合肥盆地断层活动特征及其控制因素

利用断层活动速率法定量分析了合肥盆地主要近东西向断层的活动规律,并分析了它们形成与演化的控制因素。研究表明,盆地前侏罗系基底主要发育了近东西向、南倾的逆冲断层,属于印支期前陆变形的产物。这些断层的逆冲速率向南有规律的增加,指示其动力来自南部大别造山带的碰撞造山。盆地在侏罗纪期间接受大量沉积时,并没有发生明显的断裂活动,指示属于前陆拗陷型盆地,其对应着大别造山带的快速隆升。盆地在早白垩世至古近纪期间演变为断陷盆地,印支期基底的逆断层转变为正断层活动。这些盆地内主要的近东西向正断层的伸展活动在早白垩世呈现北强南弱,而随后转变为南强北弱的变化趋势。

ACTIVITY CHARACTERISTICS AND CONTROLLING FACTORS OF THE FAULTS IN THE HEFEI BASIN

Based on calculation of fault activity velocity, the activities of the nearly EW-trending faults in the Hefei basin were analyzed. It is suggested that thrusts with nearly E-W strike direction and southward-dipping direction were developed in the pre-Jurassic basement of the basin during foreland deformation in Indosinian. Thrusting velocities of the faults gradually increase toward south in the basin, indicating that a pushing force originated from the collision orogeny in southern Dabie mountains. No obvious faulting occurred during the thick-bedded Jurassic deposition. This demonstrates that the basin was a foreland depression formed during the Jurassic period in response to quick lifting of the Dabie orogenic belts. The basin was developed into an extensional, faulted basin together with the negative inversion of the Indosinian thrusts into normal faults. Extensional activities of the nearly EW-trending normal faults show higher intensity in the north during Early Cretaceous, but higher intensity in the south thereafter.