| 光合作用微生物席主导的寒武系苗岭统崮山组均一石:以山东省泗水县圣水峪剖面为例* |
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| 引用本文： | 梅冥相.光合作用微生物席主导的寒武系苗岭统崮山组均一石:以山东省泗水县圣水峪剖面为例*[J].古地理学报,2021,23(2):335-358. |
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| 作者姓名： | 梅冥相 |
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| 作者单位： | 1.中国地质大学(北京)地球科学与资源学院,北京 100083;2.中国地质大学(北京)生物地质与环境地质国家重点实验室,北京 100083 |
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| 基金项目： | *国家自然科学基金项目(编号: 41472090,40472065,49802012)资助 |
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| 摘 要： | 作为一种缺乏沉积构造的隐晶质块状泥晶所表征的非纹层状微生物碳酸盐岩类型,均一石自从命名之后就很少被描述或自古老的地层记录之中被识别出来,再加上缺乏现代实例,造成了对这种微生物碳酸盐岩类型研究的困难。来自于山东省泗水县圣水峪剖面寒武系苗岭统崮山组中的均一石,以厚层块状、缺乏沉积构造的泥晶灰岩为主,表现为生物层状的微生物礁,与相对较深水的中厚层中至深缓坡相的条带状泥晶灰岩和泥灰岩一起,构成较为典型的潮下型碳酸盐岩米级旋回,集中发育在淹没不整合型三级沉积层序顶部的强迫型海退体系域之中,代表着相对海平面下降阶段的沉积记录。在这些主导着生物层状微生物礁灰岩的均一石中,不均匀地高密度保存着致密缠绕以及较薄的泥晶壁所成型的丝状葛万菌物质体是其最为基本的特征,表明均一石形成于光合作用微生物席复杂的钙化作用。另外,在均一石的致密泥晶组构中,局部发育毫米级至厘米级大小而且形态极端不规则的亮晶显微管状组构。基于其特别的组构特征,将这样的组构解释为具有公共鞘的丝状蓝细菌即念珠菌菌落的钙化作用残余物,其致密泥晶组构可能代表着蓝细菌公共鞘的钙化作用残余物,其中的亮晶显微管则可能为蓝细菌丝状体的钙化作用残余物,而且在这样的组构之中还发育和共生着丝状葛万菌菌落,从而延伸了对蓝细菌菌落钙化作用残余物的认识和解释,并对具这种组构的海绵木乃伊解释提供了另外一种重要的研究镜像。因此,山东省泗水县圣水峪剖面寒武系苗岭统崮山组上部生物层状微生物礁体中的均一石,不仅提供了一个较为典型的寒武纪苗岭世不借助于二氧化碳浓缩作用机制(CCM机制)的蓝细菌钙化作用的实例,而且提供了一个在丝状蓝细菌主导的微生物席之中发育着念珠菌菌落的多重状微生物席的典型实例,从而拓宽了对显生宙最高的大气圈CO2含量以及较高的大气圈O2含量条件下的较为典型的方解石海中与寒武纪后生动物大爆发相平行的蓝细菌繁荣和钙化作用的了解。
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| 关 键 词： | 均一石 光合作用微生物席 崮山组 苗岭统 寒武系 圣水峪剖面 山东省 华北地台 |
| 收稿时间： | 2020-05-20 |
Leiolites predominated by photosynthetic microbial mats of the Miaolingian Gushan Formation: an example from the Shengshuiyu section in Sishui County of Shandong Province,North China Platform |
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| Mei Ming-Xiang.Leiolites predominated by photosynthetic microbial mats of the Miaolingian Gushan Formation: an example from the Shengshuiyu section in Sishui County of Shandong Province,North China Platform[J].Journal of Palaeogeography,2021,23(2):335-358. |
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| Authors: | Mei Ming-Xiang |
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| Institution: | 1.School of Earth Sciences and Natural Resources,China University of Geosciences(Beijing),Beijing 100083,China;2.State Key Laboratory of Biogeology and Environmental Geology,China University of Geosciences(Beijing),Beijing 100083,China |
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| Abstract: | Microbialites have been defined as the organosedimentary deposits that have accreted as a result of a benthic microbial community trapping and binding sediment and/or forming the locus of mineral precipitation or teemed as the benthic microbial deposits. Microbial carbonates are understood as the calcified microbialite as well as the geological record of calcified bacterial-algal mats and biofilms or the most spectacular example of the MISSs(microbially-induced sedimentary structures). On the basis of the meso-structures,microbialites can be subdivided into four types,inlcuding stromatolites,thrombolites,leiolites and dendrolites. Leiolites were named relatively late and characterized by relatively structureless,aphanitic,mesostructures,lacking lamination or clotted structures. No examples of modern leiolite have been published and only few examples have been described or discerned in stratigraphic records since it was firstly named,which led to difficulties in the study of leiolites. Leiolites from the Miaolingian Gushan Formation at the Shengshuiyu section in Sishui,Shandong Province,are predominated by massive micrite and expressed as a biostromal microbial reef. They,together with the ribbon-like marls and micrite,make up the subtidal carbonate cycle belonging to the relatively deep-water deposits. Thus,a sedimentary succession of this type of subitidal carbonate cycles constitutes a forced regressive system tract of a third-order sequence of the Miaolingian Formation at the Shengshuiyu section,which represents a typical record of the falling stage of a third-order relative sea-level change. Within dense and massive micrite of the leiolites,a common and uneven high-density preservation of Girvanella is marked by densely tangled masses of fairly thin-walled,unbranched filaments or tubes,which indicates that these leiolites possibly resulted from the sophisticated calcification of cyanobacterial mats. In addition,a particular micro-fabric is marked by the microspar tubes of filaments within dense and dark micrites and makes up an irregular-shaped and mm-to cm-long clump. This micro-fabric is similar to the Lithocodium,described as the Lithocodium-like fabric,which can be regarded as colonies of calcified cyanobacteria. Importantly and interestingly,this micro-fabric was interpreted as the sponges including spicula sponges or non-spicula sponges in studies of microbial carbonates in recent years,which resulted in a highly different cognition. According to its fundamental feature,i.e. the microspar filaments or tubes within the dense and dark micrite,I deduced that it could be the residue of calcified Nostoc colonies with common sheathes. The microspar filaments or tubes might represent the calcified residues of filaments or tubes;the dark and dense micrite might have been formed by calcification of sheathes. This interpretation is further supported by its intergrowth with Girvanella. Leiolites predominating the biostromal microbial reefs of the Miaolingian Gushan Formation at the Shengshuiyu section not only provide an example of the Cambrian leiolites but also provide insights into the cyanobacterial calcification without the help of CCM mechanism and the sophisticated calcification of multiple cyanobacterial mats predominated by both the Girvanella and the residue of the Nostoc colonies. This study broadens further understanding of a particular calcification of cyanobacteria and a cyanobacterial blooms that are paralleled with the metazoan exploration in typical calcite sea during the Cambrian under a high atmosphere CO2 and O2. |
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| Keywords: | leiolite photosynthetic mat Ushan Formation Miaolingian Cambrian Shengshuiyu section Shandong Province North-China Platform |
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