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通过认真、系统的地震资料解释,我们在塔里木盆地西南坳陷首次发现晚新生代正断层.这些正断层发育于西南坳陷的东北部,走向NE-SW,剖面上组合成堑垒构造,个别剖面上显示负花状构造特征.正断层主要发育于新生界,向上断至的最高层位是第四系更新统下部.倾向相反的正断层向下交汇后断距消失,断层继续向下延伸的情况不清楚.根据断距变化和生长指数计算,正断层形成于上新世晚期,持续演化至更新世早期.正断层的形成演化过程与以往在阿瓦提凹陷、巴楚隆起和塘沽孜巴斯坳陷发现的晚新生代正断层基本一致,正断层活动时间为ca.3～2Ma.它们形成于一个区域性弱伸展构造应力场,代表印度—亚洲碰撞远程效应下,塔里木盆地脉式挤压冲断过程中的一个构造间歇期.“,”The Late Cenozoic extensional structures,mainly a series of Late Cenozoic normal faults,have been discovered after careful seismic interpretation in the southwestern depression,Tarim Basin.The normal faults distribute in the northeastern part of the southwestern depression.They trend in NE-SW direction,and combine into graben-horst structures in profile.On some seismic profiles,the combination of the normal faults exhibit the feature of “negative flower” structure.The normal faults develop mainly in the Cenozoic strata.They cut upward to the lower part of the Pleistocene.The normal fauhs with opposite dip-directions meet each other in the Neogene strata,and then the fault displacement disappeared,and the downward extension of the faults cannot be identified directly on the seismic profile.According to the variation of the fault displacement and the fault growth indexes,the normal faulting begun since Late Pliocene,lasted to Early Pleistocene and then died out,i.e.,ca.3 ～ 2 Ma.The same faulting time as the Late Cenozoic normal faults revealed in the Tangguzibasi depression and on the boundaries of Bachu rise and Awati sag.They were formed under a slight regional extensional tectonic background,and represent a tectonic pause between two successive thrust pulses under the far-field effect of the India-Asia collision.