Abstract

Taking the Cambrian Yuertus Formation outcrop profiles in the Aksu-Keping-Wushi areas of northwestern Tarim Basin as examples, the depositional environments of organic rich fine sediment were analyzed by examining the outcrop profiles macroscopically and microscopically. The study reveals that: (1) The lower part of the Yuertus Formation consists of organic-rich fine sediment or thin rhythmic interbeds of organic-rich fine sediment and siliceous sediment, the formation transforms to terrigenous diamictic grain shoal and inverse grading carbonate rocks upward. (2) The thin limestone interbedded with dark shale rhythmically has inverse grading. (3) The thin-bedded siliceous rock has metasomatic residual granular texture, stromatolithic structure and cementation fabric in vugs. (4) There are iron crust layers at the top of the shallowing diamictic grain shoal, beneath which exposed karst signs, such as karrens, dissolved fissures, sack-like vugs, near surface karst (plastic) breccia, breccia inside the karst system and terrigenous clastic fillings, can be seen. (5) Both the outcrops and seismic profiles show that organic-rich fine sediments above the unconformities or exposed surfaces are characterized by overlapping. The organic-rich fine sediment of the Cambrian Yuertus Formation was deposited in the anoxic-suboxidized restricted gulf lagoon environment, and its formation was controlled by high paleoproductivity and poor oxygen exchange jointly, then a shallow-water overlapping sedimentary model has been established. The results will help enrich and improve the sedimentary theory of organic-rich fine sediments.

中文翻译：

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浅水重叠沉积物中富含有机质细沉积物的沉积环境和岩石学特征：以塔里木盆地西北部的寒武纪尤尔图斯组为例

摘要

以塔里木盆地西北部阿克苏—克平—乌什地区的寒武纪尤尔图斯组露头剖面为例，通过肉眼和显微镜观察，分析了富含有机质细沉积物的沉积环境。研究表明：（1）尤尔图斯组下部由富含有机质的精细沉积物或由富含有机质的精细沉积物和硅质沉积物组成的薄节律性交叠层组成，该地层转变为陆源性的铁屑颗粒浅滩和逆分级的碳酸盐岩向上。（2）有节奏地夹杂着深色页岩的薄石灰岩具有反梯度。（3）薄层硅质岩在孔洞中具有交代残留的粒状质地，层状岩性结构和胶结构造。（4）浅层的三角洲浅滩的顶部有铁壳层，其下有暴露的喀斯特迹象，例如喀仑岩，溶裂，麻袋状的孔洞，近地表岩溶（塑性）角砾岩，岩溶系统内部的角砾岩和可以看到陆源性碎屑充填物。（5）露头和地震剖面都表明，不整合面或裸露面以上富含有机质的细小沉积物具有重叠特征。寒武纪尤尔图斯组富含有机质的精细沉积物被沉积在缺氧-亚氧化的受限海湾泻湖环境中，并受高古生产力和不良氧交换共同控制，形成了浅水重叠沉积模型。研究结果将有助于丰富和完善富含有机物的精细沉积物的沉积理论。