Spatial distribution pattern of channel steepness index as evidence for differential rock uplift along the eastern Altun Shan on the northern Tibetan Plateau.

The eastern Altun Shan is a crucial part of the Altun orogenic belt within the Tibetan Plateau. Study of the uplift rate and the related features in this area provides important clues for understanding the uplift mechanism of the Tibetan Plateau as a whole. As an important geomorphic element in landscape development, the fluvial system can record the relationship between tectonic activity and climatic change. In recent years, studies of the Channel Steepness Index K sn , have been conducted by many researchers, using the geomorphological model of equilibrium channel longitudinal profiles, combining bedrock uplift and river incision and thus making it possible to extract rock uplift history from river profiles. This research show that regional rock uplift rate is a major factor in affecting the K sn index. Regional tectonic activity and intensity, therefore, can be evaluated from variation in the K sn index, which can provide a sensitive measure of uplift rate. In this paper, the Digital Elevation Map 'ASTER GDEM', with a spatial resolution of 30 m, was utilized as basic data, and combined with ArcGIS and MATLAB software to extract the K sn index from the equilibrium channel longitudinal profiles model. Meanwhile, we employed statistical methods to analyze the K sn index. Our results suggest that averaged K sn indices, obtained from the subrange A，B，C，D, and E of the eastern Altun Shan (from west to east), are 70.93, 139.03, 108.85, 134.44 and 165.39, respectively. Further analysis implies that the variation in this index can be correlated with the distribution pattern of uplift rates within different regions. Its value increases gradually from west to east, reflecting regional uplift rate. Along the western section of the eastern Altun Shan, the uplift rate is slower and characterized by strike-slip movements, while its eastern part has uplifted faster and is controlled by thrust fault systems. Moreover, in contrast with the southern Altun Shan, the uplift rate of the northern part is high. These variations in uplift rate seem to be linked with "the imbricated thrusting transformation-limited extrusion model" of the Tibetan Plateau. Our results can be correlated with previous work on the active characteristics along the eastern Altyn Tagh Fault (ATF). • Along the eastern Altun Shan, the obtained index K sn shows a rough tendency of increasing eastward. • The index K sn from the north front of the eastern Altun Shan is higher than that from the south flank. • This distribution pattern of the index K sn is translated into the different uplift along the eastern Altun Shan. • The difference in uplift rate can be evaluated well by the fluvial incision rate obtained by terrace archives. • The analysis of the index Ksn provides an excellent insight into the extrusion model of the Tibetan Plateau. [ABSTRACT FROM AUTHOR]