辽东湾古近系震积岩特征及其时空分布规律研究

辽东湾古近系地层中发育大量与古地震有关的震积岩,通过岩芯观察识别出包括:微褶皱、阶梯状断层、震塌岩、内碎屑副角砾、液化卷曲构造、串珠状构造、震积砂球-枕状构造、火焰构造、砂泥岩脉、震裂缝、自碎屑角砾共11种震积标志,主要分布于三角洲前缘斜坡和与前三角洲相邻的坡脚。依据塑性与脆性变形建立了震积序列,将其分为I,II,III单元,其所示古地震强度为I< II< III。通过地质统计学的方法,对辽东湾震积岩时空分布规律及其所反映的古地震强度研究认为:古近纪时期郯庐断裂在辽东湾呈NNE向展布,其构造活动分为三个阶段:第一阶段为E₂s3,第二阶段为E₃s2~E₃s1,第三阶段为E₃d,其中第一、三阶段为强构造活动时期。E₂s3构造活动主要分布于辽西凸起北端,E₃s2与E₃s1主要分布于辽中凹陷A油田附近,E₃d则主要分布于辽中凹陷南端、北端和A油田,辽西凸起中部靠近A油田附近区域。结果表明:通过震积岩时空分布规律反演构造活动是可行的,该方法为今后进行盆地分析提供了新的思路。

Study on Seismite Features and Its Time-Space Distribution Law of Paleogene in Liaodong Bay Depression

Many earthquake-related seismites were discovered in Paleogene in Liaodong Bay depression. According to the observation of well core, we identified 11 indicators of seismites of Paleogene in Liaodong Bay depression, including micro-fold, step micro-fault, seismic fall-masses, liquefied breccias, liquefied fold, pinch and swell structure, ball and pillow structure, flamy structure, liquefaction sandy-silty dyke, seismic-related fracture and seismic breccias. They all distribute in delt-front or the slope toe near prodelta. We establish the seismite succession through the degree of deformation. The seismites succession has been divided into I, II and III three units from weak to strong which reflect the intensity of Paleoseismic. Through the analysis of the seismites space-time distribution and its reflection on ancient earthquake intensity by geostatistical methods, we assume Tan-Lu Fault of Paleogene in Liaodong Bay depression was in the orientation of NNE. The tectonic activity can be divided into three stages. The first stage is E₂s3. The tectonic activity mainly distribute in the northern of Liaoxi Low salient. The second stage is E₃s2-E₃s1. The tectonic activity mainly distribute in A oilfield of Liaozhong sag. The third stage is E₃d. The tectonic activity mainly distribute in A oilfield and the neighbouring area of Liaoxi Low salient, thinly distributed in the southern and northern of Liaozhong sag. The first and third stages are intense tectonic activity periods. The results show that through seismites time-space distribution to inverse the tectonic activity is feasible and it provides a new way of thinking for basin analysis.