Geomorphic expression of the Lenglong Ling area, eastern Qilian Shan, and its coupling relationship with the deep structures

Abstract

Located at the outer edge of the northeastern Tibetan Plateau, the Qilian Shan has long been considered to be the key area to address the issue of how the Tibetan Plateau generates its high topography. However, in spite of the fruitful achievements on the growth pattern and subtle crustal structures of the Qilian Shan, what we know about the regional topography evolution and its relationship with the deep structures are still lacking. In this study, the landscape features of the eastern Qilian Shan and the probable drainage evolution history of the Lenglong Ling, located within the central part of the eastern Qilian Shan, are investigated, based on the multiple geomorphic analyses (i.e., HI and steepness distributions, and the Gilbert and χ metrics). The topographic results show that high HI and steepness values distribute mainly in areas controlled by active faults (i.e., the mountain areas). In addition, the Gilbert and χ metrics suggest that the main Lenglong Ling divide is stable. According to the drainage divide stability criteria, we suggest that the presence of the uplift rate gradient in the eastern Qilian Shan (i.e., with higher uplift in the Lenglong Ling area), which is suggested by the topographic results, has driven the main divide to migrate southward and is now “holding” the divide in place. Taking the previously published magnetotelluric imaging into account, we reveal the coupling relationship between the deep structures and the regional geomorphic features, and further suggest that the Lenglong Ling Fault, or the Qilian‐Haiyuan Fault, makes a difference in regional strain transferring and relief generation.

Mobility and Location of Drainage Divides Affected by Tilting Uplift in Sado Island, Japan

“…Fixing the concavity index at a certain plausible value prior to the regression is a viable solution. The value of the concave index, 𝜃𝜃, generally has a range of 0.4-0.5 [26,27], and many previous studies had therefore adopted 0.45 as a fixed value of the concavity index, to obtain the steepness indices from regression [5,14,[29][30], where those obtained are termed as the normalized steepness index ( 𝑘𝑘 𝑠𝑠𝑠𝑠 ). This study also adopted 0.45 as the concavity index.…”

“…In the present study, 𝜒𝜒 was calculated using the TopoToolbox of MatLab's library [31]. To avoid the influence of sedimentation in the Kuninaka Plain (alluvial plain), the starting point for the integration of Equation ( 5) was set to an elevation of 70 m. The 𝑚𝑚/𝑛𝑛 value of the calculated 𝜒𝜒 is 0.45 [5,14,[29][30], the same as that used to calculate 𝑘𝑘 𝑠𝑠𝑠𝑠 .…”

“…Because the assessment of divide mobility is more accurate if the results of 𝜒𝜒 parameters and Gilbert metrics accord with each other, the combination of the Gilbert metrics and 𝜒𝜒 has recently been increasingly used [13][14][34][35]. In the case of conflict between the results of the Gilbert metrics and 𝜒𝜒, it is possible to interpret that the Gilbert metrics indicate the current divide mobility influenced by recent situation, and 𝜒𝜒 indicates the divide migration on a long-time scale [13].…”

“…Previous studies reported that, in cases of asymmetric uplift, the main divide moved from a slower uplift basin to a faster uplift basin, and observed a linear correlation between the differences in erosion rate and the divide migration rate, eventually reaching a quasi-steady state during asymmetric uplift [10][11]13]. Although several recent studies on natural landforms affected by asymmetric uplift have been conducted to elucidate the history of landform formation processes along with divide migration [3,[14][15][16], further research is required for a deeper understanding of divide migration affected by asymmetry or heterogeneous uplift.…”

Mobility and Location of Drainage Divides Affected by Tilting Uplift in Sado Island, Japan

“…Previous studies reported that, in cases of asymmetric uplift, the main divide moved from a slower uplift basin to a faster uplift basin, and observed a linear correlation between the differences in erosion rate and the divide migration rate, eventually reaching a quasi-steady state during asymmetric uplift [10,11,13]. Although several recent studies on natural landforms affected by asymmetric uplift have been conducted to elucidate the history of landform formation processes along with divide migration [3,[14][15][16], further research is required for a deeper understanding of divide migration affected by asymmetry or heterogeneous uplift. Sado Island, located in the Sea of Japan near Honshu Island (the largest island in Japan), is a tectonically active area.…”