西昆仑山前塔里木盆地叶城凹陷中新统震积岩及其地质意义

通过对6口钻井岩心的详细观察,在塔里木盆地西南缘的西昆仑山前叶城凹陷中新统克孜洛依组和安居安组发现同沉积的软沉积物变形构造,包括液化砂脉、负载及球枕构造、挤入构造、液化卷曲变形、软泥触变变形、液化底劈、软布丁构造及同沉积微断层等,分布广,且重复出现。经与典型的震积岩比较认为,它们都属于地震成因的沉积构造。分析认为,克孜洛依组和安居安组的震积岩可分为4个发育时期,时间跨度大约为5 Ma (16-11 Ma),第1、2期时间较长、构造活动较强烈,第3、4期时间较短、构造活动较弱。这是首次在塔西南地区新近系陆相地层中发现震积岩,震积岩的发育与中新世西昆仑山阶段性隆升、山前逆冲带多条逆冲断层活动引发的周期性地震活动有关。

Seismites in the Miocene at Tarim Basin Yecheng sag of West Kunlun Mountain piedmont and its geological significance

Soft sediment deformation structures were found by detailed observations of six wells’ cores in the Miocene Keziloyi Formation and Anju’an Formation in the Yecheng sag of the West Kunlun Mountain piedmont,the southwestern margin of the Tarim Basin. These structures include liquefied sand veins,load and ball-and-pillow structures,injection structures,liquefied curl deformations,soft mud thixotropic deformations,liquefied diapirs,soft boudinages and syndepositional micro-faults,which were distributed widely and recurred. Compared with typical seismites,they are all sedimentary structures of seismic origin.Seismites in the Keziluoyi Formation and Anju’an Formation can be divided into four developing periods,which spans about 5 Ma( 16-11 Ma). The first and second phases have a long time and strong tectonic activities,and the third and fourth phases have a short time and weak tectonic activities. This is the first discovery of seismites in the Neogene continental strata in the southwestern Tarim Basin. The development of these seismites is related to the periodic seismic activities that have been caused by the episodic uplift of the west Kunlun Mountains and the activities of multiple thrust faults in the frontal thrust belt of the west Kunlun Mountains in the Miocene.