Fossil microbial communities in Neoproterozoic interglacial rocks, Maikhanuul Formation, Zavkhan basin, Western Mongolia
Fossil microbial communities in Neoproterozoic interglacial rocks, Maikhanuul Formation, Zavkhan basin, Western Mongolia
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DOI：
10.1016/j.precamres.2014.01.005
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发表时间：
2014-05
影响因子：
3.8
通讯作者：
E. A. Serezhnikova;A. L. Ragozina;D. Dorjnamjaa;L. V. Zaitseva
中科院分区：
文献类型：
--
作者：
E. A. Serezhnikova;A. L. Ragozina;D. Dorjnamjaa;L. V. Zaitseva
冰川沉积广泛分布于世界各地的新元古代地层中，但只有少数冰川沉积与真实的宏观化石产出有关。在蒙古西部扎夫汗盆地新元古代Maikhanuul组中发现的有问题的圆形遗迹可能是古冰川岩石中生物构造的新记录。Maikhanuul冰碛岩沉积于732 - 777 Ma（新元古代Dzabkhan组的下伏火山岩）和632 ± 14 Ma（埃迪卡拉纪- Nemakit - Daldynian Tsagaanolom组的上覆石灰岩）之间。Tsagaanolom组微体化石组合与华南陡山沱组635-551 Ma的微体化石组合具有可比性。因此，Maikhanuul冰川事件可能与635 Ma的南沱冰川有关。形态学，埋藏学，生物统计学和地球化学的观察，使我们能够解释的问题圆形仍然是从Maikhanuul tilites微生物群落原位保存在一个古老的冰川盆地的地板上。许多来自前寒武纪地层的盘状化石已经与现存的具有相似外部形态的微生物菌落进行了比较。然而，超微结构的假设前寒武纪微生物群落，据我们所知，以前没有报道。扫描电子显微镜的圆形遗骸从Maikhanuul tillites揭示了杆状，丝状和星形的菌形结构。一些微残留物，特别是星形颗粒，富含铁（高达50%），这可能归因于细菌活动。此外，星形微遗骸可以与淡水和陆地环境中已知的现代星形细菌以及生物成因纳米赤铁矿的聚集体进行比较。虽然微生物群落的存在不能用于全球相关性，但它确实提供了有关原核生物多样性和生态学以及古环境条件的信息。
Glaciogenic deposits are widely distributed in the Neoproterozoic successions around the world, but only few of them are associated with occurrences of authentic macroscopic fossils. Problematical circular remains recovered from intertillite beds of the Neoproterozoic Maikhanuul Formation, Zavkhan basin, Western Mongolia may be a new record of biogenic structures in ancient glacial rocks. The Maikhanuul tillites were deposited between 732 and 777 Ma (the underlying volcanic rocks of the Neoproterozoic Dzabkhan Formation) and 632 ± 14 Ma (the overlying limestones of the Ediacaran – Nemakit – Daldynian Tsagaanolom Formation). The assemblage of microfossils from the Tsagaanolom Formation is comparable to the assemblage known from the 635–551 Ma Doushantuo Formation of South China. The Maikhanuul glacial event may therefore be correlated with the 635 Ma Nantuo glaciation. Morphological, taphonomic, biometric and geochemical observations have allowed us to interpret the problematical circular remains from the Maikhanuul tillites as microbial communities preserved in situ on the floor of an ancient glacial basin. Many discoidal fossils from Precambrian strata have been compared with extant microbial colonies that have a similar external morphology. However, ultrastructure of the hypothetical Precambrian microbial communities, to the best of our knowledge, has not previously been reported. Scanning electron microscopy of the circular remains from the Maikhanuul tillites revealed rod-shaped, filamentous and star-shaped bacteriomorph structures. Some microremains and especially the star-shaped particles are considerably enriched in iron (up to 50%) that may be attributed to bacterial activity. Furthermore, the star-shaped microremains can be compared with modern star-shaped bacteria known from freshwater and terrestrial environments and with aggregates of biogenic nanohematite. Although the presence of microbial communities could not be used for global correlation, it does provide information on prokaryotic diversity and ecology as well as on palaeoenvironmental conditions.