库车坳陷却勒地区新生代盐构造特征、演化及变形控制因素

The Quele Area of the Kuqa Depression,Tarim Basin,NW China:Cenozoic Salt Structures,Evolution and Controlling Factors

本文利用野外地质调查结果、遥感资料、地震资料和钻、测井数据,建立了两条库车坳陷却勒地区的区域大剖面,约束却勒地区盐构造特征和演化,分析东、西段变形差异及差异形成过程,探讨构造变形控制因素。却勒地区发育的盐构造样式主要有盐底辟、盐焊接、盐撤凹陷、大型盐推覆体、外来盐席、盐枕、盐背斜和滑脱褶皱,其中,盐撤凹陷、盐背斜和滑脱褶皱仅发育于东段,造成东、西段构造变形差异。却勒地区盐构造分为3期:①渐新世—中新世吉迪克期为构造平静期,发育盐撤凹陷和盐底辟;②中新世康村期—上新世早期构造挤压微弱,发生早期褶皱作用,却勒盐丘继续发育,北部盐底辟中新世末停止发育;③上新世晚期—现今发生大规模逆冲推覆,是褶皱-冲断带主要形成时期,发育大型盐撤凹陷、外来盐席、盐推覆构造、盐背斜和滑脱褶皱。却勒地区东、西段盐构造变形差异主要形成于上新世晚期—现今(第3期)。喀拉玉尔滚右旋走滑断层为薄皮构造,调节了却勒地区东、西段前缘的变形差异。却勒地区构造变形主要受控于盐岩沉积范围、区域构造应力及强度、上覆层应变强度和差异负载(沉积负载和局部构造负载)。

Based on field observation,Landset image,logging and seismic data,tw o regional cross sections have been constructed in the Quele area,Kuqa depressi on. The main salt structural styles in study area are salt diapirs,salt welds,salt withdrawal minibasins,large-scale salt nappe,allochthonus salt sheet,sa lt pillow,salt anticlines,and detachment folds. The main difference between ea stern and western segments is that salt withdrawal minibasins,salt anticlines a nd detachment folds only developed in the eastern segment. Salt structures forme d in three growth stages from Oligocene to present：（1） during Oligocene to earl y Miocene,salt withdrawal minibasin and passive diapirs formed; （2） from late M iocene to early Pliocene,early folding developed under weak regional compressio n,meanwhile,Quele salt dome continue to growth passively and the northern diap ir ceased at the end of Miocene; and （3） since late Pliocene to present,large-scale minibasins,allochthonus salt sheet,salt pillow,salt anticlines,and det achment folds formed. This is the major period of folding,thrusting,and squeez ing diapirs in Quele area. Deformation difference between eastern and western se gments formed mainly during the third stage. Karayulgun dextral strike-slip fau lt,which is a thin-skinned structure,adjusted the deformation difference loca ted at frontal range of Quele area. The major controlling factors of salt struct ures include the distribution of salt,regional tectonic stress and strength,st rength of overburden and differential loading （Sedimentary loading and local str uctural loading）.