辽西四合屯脊椎动物集群死亡事件:火山爆发的灾变记录

Record of the Sihetun Vertebrate Mass Mortality Events,Western Liaoning,China:Caused by Volcanic Eruptions

辽西北票以Confuciusornis-Sinosauropteryx-Zhangheotherium为代表的四合屯脊椎动物组合发现于义县组下部湖相沉积中,时代为早白垩世Barremian中期(J—K界线144 Ma)或Valanginian晚期(J—K界线136 Ma)。化石包括鱼类、两栖类、爬行类、鸟类和哺乳类及无脊椎动物和被子植物,孔子鸟类群和具"羽毛"的小型兽脚类恐龙共生。野外发掘表明,化石完整地保存骨骼硬体及羽毛、食物、胃石、卵等软体及生理组织,确认多次非正常生物集群死亡事件。在四合屯发掘剖面上,含化石正常沉积的湖相页岩与火山喷发事件形成的沉凝灰岩互层,中酸性火山爆发形成的环境突变效应是导致脊椎动物集群死亡的主要原因。

The Sihetun Vertebrate Assemblage consists of fossil fishes, amphibians, reptiles, birds and mammals, featuring birds Confuciusornis and Liaoningornis,. and feathered theropod dinosaurs Sinosauropteryx, Protarchaeopteryx, Caudipteryx and Beipiaosaurus. This assemblage was found from the lake shales interbedded with tuffs of the lower Yixian Formation, western Liaoning, China. Result of radiometric dating of tuff samples, 124. 6±0. 3 Ma and 124. 6±0. 2 Ma, suggests the middle Barremian age (J—K boundary = 144 Ma) or the late Valanginian age (J—K boundary =136 Ma) of the Early Cretaceous for the Sihetun Vertebrate Assemblage. Almost all vertebrate fossils are exceptionally well-preserved. This type of preservation reflects mass mortality and rapid burial of the animal bodies in the lacustrine environment, and indicates that the intermediate—acid volcanic eruptions are main cause of the mass mortality events.