中国晚前寒武纪至早寒武世生物事件及前寒武系—寒武系界线

<正> 35亿年前,地球上开始有生物存在,主要是兰藻和细菌。距今10亿年左右,开始出现软躯体动物所形成的遗迹化石。9亿年有蠕形动物的实体化石——淮南生物群保存。7亿年软躯体后生动物——埃迪卡拉动物群(西陵峡生物群、高家山生物群)大量繁殖,使晚前寒武纪的生物演化进入一个新阶段。6亿年左右,骨骼化动物——梅树村动物群(或托莫特动物群)的出现,开创了生物发展、演化史上的新纪元。使更多的生物能够以化石

The Chinese Late Precambrian-Early Cambrian biological events and the Precambrian-Cambrian boundary

In China, the macroalgal flora-the Huailai Biota represented by Longfengshania makes its first appearance in the Late Precambrian rocks of about 900-850 Ma BP. It is the earliest biota found in the Qingbaikou System of China, but this biota has never contained any fossil animals. In the Early Sinian (840-650 Ma BP) Liulaobei and Jiuliqiao Formations of the Huainan Group in the Huainan area of Anhui occurs the Huainan Biota dominated by chuarid, verms and vendotaenid. This group is the oldest of the horizons yielding fossil animals. In the Middle and Late Sinian rocks of 650-600 Ma BP of Hubei and southern Shaanxi occur the Xilinxia and Gaojiashan Biotas containing mainly verms, tubular fossils, pennatulids and trace fossils roughly corresponding to the Ediacara Fauna of Australia in age. During the latest Sinian and the earliest Cambrian (596.9-570.7 MaBP), the oldestskelatal fauna-the Meishucun Fauna appeared and were becoming rapidly flourishing. Theoccurrence, flourish, decline and extinction of the small shelly fauna provided a reliable basis for the placement of the precambrian-Cambrian boundary. The stratotype point is placed between the Anabarites-protohertzina Zone and Paragloborilus-Siphogonuchites Zone (i. e., the boundary between the Units 6 and 7 of the Meishucun section). The oldest shelly trilo-bites begin their range in the early Early Cambrian Qiongzhusian age and the appearance of the comparatively progressive arthropods such as trilobites represented by Parabadiella and bradorids mark a fully new stage in the evolutionaly history of organisms that was immediately followed by the Chengjiang Fauna dominated by flourishing soft-bodied metaozoans such as medusae, verms and large arthropods with soft appendage attached and the Malang Fauna consisting mainly of anomalous trilobites. Based on the study of the evolutionary sequence of the Early Cambrian small shelly and trilobite faunas from the Meishucun area of Yunnan, the Chinese Lower Cambrian strata are divided into 4 stages and 11 zones.