走滑挤压盆地──以中晚三叠世下扬子沿江盆地为例

TRANSPRESSIONAL BASIN A CASE STUDY OF MID-LATE TRIASSIC BASIN AROUND YANGTZE RIVER,LOWER YANGTZE

中晚三叠世，在扬子和华北两大板块碰撞拼接过程中，郯庐断裂产生大规模走滑运动，使下扬子沿江地区处于走滑挤压作用下，从而形成走滑挤压盆地。黄马青群是这一盆地的沉积记录，盆地内沉积中心呈侧向斜列展布，沉积物与其物源区发生错离，盆地随时间推移逐渐收缩。盆地内发育的两组共轭剪切带、斜列分布的褶皱及其伴生的逆冲推覆构造是走滑挤压应力的反映。郯庐断裂是华北、扬子两大板块间斜向拼接所形成的转换断层。

When Yangtze plate collided with North China plate in Mid-Late Triassic,large-scale strike-slip motion along Tan-Lu fault took place and this made the area around Yangtze River of Lower Yangtze be under transpression. Therefore, transpressional basin was formed. Huangmaqing Group is the sedimentary record of the basin. Its main features are the following: (1) depocentres in the basin are in enechelon arrangement and thickness difference varies considerably from the centre to the margin which indicates that basement of the basin was intensively flexed and depressed during sedimentary process, (2) sediments are dislocated from their source areas, (3) change of the lithofacies is very sharp and the coarse-elastic lithofacies in the basin margin gradually migrates toward the interior due to gradual constriction of the basin with time, (4) two groups of conjugate shear belts, en-echelon folds and associated thrusts in the basin are the products of transpression. We suggest that the motion of Tan-Lu Fault is dynamics of basin formation.