辽西四合屯脊椎动物化石群：地层、时代与古环境

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	辽西四合屯脊椎动物化石群：地层、时代与古环境
	汪筱林
学位类型	博士
导师	邱占祥
	1999
学位授予单位	中国科学院古脊椎动物与古人类研究所
学位授予地点	中国科学院古脊椎动物与古人类研究所
学位专业	古生物学与地层学
关键词	辽西四合屯义县组早白垩世生物地层古环境埋藏学脊椎动物群（组合）热河生物群
摘要	通过四合屯地区及辽西热河生物群分布区的详细野外地质调查，四合屯、张家沟及尖山沟等化石地点的大规模系统化石发掘、采集，发掘剖面高精度的地层对比和化石层位确认以及化石凝灰岩夹层~（40）Ar/~(39)Ar同信素年龄测定，建立了四合屯—尖山沟地区义县组下部由3段9层组成的完整地层层序，脊椎动物化石主要赋存在第三段湖相沉积的页岩中，包含黄半吉沟和四合屯上、下2个主要化石层位。四合屯、尖山沟、张家沟等重要化石地点属于下部化石层。全面考证并确认已记述的所有脊椎动物化石的准确产出地点和层位，在厚度12m的发掘剖面上，发现8个含鸟层，5个含兽脚类恐龙层等42个脊椎动物化石埋藏层。所有脊椎动物化石埋藏于厚度约7m的半深湖—深湖相页岩中，其中鸟类和小型兽脚类恐龙埋藏层厚度约2m。脊椎动物化石群以孔子鸟类群的带动羽毛或毛状皮肤衍生物的小型号兽脚类恐龙共生为特征。四合屯发掘剖面和尖山沟剖面化石层凝灰岩夹层的~（40）Ar/~（39）Ar同位素年龄为124.6Ma，其时代为早白垩世Barremian中期（J/K界线144Ma）或Valanginian晚期（J/K界线136Ma），证明热河生物群时代为早白垩世。鸟类和恐龙龙类存在明显的集群死亡事件，中酸性火山爆发喷出的有毒气体、有害元素和尘雾导致环境发生突变。鸟类和恐龙类产在飞翔或迁移中集群死亡，经过湖面飘浮、瞬间沉降和快速埋藏于深湖还原环境中。在此条件下，化石得以完整保存。动物群生活在温暖潮温的淡小湖泊环境。适宜的气候条件、合理的食物链结构导致生物群快速辐射演化，热河生物群反映了早白垩世一次重要的陆相生物大爆发事件。
其他摘要	A thorough geological investigation and several large-scale paleontological excavations in Sihetun, Zhangjiagou, Jianshangou and other areas that are referred to the Jehol Biota have resulted in the discoveries of hundreds of vertebrate fossils. The fossil-bearing deposits in these areas were compared based on high-resolution stratigraphic correlations. The ~(40)Ar/~(39)Ar dating of the embedded tuff deposits in the fossil-bearing shale and mud stones was conducted to help set up the complete stratigraphic sequences of the lower Yixian Formation in Sihetun-Jianshangou area which is composed of 3 members and 9 beds. Vertebrates were mainly distributed in the lacustrine shale of the third member, which comprises the upper and lower major fossil beds in Huanghbanjiezihou and Sihetun localities respectively. The fossil sites in Sihetun, Jianshangou and Zhangjiagou are referred to the lower fossil bed. All described vertebrate fossils have been matched with their exact localities and horizons. A total of 42 vertebrate depositional layers composed of 8 bird-bearing layers and 5 theropod dinosaur-bearing layers have been recognized from a section of 12 meters thickness. All vertebrate fossils have been found from the medium to deep lake shale deposits of a total of 7 meters, and birds and theropod dinosaurs are distributed only in deposits of 2 meters thickness. The vertebrate assemblages in this area are characteristic of the co-occurrence of Confuciusornis Avifauna with small-sized feathered dinosaurs. The ~(40)Ar/~(39)Ar dating of the tuffs from the Sihetun and Jianshangou sections indicates that the Yixian Formation is 124.6Ma in age and can be referred to the middle Barremian of the Early Cretaceous (J/K boundary is 144 Ma) or the late Valanginian (J/K boundary is 136 Ma). The Early Cretaceous age for the Jehol Biota is therefore accepted in this paper. The mass extinction of birds and dinosaurs in this area is clear. The mass mortality and quick preservation of thousands of birds and dinosaurs in western Liaoning have been contributed to the presence of poisonous gases, volcanic dusts, and the forest fire resulted from the volcanic eruptions that had significantly changed the environments. The fossils were deposited quickly with little transportation after death. The animals were living in warm and humid environments abundant with freshwaters. The premium climate and food chains resulted in the fast radiation of the Jehol Biota. Therefore the Jehol Biota reflects an important biological exploration at the Early Cretaceous.
页数	94
语种	中文
文献类型	学位论文
条目标识符	http://119.78.100.205/handle/311034/1740
专题	硕博论文古低等脊椎动物研究室
推荐引用方式 GB/T 7714	汪筱林. 辽西四合屯脊椎动物化石群：地层、时代与古环境[D]. 中国科学院古脊椎动物与古人类研究所. 中国科学院古脊椎动物与古人类研究所,1999.

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