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根据岩心、测井、地震、录井和薄片等资料,明确龙凤山次凹营城组的物源方向和沉积相类型,结合古地貌格局、同沉积断裂活动和古气候特征,对研究区沉积相时空演化进行了研究。研究结果表明,龙凤山次凹营城组沉积时期发育3个物源区,分别为西南部的变质岩物源区、南部的中基性岩浆岩物源区和东南部的岩浆岩物源区。研究区营城组沉积相类型以扇三角洲相和近岸水下扇相为主。扇三角洲相发育于湖盆洪水面和风暴浪基面之间的滨浅湖环境中,沿扇体展布方向从碎屑流、浊流沉积转化为牵引流沉积;近岸水下扇相发育于风暴浪基面之下的半深湖—深湖环境中,沿扇体展布方向从滑动滑塌逐渐转变为碎屑流和浊流沉积。研究区古地貌南高北低,坡度自西向东逐渐变陡,来自东南物源区的碎屑物质沿陡坡滑动滑塌快速入湖,形成近岸水下扇相;受同沉积断裂活动的影响,断裂两盘高差增大,在古地貌上形成向湖盆深处延伸的断槽,来自西南和南部物源区的碎屑物质受洪水搬运并沿断槽深凹处堆积,形成扇三角洲相;受古气候逐渐温热潮湿的影响,季节性洪水频发,导致研究区西南断槽带和南部断槽带发育进积为主的扇三角洲相砂砾岩体,东南陡坡带营Ⅴ砂组沉积时期开始发育进积为主的近岸水下扇相砂砾岩体,不同沉积相类型的砂砾岩体连片分布,紧邻东北洼陷带的半深湖—深湖相泥岩,形成研究区良好的源储对接关系。
Based on the data of cores, logs, earthquakes, mud logs and thin slices, the source direction and sedimentary facies of the Yingcun Formation in Longfengshan are identified. Based on the analysis of paleogeomorphology, synsedimentary fault activity and paleoclimate, Phase-space evolution has been studied. The results show that there are three provenance areas during the deposition of the Longcun Mountain sub-Au Yingcheng Formation, namely the metamorphic source area in the southwestern part, the mafic source area in the south and the source area of magmatic rocks in the southeast . The sedimentary facies of Yingcheng Formation in the study area are dominated by fan delta facies and nearshore subaqueous fan facies. Fan delta facies developed in the shallow lake environment between the lake basin flood surface and the storm wave basal plane, which transforms from debris flow and turbidity flow deposition into traction flow deposition along the fan spreading direction. The nearshore subaqueous fan phase develops In semi-deep lacustrine-deep lacustrine environment under the stormwave waves, the slides gradually changed from debris to debris flow and turbidity flow along the fan spreading direction. The palaeogeomorphology in the study area is high in the south and low in the north, and the gradient gradually steep from west to east. The debris from the southeastern provenance area slides along the steep slopes and rapidly enters the lake to form a nearshore subaqueous fan facies. Influenced by synsedimentary faulting , And the height difference between the two plates increases. On the paleogeomorphology, there are fractures that extend to the depths of the lake basin. Debris from the southwest and south provenance areas are transported by the floods and piled up along deep depressions in the fault grooves to form fan delta Due to the gradual warm and humid climate, the seasonal floods frequently led to the fan deltaic sandstone and conglomerate bodies in the southwest fault zone and the southern fault zone in the study area, and the Ⅴ sand group in the southeast steep slope zone In the depositional period, the nearshore subaqueous fan-shaped sandstone conglomerate bodies are predominantly developed and congealed. The conglomerate bodies of different sedimentary facies are contiguously distributed and are close to the semi-deep lake-deep lacustrine mudstone in the northeastern subside zone, forming a good study area The source of storage docking.