Yunnan is at the far eastern edge of the Himalayan uplift, and was pushed up in the Pleistocene, primarily in the Middle Pleistocene, although the uplift continues into the present. The eastern part of the province is a limestone plateau with karst topography and unnavigable rivers flowing through deep mountain gorges. The main surface formations of the plateau are the Lower Permian Maokou Formation, characterized by thick limestone deposits, the Lower Permian Qixia Formation, characterised by dolomitic limestones and dolomites, the Upper Permian basalts of the Ermeishan Formation (formerly Omeishan plateau basalts), and the red sandstones, mudstones, siltstones, and conglomerates of the Mesozoic–Paleogene, including the Lufeng Formation and the Lunan Group (Lumeiyi, Xiaotun, and Caijiacong formations).