Structural evolution of the Neogene Gar basin, western Tibet: Implications for bend development and drainage patterns

The Gar basin in western Tibet provides unparalleled opportunities to study the structural development of releasing-bend basins. The complex interaction between basin-bounding faults, intrabasinal structures, and basin fill provides a glimpse at the evolution of the Karakoram fault, a major strike-slip system thought to accommodate motion between Tibet and the Himalayas. Three aspects of the structural evolution of the Gar basin-Karakoram fault system are considered: development of releasing-bend basins, drainage patterns, and depocenter migration with respect to master fault evolution. Geomorphologic analyses include stream-length gradient, basin asymmetry, and topography. Structural characteristics highlight an active western margin which dictates the development and deformation of the basin fill. Broad folding of the fill can be explained by top-to-the-E-SE motion along a listric master fault. Basin fill preservation potential is low due to basinward propagation of the master fault. Detailed field mapping and geomorphic analyses suggest releasing bends migrate in the direction of hanging wall propagation.