The Ediacaran Period
The Ediacaran Period
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DOI：
10.1016/b978-0-444-59425-9.00018-4
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发表时间：
2012-06
期刊：
影响因子：
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通讯作者：
G. Narbonne;S. Xiao;G. Shields;J. Gehling
中科院分区：
文献类型：
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作者：
G. Narbonne;S. Xiao;G. Shields;J. Gehling
2004年，埃迪卡拉体系和期被批准，这是一个多世纪以来第一个在地质时间尺度上增加的时期水平。埃迪卡拉纪底部的GSSP标志着马里诺冰期的结束，这是最后一次真正大规模的全球冰期，它破坏了新元古代中期的世界，并且可以通过c同位素的扰动和作为这次冰期的结果而沉淀的独特的“帽碳酸盐岩”的出现进一步在世界范围内得到确认。至少3次极负的同位素偏移和急剧上升的海水87Sr/86Sr值是埃迪卡拉纪的特征，同时也提供了深海环境氧合增加的地球化学证据。埃迪卡拉纪（635e541 Ma）标志着生命历史上的一个关键位置，介于主导经典“前寒武纪”的微观的、主要是原核生物的组合，以及主导寒武纪和显生宙早期的大型、复杂的、通常是壳状动物的组合之间。各种各样的大型多刺兽和简单的动物胚胎出现在埃迪卡拉纪底部的正上方，至少分布在埃迪卡拉纪的下半部分。中埃迪卡拉纪Gaskiers冰期（584e582 Ma）紧接着出现了主要由软体埃迪卡拉生物群组成的Avalon组合（579 Ma）。最早丰富的双边洞穴和印痕（555 Ma）和钙化动物（550 Ma）出现在埃迪卡拉纪末期。
The Ediacaran System and Period was ratified in 2004, the first period-level addition to the geologic time scale in more than a century. The GSSP at the base of the Ediacaran marks the end of the Marinoan glaciation, the last of the truly massive global glaciations that had wracked the middle Neoproterozoic world, and can be further recognized worldwide by perturbations in C-isotopes and the occurrence of a unique “cap carbonate” precipitated as a consequence of this glaciation. At least three extremely negative isotope excursions and steeply rising seawater 87Sr/86Sr values characterize the Ediacaran Period along with geochemical evidence for increasing oxygenation of the deep ocean environment. The Ediacaran Period (635e541 Ma) marks a pivotal position in the history of life, between the microscopic, largely prokaryotic assemblages that had dominated the classic “Precambrian” and the large, complex, and commonly shelly animals that dominated the Cambrian and younger Phanerozoic periods. Diverse large spiny acritarchs and simple animal embryos occur immediately above the base of the Ediacaran and range through at least the lower half of the Ediacaran. The mid-Ediacaran Gaskiers glaciation (584e582 Ma) was immediately followed by the appearance of the Avalon assemblage of the largely soft-bodied Ediacara biota (579 Ma). The earliest abundant bilaterian burrows and impressions (555 Ma) and calcified animals (550 Ma) appear towards the end of the Ediacaran Period.