Effects of differential hillslope‐scale water retention characteristics on rainfall–runoff response at the Landscape Evolution Observatory

Hillslopes turn precipitation into runoff and thus exert important controls on various Earth system processes. It remains difficult to collect reliable data necessary for understanding and modeling these Earth system processes in real catchments. To overcome this problem, controlled experiments are being conducted at the Landscape Evolution Observatory at Biosphere 2, The University of Arizona. Previous experiments have revealed differences in hydrological response between 2 landscapes within Landscape Evolution Observatory, even though both landscapes were designed to be identical. In an attempt to discover where the observed differences stem from, we use a fully 3‐dimensional hydrological model (CATchment HYdrology) to show the effect of soil water retention characteristics and saturated hydraulic conductivity on the hydrological response of these 2 hillslopes. We also show that soil water retention characteristics can be derived at hillslope scale from experimental observations of soil moisture and matric potential. It is found that differences in soil packing between the 2 landscapes may be responsible for the observed differences in hydrological response. This modeling study also suggests that soil water retention characteristics and saturated hydraulic conductivity have a profound effect on rainfall–runoff processes at hillslope scale and that parametrization of a single hillslope may be a promising step in modeling rainfall–runoff response in real catchments.     

Late Quaternary loess deposition in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland and its palaeoclimatic implications

The piedmont aeolian sediment in Central Asia is has been widely used for Quaternary palaeoclimatic reconstructions. Here we present detailed sedimentological and rock magnetic investigations on 188 samples from the ~9.4‐m‐thick Urumqi River section (URS) in the southern Chaiwopu Basin of the northern Chinese Tian Shan foreland. Optically stimulated luminescence (OSL) dating constrains the time‐span of the URS loess sedimentation from c. 28 to c. 6.8 ka. This chronology implies that the onset of the URS loess sedimentation is approximately synchronous with the Shangwangfeng Glaciation (MIS 2) in the headwaters of the Urumqi River. Analyses of sediment grain size and rock magnetic parameters indicate that sediment grain‐size composition controls magnetic properties of the URS loess, i.e. the wind intensity model, distinct from the pedogenic model interpreting the variations in magnetic properties of the loess in the Chinese Loess Plateau (CLP). Overall, the variations in sediment grain size and magnetic properties throughout the URS indicate that the present study area was dominated by a climate of strengthened wind associated with gradually intensified aridity during the latest Pleistocene. In contrast, the intensity of aridity and coldness during the early Holocene gradually became relatively weakened.     

Discontinuous deformation analysis based on the multiplicative decomposition of the displacement

Updating the block configuration on the basis of additive decomposition and its linearized expression of the displacement increment leads to the low calculation accuracy of the original discontinuous deformation analysis (DDA) and false volume expansion. In this study, the displacement expressions of a small deformation, a large rotation, and the corresponding velocity and acceleration terms on the basis of the initial configuration are presented using multiplicative decomposition. With the use of the principle of virtual work, the stiffness matrix, mass matrix, and force vector of blocks are obtained. Compared with the original DDA, each of the block deformation parameters has obvious physical meaning as a parameter of mechanics, which can be obtained by adding the incremental deformation components of each time step directly without co-ordinate transformation. Moreover, the proposed modification automatically considers the block deformation produced by centrifugal and Coriolis forces. The analysis of some typical numerical examples have verified the accuracy of the strain and stress calculated by the proposed method, and the current configuration is updated by the total displacements, which completely overcomes the false volume expansion and provides reasonable linear strains.     

Influence of stress conditions on shear behavior of slip zone soil in ring shear test: an experimental study and numerical simulation

Natural Hazards - Hurricanes and tropical storms pose a significant threat to developed coastal regions around the world. In the United States, hurricanes cause billions of dollars in damage each...     

青海南部二叠纪类生物古地理区系

冈瓦纳与欧亚大陆间的昌都地块构造属性存在争议,解决问题的关键是生物古地理区系判别.青海南部二叠纪类化 石群的研究表明昌都地块该生物群一直表现为暖水的特提斯型,与华南地区始终表现出更多的相似性,其生物古地理归属应 为特提斯大区华夏-特提斯区华南亚区.昌都地块南界龙木错-双湖-澜沧江缝合带在早二叠世为划分青藏高原暖水型特提 斯区的南界,不仅是华南亚区与藏北冷暖混合亚区的分界线,也是特提斯大区与冈瓦纳大区的分界线.中二叠世以后该带不再 构成大区界线,但在确定次一级分区界线上仍是一个很好的划分标志;北界金沙江缝合带二叠纪两侧生物群表现出一致性, 未形成浅海底栖生物自由迁移的障碍,不具有生物古地理分区意义.      

柴北缘察汗诺辉长岩成因:岩石地球化学、锆石U-Pb年代学与Lu-Hf同位素制约

柴北缘察汗诺地区广泛发育中生代辉长岩、闪长岩、花岗闪长岩和花岗岩。LA-ICP-MS锆石U-Pb测年结果表明, 辉长岩²⁰⁶ Pb/²³⁸ U加权平均年龄为246±0.7 Ma, 形成于中三叠世早期。辉长岩SiO₂(50.61%~54.41%)和全碱含量(2.36%~3.72%)低, 里特曼指数为0.54~1.12, 属于中钾钙碱性系列岩石; Mg^#(73~79)和Cr(342×10^-6~753×10^-6)、Ni(45.1×10^-6~145×10^-6)含量高, LREE/HREE为4.74~5.67, 富集U、Th等大离子亲石元素, 亏损Nb、Ta、Ti等高场强元素, 呈现出与典型俯冲作用密切相关的弧岩浆岩特征。锆石Lu-Hf同位素分析结果显示, 辉长岩ε_Hf(t)值为-2.24~+1.37, 研究表明察汗诺辉长岩岩浆源区因受俯冲板片流体交代而富集, 岩石主要起源于富集地幔的部分熔融。空间上, 察汗诺辉长岩与东昆仑布尔汗布达、鄂拉山以及西秦岭同仁-泽库等同时代的钙碱性岩浆岩, 共同构成了古特提斯洋向北俯冲的大陆边缘弧。     

腾格里沙漠南缘末次间冰期5e亚段的微量元素特征及其反映的古气候

腾格里沙漠南缘土门剖面TMS5e层段由16层风成砂、11层湖积黄土和5层湖相沉积构成,其年代相当于深海氧同位素5e。分析结果表明,TMS5e的10种微量元素的含量依次为PMnSrRbVCrZnNiCuNb。就平均值来看,古流动沙丘砂的各微量元素含量最低,其次为古半固定-固定沙丘砂,但两者的各微量元素含量都明显低于整个TMS5e层段相应平均值;黄土状亚砂土微量元素含量稍低于整个TMS5e层段相应平均值;湖相沉积和湖积黄土的各微量元素含量相差较小,且明显都高于整个TMS5e层段、古流动沙丘砂和黄土状亚砂土的平均值。土门剖面TMS5e层段的微量元素指示的MIS5e腾格里沙漠南缘的气候是不稳定的,经历了14.5次暖湿与冷干交替的气候波动,且可划分为TMS5e5(139~129.30ka BP)、TMS5e4(129.30~124ka BP)、TMS5e3(124~119.50ka BP)、TMS5e2(119.5~116.5ka BP)和TMS5e1(116.5~113.70ka BP)等5个亚段,分别可与格陵兰GRIP冰芯氧同位素所反映的MIS5e5、MIS5e4、MIS5e3、MIS5e2、MIS5e1等气候波动在性质和相位上相对应。     

Experimental study on grain size and soluble salt of saline soil in western Jilin Province, China

Western Jilin Province is a typical seasonal frost region, and is also one of the severest salinization areas of China. In this study, we aim to examine the saline soil in Da'an and Wukesong areas, western Jilin Province, and mainly analyze the granulometric composition and distribution of salt in soil profiles. Four sampling sites, two in Da'an and two in Wukesong respectively, are chosen for study. The granulometric composition, especially silt and clay content change in different sites and soil depths are analyzed. Analysis of total and components of soluble salt shows that the surface soil is weak carbonate saline, in which the main cation is Na⁺ and the main anion is HCO₃^-. The total amount of soluble salt presents a decreasing tendency with increasing depth. The comprehensive analysis of granulometric composition and soluble salt shows that the clay content and soluble salt content present similar variation tendency with an increase of depth.