惠民凹陷中生代和新生代断层发育特征及其对沉积的控制作用

断裂是断陷盆地内构造变动的主要形式,它不仅控制了盆地的沉积建造和构造发育,也控制着油气聚散。对惠民凹陷18条地震剖面进行了详细解析,并对该凹陷的10余条断层活动性进行了定量分析,总结了各断层的活动特征。惠民凹陷的断层发育可分为6个期次:①印支末期(T3),主要发育两条北西向逆推断层,平面上平行排列,剖面上呈叠瓦状组合;②燕山早期(J1+2),北西向断层继承性活动,活动强度弱;③燕山中、晚期(J3+K),北西向断层发生构造反转,由逆断层转变为正断层,该时期末北西向断层活动性逐渐减弱直至停止活动;④燕山喜马拉雅过渡期(Ek—Es4),为盆地转型期,北东向断层开始活动;⑤喜马拉雅早中期(Es3—Ed),北东向断层活动达到高峰,并伴随有次级北东(东)向断层的产生,为新生代惠民凹陷发育的主要时期;⑥喜马拉雅晚期(N-Q)断裂活动明显减弱,甚至消亡。各个时期的地层展布特征体现了断裂发育对沉积的控制作用。

Development characteristic of faults in Mesozoic and Cenozoic of Huimin Sag and its control to sediment

The fault is the main form relative to structure change in the faulted basin and controls not only sediment and structure of basins but also accumulation and seepage of oil and gas. The fault moving velocities in Huimin Sag were calculated using seismic sections, and the activities of faults were quantitatively analyzed. The Huimin Sag is divided into six development periods. In the latter Indonesian stage (T_3), two north-west-trending faults were developed. In the early Yanshan stage (J_(1+2)), the faults went successive action and had weak activities. In the middle and latter Yanshan stage, the structural reversal of faults took place. The reversed faults turned into the normal faults. In the terminal stage, the activities of north-west-trending faults became weaker and weaker until stopped. In the Yanshan-Himalayan stage (Ek-Es_4), the north-east-trending faults began acting. In the middle of Himalayan stage (Es_3-Ed), the activities of the north-east-trending fault got the strongest and were accompanied by many secondary north-east-trending faults. In the latter Himalayan stage (N-Q), the activities of faults became less, even the activities of some faults stopped. The strata distribution of every stage indicated the controlling effect of faults on the sediment.