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Diversified calcimicrobes in dendrolites of the zhangxia formation, Miaolingian Series(Middle Cambrian) of the North China craton

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Journal of Palaeogeography 2021年第2期10卷 157-181页

作者： Ming-Xiang Me Muhammad Riaz Zhen-Wu Zhang Qing-Fen Meng Yuan Hu School of Earth Sciences and Resources China University of GeosciencesBeijing 100083China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesBeijing 100083China State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Chengdu University of TechnologyChengdu 610059China College of Energy Resources Chengdu University of TechnologyChengdu 610059China Centre for Geographical Information System University of the PunjabLahore 54590Pakistan.

As a type of non-laminated microbial carbonates, dendrolites are dominated by isolated dendritic clusters of calcimicrobes and are distinct from stromatolites and thrombolites. The dendrolites in the upper part of the Miaolingian zhangxia formation at Anjiazhuang section in Feicheng city of Shandong Province, China, provide an excellent example for further understanding of both growth pattern and forming mechanism of dendrolites. These dendrolites are featured by sedimentary fabrics and composition of calcified microbes as follows.(1) The strata of massive limestones, composed of dendrolites with thickness of more than one hundred meters, intergrade with thick-bedded to massive leiolites, formimg the upper part of a third-order depositional sequence that constitutes a forced regressive systems tract.(2) A centimeter-sized bush-like fabric(shrub) typically produced by calcified microbes is similar to the mesoclot in thrombolites but distinctive from clotted fabrics of thrombolites. This bushlike fabric is actually constituted by diversified calcified microbes like the modern shrub as a result of gliding mobility of filamentous cyanobacteria. Such forms traditionally include: the Epiphyton group(which actually has uncertain biological affinity), the Hedstroemia group which closely resembles modern rivulariacean cyanobacteria,and the possible calcified cyanobacteria of the Lithocodium–Bacinella group.(3) Significantly, dense micrite of leiolite is associated with sponge fossils and burrows, and is covered by microstromatolite. The Lithocodium–Bacinella group is a controversial group of interpreted calcified cyanobacteria in the Cambrian that has also been widely observed and described in the Mesozoic. Therefore, dendrolites with symbiosis of leiolites in the studied section provide an extraordinary example for further understanding of growing style of bush-like fabrics(shrubs) of the dendrolites dominated by cyanobacterial mats. Furthermore, the present research provid

关键词： Calcified microbe Dendrolite Leiolite Epiphyton Lithocodium–Bacinella Cambrian Miaolingian zhangxia formation

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Giant ooids of microbial origin from the zhangxia formation(Cambrian Miaolingian Series)in North China

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Journal of Palaeogeography 2022年第1期11卷 52-68页

作者： Ming-Yue Dai Hua-Shan Zhang Wei Zheng Yong-An Qi Zhi-Feng Xing Zhen Zhang School of Resources and Environment Henan Polytechnic UniversityJiaozuo 454003China Key Laboratory of Biogenic Traces and Sedimentary Minerals of Henan Province Henan Polytechnic UniversityJiaozuo 454003China

The role of microorganisms in the formation of giant ooids is one of the areas of long-term controversy in ooidal research,but it has not been confirmed *** giant ooids developed in the zhangxia formation of the Cambrian Miaolingian Series in North *** ooids in the study area were examined by using Polarized Light Microscopy and Field Emission Environmental Scanning Electron *** nuclei of the ooids consist of micritic pellets or radial ooids with diameters less than 2 mm and are formed in a weak-agitating seawater *** cortices are concentric,and are characterized by the alternations of the dark laminae of micritic calcite or Girvanella filaments and light laminae of microsparry *** the environments of inter-bank sea with the alternating development of medium and low energy and chiefly weak-agitating conditions,giant ooids were formed under the joint action of Girvanella filamentous growth,biologically-induced calcification and/or biologically-influenced calcification and inorganic calcium carbonate *** microfossils of Girvanella are distributed in inner and outer cortices of giant ooids,especially dense in the *** distinctly indicates that microbes play a significant role in the formation of giant ooids,and also provides a vital example for discussing the microbial origin of giant ooids.

关键词： Girvanella filament Microbial origin Giant ooid Cambrian Miaolingian Series zhangxia formation North China

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Composition and Construction of High-and Low-Energy Ooid Shoals and Their Relationships with Environmental Changes: A Case Study from the Cambrian zhangxia formation in the Ordos Basin, North China

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Journal of Earth Science 2023年第1期34卷 156-172页

作者： Zhen Wang Yiming Gong State Key Laboratory of Biogeology and Environmental Geology School of Earth SciencesChina University of GeosciencesWuhan430074China

On the basis of systematic study of sedimentary facies, microfacies and geochemistry of measured strata sections and wells, the ooid shoals of the Cambrian Miaolingian zhangxia formation in the southern Ordos Basin are composed of both high-and low-energy ooid shoals. The characteristics of the high-energy shoals are sparry cementation, with moderate to well sorting, large grain size, high ooid content and low micrite, weak micritization, and well-preserved internal textures of the ooids. Macroscopically, the high-energy ooid shoals display a thick-bedded aggradational stacking pattern in upward coarsening and thickening sequences. The low-energy ooid shoals are mainly made up of micritic cementation, with moderate to poor sorting, relatively small grain size, lower ooid content and higher micrite, strong micritization, and poorly-preserved internal textures of the ooids. Macroscopically, the low-energy ooid shoals show a thin-bedded, interbedded stacking pattern in upward fining and thinning sequences. The sedimentological evidence and carbon isotope data show that the differences of internal fabric and sedimentary evolution of both high-and low-energy ooid shoals are closely related to the sea-level change.

关键词： Cambrian sedimentary model North China ooid shoals Ordos Basin zhangxia formation

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