关键词: 构造转换带, 构造解析, 盐构造, 构造转换机制, 库车坳陷

Abstract: The middle Qiulitage structural belt (Zhongqiu belt) in the Kuqa Depression is located in the overlapping area of the Kumugeliemu (K1-2 km) salt and Jidike (N1 j) salt. Divided by the Yanshui river of the Zhongqiu belt, significant differences in structural deformation styles are presented on the eastern and western sides, inferred that there are structural transformation characteristics. Based on field geological investigations and structural interpretation of seismic profiles, the structural characteristics of the Zhongqiu belt are analyzed in detail, and the structural transformation characteristics of the Zhongqiu belt are further determined, and the differentiated structural transformation mechanism between the suprasalt and subsalt strata is clarified. The results show that the suprasalt strata in the Zhongqiu belt experienced two stages of structural evolution. The first stage was dominated by folding deformation from the end of the Kangcun Formation (N1k) to the early Kuqa Formation (N2k), primarily forming the Kuqa-Tawu anticline and southern Qiulitage anticline arranged in an offset pattern in the Zhongqiu belt. The second stage was primarily dominated by thrust faulting from the early N2k to the Quaternary. Under the effect of fault activities, the anticlines were further uplifted and deformed, gradually forming the front zone, uplift zone, torsional core zone, and gentle slope zone, distributed sequentially from south to north in the Zhongqiu belt. The structural deformation of the torsional core zone is the most severe, and the different structural styles on the eastern and western sides indicate that strike-slip faults may develop in this zone to release the compression-torsion stress caused by the differential displacement on both sides. The structural transfer model of suprasalt strata in the Zhongqiu belt is characterized as a synthetic type, where displacement is transferred between faults with similar dip angles, leading to features such as twisting and branching of surface folds. The subsalt structural transformation is mainly accomplished by the variation of the extension distance of thrust faults along strike and the variation of fault dip angles. The structural transformations in both suprasalt and subsalt strata are influenced by salt layers. The multi-layer distribution and thickness variations of salt layers in the east-west direction are key factors contributing to the differential development locations of the Kuqa-Tawu anticline and southern Qiulitage anticline. The subsalt faults of the southern Qiulitage anticline extend farther to the south under the control of double salt layers (K1-2km and N1 j salt layers), whereas the subsalt faults of the Kuqa-Tawu anticline, controlled by a single salt layer ( N1 j salt layer), have relatively shorter extension distances. 

Key words: structure transfer zone, structural interpretation, salt-related structure, structural transfer mechanism, Kuqa Depression