埃迪卡拉纪

埃迪卡拉纪（Ediacaran），又称艾迪卡拉纪、震旦纪（Sinian）、文德纪（Vendian），是元古宙最后的一段时期，其后紧接着便是显生宙的开端──古生代的寒武纪。埃迪卡拉纪一般指6.35-5.41亿年前。学者曾用这个名字指称不同阶段，直到2004年5月13日，国际地质科学联盟明确定义其年代，这是这个组织120年来首次对其加时期定义。最古老的动物遗迹可追溯至十亿年前，但最早的动物化石出现于埃迪卡拉纪。

**命名**
埃迪卡拉生物群因为发现于南澳洲的Ediacara Hills而得名。1946年，一位澳洲地质学家Reg Sprigg在古代的沙岩板中留意到一曾在这里发现显生宙以前的化石。研究这些化石的科学家Martin Glaessner认为这是珊瑚、水母和蠕虫的先驱。以后几十年，南澳洲还找到很多的隐生宙化石，其他各大洲也找到一些。这些化石都叫作埃迪卡拉动物。一开始，人们认为埃迪卡拉动物是寒武纪的动物，但经过仔细的观察，埃迪卡拉生物群比寒武纪还久远，应属于埃迪卡拉纪。
本纪曾被一些人称为震旦纪（Sinian）。震旦纪的名称来源于中国，“震旦”是中国的古称。由于古印度人称中国为Cinisthana，在佛经中被译为震旦，故名震旦纪。时至今日，中国学者仍经常这幺称呼，中国教科书上一直称此纪为震旦纪。俄国人又把埃迪卡拉纪称为文德纪（Vendian），他们在这一时期的地层中又发现了一些古线虫动物的化石。

**上下边界**
全球界线层型剖面和点位（GSSP）的“金钉”
标志着 GSSP 的“金穗”
埃迪卡拉纪上边界的GSSP是纽芬兰东南海岸寒武纪的下边界，埃迪卡拉纪的下边界的GSSP位于碳酸盐盖Nuccaleena 组的底部，紧邻南澳大利亚弗林德斯山脉布拉奇纳峡谷 Enorama Creek 剖面的 Elatina 杂岩上方。

**细分**

**绝对年代**
由于缺乏上覆的火成岩材料，南澳大利亚埃迪卡拉纪岩石类型剖面的年代难以准确测定。因此，6.35 至 5.388 亿年的年龄范围是基于其与可以测年的其他地层的相关性得出的。

**生物群**
埃迪卡拉生物群生态复原
埃迪卡拉生物群（Ediacaran biota）是1946年发现于南澳洲Ediacara Hills的末远古系庞德石英岩中的化石群，这类化石群已在世界30多个地点被发现。它们是迄今已知最早的复杂多细胞生物。
埃迪卡拉动物和今天的大多数动物截然不同，牠们既没头、尾、四肢，也无口部和消化器官，因此牠们大概只能从水中摄取养份。大多的埃迪卡拉动物固着在海底，和植物十分相近，其他的则平躺在浅海处，等待营养顺水流而送上门来。埃迪卡拉动物化石出土越多，反而越没有规律。有一些化石比较像后来动物的先驱。
在埃迪卡拉纪末期，埃迪卡拉动物分成两支，牠们有的成功演化成更有活力，更具进攻性的动物，并在之后的寒武纪大爆发中大放异彩，成为现今大多数动物门的祖先。而有的则走向灭亡，牠们的特征也永远消失于历史舞台上。

**天文因素**

**参见**
 List of fossil sites- 阿瓦隆大爆发- 埃迪卡拉纪末期灭绝事件

**参考资料**

**脚注**

**书目**
  A. Knoll, M. Walter, G. Narbonne, and N. Christie-Blick (2004) " The Ediacaran Period: A New Addition to the Geologic Time Scale.date=20181004145407 " Submitted on Behalf of the Terminal Proterozoic Subcommission of the International Commission on Stratigraphy.- Knoll, A. H.; Walter, MR; Narbonne, G. M; Christie-Blick, N (2004). " A new period for the geologic time scaledate=20110607104121 ". Science 305 (5684): 621–622. - Knoll, A. H., Walter, M. R., Narbonne, G. M., and Christie-Blick, N. (2006). " The Ediacaran Period: A new addition to the geologic time scale". Lethaia 39: 13–30. - " Geological time gets a new period: Geologists have added a new period to their official calendar of Earth's history—the first in 120 yearsdate=20170823181357 ". London: BBC. 2004-05-17. Accessed 27 December 2010.- "South Australian Museum Newsletter April 2005" Accessed 9 August 2010.- B. M. Sokolov (1952). "On the age of the old sedimentary cover of the Russian Platform". Izvestiya Akademii Nauk SSSR, Seriya eologicheskaya 5: 21–31.- Sokolov, B.S. (1997). "Essays on the Advent of the Vendian System." 153 pp. KMK Scientific Press, Moscow. (in Russian)- Sokolov B. S. (1965) "Abstracts of All-Union Symposium on Paleontology of the Precambrian and Early Cambrian." Nauka, Novosibirsk.- Rozanov, A.Y., Missarzhevskij, V.V., Volkova, N.A., Voronova, L.G., Krylov, I.N., Keller, B.M., Korolyuk, I.K., Lendzion, K., Michniak, R., Pykhova, N.G., and Sidorov, A.D. (1969). "The Tommotian Stage and the problem of the lower boundary of the Cambrian". Trudy Geologičeskogo Instituta AN SSSR 206: 1–380.- M. A. Fedonkin, B. S. Sokolov, M. A. Semikhatov, N. M. Chumakov (2007). "Vendian versus Ediacaran: priorities, contents, prospectives". In: " The Rise and Fall of the Vendian (Ediacaran) Biota date=20131112154205 ". Origin of the Modern Biosphere. Transactions of the International Conference on the IGCP Project 493n Moscow: GEOS. August 20–31, 2007.- Khomentovsky, V. V. (2008). "The Yudomian of Siberia, Vendian and Ediacaran systems of the International stratigraphic scale". Stratigraphy and Geological Correlation 16 (6): 581–598. - Comments By B. S. Sokolov, M. A. Semikhatov, And M. A. Fedonkin. (2004) Appendix 2 in: " The Ediacaran Period: A New Addition to the Geologic Time Scaledate=20181004145407 ." Submitted on Behalf of the Terminal Proterozoic Subcommission of the International Commission on Stratigraphy. pp. 32–34- Bristow, T. F. and Kennedy, M. J. (2008). "Carbon isotope excursions and the oxidant budget of the Ediacaran atmosphere and ocean". Geology 36 (11): 863–866. Retrieved 2007-05-05.- Le Guerroué, E., Allen, P. A., Cozzi, A. (2006). " Chemostratigraphic and sedimentological framework of the largest negative carbon isotopic excursion in Earth history: The Neoproterozoic Shuram Formation (Nafun Group, Oman)". Precambrian Research 146 (1–2): 68–92.- Le Guerroué, E.; Allen, P. A., Cozzi, A., Etienne, J. L. and Fanning, C. M. (2006). " 50 Myr recovery from the largest negative δ13C excursion in the Ediacaran ocean date=20160307032336 ". Terra Nova 18 (2): 147–153.- Le Guerroué, E.; Allen, P. A., Cozzi, A. (2006). " Parasequence development in the Ediacaran Shuram Formation (Nafun Group, Oman): primary origin stratigraphic test of negative carbon isotopic ratios date=20150909152314 ". Basin Research 18 (2): 205–220.- A. Ragozina, D. Dorjnamjaa, A. Krayushkin, E. Serezhnikova (2008). "Treptichnus pedum and the Vendian-Cambrian boundary". 33 Intern. Geol. Congr. August 6–14, 2008, Oslo, Norway. Abstracts. Section HPF 07 Rise and fall of the Ediacaran (Vendian) biota. P. 183.- Hoffmann, K.H.; Condon, D.J.; Bowring, S.A.; Crowley, J.L. (2004-09-01). " U-Pb zircon date from the Neoproterozoic Ghaub Formation, Namibia: Constraints on Marinoan glaciation date=20160222213956 ". Geology 32 (9): 817–820.- Condon, D., Zhu, M., Bowring, S., Wang, W., Yang, A., and Jin, Y. (1 April 2005). " U-Pb Ages from the Neoproterozoic Doushantuo Formation, China date=20151031103930 " (abstract). Science 308 (5718): 95–98.- Calver, C.R.; Black, Lance P.; Everard, John L.; Seymour, David B. (2004-10-01). " U-Pb zircon age constraints on late Neoproterozoic glaciation in Tasmania date=20160222214007 ". Geology 32 (10): 893–896.- Ogg, J. G. (2004). "Status of Divisions of the International Geologic Time Scale". Lethaia 37 (2): 183–199.- Amthor, J. E.; Grotzinger, John P.; Schröder, Stefan; Bowring, Samuel A.; Ramezani, Jahandar; Martin, Mark W.; Matter, Albert (2003). "Extinction of Cloudina and Namacalathus at the Precambrian-Cambrian boundary in Oman". Geology 31: pp 431–434.- " Earliest Animal Footprints Ever Found -- Discovered in Nevada date=20190524224223 " Newswise, Retrieved on October 5, 2008. Reporting on a poster session at the Geological Society of America
分类:新元古代