Zhijiu Cui

Quaternary geomorphological evolution of the Kunlun Pass area and uplift of the Qinghai-Xizang (Tibet) Plateau

Abstract There is a set of Late Cenozoic sediments in the Kunlun Pass area, Tibetan Plateau, China. Paleomagnetic, ESR and TL dating suggest that they date from the Late Pliocene to the Early Pleistocene. Analyses of stratigraphy, sedimentary characteristic, and evolution of the fauna and flora indicate that, from the Pliocene to the early Quaternary (about 5–1.1 Ma BP), there was a relatively warm and humid environment, and a paleolake occurred around the Kunlun Pass. The elevation of the Kunlun Pass area was no more than 1500 m, and only one low topographic divide existed between the Qaidam Basin and the Kunlun Pass Basin. The geomorphic pattern in the Kunlun Pass area was influenced by the Kunlun–Yellow River Tectonic Movement 1.1–0.6 Ma BP. The Wangkun Glaciation (0.7–0.5 Ma) is the maximum Quaternary glaciation in the Pass and in other areas of the Plateau. During the glaciation, the area of the glaciers was 3–5 times larger than that of the present glacier in the Pass area. There was no Xidatan Valley that time. The extreme geomorphic changes in the Kunlun Pass area reflect an abrupt uplift of the Tibet Plateau during the Early and Middle Pleistocene. This uplift of the Plateau has significance on both the Plateau itself and the surrounding area.

Glacial valley cross-profile morphology, Tian Shan Mountains, China

Abstract The morphology of glacial valley cross-sections can be described in terms of power law ( y = ax b ) or quadratic equations ( y = a + bx + cx 2 ) fitted to empirical data. The quadratic solution provides a more robust way of describing the morphology of glacial valley cross-sections, whereas the power law has more potential in understanding the cross-sectional shapes and their evolution. These two functions are used to study the cross-sectional morphology of glacial valleys in the middle and western Tian Shan Mountains and to discuss the comparison with fluvial channels. The major conclusions are: (1) Power law equation parameters ( a and b ) are sensitive to the origin selection with larger sensitivity in vertical and A ( A =ln a ) values. Conversely, c values of the quadratic equation are more stable regardless of different origins selected. (2) Hirano and Aniya [Earth Surf. Processes Landforms 13 (1988) 707–716] suggested two characteristic patterns in the relationship between the power law exponent, b , and the valley form ratio, FR . However, glacial valleys in these areas do not fit the Rocky Mountain model for b–FR values described by Hirano and Aniya for alpine glacial valleys. This indicates that this Rocky Mountain model cannot be applied to all alpine glacial areas. (3) The c values of the quadratic equation represent a curvi-linear trend with its corresponding FR s. At the same time, power law parameters ( A and b ) fit a closed linear relationship both from these areas and others in the published literature. (4) The cross-sectional shapes of glacial valleys show clear differences with fluvial channels by comparing A–b values of glacial valleys with the hydraulic geometry of fluvial channels. This implies that the A–b relationship and the variation range of b values (commonly with 1.5–2.5) may be helpful to differentiate valleys formed by different processes.

Debris-Flow Susceptibility Assessment Model and Its Application in Semiarid Mountainous Areas of the Southeastern Tibetan Plateau

AbstractDebris flow is one of the most common natural hazards in the semiarid mountainous areas of the Southeast (SE) Tibetan Plateau. Because of unique geology, geomorphology, and diverse climate conditions, debris-flow susceptibility in the mountainous areas shows significant regionalism. In this study, an index entropy model is adapted for sensitivity analysis of the impact factors of debris flows in the semiarid areas, and the Benzilan-Changbo segment of the upper reaches of the Jinsha River are selected as an area of interest in a case study. Based on the sensitivity analysis, six factors, including, lithology, slope gradient, slope aspect, relative relief, catchment system geomorphologic entropy, monthly average precipitation (June–September), and normalized difference vegetation index (NDVI) are considered debris-flow susceptibility assessment factors. The results show that landform, lithology, and vegetation are the three most important factors affecting the susceptibility of the debris flow in se...

Origins of Soft-Sediment Deformation Structures from the Batang Paleodammed Lakes in the Upper Jinsha River, SE Tibetan Plateau

Multiple levels of preserved soft-sediment deformation structures occur in sediments deposited in the paleodammed lakes in the Batang-Zhongza reaches of the upper Jinsha River Valley, southeast Tibetan Plateau. These deformation structures include folded layers, convoluted layers, ball-and-pillow structures, recumbent lamination, waterescape structures, and small-scale landslide. Combining the assessments of depositional facies, potential triggers, paleoenvironmental context, we conclude that the probable trigger agents of this deformation were earthquakes, slides, and debris flows. The seismically-induced soft-sediment deformation structures provide new substantial evidence for the existence of active tectonics and paleo-earthquakes in the Batang area since the Holocene.