摘要
对广西南洞剖面的研究表明，弗拉阶－法门阶（Ｆ－Ｆ）生物事件（也称为Ｋｅｌｗａｓｓｅｒ生物事件）是阶梯式灭绝事件，生物种类锐减发生于ｌｉｎｇｕｉｆｏｒｍｉｓ带最晚期，持续时间约为０．１Ｍａ。在Ｆ－Ｆ界线有３个Ｎｉ－Ｉｒ异常层，该异常层同时也富含亲铜元素，并伴有碳同位素负异常以及微玻陨石。紧随着覆盖有海啸岩。Ｆ－Ｆ事件实际上是生物－地球化学－沉积综合事件。像这样的综合事件，在中、晚泥盆世共发生了５次。发生的频率为４．６×１０－６ａ－１。讨论了Ｆ－Ｆ大灭绝事件的可能原因。
Study on the Nandong Section of South China reveals that the Devonian Frasnian Famennian (F F) bio event was a stepwise mass extinction.The devastating diversity loss occurred in the latest linguiformis Zone,which was 0 1 Ma in duration.Across the F F boundary there are three nickel iridium moderate anomaly beds,which are also enriched in chalcophile elements,and also accompanied with the carbon isotope negative anomalies and microtektites.The last Ni Ir anomaly was followed immediately by tsunamis.In fact,the F F event is an integrative event—biotic,geochemical,sedimentologic.Such integrative events occurred five times in the Middle and Upper Devonian with a frequency of 4 6×10 -6 a -1 (year -1 ).This frequency approximates to the frequency of the impact of 1 km sized asteroids on Earth,estimated by Shoemaker(1990).The possible cause of the F F mass extinction is herein discussed.Asteroids(probably 1 km sized)struck the Earth with a frequency of 4 6×10 -6 a -1 .These impacts intensified the global(or vast regional)hydrothermal activities on fracture zones,with anomalous Ni Ir and chalcophile deposits ensuing.The main Ni Ir excess might have a hydrothermal origin.Hydrothermal metal toxicity might be one of the kill mechanisms in mass extinction.Sea level change and regressive anoxia excursion were ongoing phenomena which might create appropriate stagnant condition for the preservation of element excess,but might not be the main causative factor of mass extinction.
出处
《北京大学学报（自然科学版）》
CAS
CSCD
北大核心
1998年第2期363-369,共7页
Acta Scientiarum Naturalium Universitatis Pekinensis
基金
高等学校博士学科点专项科研基金
