Internal deformation features of detachment layers in the front of the Kuqa foreland fold-thrust belt

Abstract：The evaporite beds of the Paleogene Kumugeliemu Formation and Neogene Jidike Formation form regional detachment layers in the Kuqa foreland fold-thrust belt. In the front of the Kuqa foreland fold-thrust, the evaporite bed underwent plastic flow and various structural styles formed inside the detachment with plastic flow of evaporite beds. Based on the field observations, seismic and well data, the deformation structures recognized inside the evaporite bed in the Qiulitag structural belt include salt pillows, salt walls, salt nappes, fish-tail structure, salt welds (fault welds), salt neckening, lentoid thickening and salt stacks. The formation and evolution of various salt structures have a certain sequence. On the whole, the salt structures in the northern part of the Kuqa foreland fold-thrust belt formed earlier than those in the south, while the salt structures in the western Qiulitag structural belt also formed earlier and are of larger size, whereas in the eastern portion the salt structures developed later, with smaller size. The salt structures such as salt nappes, salt welds and salt pillows developed in the Qiulitag structural belt formed earlier than salt walls.