Identification of ancient river-blocking events and analysis of the mechanisms for the formation of landslide dams in the Suwalong section of the upper Jinsha River, SE Tibetan Plateau

Abstract

The Suwalong section of the upper Jinsha River is located on the southeastern margin of the Tibetan Plateau. Affected by the rapid uplift of the Tibetan Plateau, steep slopes have been formed by the rapid downcutting of rivers in this section. Tectonically, the Suwalong section is located in the Jinshajiang suture zone and features intense tectonic activity, making this section prone to geological disasters such as landslides. Through field investigation, four old accumulation bodies were found in the Suwalong section, and lacustrine sediments were observed upstream of these bodies. By analysing the surrounding landforms, appearance features, and internal rocks of the old accumulation bodies, we conclude that these four old accumulation bodies represent the remains of dams that blocked the river. These dams formed through the deposition of rockslides, rock avalanches, or debris flows that occurred on the slopes on both sides of the river. By comparing the top elevation information and the chemical and mineral compositions of the lacustrine sediments around these residual dams, the order of the demise of two dammed lakes was obtained, and the order was confirmed by optically stimulated luminescence (OSL) dating. The method in this paper has great applicability for identifying river-blocking events in other regions.