沾化凹陷沙河街组盆内同沉积断裂活动及其对沉积充填的控制

Shahejie Formation synsedimentary faulting activity in Zhanhua Sag,Bohai Bay Basin and its control on sedimentary filling

以渤海湾盆地沾化凹陷中最主要盆内坡折带垦利断裂带为研究对象,综合利用钻井资料与地震数据识别沉积微相类型,揭示微相平面展布规律,并结合对应时期的断裂活动特征探讨其耦合性。结果表明该断裂带在沙河街组时期具有明显分带性,可将其分为西、中、东3段,分别控制富林洼陷的3个次洼。沙三下亚段沉积时期中段、东段活动性强,对应的垦利凸起东西两段供源,在周围发育近岸水下扇;沙三中、上段沉积时期东段断裂活动强度减弱,凸起东段被湖水淹没,仅西段向洼陷充注物源,物源受凸起阻挡在西段与东段交界处推进,发育辫状河三角洲;沙二沉积时期断裂活动显著减弱,凸起整体处于水下,较浅处沉积砂质滩坝;沙一沉积时期断裂活动性再次减弱,水下凸起高部位沉积碳酸盐滩坝,洼陷周围发育小规模辫状河三角洲。沾化凹陷内同沉积断裂在沙河街组沉积时期长期活动形成的地貌分异控制了盆内凸起周缘砂体的沉积,各时期断裂活动的差异又进一步决定了凸起周缘砂体的沉积规模与沉积样式。

Drilling and seismic data from the intra-basin slope break zone in the Zhanhua sag,Bohai Bay Basin are used to identify the type of sedimentary microfacies,reveal the plane distribution pattern of microfacies and discuss the coupling characteristics of the faulting activity in the corresponding period.The results show that the Kenli fault belt has obvious zoning character during the period of Shahejie Formation,and the zoning can be divided into west,middle and east sections respectively,which control three sub-sags in Fulin depression.Strong activities during deposition of the lower part of Es3 occurred in the middle and east sections and resulted in the formation of Kenli bulge,and brought about the development of near-shore subaqueous fans in the surrounding area.The faulting activity became weak during the deposition of middle and upper parts of Es3.The east section of the bulge was flooded by lake water and only the western section provided materials for the filling of depression.Supplement material source was blocked by the bulge and resulted in the formation of braided river delta at the junction of the west-eastern section.During the period of Es2 deposition,the faulting activity was significantly weakened,but the whole uplift was under water and sandy beach bar was deposited in the shallower part.The faulting activity weakened again during the period of Es1 deposition,carbonate beach dam was deposited at the high part of the underwater uplift,and a small braided river delta developed around the depression.It is realized that the geomorphic differentiation caused by the long-term activities of syn-sedimentary faulting in the Zhanhua Sag during the Shahejie Formation period controlled the deposition of the sand bodies around the bulge in the basin.