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Through field investigation in the Zoige Basin of the eastern Tibetan Plateau, a natural and complete sedimentary profile was found on the steep cliff of the first terrace of the right bank of the Yellow River in the Maqu reach. Careful field observation, analysis of particle size characteristics, and optically stimulated luminescence dating were conducted. The results showed that the paleo-riverbed pebble layer and the floodplain sandy silt layer at the bottom of the sedimentary profile constituted a typical binary sedimentary structure layer, in which the shallow depression bog mud layer that formed during 5.0–4.2 ka was lenticularly sandwiched in the floodplain sandy silt layer, indicating that the first terrace of the Yellow River in this reach began to form at 5.0 ka. The climate was dry and cold during 4.2–4.0 ka, and strong wind on the plateau surface transformed the floodplain sediments into aeolian sand. The paleoflood slackwater deposits sandwiched in the aeolian sand layer indicated that the source of the Yellow River has experienced several catastrophic flood events during this period, inundating the first terrace ground. During 4.0–2.8 ka, mud bogs formed in shallow depressions of the terrace under the relatively humid climate. After 2.8 ka, sandstorms drove the accumulation of coarse silt over the terrace ground, forming aeolian loess. The upper part developed into modern subalpine meadow black soil with granular structure through biological weathering since 2.0 ka. The study results revealed the formation age and its surface development process of the first terrace of the Yellow River in the Zoige Basin, which has important scientific significance for in-depth understanding of the water system evolution and environmental changes in the source area of the Yellow River. OSL dating and stratigraphic framework comparison with XCC profile and WDT profile (Chai et al., 2021) indicated that the first terrace began to form at 5.0 ka along the Maqu reach of the Yellow River in the western margin of the Zoige Basin, Eastern Tibetan Plateau. [Display omitted] [ABSTRACT FROM AUTHOR]

The Yellow River is usually assumed to record tectonic activities and climatic changes; however, a systematic study was lack in the sedimentology, stratigraphy, geomorphology and geochronology for the entire Yellow River though various geologic scholars have conducted numerous works in individual basins. This review focused on well-preserved fluvial terrace sequences that formed along this river on northeastern (NE) Tibetan Plateau and Ordos Block over the past 2.6 Ma. After comparing numerous initial incision ages at different segments along the Yellow River, we found out that the youngest initial incision may occur at ca. 150 ka at the Longyang Gorge. The Yellow River may transit from multiple separated endorheic drainages to an entire external drainage after 150 ka, which may cause differentiations in the apparent incision rates before and after 150 ka; thus apparent net incision rates were calculated respectively for the Yellow River before 150 ka and the drainage network post 150 ka. Apparent net incision rates prior to 0.15 Ma were calculated as 0.15, 0.29, 0.10, 0.12 and 0.03 mm/a respectively in Tongde-Xunhua, Lanzhou-Linxia basins, Heishan, Jinshan and Fenwei-Sanmen Gorges in this review, which mainly reflected Kunhuang-Gonghe Tectonic Event, generated by the Indo-Asian collision and diminishing as the NE Tibetan Plateau eastward extruding at ca. 1.8–0.15 Ma. Apparent net incision rates post 0.15 Ma were calculated respectively for NE Tibetan Plateau and Ordos Block, considering their different base level. On NE Tibetan Plateau, four fluvial degradational phases were identified between ca.105∼70, 53∼40, 25∼16 and 12∼6 ka associated with terrace levels respectively, at average elevations of 96, 40, 20 and 10.5 meters above the current river level (m arl) within a range of 5 ∼ 96 m arl; and four broad periods in the last 150 ka on Ordos Block: possibly marine oxygen isotope stage (MIS) 5, ca. 118 to 72 ka, most of MIS 3, ca. 44∼28 ka, transition from LGM to last deglacial ca. 20 to 16 ka, and 4∼3 ka at average elevations of 67.5, 26, 19 and 11.5 m arl. These degradational phases post 0.15 Ma were associated with multiple processes including enhanced fluvial discharge with an increase in monsoonal precipitation and/or melt water in deglaciation. [ABSTRACT FROM AUTHOR]

Tectonic uplift and climate changes are the two critical factors controlling the evolution of river landscapes and the formation of terraces. However, little is known about the effect of river blockage events on terrace formation along valley areas. In this paper, we investigated the geomorphology, sedimentology, and chronology of Tuanjie (seven staircases) and Taiping (three staircases) Terraces in Diexi. These represent two typical fluvial terraces in the upper Minjiang River in the eastern Tibetan Plateau. These terraces are composed, from bottom to top, of lacustrine deposits, gravels, loess, and paleosol. Taiping Terrace 3 (T3) has two sets of mud-phyllite clasts sequences. Field investigation, Digital Elevation Model (DEM) data, lithofacies, and dating results confirm that terraces T1 to T3 in Taiping correspond to terraces T5 to T7 in Tuanjie. These findings suggest that two damming and four outburst events occurred in the area during the late Pleistocene. The palaeo-dam blocked the river around 32.40±1.91 ka, followed by the first outburst at 27.11±0.18 ka. Then, the palaeo-dam blocked the river again between 27 to 17 ka, and suffered a second dam-breaking event at 17 ka. The third and fourth gradual collapse events respectively occurred at ~10 ka and ~9.35 ka. Combined with the tectonic uplift rate, river incision rate, and high-resolution climate data, our analysis shows that the blockage and collapse of the palaeo-dam have been a major factor in the formation of tectonically active mountainous river terraces. Tectonic movement and climatic fluctuations, on the other end, play a minor role. [ABSTRACT FROM AUTHOR]

River terraces are significant geomorphic markers of climate and tectonics. However, the competing roles of bedrock uplift and climatic change in the formation of fluvial terraces remain uncertain. A series of well-developed terrace sequences of the Yellow River and its tributaries formed in intermontane basins and on mountains on the NE Tibetan Plateau. A flight of 10 river terraces has been preserved along the lower Huangshui River, a major tributary of the Yellow River. Based on electron spin resonance (ESR) analyses we found that the oldest river terrace of the lower Huangshui River on Alagu Mountain formed at ∼1.2 Ma. Moreover, the results of provenance analysis based on detrital zircon U–Pb dating showed that the fluvial system of the modern Huangshui River was established before ∼1.2 Ma. After comparing the ages of the oldest river terraces of major rivers on the NE Tibetan Plateau, we found that they are essentially synchronous. Then, we comprehensively analyzed the climate and tectonic conditions, and suggested that the abrupt climate change dominated the synchronous formation of the oldest terraces of major rivers at approximately 1.2 Ma on the NE Tibetan Plateau. Moreover, to assess the effects of the rock uplift rate on river terrace formation, we integrated 22 terrace sequences with long timescales on the NE Tibetan Plateau, and we found that the preservation rate of river terraces is linearly correlated with the rock uplift rate. Thus, our results suggest that the timing of terrace formation is controlled by abrupt climate change and that the amount of terrace formation/preservation is controlled by the rock uplift rate on the NE Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Understanding the processes of fluvial geomorphic evolution is based on thorough evaluation of how rivers respond to tectonic activity and climatic change, with river terraces representing a key archive of alternating deposition and incision in response to such forcing, enabling an excellent means for correlation with tectonic and climatic records. An example presented here points to a difference in fluvial response to climate fluctuations along a trunk river and its tributary: the Yellow River and its tributary the Xike River, which has incised the Lajia Gorge to pirate the Zoige Basin, in the eastern Tibetan Plateau. Based on Accelerator Mass Spectrometry 14C dating, the chronological sequence of basin fill top and fluvial terraces below has been established, defining the drainage reorganization of the Yellow River excavation through the Zoige Basin since the Last Glacial Maximum. Spatial and stratigraphic comparison between the two fluvial sequences, combined with correlation with high-resolution climatic records, indicates that the tributary Xike River formed more terraces in response to trunk incision (base-level variation), climatic fluctuations, and underlying weak bedrock than the Yellow River. Thus, our results not only demonstrate a combined archive of climatic fluctuation and tectonic uplift recorded in the fluvial terrace sequences, but also suggest that the generation of fluvial terraces may be influenced by the underlying bedrock within the same tectonic and climatic settings. • The Yellow River excavating through the Zoige Basin is constrained before 19 ka. • Fast uplift drives a sensitive fluvial response to sub-orbital climatic cycles. • Drainage scale affects the sensitivity of fluvial response to climate change. • Fluvial terrace is archive of the coupling between uplift and climate change. [ABSTRACT FROM AUTHOR]

The interplay of tectonics, climate and topography shapes the river dynamics that give rise to terrace formation in mountainous regions. Unraveling the distinct influences of these factors on fluvial processes is a complex challenge due to their intricate interactions. By combining field observations with optically stimulated luminescence (OSL) dating, we have discerned and examined the sedimentary and geomorphological attributes of terraces, as well as the distinctive event sediments linked to recurrent mass movement across four varied reaches of the Upper Yangtze River. Each reach exhibits distinct tectonic settings, such as subsidence depressions, uplift gorges, or relict planation topography, which have imparted varied responses of river processes since the penultimate glacial period. Evidence from all study reaches indicates the presence of two cycles of fluvial aggradation-incision, yet the differentiated tectonic activities, precipitation patterns, and topographic reliefs have elicited divergent river behaviors across different reaches. In the subsidence depression, a single set of terraces has been formed, whereas in the most upstream region, characterized by relict planation topography, two superimposed sets of terraces have developed. In contrast, two separate sets of terraces have emerged in the uplifted gorge since the post-penultimate glacial period. The striking differences in terrace configurations across the valley reaches suggest that the magnitude of environment perturbations has exceeded critical thresholds of the different equilibrium conditions. One transition in equilibrium conditions relates to the minimum riverbed sediment thickness required to supply abrasive agents necessary for riverbed armoring. Another transition triggers a shift from fluvial-dominated processes to those dominated by extreme events, with critical sediment inputs modulating this transition, particularly within the gorge setting. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP), often known as the "Asia Water Tower", is the source region of several continental-scale rivers. However, due to the extremely difficult access and harsh living conditions in the interior plateau, fluvial processes in the headwaters of these large rivers and their connections to global climate changes remain unknown. In this study, the luminescence (using both quartz and K-feldspar) and AMS 14C dating techniques were employed to date the four terraces of the Zado Basin in order to elucidate the aggradation and incision history of the initial intermontane basin in the headwater of the Mekong River. One sample from the upper part of T4 terrace (which features a 12 m thick gravel layer, the base of which is unexposed) provides a K-feldspar pIR 50 IR 225 age of 125 ± 10 ka, indicating that the initial deposition of this terrace could predate marine isotope stage (MIS) 5. Considering the margin of error, this age also suggests that the onset of incision on T4 terrace during the climate transition from MIS 6 (glacial) to early MIS 5 (interglacial). This incision likely occurred due to increased meltwater and precipitation, causing the Mekong carving into the bedrock for more than 50 m. Eight luminescence samples are collected from T3 terrace (26.5 m in thickness) with ages ranging from 83 ± 7.6 ka to 22.3 ± 1 0.2 ka, indicating T3 formation/aggradation from late MIS 5 to the Last Glacial Maximum (LGM), possibly owing to reduced precipitation and enhanced sediment supply from intensive glacial activities. At around 22 ka, the Mekong once again shifted towards incision, crafting the T3 terrace, situated roughly 28 m above the current floodplain. This incision event was recorded by two luminescence samples from a sandy lens located at the top of gravel layer of T3, with OSL ages of about 22 ka. Floodplain samples from T2 and T1, dated at 16 ka and 2.8 ka respectively, demonstrate that from the last deglaciation to the Holocene, the Mekong continued its downward incision. This erosion developed two cut and fill terraces at elevations of 22 m and 11 m above the present floodplain, likely due to increased precipitation and enhanced vegetation at that time. Overall, the glacial–interglacial climate changes were the most likely driving force behind fluvial processes in the upper Mekong basin since the Late Pleistocene, with aggradation occurring during the glacial period while incision in deglacial and interglacial periods, suggesting a close link between the fluvial geomorphic evolution and orbital-scale climate changes. • Four Mekong River terraces in the Zado Basin of Tibet were dated by luminescence. • At c. 125 ± 10 ka T4 incision (into bedrock by > 50 m) initiated due to global warming. • T3 has been deposited since 83 ka and began downcutting at ∼22 ka in deglacial. • These terraces generally accumulate during glacial and cut down since deglacial. [ABSTRACT FROM AUTHOR]

• A series of river terraces are developed in the upper Jinsha River. • The short-term incision rate of the upper Jinsha River is 0.18–5.47 mm/yr. • The two depth intervals of the incision are 1200 ± 220 m and 340 ± 250 m respectively. • The main driving force of river incision is tectonic uplift. • Climate change is the switch button of river incision and accumulation behavior. The region occupied by three parallel rivers on the southeastern edge of the Tibetan Plateau is a zone with dramatically fluctuating topography and a complex tectonic setting. Deeply incised river valleys have become an ideal place for scholars to study the coupling relationships among river erosion, climate change and regional uplift. The fluvial terraces preserved in the upper Jinsha River provide the basis for exploring the history of river erosion. Through field investigation and dating results of terraces, the short-term incision rates of the upper Jinsha River are determined to be 0.18–5.47 mm/yr. In addition, the palaeo-profiles, which were reconstructed using two analytical methods, show that there are two depth intervals for the incision in the Jinsha River, namely, 1200 ± 220 m and 340 ± 250 m. They correspond to two early planation surfaces of the river, and the long-term average incision rates of the upper Jinsha River are estimated to be 0.23–0.34 mm/yr. By analysing the relationship between fluvial terrace formation and climate change, combined with the formation history of the early planation surface, it is recognized that the main force driving incision in the upper reaches of the Jinsha River comes from regional uplift. Climate change causes a continuous alteration between river incision and sediment accumulation, and this transition is also perturbed by mass flow events. [ABSTRACT FROM AUTHOR]

Solifluction terraces are a topographic and sedimentary signature for understanding the mechanism of solifluction occurrence and the past climate (e.g., paleoclimate), and have also impacts on hillslope stability. Traditional field surveys and aerial remote sensing have been primarily employed to map solifluction terraces, but they have challenges in large-scale mapping, which results in little knowledge of spatial distribution of solifluction terraces in many areas of the world. In this study, we made a first attempt at large-scale mapping of solifluction terraces based on high-resolution satellite remote sensing images and deep learning in the Luhuo and Xinduqiao areas, located in the southeastern Tibetan Plateau. Enriched training samples were firstly generated through manually delineated 1057 solifluction terrace and non-solifluction terrace polygons in Luhuo and data augmentation. The DeepLabv3+ model (Chen et al., 2018) was then trained by these diverse and abundant samples, and employed to Gaofen-2 satellite images for extraction of solifluction terraces in both the Luhuo and Xinduqiao areas. The performance estimation showed that the F 1 -score, precision, and recall reached 91.15 %, 84.56 %, and 98.85 % in the Luhuo area, and 84.30 %, 84.90 %, and 83.71 % in the Xinduqiao area, respectively. The extracted results of solifluction terraces were also validated by field investigations in the Xinduqiao area. Moreover, we found that the solifluction terraces were mainly distributed around the slope angle of 21° and concentrated in the altitude range of 3000–3900 m, but the slope orientations were heterogeneous in both areas. Our results demonstrated that the combination of high-resolution satellite images and deep learning had a significant potential for mapping solifluction terraces at regional and global scales. • Satellite images and deep learning are proposed to map solifluction terraces (STs). • Deep learning-based method is validated with an F 1 -score >80 %. • A large-scale distribution of STs in Tibetan Plateau is obtained for the first time. • STs are mainly around the slope angle of 21° and the altitude range of 3000–3900 m. • The proposed method has a potential to be used in global ST mapping. [ABSTRACT FROM AUTHOR]

• The total shortening rate of the Huoshaogou anticline estimated from deformed fluvial terraces is ~0.91 ± 0.37 mm/a. • The shortening of the fold deformation is more significant than the shortening of the fault dislocation. • The northward growth of the Tibet Plateau causes fault-related folding in the shallow layer throughout the Jiuxi basin. Active thrusting and folding at the foot of the Qilian Shan Mountains has accommodated the northward growth of the Tibetan Plateau. However, the slip history of individual thrusts and fault-related folds over different timescales remain largely unknown. In particular, the growth of a series of active fault-related folds suggests a relatively young deformation history in the sedimentary basin of the Hexi corridor. Here, we show the kinematics of the active Huoshaogou Anticline (HSGA) through stratigraphic sequences, and the shortening rate of the anticline using a balanced cross-section in the Jiuxi Basin, located at the western end of the Hexi Corridor. The total shortening rate (0.91 ± 0.37 mm/a) was estimated from deformed fluvial terraces, including the shortening of folding (0.74 ± 0.34 mm/a) and the shortening of the Xinminpu Fault (0.16 ± 0.07 mm/a) within the HSGA region. The results show that the shortening of fold deformation is more significant than the shortening of the fault dislocation. This indicates that the northward growth of the Tibetan Plateau not only affects the mountain foot of the Qilian Shan but also cross the Hexi Corridor to the southern boundary of the Gobi-Alashan Block. [ABSTRACT FROM AUTHOR]