Thrusting and the associated folding are crucial geological processes accommodating the crustal shortening in a foreland setting. This work focuses on the late Quaternary thrusting of the Banfanggou fault (BF) in the southern Chaiwopu Basin, northern Chinese Tian Shan foreland. The outcrops at the Urumqi River in the western part of the southern margin of the basin show that the BF, dipping south with angle of 60–80 °, has thrust the Neogene mudstone onto the Quaternary gravels and has displaced the terrace surfaces. In contrast, the eastern segment of the BF exists as a blind thrust fault. By using the geomorphic surface (river terrace and alluvial fan) as the reference, the average rate of vertical slip on the western segment of the BF over the past ~12 ka is estimated to ~1.7 mm/year, and the estimated rate at the eastern segment of the fault is ~1.0–1.3 mm/year. Despite of the uncertainties of the rates deriving from the vertical offsets and the geomorphic ages, the resultant vertical slip rates might imply relatively high seismic risk in the southern Chaiwopu Basin.

This work focuses on the incision process over the Tuostai anticline, a fold of the proximal structure Belt I in the northern Chinese Tian Shan foreland, where the Sikeshu River has incised deeply into the alluvial gravels and the fold's underlying bedrock strata. Field investigation and geomorphic mapping define five terraces of the Sikeshu River (designated as T1 to T5 from oldest to youngest) preserved within the Tuostai anticline. 10Be surface exposure dating and optically stimulated luminescence dating constrain stabilization of the highest three terrace surfaces at about 80 ka (T1), 16 ka (T2), and 15 ka (T3), respectively. Around 16 ka, the calculated river incision rates significantly increase from <2 mm/yr to >6 mm/yr. Undeformed longitudinal profiles of terraces T2, T3 and T4 over the Tuostai anticline suggest that this structure may have been tectonically inactive since stabilization of these three terraces. We thus think that the observed rapid river incision over the Tuostai anticline has not been largely forced by tectonic uplift. Instead, the progressively warmer and wetter palaeoclimatic condition within the Tian Shan range and its surrounding area during the period of ∼20–10 ka may have enhanced river incision across the Tuostai anticline. A reduced sediment/water ratio might have lowered the gradient of the Sikeshu River.

How to extract tectonic activity information from the existing geomorphic form is an important part of geomorphic research.The river slope index SL can indicate the local slope of the longitudinal profile of the river,and is often used to discuss the problem of tectonic activity (fault) or lithology difference.The Hack profile can reflect the changes in the longitudinal profile of the river and is often used to indicate the structural movement of larger time scales.In this paper,we choose the stream length-gradient SL index,Hack profile and gradient index (SL/K)with the method of ArcGIS statistical analysis technology to interpolate the basin K value and meanSL/K value.Combining the spatial distribution characteristics of the K value and the meanSL/K value with the lithology,we discusses four partitions tectonic division of neotectonic activity and landform evolution stage of the (U)rümqi River.The Jrümqi River is one of the main rivers in the northern Tian Shan foreland,which flows through the Tianshan uplift zone,Houxia graben,Nanshan uplift zone and piedmont depression successively.The strata are distributed in succession from old to new.The Tianshan uplift zone is mainly Paleozoic.The Houxia graben is mainly dominated by Mesozoic strata.The Nanshan uplift zone is composed mainly of Carboniferous tuff and tuffaceous siltstone.The piedmont depression is mainly composed of Quaternary alluvial and gravel.The digital elevation model(DEM)data used in this paper are derived from the ASTER GDEM elevation data with an initial resolution of 30 m × 30 m.Based on the analysis of SL and Hack profiles of river slopes in the mainstream of the ~rümqi River Basin and its four major structural strata,this paper draws the following conclusions:(1) The whole Hack profile of the (U)rümqi River basin is on convex form and the balancing grade index K value is high(K=531),which shows that current structure in this basin is still active.(2) Analysis of 4 partitions in the (U)rümqi River basin about SL and Hack profile reveal that the Tianshan uplift zone and partition of nanshan Hack profile present convex curve;Houxia graben after integral to Hack profile curve tends to sink;in the Nanshan uplift zone and piedmont depression junction,Hack profile is convex shape with the downstream into a linear form.Additionally,the four partitions balancing grade index K value are 149,653,1388 and 653,respectively.These show that Tianshan uplift zone and partition of Nanshan interior is currently in a state of intense tectonic uplift;Houxia graben is in the weak current tectonic activity;Nanshan uplift zone and piedmont depression are due to the southern margin of Junggar fault dislocation effects,which might be in a new equilibrium profile adjustment stage.(3) There are 9 abnormally high values of the SL/K in the mainstream reach of the (U)rümqi River Basin.These values from the upstream to the downstream are about:2.1 (2400m),6.0 (2275 m),6.2 (2100m),4.8(2070 m),6.0 (2010 m),48.0 (1900 m),11.0 (1700 m),10.0 (1575 m) and 10.8 (1550 m),respectively.These anomaly values correspond to the position of the Hack profile curve,which indicates that there is a good topography correspondence between the SL/K and the Hack profile in the (U)rümqi River Basin.The causes of abnormal high values of SL/K in the mainstream slope of the (U)rümqi River Basin are due to tectonic activity,lithological change,tributary import,etc.The high value of SL/K at 2100 m above sea level is affected by tectonic activity,lithological change and tributary import.The high value of SL/K at an altitude of 1550 m is mainly affected by the fault structure and tributary import.The high value of SL/K anomaly at 1900 m is mainly affected by lithological differences and fracture structures.Among them,the high value of SL/K at the altitude of 2400 m,2275 m,2010 m,1575 m and 1700 m is mainly affected by the tributary import.

The Qiantang River drainage basin is located in Eastern China,which crosses the tectonic units of Jiangnan (including Jiangnan uprise platform and northwest Zhejiang) and Huanan subzones.There are three main northeast-trending faults developed in the Qiantang River drainage basin,i.e.,Jiangshan-Shaoxing Fault (F1),Qiuchuan-Xiaoshan Fault (F2),and Majin-Wuzhen Fault (F3).In recent years,geomorphic indexes are more and more used to quantitatively express geomorphic process in the study of tectonic geomorphology.In order to evaluate tectonic activity and characterize geomorphic evolution of the Qiantang River drainage basin,this work extracted several geomorphic indexes,including Hypsometric Integral (HI),area elevation integral integral curve (HC),slope,drainage basin asymmetry (AF),and drainage basin shape (Bs) from 87 sub-basins of the the Qiantang River drainage basin based on the ASTER GDEM data and the spatial analysis technique of GIS.Together with the lithology characteristics and the physical geography background,the development stage of the Qiantang River drainage basin and the tectonic activity of the three major faults developed in the basin were discussed.The main results are as following:(1) In the case of the area threshold less than 9km2,the HI value in the area covered by the volcanic rock with strong anti-erosion ability is usually high,whereas in the area with the shale and sandstone that is erodible,the HI value is relatively low.In the larger spatial scale,the HI value may be mainly related to tectonic activity.It opens out the spatial and area dependence of the HI.(2) The mean HI values of sub-basins which cross the three faults (F1,F2,and F3) developed in the Qiantang drainage basin are 0.2221,0.2328,and 0.2722 respectively,the results indicate that the activity of the three faults descends from northeast to southwest.(3) The calculated results for AF and Bs value illustrate that the two values range from 0.11 ～42.57 and 0.36～6.86 respectively of sub-basins in Qiantang River drainage basin.Compared to the HI index,AF and Bs are more helpful to reveal the spatial difference of tectonic activity.(4) Based on the analysis of HI,AF,Bs,and slope gradient,it shows that the northern segments of Jiangshan-Shaoxing Fault and the Qiuchuan-Xiaoshan Fault are weaker than the southern segments in the activity,while the difference in the activity between the southern and northern segments of the Majin-Wuzhen Fault is not significant.(5) From the results of geomorphic indexes (HI =0.217,|AF-50 | =4.27,Bs =0.77,the concave hypsometric curve),it can be concluded that the geomorphic evolution of Qiantang River drainage may be in the stage of old age.

亚洲内陆晚新生代干旱化历史及其驱动机制是非常重要的科学问题.选择天山北麓柴窝堡盆地南缘乌鲁木齐河剖面为研究对象,基于磁性地层年代学研究建立的时间标尺,分析了该剖面碎屑沉积物岩石磁学特征及其控制因素,进一步探讨了柴窝堡盆地晚新生代古气候特征.磁性地层年代学研究约束乌鲁木齐河剖面底界年龄为～6.8 Ma,顶界年龄为～3.3 Ma.详细的岩石磁学测量及漫反射光谱分析结果表明,乌鲁木齐河剖面沉积物中磁性矿物主要包括磁铁矿、赤铁矿等,磁学参数clf、cARM、SIRM、S-100mT、S-300mT、cARM/SIRM等在～6.3 Ma、～5.2 Ma存在明显变化,揭示磁性矿物粒度、含量等存在相应变化,如在～6.3 Ma前后,磁性矿物颗粒逐渐变粗、含量降低;在～5.2 Ma前后,磁性矿物颗粒逐渐变细后趋于稳定、含量逐渐增多.基于稀土元素分析、沉积粒度与磁学参数相关性分析,认为沉积物源与沉积物粒度不是导致乌鲁木齐河剖面磁学性质变化的主要因素,自~6.8 Ma以来逐步干旱化的气候条件可能是导致该剖面磁学特征变化的重要原因.基于漫反射光谱分析得到的红度与亮度数据结果也揭示了同样的古气候特征.

Alluvial units are important in understanding the interactions of antecedent drainage evolution with fold growth along the flanks of active orogenic belts. This is demonstrated by the Anjihai River in the northern Chinese Tian Shan foreland, which at present flows northward cutting sequentially through the Nananjihai anticline, the Huoerguos anticline, and the Anjihai anticline. Three episodes of alluviation designated as fans Fa, Fb, and Fc are identified for the Anjihai River. These three alluvial terrain features comprise a series of terraces, where the topographic characteristics, geomorphologic structure, and up-warped longitudinal profiles indicate continuous uplift and lateral propagation of the Halaande anticline and the Anjihai anticline over the past 50ky. Shortly after ~3.6ka when the oldest terrace during the period of the fan Fb sedimentation was formed, significant rock uplift at the overlapping zone of the Anjihai anticline and the Halaande anticline led to the eastward deflection of the antecedent Anjihai River. A series of local terraces with elevation decreasing eastward indicate the gradual eastward migration of the channel of the Anjihai River during the period of the fan Fc sedimentation. Finally the Anjihai River occupied the previous course of the Jingou River when the latter was deflected eastward in response to rock uplift of the Anjihai anticline, presently flowing across the eastern tip of the Anjihai anticline.

天山地区黄土磁学特征及古气候意义受到广泛关注.本文以天山北麓乌鲁木齐河T7阶地上覆黄土为研究对象,基于光释光测年建立的时间标尺,通过岩石磁学、沉积学与地球化学等方面的分析,探讨该地区晚更新世古气候特征.光释光测年结果表明,天山北麓乌鲁木齐河T7阶地上覆黄土底界6.8m处的年龄为约41ka,顶部年龄为约14ka;稀土元素分析结果显示该时期黄土物源可能没有发生明显变化;黄土沉积粒度与岩石磁学参数分析结果显示,黄土磁化率、磁颗粒参数(xARM/xlf和xARM/SIRM)等磁学参数与砂粒组分(＞63μm)、中值粒径等粒度参数呈正相关关系,这表明研究区晚更新世黄土磁学性质主要受沉积粒度的控制,符合西北地区黄土磁学增强机制的风动力模式;黄土砂粒组分的变化揭示约41～14ka期间,研究区晚更新世气候呈逐渐干旱化的趋势,但具有不稳定的特点.