北部湾盆地涠西南凹陷沉降史研究

Study on Subsidence History of Weixinan Depression in Beibuwan Basin

应用EBM盆地模拟系统对北部湾盆地涠西南凹陷的沉降史回剥分析表明:由裂陷期到坳陷期和裂后加速沉降期,沉降速率的变化呈"幕"式特点;构造沉降速率占总沉降速率的份额由下第三系裂陷期的3/5逐渐演变为上第三系的1/2,再到裂后加速沉降期的1/3;上述事实表明盆地产生沉降的主导原因在早期为构造活动、晚期演变为非构造因素为主。北部湾盆地涠西南凹陷岩石圈拉伸系数β值(1.85)对应于一个较强—强的生烃强度值,这为有效烃源岩的评价、油气勘探提供了可靠的地质依据。

The paper analyses the sedimentary evolution of Weixinan depression, Beibuwan Basin with EBM Basin Model System. Then the conclusion is arrived at: From rift to depression and then sedimentary period, rate of change is 'episode': the percentage of the structural sedimentary rate in total sedimentary rate from 1/2 in rift era to the 1/3 after rift era at upper tertiary. The results show that the main reason for sediment is structural activity in the early period, which became non-structural factors during late period. The extension exponent in lithosphere correlates with the generation intensity in Weixinan depression, which provides credible evidence for petroleum exploration.