环渤海湾盆地寒武系混合沉积研究

The Cambrian Mixed Sedimentation around Bohai Sea Bay Basin

环渤海湾地区寒武系发育陆源碎屑与海相碳酸盐的混合沉积。综合前人研究成果,结合大量的区域地质资料、野外露头资料和钻井资料等,对环渤海湾地区寒武系混合沉积进行了详细的研究。研究结果表明研究区混合沉积特征宏观上表现为由陆源碎屑与碳酸盐交互沉积、陆源碎屑与混积物交互沉积、碳酸盐与混积物交互沉积和混积物本身的交互沉积构成的混积层系,微观上表现为同一岩层内由陆源碎屑组分与碳酸盐组分混合沉积所形成混积岩;混合沉积类型有渐变式混合沉积、突变式混合沉积和复合式混合沉积Ⅰ,但是各种类型的混合沉积常相互叠加,频繁交替,形成类型复杂的混合沉积复合体;混合沉积环境为古陆边缘和陆表海,发育混积潮坪相、混积局限台地相和混积开阔台地相,微相类型有混积泥坪、混积灰坪、混积云坪、混积泻湖、混积浅滩和混积滩间等。最后结合混合沉积的成因、沉积机理、产出部位及沉积环境等因素,以沉积学原理为指导,建立了环渤海湾地区寒武系的混合沉积模式,进而对混合沉积的控制因素进行了讨论。

Mixed deposits composed of terrigenous fragment and carbonate of marine facies are developed extensively in the Cambrian Bohai Sea Bay basin. This paper studied the mixed deposit in this area based on a number of regional geological data, outcrops and well logging data. Research results show that the area is characterized by interactive depositition of terrigenous fragments and carbpmate, and of terrigenous fragments and mixed sediments, and the mixed layer system formed by various types of sediments. The mixed rock composed of terrigenous sediments and carbonate are present in the same layer. Mixed sedimentary type could be divided into three categories, gentle mixed sedimentation, salutatory mixed sedimentation and complex mixed sedimentation I. But various types of sedimentation are superimposed on each other to form more complicated compound geological units. Mixed sedimentary environments are ancient continental margin and epicontinental sea. There are occurrence of sedimentary facies such as mixed tidal flat, mixed restricted platform, mixed open platform, and sedimentary tiny facies of mixed mud flat, mixed limestone flat, mixed dolomite plat, mixed lagoon and mixed shallow, etc. Combined with the mixed sedimentation, deposition mechanism, location and deposition environment, and under the guide of sedimentary principle, the paper proposed a mixed sedimentation model of Cambrain in the Bohai Sea Bay and further discussed controlling factors of the mixed sedimentation.