Organic Bioherms and Their Forming Models of Changxing Formation in ManyueGanquan Section of Kaixian, Northeast Sichuan
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摘要: 川东北开县满月甘泉剖面长兴组早期发育两期生物丘，分别位于两个向上变浅的沉积旋回中上部。通过露头解剖、镜下鉴定和X衍射等手段，对该剖面生物丘构成进行精细研究发现：第一期生物丘在角砾灰岩的基础上发育，造丘生物以蓝绿藻为主；岩性为泥晶灰岩和含云灰岩；由丘基和丘核构成。第二期生物丘在生物碎屑滩的基础上发育，造丘生物早期主要为蓝绿藻和粗枝藻，后期以各类海绵和珊瑚为主；岩性为泥—微晶灰岩，局部白云岩化；发育丘基、丘核和丘顶，最终向礁骨架演化。在此基础上，探讨了两期生物丘成丘模式：前者属于低能生物丘，形成于台缘前斜坡相带内，经历了两个演化阶段；而后者属于高能生物丘，形成于台地边缘生物礁滩相带内，经历了四个演化阶段Abstract: Two phases of bioherms are respectively developed in the middleupper of two descending cycles in the forepart of Changxing Formation in ManyueGanquan section of Kaixian, northeastern Sichuan. By the outcrop surveying, observation by microscope and diffraction of Xray, the composition of bioherms is researched in detail. It is found that the first phase of bioherm in which the biohermbuilding organisms are dominated by cyanobacteria and the lithology includes micrites and dolomitised limestone is composed of biohermbottom and biohermcore. The second phase of bioherm in which the biohermbuilding organisms are dominated by algae primarily and types of sponges and corals later and the lithology includes micrites with partly dolomitation is composed of biohermbottom, biohermcore and biohermtop and turns to reef finally. Based on that, the biohermforming models of two bioherms are discussed: the former which develops on the platform margin shoalslope is low energy bioherm and has two phases of evolvement, while the latter which develops on the platformmargin shoal and reef is high energy bioherm and has four phases of evolvement.
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Key words:
- bioherm /
- biohermforming model /
- Changxing Formation /
- Northeast Sichuan
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