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首页> 外文期刊>Palaeogeography, Palaeoclimatology, Palaeoecology: An International Journal for the Geo-Sciences >Early Middle Triassic stromatolites from the Luoping area, Yunnan Province, Southwest China: Geobiologic features and environmental implications
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Early Middle Triassic stromatolites from the Luoping area, Yunnan Province, Southwest China: Geobiologic features and environmental implications

机译：中国云南省罗平地区中三叠世早期叠层石：地质生物学特征和环境意义

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摘要

An early Middle Triassic stromatolite deposit is documented from the Guanling Formation of the Luoping area, Yunnan, SW China. The Luoping stromatolite shows five types of constructional microbial forms in various magnifications: 1) typical stratified columnar structures, up to 20 cmhigh, with crinkled laminae. Dark coloured laminae, 1 mmthick, are composed of upright filamentous tubes, averagely 29.4 μm in diameter, showing a vertical growth fabric. 2) Laminoid fenestrae, 0.5-1 mm wide, and 3) prostrate filaments, which are reflected by strong fluorescence in sharp contrast to dolomite cement in fluorescent images. 4) Rod-like aggregates, 4.6-18 μmin diameter, composed of minute dolomite rhombs, are very common in stromatolitic laminae; they resemble present-day cyanobacterial trichome, and thus may represent putative fossilized cyanobacteria. 5) Moreover, small pits, coccoid-like spheroids, calcified biofilms, and fibrous structures are also common in stromatolitic laminae. The last twomay represent calcified extracellular polymeric substances (EPS) that contributed to the development and lithification of stromatolites. Authigenic quartz grains are common and may also have involved biological processes in stromatolite formation. Of these microbial functional-groups driving accretion and lithification processes of stromatolite documented in literature, both lithified cyanobacteria/oxygenic phototrophs and possible sulfate-reducing bacteria (SRB), which induced microbial formation of dolomite and contributed to the accretion of the Luoping stromatolite, are suggestive of biogenic origin. The Luoping stromatolite differs fromthe Permian-Triassic boundary microbialites (PTBMs) in having abundant filamentous structures and growing in an oxic marine environment. Both sedimentary facies analysis and abundant fossilized cyanobacteria may indicate proliferation of oxygenic phototrophs in a normal, oxic habitat during the middle Anisian (earlyMiddle Triassic), a period when hospitable environments, coupled with biotic diversification, prevailed in South China and set an agenda for the full recovery of marine ecosystems in middle-late Anisian. However, the post-extinction stromatolites and other anachronistic facies are not necessarily indicative of anoxic or oxic conditions, and their environmental settings are much more complex than previously thought.
机译：中国西南云南罗平地区的关岭组有中三叠世早期的层积岩记录。罗平叠层石以不同的放大倍数显示出五种类型的构造微生物形式：1）典型的分层柱状结构，高达20厘米高，具有褶皱的薄片。 1毫米厚的深色薄片由直立的丝状管组成，平均直径为29.4μm，显示出垂直生长的织物。 2）宽0.5-1 mm的Laminoid窗饰，和3）strate丝，在荧光图像中，其与白云石水泥形成鲜明的对比，被强荧光反射。 4）层状薄片中很常见的是直径为4.6-18μmin的杆状聚集体，由细小的白云石菱形组成;它们类似于当今的蓝细菌毛状体，因此可能代表假定的化石蓝细菌。 5）此外，在层间质薄片中也常见小凹坑，类球状球状体，钙化生物膜和纤维结构。最后两个可能代表钙化的细胞外聚合物（EPS），它们有助于叠层石的发展和石化。自生石英颗粒是常见的，也可能涉及叠层石形成的生物过程。在文献中记载的驱动叠层岩增长的微生物功能基团和​​石化过程中，既有板化的蓝细菌/产氧光养菌，也有可能是硫酸盐还原菌（SRB），它们引起白云石的微生物形成并有助于罗平叠层石的增生。提示生物起源。罗平叠层石与二叠系-三叠纪界微微生物体（PTBM）的不同之处在于其具有丰富的丝状结构并在有氧海洋环境中生长。沉积相分析和丰富的化石蓝细菌都可能表明，在中美洲尼斯（中三叠世早期），一个正常的有氧生境中，氧光养菌的繁殖，这是一个好客的环境，加上生物多样化的时期，在华南盛行，并为华南制定了议程。全面恢复中后期阿尼西亚人的海洋生态系统。但是，灭绝后的叠层石和其他过时的相不一定指示缺氧或有氧条件，它们的环境设置比以前认为的要复杂得多。

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