A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural we...A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural wedge and Qimugen structural wedge,and the exposed Yengisar anticline.The thrust belt displays a right-stepping en echelon pattern.The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge,and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline.Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt,recording the deformation sequence of the thrust belt.The depth of the Cenozoic growth strata decreases from south to north.The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation（N2a）,the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation（Q1x）,and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation（Q1x）.Combined with magnetostratigraphic studies in the western Tarim basin,it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward.The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation,suggesting that the thrust belt was formed in a transpressional tectonic setting.展开更多
The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion ...The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion geometry and timing of the Wupoer thrust belt at the northeastem margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene （N2） and the underlying Miocene （NI） or Paleogene （Pg） strata associated with two other local unconformities between Lower Pleistocene （Q1） and N2 and between Middle Pleistocene （Q2-4） and Q1 strata. Results of structural restorations suggest that compres- sional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, com- bined with previous studies on the Kongur and Tarshkor- gan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concur- rent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a decollement along which both the extensional and compressional faults merged.展开更多
基金funded by the National Natural Science Foundation of China(No.41272230)
文摘A thrust belt formed in the basin along the eastern margin of Pamir.The thrust belt is about 50 km wide,extends about 200 km,and includes three compressive structures from south to north：the blind Qipan structural wedge and Qimugen structural wedge,and the exposed Yengisar anticline.The thrust belt displays a right-stepping en echelon pattern.The Qipan structural wedge dies out northward to the west of the Qimugen structural wedge,and the Qimugen structural wedge dies out northward to the west of the Yengisar anticline.Detailed analysis of seismic reflection profiles of the western Tarim Basin reveal that fan-shaped growth strata were deposited in the shallow part of the thrust belt,recording the deformation sequence of the thrust belt.The depth of the Cenozoic growth strata decreases from south to north.The growth strata of the Qipan structural wedge is located in the middle-lower section of the Pliocene Artux Formation（N2a）,the growth strata of the Qimugen structural wedge is close to the bottom of the Pleistocene Xiyu Formation（Q1x）,and the growth strata of the Yengisar anticline is located in the middle section of the Xiyu Formation（Q1x）.Combined with magnetostratigraphic studies in the western Tarim basin,it can be preliminarily inferred that the deformation sequence of the thrust belt along the eastern margin of Pamir is progressively younger northward.The geometry and kinematic evolution of the thrust belt in the eastern margin of Pamir can be compared with previous analogue modeling experiments of transpressional deformation,suggesting that the thrust belt was formed in a transpressional tectonic setting.
文摘The Pamir region, located to the northwest of the Tibetan Plateau, provides important information that can aid the understanding of the plateau＇s tectonic evolution. Here we present new findings on the deforma- tion geometry and timing of the Wupoer thrust belt at the northeastem margin of Pamir. Field investigations and interpretations of seismic profiles indicate that the eastern portion of the Wupoer thrust belt is dominated by an underlying foreland basin and an overlying piggy-back basin. A regional unconformity occurs between the Pliocene （N2） and the underlying Miocene （NI） or Paleogene （Pg） strata associated with two other local unconformities between Lower Pleistocene （Q1） and N2 and between Middle Pleistocene （Q2-4） and Q1 strata. Results of structural restorations suggest that compres- sional deformation was initiated during the latest Miocene to earliest Pliocene, contributing a total shortening magnitude of 48.6 km with a total shortening rate of 48.12%, most of which occurred in the period from the latest Miocene to earliest Pliocene. These results, com- bined with previous studies on the Kongur and Tarshkor- gan extensional system, suggest an interesting picture of strong piedmont compressional thrusting activity concur- rent with interorogen extensional rifting. Combining these results with previously published work on the lithospheric architecture of the Pamir, we propose that gravitational collapse drove the formation of simultaneous extensional and compressional structures with a weak, ductile middle crustal layer acting as a decollement along which both the extensional and compressional faults merged.
