MICROBIALITES ORGANOSEDIMENTARY DEPOSITS OF BENTHIC MICROBIAL COMMUNITIES
MICROBIALITES ORGANOSEDIMENTARY DEPOSITS OF BENTHIC MICROBIAL COMMUNITIES
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DOI：
10.2307/3514674
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发表时间：
1987-01-01
期刊：
影响因子：
1.6
通讯作者：
MOORE L S
中科院分区：
文献类型：
--
作者：
BURNE R V;MOORE L S
微生物岩是底栖微生物群落与碎屑或化学沉积物相互作用形成的有机沉积物。钙质微生物的形成过程包括碎屑沉积物的捕获和结合（形成微生物边界石）、无机钙化（形成微生物凝灰岩）和生物影响的钙化（形成微生物骨架石）。后一个过程可能是与光合作用有关的化学变化的结果，或者是微生物的多糖鞘上的晶体成核的结果。这些晶体中升高的δ 13 C值可能反映了与矿化的生物背景相关的同位素分馏。微生物岩与其他生物沉积物不同，它们通常不是由骨骼遗骸组成的。一旦形成，微生物岩的原生骨架就成为次生胶结作用的场所。为了区别于生物丘和骨骼生物层，微生物岩堆积被称为“微生物石丘”或“微生物石层”。这些构造的形态是环境影响、生物和生态控制、以及石化过程和速率的函数。微生物岩的内部结构最好通过描述性术语来识别，这些术语并不意味着特定的起源。用于描述微生物岩内部结构的术语包括叠层石、血栓石、核石（同心层状）、球晶和隐晶。对术语“叠层石”的考虑表明，它目前至少以三种不同的方式使用：通常指微生物沉降的产物，描述可能的微生物来源的层状结构，或描述离散的层状锂田体。我们建议将该术语限定为具有精细的、或多或少平面叠层的内部结构的微生物岩。根据当今澳大利亚发生的一些事件，对已发表的血栓石（以凝块内部结构为特征的微生物岩）和层积石之间的区别进行评估，结果表明血栓石并不总是由球菌为主的BMC构成，层积石也不总是由球菌为主的BMC构成。虽然我们已经观察到的例子，现代血栓形成的生物影响的钙化占主导地位，叠层石结构形成的碎屑沉积物或季节性沉淀的碳酸盐占主导地位的捕获和绑定，这两种结构可以产生其他过程。人们希望，能够区分的过程中所涉及的微生物岩的成因将导致更好地了解这些因素的微生物岩的形态发生，它们的演变，通过地质时代，和它们的潜力作为工具的生物地层对比。
Microbialites are organosedimentary deposits formed from interaction between benthic microbial communities (BMCs) and detrital or chemical sediments. Processes involved in the formation of calcareous microbialities include trapping and binding of detrital sediment (forming microbial boundstones), inorganic calcification (forming microbial tufa), and biological influenced calcification (forming microbial framestones). The latter process is probably the result either of chemical changes associated with photosynthesis, or the nucleation of crystals on the polysaccharide-bearing sheaths of the microorganisms. Elevated .delta.13C values in these crystals may reflect isotopic fractionation associated with the biological setting of the mineralization. Microbialites contrast with other biological sediments in that they are generally not composed of skeletal remains. Once formed, the primary framework of the microbialite becomes the locus of secondary cementation. To distinguish them from bioherms and biostromes of skeletal origin, microbialite buildups are termed "microbial lithoherms" or "mircrobial lithostromes". The morphogenesis of these structures is a function of environmental influence, biologic and ecologic controls, and process and rates of lithification. The internal structures of microbialites are best identified by descriptive terms that do not imply a particular origin. Terms used to describe internal structures of microbialites include stromatolitic,thrombolitic, oncolitic (concentrically laminated), spherulitic, and cryptic. Consideration of the term "stromatolite" shows that it is currently used in at least three distinct ways: to refer to products of microbial sedimentation in general, to describe laminated structures of p obable microbial origin, or to describe discrete laminated lithifield bodies. We recommend that the term be restricted to refer to microbialites with an internal structure of fine, more or less planar laminations. Assessment of published distinctions between thrombolites (microbialites characterised by a clotted internal structure) and stromatolites in the light of some present-day Australian occurrences shows that thrombolites are not always constructed by coccus-dominated BMCs, nor are stromatolites always constructed from filament-dominated BMCs. Although we have observed examples of modern thrombolitic structures forming where biogenically influenced calcification dominates, and stromatolitic structures forming where trapping and binding of either detrital sediment or seasonally precipitated carbonate dominates, both structures could be produced by other processes. It is hoped that the ability to differentiate between the processes involved in the genesis of microbialites will lead to a better understanding of such factors as the morphogenesis of microbialites, their evolution through geologic time, and their potential as tools for biostratigraphic correlation.