济阳坳陷细粒沉积岩形成环境及沉积构造

Formation environment and sedimentary structures of fine-grained sedimentary rock in Jiyang depression

根据膏岩盐、碳酸盐岩分布规律和地层水特征,结合锶同位素、碳同位素和薄片资料,研究济阳坳陷沙四上—沙三下亚段高灰质泥页岩细粒岩沉积形成环境.结果表明:沉积岩属于封闭半咸化—咸化安静湖盆的产物,不仅发育大量代表静水条件的纹层,还发育代表水动力较强环境的交错层理、冲刷面等沉积构造.纹层主要包括波状钙质纹层、水平隐晶钙质纹层、水平亮晶钙质纹层、水平泥质纹层和水平含粉砂泥质纹层,形成主要受气候、盐度、水深及物源供给等因素控制;交错层理和冲刷面为该地区最为特殊的沉积构造,成因与风暴、泥质浊流和絮凝作用有关;脊突构造与泥岩中水快速排出有关.这些沉积构造在一定程度上影响细粒沉积动力机制研究,也为细粒沉积体系划分、细粒沉积层序地层等研究提供依据.

Using the distribution law of gypsum-salt rock and carbonate rock,we analyzed the features of formation water,associated with strontium isotope,carbon isotope and lamella datum to study the formation environment of the fine-grained rock containing high limy mineral content in the formations of upper Es4-lower Es3 in Jiyang depression.Based on core observation and thin section analysis,such deposition is considered to be the product of a closed,semi-saline to saline and quiet lake basin,in which not only developed a large number of lamina under hydrostatic condition,but also many kinds of sedimentary structures in strong hydrodynamic environment such as cross-bedding,erodsion surface.Lamina mainly have five types,including waving calcareous lamina,horizontal cryptocrystal calcareous lamina,horizontal sparry calcareous lamina,horizontal argillaceous lamina and horizontal silty argillaceous lamina,their formation is mainly affected by climate,salinity,water depth,source supply and so on.Cross-bedding and erosion surface are the most special sedimentary structures in the region,the cause of which is closely associated with storms,argillaceous turbidity flows and flocculation.The keel structure is related to rapid drainage in the mudstone.These sedimentary structures will affect study on dynamics mechanism of fine-grained in certain extent,and provide a basis for division of fine-grain sedimentary system and fine-grain sedimentary sequence.