• 责任者：Liu Hejuan (Institute of Petroleum Engineering ; Clausthal University of Technology ; Clausthal-Zellerfeld 38678 ; Germany) ; Sun Xiaoling
• 刊名：Journal of Earth Sciences and Environment
• 出版年：2013
• 卷期：35(3)
• 关键词：前寒武 ; Precambrian ; 沉积构造 ; sedimentary structure ; 天津 ; Tianjin
• 页码：p.44-54
• 图表：6 illus., 1 table, 44 refs.
• 分类号：0803
• issnNo：ISSN1672-6561
• isbnNo：CN61-1423/P

     The special sedimentary structures develop in Proterozoic of Jixian section. Sand dyke structure and molar-tooth structure （microsparite aggregate） developed in Jixian section werecontrasted through three aspects, such as macroscopic, microscopic features and the location of sequence stratigraphic development, the difference and similarity of these structures were summarized, including appearance, contact relationship with substrate, relationship with bedding, mineral composition, sedimentary environment, diagenetic characteristic, expanded mode of pore system, distribution time limit, genetic model and so on. Furthermore, according to the microscopic characteristic of molar-tooth structure intergrowthing with macro algae fossil, the microbial effect of molar-tooth structure was explained. Sand dyke structure develops from the transgressive period to the early stage of high water level period, but molar-tooth structure forms in the deep water environment after the maximum flooding period, develops frequently around the storm wave base, and is affected by convection and infiltration of storm flow and original pore fluid. The extensive transgression of sea causes the multiplication of microbe community. The microbial mats develop above the sedimentary substrate, dehydrate and split after the exposure. Sand dyke structure forms for the filling of the splitting fractures by the elastic particles under the hydrodynamic action, which belongs to the redeposition caused by physical geological function. By comparison, the formation of molar-tooth structure is more complicated, the several waves of CO2 partial pressure in the atmosphere of Proterozoic are the main factors controlling the formation of microsparite and results in higher supersaturation of calcite in the sea. The initial elastic particle of microsparite nucleation is found under the mixing action of storm flow and rapid seepage of pore fluid, and the participant of microbe causes microsparite nucleates rapidly and grows crystally in the existent crack or substrate pore space. Associated with microsparite growth, pore fluids discharge from the pore and transfer to peripheral porous media, causing the pore pressure accumulates in the nearby medium, so that the crack further develops and the morphology of molar-tooth structure is complicated, which belongs to the redeposition phenomenon caused by geochemical processes under the action of storm, involving microbilogical-chemical-hydrodynamics coupling effect. Both sand dyke structure and molar-tooth structure undergo the development-burial-dehydration and degasification of microbial mats, so that they can be classified into primary sedimentary structure induced by microbe.