Quantitatively characterizing the geometry, kinematics, and deformation rate of fold-thrust belts in intermontane basins is the key to understanding strain partitioning within the Tian Shan range. This work focuses on the Bayin anticline in the Youludusi Basin, a typical intermontane basin located within the eastern Tian Shan. The Kaidu River cuts through the Bayin anticline and has developed three levels of terraces (T-1-T-3) across the structure. By using cosmogenic nuclide and optically stimulated luminescence dating methods, the formation ages of terraces T-1 and T-3 are constrained to 11.54 +/- 0.55 ka and 42 + 7.0/-7.1 ka, respectively. When applying a listric thrust fault model to the Bayin anticline and using terraces as references, the vertical displacements are estimated to be 16.45 + 6.46/-3.19 m (T-1), 32.08 + 12.85/-6.19 m (T-2), and 95.93 + 38.94/-18.6 m (T-3), and the shortening amounts are 10.56 + 8.33/-5.04 m (T-1), 20.46 + 16.68/-9.64 m (T-2), and 61.24 + 50.22/-28.93 m (T-3). Based on this listric thrust fault model and terrace T-1-T-3 ages, the rate of fault slip controlling the growth of the Bayin anticline is determined to be 1.6 +/- 1.0 mm/yr, and the crustal shortening rate of the anticline is 1.0 + 0.7/-0.6 mm/yr. The estimated crustal shortening deformation of the Bayin anticline accounts for similar to 12 % of the total deformation in the Youludusi Basin. In terms of the entire orogenic belt, the crustal shortening absorbed in the southern, central, and northern parts accounts for 24 %-56 %, 46 %-71 %, and 19 %-74 %, respectively, of the total strain across the eastern Tian Shan. Therefore, we believe that the Eastern Tianshan undergoes uniform deformation.

As a typical intracontinental orogenic belt, the Tian Shan is a natural lab for the understanding of ongoing intraplate deformation and related geodynamic mechanisms. Knowledge of the spatial and temporal patterns of uplift and exhumation of the range can provide critical insights into this issue. This work used apatite U-Th/He thermochronological analysis and river profile inversion to reveal the histories of exhumation and uplift of the Sikeshu catchment, northern Chinese Tian Shan. Also, the spatiotemporal variations in the rate of exhumation across the Tian Shan were investigated, by inverting from a dataset of 1817 compiled apatite and zircon fission track and U-Th/He ages. The results indicated that, the exhumation across the entire Tian Shan primarily began during the early Miocene, with a significant, range-wide enhancement of exhumation occurring around 10 Ma. When combining the independent evidence of mountain uplift from sedimentology, rock magnetism, and structural modelling, we propose a two-stage model of exhumation, uplift, and basinward propagation of the modern Tian Shan, i.e., initial, range-wide rejuvenation around 20 Ma and intensive uplift and rapid exhumation since about 10 Ma. By integrating previous geophysical and geological studies on the Tibetan Plateau, the significantly enhanced exhumation across the entire Tian Shan since similar to 10 Ma can be attributed to the IndianTarim collision at this age.

The forcing mechanism behind river incision and terrace formation is one of hot topics in the study of fluvial geomorphology. This work focused on the late Quaternary alluvial sequence in the south piedmont of the Chinese Altay Shan in the arid inland of Asia. In order to reveal the mechanism controlling the development of late Quaternary fluvial features along the mountain front, we conducted detailed fluvial geomorphological investigations on eight rivers, including geomorphic mapping, optically stimulated luminescence (OSL) dating, and differential global position system (dGPS) surveying. By utilizing the Monte Carlo simulation with terrace data, the late Quaternary rates of river incision along the south piedmont of the Chinese Altay Shan were determined. The results show that (1) the terraces developed by the piedmont rivers are not more than four levels and the depth of river incision in the piedmont is only dozens of meters, with deeper valleys displayed by the western piedmont rivers; (2) terrace alluviums along the mountain front were accumulated during glacial stages, and the subsequent incision occurred during interglacial stages; (3) the rate of river incision was accelerated during the Holocene, when the regional climate was characterized by progressively increasing wetness. When combining with the regional tectonic setting, we propose that the climate could have played the key role in driving the alluvial accumulation and the subsequent incision in the south piedmont of the Chinese Altay Shan during the late Quaternary. Together with the similar observations from the northeastern margin of the Tibetan Plateau and the Tian Shan, we further propose that climatically-driven fluvial geomorphological development could be a common phenomenon during the late Quaternary in the arid interior of Asia.

Subsurface fault geometry and deformation rates can be estimated by combining the pattern of terrace deformation with kinematic model and geomorphic age. Quantifying the geometry, kinematics and deformation rate of the thrust-and-fold belt is the key to exploring tectonic deformation and strain distribution of the Tianshan intermontane basin. This is demonstrated by the Bayan anticline in Youlududsi basin in the eastern Chinese Tianshan. The Kaidu River, flowing through the central part of the Bayan anticline, has formed three terrace levels at tilted fold backlimbs. Based on the field geological investigation, warped and tilted terraces in the Bayan anticline are characterized by broad, continuous backlimbs and abrupt forelimbs and suggest folding through progressive limb rotation of listric thrust model. Combining with the kinematic model and geomorphic age, the slip rate and crustal shortening rate of the underlying fault in Bayan anticline is （0.35-0.06）-（0.35+0.16） mm/a and （0.23-0.04）-（0.23+0.10） mm/a, respectively. This shortening represents over 15%-20% of the total deformation in Youludusi basin and ～2% of the 8.5±0.5 mm/a total shortening rate measured from GPS velocity across the entire range in East Tianshan.Therefore,a significant fraction of the total Quaternary deformation is accommodated within the central part of the East Tianshan.

Quantifying erosion rates over various temporal and spatial scales is the key to understanding the respective roles of tectonic and climatic factors in driving the topographic evolution of an active orogenic belt. This work focuses on the spatiotemporal patterns of denudation rate in the Tian Shan and its implication for topographic evolution by utilizing low-temperature thermochronological analyses. Apatite (U-Th)/He thermochronological analyses and thermal history modelling were conducted on eight samples taken from a -0.7-km elevation transect at the glaciated headwaters of the Urumqi River in the northern Chinese Tian Shan. The results reveal dominant Mesozoic thermochronological ages and limited Cenozoic exhumation, although the sampled area was subjected to intensive glaciation at least during the late Quaternary. The restrained late Cenozoic exhumation at the glaciated Urumqi catchment is also revealed in the other parts of Tian Shan. The inversion of-1780 published thermochronological ages shows that, although the exhumation in the Tian Shan has been enhanced since the late Oligocene due to tectonic rejuvenation and pulsed uplift of the range, the long-term exhumation rates in most of the Tian Shan are generally < 0.2 km/Myr, obviously lower than that in some other active orogenic belts characterized by a more humid climate. Given the fact that the late Cenozoic climate in the Tian Shan was characterized by stepwise aridification due to uplifting topographic barrier of the range for the Westerlies, we propose that climate aridification beginning since the late Oligocene could have acted as the equalizer of range -scale denudation, thus restraining the late Cenozoic denudation of the Tian Shan, a typical reactivated orogen belt in the arid inland of Asia.

河流地貌,特别是河流阶地是新构造与构造地貌、活动构造研究的一个重要对象,常用来刻画下伏构造变形的速率与时空模式,但利用河流地貌约束构造变形速率存在潜在的不确定性.基于十多年在天山北麓开展的构造地貌研究,认为不确定性主要包括以下4个方面:①与阶地定年策略有关的不确定性.对于晚更新世末—全新世的年轻阶地,利用阶地沉积顶部年龄和上覆堆积底界年龄分别约束得到的变形速率可能存在比较大的差异,本研究中这种差异为50％;对于更老阶地,用这两个年龄限定的变形速率差异不大.②与阶地对比有关的不确定性.沿背斜走向,河流过程对构造活动(如背斜基岩抬升)的响应存在时间上的不同步性.因此,对于发育在同一背斜构造上的不同河流,用某条河流已定年阶地的年龄,基于河流间的阶地对比确定另一条河未定年阶地的年龄,可能会导致阶地年龄不可忽视的偏差,进而造成对变形速率及其时空模式的误判.③与河流阶地位相相关的不确定性.不同成因的阶地均能呈现特定的阶地位相(向下游收敛或发散),这不利于基于阶地拔河高度的上下游阶地对比,也不利于利用阶地探讨构造活动的空间特征.④对于跨背斜或者断层的地貌面,由于背斜翼部或断层下降盘相对构造下沉,早期形成的地貌面将被后期的沉积物埋藏,这增加了利用该地貌面准确刻画下伏构造变形特征的难度,相关工作也要求构造两侧的变形参考面为同级地貌面.以上不确定性在利用河流地貌刻画逆断裂-褶皱构造变形特征的研究中需要予以注意.

The source‐to‐sink relationship between a sedimentary basin and its adjacent mountain range is vital for understanding the genesis of piedmont coarse‐grained sediments and the evolution of mountain topography. By integrating zircon U‐Pb dating and heavy mineral assemblage analyses on 15 samples, this work focuses on the change of the provenance with time in the Urumqi River Neogene‐Pleistocene continental sequence in the northern Chinese Tian Shan foreland, which has been chronologically constrained to range from ∼6.8 to ∼0.55 Ma. The results of the integrated provenance analyses reveal two shifts in provenance during the periods of 4.6–2.5 and 0.9–0.55 Ma, yielding new zircon U‐Pb age signals from the glacier‐covered headwaters of the Urumqi River. These two identified provenance adjustments are causally related to enhanced glacial erosion in the high mountain. We propose that enhanced glacial erosion could have caused southward expansion of the Urumqi River drainage basin, increased production of coarse‐grained materials with new zircon U‐Pb age signals, and finally accumulation of piedmont alluvial gravel. The observed topographic and sedimentary responses to enhanced glaciation could have been common phenomena during the late Quaternary in alpine areas, where a large number of alluvial fans are widely distributed like aprons along the mountain front, as seen in the piedmonts of the Tian Shan in the arid interior of Asia.

Surface erosion shapes the topography of an active orogenic belt with a rate depending on the time and space scales. Quantifying erosion rates over various temporal and spatial scales is thus crucial for understanding the topographic evolution in active orogenic belts. This work focused on the decadal catchment-basin erosion rate and its controlling factors in the northern Chinese Tian Shan. Nine mountainous catchment basins were selected to quantify the decadal-scale erosion rates from hydrological data measured during the years 1964-2011. The contributions of the suspended load, bed load, and solute load in the river sediment load were first determined. The erosion rate was then calculated for each analyzed catchment basin. The results show that the average rate of catchment-basin erosion is similar to 0.15 mm yr (-1), whereas the rate varies from one catchment basin to the next (the minimum rate of 0.05 mm yr(-1) in the Urumqi and the maximum rate of 0.30 mm yr? 1 in the Manas). In order to explore the possible effects of climate, topography, lithology, vegetation, and tectonics on catchment-basin erosion, correlation analyses were conducted between these factors and the erosion rate. The results indicate that the catchment-basin erosion rate is more closely correlated with topographic factors (basin area and basin relief) and climatic variables (discharge, run off, run off depth, and mean temperature), indicative of the main controlling of topography and climate on catchment-basin erosion. The erosion rates reported in this work are approximately consistent with the paleo-erosion rate of < 0.5 mm yr (-1) over the last 1.5 Myr derived from in situ produced cosmogenic 10Be concentrations in the Kuitun catchment basin in the west part of the range. Such a consistency is likely to imply relatively stable erosion during the late Quaternary in the northern Chinese Tian Shan.

Active orogenic belts provide natural laboratories for investigat-ing the mechanisms of tectonic deformation and landscape evolu-tion.Along their foreland basins,the relatively continuous sedimentary archives and varied geomorphic units have docu-mented the history of the tectonic uplift of the adjacent orogenic belts.Geological records(e.g.,low-temperature thermochronology and sedimentology)can reveal the history of mountain building on a timescale of tens of millions of years.

变形速率是衡量构造活动强弱的重要参数,对其准确限定一直是构造地貌、活动构造研究的重点.以河流地貌作为参考面限定构造变形速率是目前研究中最常用的手段.基于近年来的研究体会和具体的研究案例分析认为,虽然目前已能获得可靠的变形量和地貌年龄数据,但若想获得合理、可靠的变形速率,需要关注这两类数据之间的匹配关系与由其构建的断裂滑动历史的合理性.相较于通过位错量与构造变形时间的比值,或利用两者进行线性回归的方法来限定变形速率,从模拟合理的断裂滑动历史的角度出发,蒙特卡洛方法可有效减小变形速率估计的不确定性,使变形速率估计更加合理,从而为地震风险评价等提供可靠的基础资料.

流域侵蚀速率的时空变化对于理解活动造山带的地貌演化具有重要意义.以阿尔泰山8个山地流域为研究对象,利用1964—2011年的水文数据,采用河流输沙量法估算了年代际山地流域侵蚀速率.首先确定悬移质、推移质和溶解质对河流输沙量的贡献,然后计算各流域的年代际侵蚀速率,并结合已有研究结果,探讨了阿尔泰山流域侵蚀速率的时空特征及其控制因素.结果表明:阿尔泰山8个山地流域的平均侵蚀速率为0.03 mm·a-1,其中乌伦古河山地流域侵蚀速率最小(0.01 mm·a-1),额尔齐斯河支流克兰河山地流域侵蚀速率最大(0.05 mm·a-1).进一步对侵蚀速率与气候、地形、岩性、构造和植被等因素进行相关分析,发现流域侵蚀速率与地形因子(流域面积、地形起伏度)和气候因子(径流深度、平均温度)的相关性较强,表明这些因素可能对阿尔泰山山地流域侵蚀起主要影响.与阿尔泰山百万年尺度的剥蚀速率(0.07～0.3 mm·a-1)相比,研究时段内的流域侵蚀速率偏低,这表明中亚地区晚新生代持续的干旱气候可能制约了阿尔泰山地表侵蚀.

The Asian Summer Monsoon (ASM) margin is vulnerable to climate change and a distinct boundary of population and archeological sites exists along the margin. Although lots of studies have been undertaken along the margin, the Holocene history of climate variation is highly debated; for example, whether the climatic optimum occurred in the early Holocene or middle Holocene. In addition, moisture variations on millennial to centennial timescales remain unclear. In this study, we reconstruct moisture variation at the modern junction of the ASM and the Westerlies based on a well-dated (13.3-0.5 ka) loess section in northwest China. On an orbital timescale, moisture variations generally follow changes in insolation with the longest and most intense humid period from 11.3 ka to 8.7 ka, supporting the concept of an early Holocene climatic optimum in the ASM margin. On millennial to centennial timescales, four sequences of long-term gradual wetting and subsequent abrupt drought are noted, i.e., thousands of years were required to reach a favorable environment in the ASM margin, while in only a few hundred years of drought would occur subsequently. Terminations of humid periods correspond to the occurrences of cold events in the North Atlantic realm, indicating an important role for the Atlantic Meridional Overturning Circulation (AMOC) on millennial to centennial timescales. We suggest solar insolation and the AMOC as the dominant factors on orbital timescale and millennial to centennial timescales, respectively. Both factors modulate moisture variations in the ASM margin by influencing the interplay between the ASM and the Westerlies.

Characterizing active deformation of a piedmont structure is particularly helpful for understanding the dynamics of deformation of its adjacent active orogenic belt. This work focuses on fluvial geomorphology of the Kuitun River, which flows northwards out of the high mountains and perpendicularly cuts the E-W-striking Dushanzi anticline, a structure of the outermost fold-and-thrust belt in the northern Chinese Tian Shan foreland. Four episodes of alluvial fan development (fans F1-F4, sequentially younger in abandonment age) were identified. Based on the fluvial geomorphological framework constructed by these four alluvial fans, six terraces (terraces T-1-T-6, sequentially increasing height above the riverbed) were then defined. The topographic analyses and 10Be dating of these alluvial landforms show that the Kuitun River originally flowed northwestwards before at least 80 ka. Subsequent rock uplift caused by fold growth could have resulted in an eastward deflection, after which the river began to flow northeastwards to construct fan F2. At ~67 ka, accumulation of fan F-2 ended, and the Kuitun River deflected westwards to flow northwards and began to construct fan F3. The final stabilization of the Kuitun River channel occurred at ~13 ka due to intense river incision forced by climate change, when the river began to incise a 200-m deep canyon and form a flight of strath terraces flanking the valley. By using geomorphic surfaces as the references, the Late Pleistocene and Holocene shortening rates of the Dushanzi anticline were estimated to be 0.71 + 0.17/-0.16 mm/yr (over the past ~67 kyr) and 1.6 + 0.39/-0.37 mm/yr (over the past 13 kyr), respectively. When combined with the long-term shortening rate of ~0.44 mm/yr since initiation of fold growth, it is inferred that the Dushanzi anticline likely experienced an acceleration of deformation during the late Quaternary. With respect to the entire orogenic belt, both fluvial geomorphic records and GPS surveys indicate that most of N-S crustal shortening (likely > 70%) across the Tian Shan has been absorbed in the piedmonts of the range, a typical active orogenic belt in the interior of Asia.

系统的地貌计量指标分析有助于理解造山带新构造活动特征与地貌演化.太行山地处中国第二、三地形阶梯的边界,具有重要的构造地貌意义.基于ASTER GDEM地形数据,对太行山按流域进行了面积高程积分、河长坡降指标(SL)和Hack剖面等地貌计量指标的分析,结合地层、构造等资料,探讨了太行山构造地貌演化特征.结果表明,在分析的11条河流中,7条河流的面积高程曲线(HC)呈S形,面积高程积分值(HI)在0.35～0.60之间,表明其地貌演化处于壮年阶段,4条河流的HC呈凹形,HI值小于0.35,表明其地貌已遭受强烈侵蚀改造,目前处于地貌演化的老年阶段;7条河流的Hack剖面呈上凸形态,均衡坡降指标值(K)偏高,表明流域所在区域新构造活动较为活跃,4条河流的Hack剖面近似直线,K值偏低,表明河流所在区域新构造活动性较弱;从整体上看,太行山的HI平均值为0.36,HC为接近凹形的S形,表明太行山地貌演化整体上处于"壮年期"向"老年期"过渡阶段;太行山新构造活动性(断裂活动)在空间上存在差异性,东部活动性较强,西部地区活动性相对较弱.

Along‐strike distributions of both the displacement and slip rate of a fault are crucial for understanding its kinematics. This work focuses on along‐strike pattern of the rate of slip on the Huoerguos fault (HF), a thrust fault controlling growth and propagation of the E‐W striking Huoerguos anticline in Fold‐and‐Thrust Belt II in the northern Tian Shan foreland, northwestern China. By using morphological analyses and optically stimulated luminescence (OSL) dating on the terraces, the Late Pleistocene slip rates of the HF have been determined at the north‐flowing Jingou and Sangequan rivers, which are ∼15 km apart and incise deeply the Huoerguos anticline roughly perpendicular to its strike. Our results show that the rate of slip on the HF at the Jingou River is 1.0 + 0.22/−0.15 mm/yr over the past ∼13 kyr. This rate is consistent with the slip rate at the Sangequan River, cutting through the anticline's eastern part, which has been determined between 0.69 + 0.18/−0.11 mm/yr and 1.02 + 0.15/−0.13 mm/yr. This consistence implies that the Late Pleistocene slip rate of the HF is relatively uniform along its strike. Our new data also suggest that the time interval between the age of the topmost terrace alluvium and the basal age of its overlying sediments might not be ignored. Using these two ages as the abandonment age of a given terrace would yield two deformation rates with obvious difference, especially when this terrace has a relatively young abandonment age.

The Chinese Tian Shan is one of the most actively growing orogenic ranges in Central Asia. The Late Miocene-Quaternary landscape evolution of northern Tian Shan has been significantly driven by the interaction between tectonic deformations and climate change, further modulated by the erosion of the upstream bedrocks and deposition into the downstream basins. In this study, only the accessible Kuitun River drainage basin in northern Tian Shan was considered, and detrital zircon geochronology and heavy minerals were analyzed to investigate the signature of the driving forces for Miocene sedimentation in northern Tian Shan. This study first confirmed a previously recognized tectonic uplift at ca. 7.0 Ma and further revealed that the basin sediments were mainly derived from the present glacier-covered ridge-crest regions during 3.3–2.5 Ma. It is suggested Late-Pliocene to Early Pleistocene sedimentation was likely a response to the onset of the northern hemispheric glaciation. Although complicated, this study highlights that the tectonic-climatic interaction during the Late Cenozoic orogenesis can be discriminated in the northern Chinese Tian Shan.

The provenance data (zircon U-Pb dating and heavy mineral assemblage) of the Urumqi River Late Cenozoic terrigenous sediments in the northern Chinese Tian Shan foreland. These data have been used in our paper by Honghua Lu and the co-authors: Document and date shifts in sediment provenance in the northern Chinese Tian Shan: Insights into origin of late Quaternary gravel and landscape evolution.

冲积扇作为区域环境演变的敏感记录器,日益受到学界关注.通过文献调研,对冲积扇形态特征和动力学控制因素进行了总结梳理.首先对比分析了不同类型冲积扇的沉积学和地貌学特征.进而分别阐明了上游流域基岩岩性、构造运动和气候变化对冲积扇的形态、规模和沉积层序的影响.最后介绍了有助于冲积扇精细化研究的一系列新技术和新方法的应用以及未来研究的发展方向.主要提出重力流和牵引流沉积过程分别塑造碎屑流型和河控型冲积扇两类,并表明冲积扇是多种因素相互控制下的产物:流域基岩性质影响下游冲积扇规模和沉积物组成;构造活动提供山前沉积空间,影响冲积扇形态特征;气候变化决定着第四纪冲积扇沉积层序发育,特别是引发洪水事件的极端气象事件.进一步指出未来需要采用新的手段深入解读冲积扇所蕴含的环境信息.

The Qilian Shan, located in the northeastern Tibet, is under strong tectonic activity and earthquake motion due to the propagation of the plateau. At the mountain front of the eastern Qilian Shan, the Tongziba River, in the southern Zhangye Basin, flows northward and successively cuts the Minle-Damaying Fault and the Yonggu Anticline, two parallel structures within the Frontal Thrust system of the Qilian Shan. Here we present a detailed record of seven strath terraces of this river that documents the history of active deformation of the two structures. Based on the estimated crustal shortening distance from the deformed terraces and the terrace formation age constrained by AMS C-14 and optically stimulated luminescence (OSL) dating, a horizontal slip rate of 1.4 +/- 0.5 mm/year of the Minle-Damaying Fault is constrained since 16.7 +/- 1.8 kyr, and a shortening rate of 1.3 +/- 0.4 mm/year across the Yonggu Anticline has been estimated in a similar time frame, respectively. In total, the shortening rate across the mountain front is estimated to be 2.7 +/- 0.6 mm/year. GPS data show a similar modern shortening rate in this area, which indicates the rate of crustal shortening may be comparable in the modern and 10(4)-year scales. Our study supports a higher crustal shortening rate along the mountain front of the eastern Qilian Shan than that of the western Qilian Shan since the Late Quaternary.

River-incision rate is widely used to track changes in tectonics or climate over time and space. However, the feasibility of utilizing the spatial variations of river incision to reconstruct past tectonic and climatic processes remains unclear. Here, we focus on the spatial patterns of river incision along the northern Chinese Tian Shan foreland. Three alluvial fans FP, FeH, and FlH are determined as the alluvial fan context of river incision and terrace classification providing the geomorphological framework across the foreland region. Four rivers (i.e. the Kuitun, Jingou, Manas, and Urumqi Rivers from the western, central, and eastern part of the foreland) are used to reconstruct the paleogeomorphology from the reference, which is the best-preserved terrace of each river system with ages clustering in different parts of the Latest Pleistocene-Early Holocene. The depth of incision constrained by the reference terrace of each river is obtained by comparing the present-day topography and the reconstructed one. The resulting profile of channel incision (depth and rate) of each analyzed river displays an overall decreasing-downstream trend from the maximum where the river exits from the mountain range, to zero. Such a trend has been attributed to the progressive lowering of the river gradient that was caused by the adjusted ratio of sediment input versus water discharge induced by climate change. Superimposing on the decreasing-downstream trend, an obvious step can also easily be observed onto the profile of channel incision of each river, downstream of which channel incision is significantly less. The step occurs near the thrust fault controlling growth of the outermost anticline through which each river cuts, thereby implying the key role of local rock uplift in forming the river-incision step. The former observation implies that, at the same timescale, more river incision at the exit from the mountain range does not necessarily mean stronger climatic forcing of incision there. We thus propose that, in a foreland setting, it should be the temporal pattern of river incision rather than its spatial variation that is helpful for unraveling the change in the forcing factor of downcutting.