Geological landform and structure formation model of the Paleogene Ochirbat salt diapir in the western Kuqa, Xinjiang

As the Paleogene Ochirbat salt diapir in the western Kuqa foreland thrust belt is the most typical salt diapir structure in China, it can serves as a natural laboratory for the study of salt structure. Based on previous researches, the methods of field mapping, seismic interpretation, remote sensing images interpretation and InSAR (interferometric synthetic aperture radar) technique were used to analyse the salt karst landform characteristics, formation mechanism and rheological model of the Ochirbat salt diapir. The salt karst landforms are mainly developed on the surface of the salt diapir. Karst caves and gullies can be seen on the weathering surface of the diapir, while rillen karrens and miniature karst peak cluster can be seen on the fresh surface. Further more, collapse structures belonging to salt karst landforms can also be regularly seen in the diapir. The formation of the salt diapir was controlled by many factors, including the thrust fault, the erosion of the overburden, the differential loading and buoyancy, and the evolution process of the diapir can be divided into 4 main stages, including thrust piercement, erosion piercement, active piercement and passive piercement stages. It is summarized that after coming out from the underground, the salt flowed from the core to the periphery of the diapir under the gravity, forming salt glacier, and the seasonal river restricted the salt spreading to east, northeast and north directions, resulting in the asymmetric rheological model of the diapir.