40232025)
