东非裂谷系Albert湖凹陷新生代构造沉降特征

新生代形成的东非裂谷是威尔逊旋回萌芽阶段的典型陆内裂谷，长期以来备受国内外地质学家关注。Albert湖凹陷位于东非裂谷系的西支最北端，整体呈北西向带状展布的不对称(半)地堑。目前，该区已有较好的工业性油气发现，分析其沉降演化规律对进一步揭示该凹陷的构造沉降特征及其油气勘探潜力具有重要的意义。基于钻井资料，结合地震资料解释、沉降史、埋藏史与断层活动性分析，重新划分了构造单元，总结了构造沉降特征，探讨了沉降与断裂的关系、沉降中心迁移的规律及其对油气勘探的指示意义。研究表明:Albert湖凹陷东部的次级构造单元主要受到东部边界断裂的控制，F₁、F₂断层对东部陡断带、东部断阶带以及三个构造调节带的沉降变化及其形成起主要控制作用；南部次凹在早期沉降速率较大，有利于晚中新世形成巨厚的烃源岩，随着沉降中心向北迁移，北部次凹发育了上中新统和下上新统烃源岩；沉降中心周缘的构造带是油气运聚的有利指向区。研究成果为东非裂谷系Albert湖凹陷油气进一步勘探提供了新的依据。 

Cenozoic tectonic subsidence characteristics of Albert Lake Depression in East African Rift System

The Cenozoic East African Rift is a typical intracontinental rift at the germination stage of the Wilson cycle, which has long attracted the attention of geologists at home and overseas. The Albert Lake Depression is located at the northern most end of the west branch of the East African Rift System.It is an asymmetric (half) graben with a NW orientation. At present, good industrial oil and gas have been discovered in this area.The analysis of the subsidence evolution is of great significance to further reveal the tectonic subsidence characteristics and petroleum exploration potential of this depression.Based on drilling data, combined with seismic interpretation, and analysis of subsidence history, burial history and fault activities, this paper reclassifies tectonic units, and summarizes the characteristics of tectonic subsidence. The relationship between subsidence and fault activities, the law of subsidence center migration and its indicating significance for petroleum exploration were discussed in this study. The results show that the secondary structural units in the east of the Albert Lake Depression are mainly controlled by the eastern boundary faults, and the F₁ and F₂ faults play a major role in controlling the subsidence and formation of the eastern steep fault belt, the eastern fault terrace zone and the three structural adjustment belts. The subsidence rate of the southern sub sag was large in the early stage, which was conducive to the formation of extremely thick source rocks in Late Miocene.With the northward migration of the subsidence center, the Upper Miocene and Lower Pliocene source rocks were developed in the northern sub sag.The structural belt around the subsidence center is the favorable direction area for hydrocarbon migration and accumulation. This study provides a new basis for further petroleum in Albert Lake Depression of the East African Rift System.