华北串岭沟组软沉积物变形构造及其构造古地理意义

Soft-sediment Structures Developed in Northern part of North China Paleocontinent and Their Constraint on Geodynamic Environment of Sedimentary Basin

华北古陆北缘中元古代串岭沟组是整个华北古陆沉积环境从以滨浅海陆源碎屑岩为主体的沉积体系向以碳酸盐岩为主体的陆表海沉积体系的转折点。串岭沟组发育了大量的软沉积物变形构造:水塑性变形构造,液化构造,流化构造,均是与地震驱动相适配的变形构造,它们赋存于特定的层内,并在空间上呈规律变化,为典型震积岩。地震中心主要为蓟县—兴隆区域,东西向展布的断裂控制相带分布,南北向控制沉积类型。软沉积变形构造可以作为重要沉积标志来限定大陆裂解引发的伸展构造运动时间。因此综合研究串岭沟组发育的软沉积物变形构造类型、特征、层位和空间位置对于认识原型盆地的断裂构造活动特征具有重要意义。

Objectives ： The Chuanlinggou Formation of the Mesoproterozoic stratum which developled in the northern part of the North China Paleocontinent was the turning point which the sedimentary system change from littoral neritic terrigenous clastic rocks to epicontinental sea carbonatite rocks. Though some liquefaction structures which developed at the bottom of the Chuanlinggou Formation have been performed to reveal the seismogenic origin, but very few work on other soft-sediment deformation structures, such as hydro plastic deformation and fluidization have been done. We study such a comprehensive study on types, features, layers, and spatial location of soft-sediment deformation structures developed in the Chuanlinggou Formation has great significance for understanding the characteristics of fault activity in prototype basin. Methods： We apply a method called the large-cale spatial and temporal research to North China archicontinent for delineation of deformation structures developed in the Chuanlinggou Formation. A lot of soft- sediment deformation structures, such as hydro plastic deformation, liquefaction structure and fluidization which developed at the bottom of the Chuanlinggou Formation, are consistent with seismogenic origin. They were restricted to special layers and had rule changes in space. They are typical seismites. The main center of the earthquake was the Jixian--Xinglong area. It is the EW stretching fracture system that controlled the distribution of main facies of the Chuanlinggou Formation, while NS stretch fracture controlled the deposition type. Soft sedimentary deformation structures, on the other hand, can be used as an important indicator to constraint the time of extensional tectonic movements caused by continental breakup. Overall, such a comprehensive study on types, features, layers, and spatial location of soft-sediment o deformation structures developed in the Chuanlinggou Formation has great significance for understanding the characteristics of fault activity in prototype basin. Results： The ridge coefficient images show Chuanlinggou Formation is not only the oldest black mudstone in Mesoproterozoic strata, but also the ore-bearing horizon of Xuanlong sedimentary iron deposit. It has intensity differentiation of sedimentary facies and variation of formation thickness and can be divided as eastern black mudstone area and western iron area by stratigraphic features. A lot of soft-sediment deformation structures, such as hydro plastic deformation, liquefaction structure and fluidization, developed at the bottom of Chuanlinggou group which was Mesoproterozoic black rock series in the North China area. They were restricted to special layers and had rule changes in space. They are typical seismites. The cente of the quake was Jixian--Xinglong area. EW stretching fracture controlled the distribution of Chuanlinggou main facies. NS stretch fracture controlled deposition type. Conclusions： The method of large-cale spatial and temporal research has been successfully applied to North China Paleocontinent for deformation structures which developed in the Chuanlinggou Formation, providing some new evidences for for understanding the characteristics of fault activity in prototype basin.