主动大陆边缘增生楔构造发育及沉积特征分析:以缅甸增生楔为例

Accretionary Wedge Tectonic and Sedimentation Research of Active Continental Margin:An Example of Accretionary Wedge in Myanmar

增生楔是主动大陆边缘"沟-弧-盆"构造体系的重要组成部分,在全球范围内广泛分布。由于其处于板块俯冲前缘,增生楔地质背景复杂,构造改造强烈,同时大规模推覆构造导致地层多期重叠,沉积发育复杂,给增生楔地区的石油地质条件研究带来难度。以缅甸增生楔为例,通过选取代表性的区域地质剖面,结合相关地层资料,对增生楔地区构造变形、沉积条件进行了分析。结果表明,增生楔形成初期,由于构造运动强烈,增生楔盆地处于发育初期,整体勘探潜力较小。到了中期,增生楔盆地由于地层沉积厚度较大,新地层受构造改造作用影响较小,为勘探有利区,而增生楔斜坡虽然沉积厚度较大,但由于其构造作用强烈,不利于大型油气田的形成。在增生楔发育后期,海沟盆地下部发育海相地层,而上部处于滨浅海环境,地层沉积厚度较大,具有一定的勘探潜力;同样,在发育成熟的增生楔盆地,由于其沉积厚度及盆地面积较大,具有一定的勘探潜力。

Aeeretionary Wedge is an important part of the active continental margin trench-arc-basin sys- tem, which spreads all over the world. Because accretionary wedge locates in the front of plate subduction zones, it has a complex geology background and tectonic intensive reforming. Meanwhile, the large scale nappe structure results in the multiple folding formation and complicated sedimentation. For these rea- sons, it is difficult to investigate the geological condition of petroleum. This paper takes the accretionary wedge of Myanmar as an example, analyzing the tectonic deformation and sedimentary conditions by typi- cal geology section and related formation data. The results indicate that at the beginning of accretionary formation because of the strong tectonic movement and the accretionary basin is at the initial stages, the whole region has hardly any potential for oil prospecting. In the middle stage development of accretionary wedge, the formation thickness in accretionary basin is larger, and new formation is low reforming, and accretionary basins are favorable exploration regions. Although the formation thickness of accretionary slope is large, the intensively tectonic reforming made it difficult to form large oil and gas field. In the late development stage of aceretionary wedge, the trench basin has low marine strata, while the upper forma- tion is thicker by offshore sediment. Trench basin is a favorable exploration region because of the large thickness of formation and the large size of the basin spread. The mature aecretionary basin also has a great exploration potential.