Age and Provenance of Loess deposits on the Northern Flank of Tianshan Mountain

Abstract: The distribution, optically stimulated luminescence dating and granulometric properties suggest that the loess on the northern flank of Tian Shan should be divided into two types. One which is like mantle and is named type A, is located on the windward slopes and dated to about 54.5±5.73?Ka. The other, called type B, lies flatly on the terraces of the rivers or low hills and penetrated 30.8±2.05?Ka ago. Here we study the origin and the age of two types of loess, and a model of loess formation is proposed. The dust was entrained from the Gobi Desert located to the north of Tian Shan by the monsoon from Mongolia, obstructed by the high mountains and deposited on the windward slopes of the mountains. The rivers and flows then transported the aeolian loess to low terraces and piedmont alluvial plains.     

Causes of Land Subsidence in the Kingdom of Saudi Arabia

The occurrence of land subsidence in the Kingdom Saudi Arabia is either natural or man-made. Natural land subsidence occurs due to the development of subterranean voids by a solution of host rocks in carbonate and evaporite terrains, over many areas of Saudi Arabia. Man-induced land subsidence is either due to the removal of groundwater in the agricultural areas or to wetting of unstable soils. Therefore, earth fissures and a lowering of the ground surface in unconsolidated sediments took place in alluvial plains and volcanic vent terrains. Unstable soils include Sabkha soils and loess sediments. These types of soils occur in coastal plains, desert areas and volcanic terrains. When this soil is wetted either during agricultural activities, waste disposal or even during a rain storm, subsidence takes place due to either the removal of salts from the Sabkha soil or the rearrangement of soil particles in loess sediments.     

Late Quaternary glaciation of the northern Urals: a review and new observations

This is a synthesis of the glacial history of the northern Urals undertaken using published works and the results of geological surveys as well as recent geochronometric and remote sensing data. The conclusions differ from the classical model that considers the Urals as an important source of glacial ice and partly from the modern reconstructions. The principal supporting evidence for the conventional model – Uralian erratics found on the adjacent plains – is ambiguous because Uralian clasts were also delivered by a thick external ice sheet overriding the mountains during the Middle Pleistocene. Alternative evidence presented in this paper indicates that in the late Quaternary the Ural mountains produced only valley glaciers that partly coalesced in the western piedmont to form large piedmont lobes. The last maximum glaciation occurred in the Early Valdaian time at c. 70–90 ka when glacial ice from the Kara shelf invaded the lowlands and some montane valleys but an icecap over the mountains was not formed. The moraines of the alpine glaciation are preserved only beyond the limits of the Kara ice sheet and therefore cannot be younger than MIS 4. More limited glaciation during MIS 2 generated small alpine moraines around the cirques of the western Urals (Mangerud et al. 2008: Quaternary Science Reviews 27, 1047). The largest moraines of Transuralia were probably produced by the outlet glaciers of a Middle Pleistocene ice sheet that formed on the western plains and discharged across the Polar Urals. The resultant scheme of limited mountain glaciation is possibly also applicable as a model for older glacial cycles.     

北京岩溶水系统划分及特征分析

岩溶水是北京市重要的战略后备水源,在城市供水方面发挥了重大作用,岩溶水系统划分对于掌握岩溶水资源、合理开发利用岩溶水是至关重要的。本文结合地质构造、地形地貌、水文地质条件,考虑含水岩组的连续性、不同级别地表水分水岭、地质构造的水文地质性质,将北京地区划分为3个一级岩溶水系统、7个二级岩溶水系统、16个三级岩溶水系统。其中隐伏型岩溶水系统无裸露的可溶岩或零星分布,天然资源少,地下水径流方向主要受开采影响,与上覆孔隙水有密切的水力联系。山前型岩溶水系统可溶岩分布于山区和平原,岩溶水天然补给资源丰富,含水层厚度大、分布广,调蓄能力强,开发利用程度高,排泄区有明显的阻水边界,储水能力强。山区型岩溶水系统可溶岩分布于山区,地下水向河谷、低洼处径流,排泄速度快,储存能力差,开采井零星分布,开发利用程度低。     

AN EXPERIMENT ON THE APPLICATIONS OF GEOBOTANICAL GUIDES IN DISTINGUISHING BETWEEN LITHOLOGICALLY SIMILAR STRATA OF DIFFERENT ORIGIN

This article will present the techniques and the various steps followed in the utilization of geobotanical indicators for geologic mapping of areas east of and adjacent to the Mugodzharskiye mountains. It was found that despite the apparent homogeneity of the plant cover on lithologically similar rocks, a geobotanical analysis reveals a number of fundamental differences. Even when the floristic composition of associations is the same, other differences are seen in quantitative ratios of species, in the occurrence of some species in the plant cover, and finally, in the development cycle of an association as a whole, or of its individual species. In many instances also considerable floristic differences are observed in the plant cover found on lithologically similar rocks. Differences in plant cover on lithologically similar formations result from the physical chemical properties of rocks, which in turn result from the origin of rocks, the conditions of their formation, and the depths of their occurrence. In utilizing geobotanical data for lithological,mapping, of great importance is the character of plants growing at the contacts of formations which emerge at the surface. The following regularly occurring characteristics were noted. a) Hydrophytes develop at the contacts of rocks of different lithologic composition when impermeable rocks underlie permeable and moderately permeable rocks (sandstone, marly sandstone). b) At the contact of rocks of a different lithologic composition, when water-impermeable rocks (clays) overlie water-permeable rocks (sand, sandstone, manly sandstone) vegetation quickly dries up because the overlying rocks are dry as a result of being separated from the ground water. c) A transitional zone of plants is observed at the contacts of lithologically similar rocks and makes possible the determination of the boundaries of these rocks. The boundaries may be very sharp if the lithologically similar rocks have a different type and amount of salinity. — M. Russell     

土壤元素异常成因研究及生态风险评价

山区岩石与水系沉积物,对山前平原土壤物质组成具有控制作用。土壤地球化学调查,查明北京某地区土壤存在着大面积同心圆状的镉、铜、铅等多金属元素异常。研究表明,西北侧山区分布着种类繁多的岩浆岩、变质与沉积岩,但与山前土壤具有高度正相关的元素组合特征的主要是燕山期中酸性岩浆杂岩体,而且杂岩体周边及其下游的BY沟水系沉积物中的多金属元素也呈现出明显的高背景含量特征。同时,铅同位素组成亦指示山前平原土壤铅与山区岩浆岩铅、沉积岩铅具有一致的物质来源,从而证实山前土壤多金属元素异常主要来源于山区岩浆杂岩体。由于山前平原土壤呈现为碱性且农田仅种植旱地作物,故富含多金属的土壤对农作物生长的生态风险程度低下。     

Geochemical, mineralogical and sedimentological studies on the Taklimakan Desert sands

Major-element composition, mineral composition and grain-size distribution have been studied for Quaternary aeolian sediments from the Taklimakan Desert, north-western China, together with the variation of chemical and mineralogical compositions of different grain-size fractions. Aeolian sediments from the Taklimakan Desert have higher ratios of feldspar/quartz and calcite/quartz, finer grain size, poorer roundness of quartz and feldspar grains and lower abundances of frosted quartz, than found in aeolian sediments from other deserts such as the Saudi Arabian Desert. In spite of these immature mineralogical and sedimentological features, the aeolian sediments from the Taklimakan Desert show low regional variations in major-element and mineral compositions and are homogenized. These observations confirm that two processes, glacial activity within surrounding mountains and aeolian activity at the Tarim Basin, are important in the homogenization of the Taklimakan Desert sands. Taklimakan Desert sediments are constantly and effectively supplied from basement rocks in the surrounding mountains by glacial erosion. The supplied sediments are further homogenized by aeolian activity in the desert and are partly blown away, serving as the source of Chinese aeolian loess. Compositional differences are observed between loess (mainly 10–40 μm particles) and the <45 μm fraction of the Taklimakan Desert sediments, as well as between loess and whole rock of the Taklimakan Desert sediments. These observations provide constraints for precise modelling of loess formation, and for assessment of the chemical composition of the upper continental crust based on the chemical composition of aeolian loess.     

Engineering-geological problems of loess in Poland

Grabowska-Olszewska, B., 1988. Engineering-geological problems of loess in Poland. Eng. Geol., 25: 177–199.

In Poland, loess covers are limited to a latitudinal belt in the southern part of the country. The covers vary from 2 to 30 m in thickness and the loesses are developed in three major facies: eolian, deluvial and alluvial. Stratigraphically, they represent four major horizons correlated with the Vistulian (Würm) Glaciation and some older ones. The paper presents characteristics of granulometric, mineral and chemical compositions with reference to origin, facies and stratigraphic position of these soils, as well as their lithofacies classification. The classification gives the basis for analysis of local and regional variability in engineering-geological properties of the loess.     

The nature and provenance of Golestan loess deposits in northeast Iran

Mineralogical, textural, geochemical, and weathering characteristics of loess deposits in Golestan province of Iran suggest that they are mostly derived from felsic igneous rocks and are related to Quaternary palaeoclimate. Whole‐rock analyses indicate heavy minerals such as zircon, tourmaline and phyllosillicate minerals (e.g. muscovite, chlorite, illite) exert a significant control on the chemical composition. The loess samples display uniform chemical composition, indicative of similar alteration history. Chemical index of alteration suggests a weak to moderate degree of weathering in a felsic source area. Scanning electron micrographs of quartz grains reveal abundant silt‐sized quartz particles, a result of glacial grinding during the Late Pleistocene in Central Asia. Subsequently, these silt particles were transported from Central Asia to their depositional site by wind and paraglacial processes. Local topography of northeast Iran (Alborz Mountains) acted as a major barrier, entrapping the airborne particles on the plains of Golestan province. Copyright © 2012 John Wiley & Sons, Ltd.     

Grain size characteristics and genesis of the Muxing loess in the Muling-Xingkai Plain,Northeast China

Thick loess is deposited on the platform in the piedmont zone of Muling-Xingkai Plain(Muxing Plain), but the genesis of the Muxing loess is still unclear. The aims of this study are to analyze the grain size characteristics of Muxing loess collected from the cores of a typical borehole(ZK1) in the piedmont zone of Muxing Plain, and to verify its genesis. The Muxing loess is mainly composed of the particles with diameter less than 50 μm, with an average content of 92.48%. The coarse silt particles with diameter of 10-50 μm are the basic composition of aeolian sediments, and their average content is 44.34% for the Muxing loess, which is the mode class among the particles with different diameters. The grain size parameters and frequency curves are similar to those of the typical aeolian sediments. The distribution characteristic of the Muxing loess in the C-M scatter diagram is consistent with that of the Xi Feng loess. In addition, the discriminant analysis shows the Muxing loess mostly consists of aeolian sediments. Therefore, it can be concluded that the Muxing loess mainly resulted from aeolian deposition based on the grain size characteristics. Muxing Plain is dominated by the monsoon climate, and the wind-blown dusts are gradually deposited after being transported over long distances.     

北京斋堂盆地黄土结构构造与形成环境

斋堂盆地的马兰黄土,是我国晚更新世标准地层之一。为了揭示该地黄土的生成及其形成古环境,本文着重对该盆地黄土进行了构造、结构、颗粒成分、碳酸盐以及铁锰集合体等综合研究。研究结果表明,斋堂盆地的马兰黄土同黄河中游的马兰黄土在组织结构、构造以及颗粒成分上极为类似,同属风成沉积;离石黄土同黄河中游离石黄土之间存在明显差异,在其形成过程中,曾经遭受过多次坡洪积作用参与。在马兰黄土中不遭受若干次冻融作用,表明     

渭北中部筛珠洞泉补给来源的再认识

筛珠洞泉位于中低山区与渭北黄土台塬区衔接地带。筛珠洞泉区地势整体趋势为西北高东南低,北部以中低山为主,海拔在1 200-1 600 m之间,多由裸露和隐伏碳酸盐岩组成;西南地势逐渐降低,海拔在800-1 000 m之间,为以唐王陵向斜为主的一系列褶皱构造,由奥陶系碎屑岩和碳酸盐岩组成;东南部地势呈阶梯状下降,山前地带海拔多在400-500 m之间,为裸露碳酸盐岩区与山前冲洪积扇区的接触地带。筛珠洞泉作为渭北中部最大的岩溶泉,对于其补给来源前人已做了大量的研究,较为一致的认识是泾河渗漏是筛珠洞泉最主要补给来源,且筛珠洞泉是渭北中部筛珠洞泉域隐伏岩溶系统的集中排泄点。本文根据氢、氧和锶同位素的研究成果,结合水文地球化学及岩溶水文地质条件,对筛珠洞泉的补给来源提出了与前人研究不同的认识,即筛珠洞泉的补给以筛珠洞泉域外西南部岩溶地下水为主;在所有的补给来源中,大气降水、河水及岩溶水所占比例分别为11%、37%和52%;在岩溶水补给中,西南部、西北部及坝址区岩溶水所占比例分别为77.9%、19.7%和2.4%。在此基础上,本文还根据氚同位素资料估算筛珠洞主泉岩溶水的平均滞留时间为62-64年。     

冻融循环作用下黄土基本物理性质变异性研究

以陕西富平重塑黄土为研究对象, 引入有关变异性分析的变化量和变异系数两个参数, 对历经不同冻融循环次数后黄土的物理性质指标进行清晰全面的描述. 结果表明:土样的密度和孔隙比的变化量呈现"共轭"变化, 水理性质指标的变化量均随冻融次数的增加而变小; 各项指标的变异系数均随冻融次数逐渐减小, 即土样内部形成新的结构, 并趋于稳定. 在分析黄土基本物理性质变异性的基础上, 可进一步探讨其内部颗粒排列、粒度成分及矿物成分等的发展转变, 为解决该地区冻融黄土的土工问题提供了参考, 同时, 也是判断其工程性质最基本的依据之一.     

新疆高山与盆地地貌分带的一些资料

下面发表的这篇手稿,可能是80年代袁老在整理其参加西北科学考察团阶段的笔记而写出的。可以看出,早在1927—1932年他就在地质考察中进行综合性的观察和纪录,他对天山—准噶尔盆地之间地貌分带的描述生动如画——“天山雪云常不开”“万里栏杆千丈冰”,锵锵有声——“隆隆震耳类似滚雷”,使你对皑皑白雪分布的山顶带和霜劈、冻土现象为主的崩塌带有如身临其境的感觉。往下是两级高山夷平面所构成的高、低草原带,它们之间以悬崖陡坎带相连,从生物和人类在这三带的活动来反映这三带的地形、植被和气候。再往下黄土开始出现;山前阶地十分发育;乌鲁木齐市所在的山前夷平面和由不同外力作用所形成的各成因类型沉积物堆积带……,它们表面的地貌特征、沉积特点以及生物状态,甚至看到风力剥蚀带所裸露的动植物化石、琳琅满目的风蚀石……。这些生动的描绘和深刻的分析,显示出袁老师的敏锐观察和丰富联想,是一篇宝贵的科学资料。     

阜平大沙河沿岸黄土组成特征及成因研究

阜平大沙河段位于太行山中北部地区,黄土类型与西部黄土高原一致,是黄土高原向东延伸的一部分。构成黄土高原的东部边缘,该区黄土复杂多样,厚度变化较大,成点状或片状分布。阜平沙河沿岸阶地之上、山麓背风地带、断裂带出露区发育有厚度不一的黄土层堆积。阜平沙河黄土物质来源复杂、既有西北风搬运来的物质,又有近地表生成的颗粒,堆积期间又经过明显的流水作用的干扰。大沙河黄土、古土壤的堆积、发育与更新世气候变化关系密切,同时又受到本区地貌和构造的影响。     

Structure,composition, and depositional environments of the lower cretaceous rocks of the Zhuravlevka terrane,Central Sikhote Alin

The structure, mineralogical-petrographic composition, and formation settings of the Berriasian-Albian terrigenous rocks of the Zhuravlevka terrane (Central Sikhote Alin) are considered. The rocks are interpreted as sediments accumulated in a virtually nonvolcanic basin along the transform plate boundary. Judging from the composition of terrigenous rocks, the main sources of clastic material were represented by the eroded granitic-metamorphic rocks of a mature continental crust, and, possibly, granitoid intrusions of ancient arc roots. Genetic features of the sediments suggest their accumulation on the shelf, underwater slope, foothill, and the adjacent basin plains of an oceanward-open marginal sea.     

Geotechnical Hazards Associated with Desert Environment

The aridity of the Arabian Peninsula's deserts ranges between arid to hyperarid with hot dry climate, scarce precipitation and sparse vegetation. These harsh environmental conditions enhance some geomorphologic processes more than others, cause specific geotechnical problems, and increase desertification.From west to east, the general physiography of Saudi Arabia shows the Red Sea coastal plains and the escarpment foothills called Tihama followed by the Arabian Shield mountains, the Arabian Shelf plateau and finally the Arabian Gulf coastal plains. Sand moves by wind either as drifting sand or migrating dunes in four major sand seas, over the Arabian Shelf, and in the inter-mountain valleys, in the Arabian Shield causing problems of erosion and deposition. Human activities in the deserts may cause more instability to the sand bodies, enlarging the magnitude of the problem. Fine silty soil particles also move by wind, depositing loess mainly in selected areas downwind in the Tihama. These loess deposits subside and may form earth fissures by the process of hydrocompaction upon wetting. The addition of water can be either natural through storms or man-made through human agricultural or civil activities. Extensive sabkhas exist along the coastal plains of both the Red Sea and Arabian Gulf. The sabkha soil may also heave by salt re-crystallization or collapse by wetting. The shallow groundwater brines present in sabkhas also attack and corrode civil structures. Urbanization and excessive groundwater pumping may also deplete the fresh groundwater resources and may cause subsidence, ground fissuring and surface faulting as observed in some locations in the Arabian Shield. Although the average annual precipitation is very low, rain usually falls in the form of torrential storms, collected by dry valley basins and causing floods to unprotected downstream areas on the coastal plains of the Red Sea.The desert environment, being a fragile echo system, needs to be treated with care. Intercommunications between different national and international agencies and education of the layman should help to keep the system balanced and reduce the resulting environmental hazards. In addition, any suggested remedial measures should be planned with nature and engineered with natural materials.     

乌鲁木齐河流域的黄土研究

本文较详细地论述了乌鲁木齐河流域的黄土,对部分黄土样品进行了粒度分析和矿物鉴定,利用¹⁴C和热释光方法做了年龄测定,指出这个地区的黄土大部分是在晚更新世中晚期干旱、寒冷的气候条件下形成的,与马兰黄土相当,有一些后来受流水改造成为次生黄土。分布在河源末次冰期冰碛上的黄土主要形成于全新世,属于天山“托木尔型”黄土。     

循环荷载下压实黄土动强度特性研究

移山填沟进行新区建设或修建机场, 是黄土地区应对建设用地不足而采取的一项新措施。进行压实黄土的动强度特性研究, 对高烈度黄土地区大规模移山填沟具有重要的理论和现实意义。本文利用GDS振动三轴仪对吕梁压实黄土的动强度特性进行了研究, 分析了含水率、干密度和加载频率对其动强度的影响规律。结果表明:压实黄土的动强度随含水率的增大而减小, 随干密度和加载频率的增加而增大; 含水率对压实黄土的动强度影响显著; 压实黄土的动强度随着振次的增加而减小, 用半对数坐标系下的直线方程拟合效果较好。     

Paleogeographic provinces of the periglacial loess association in the middle Volga basin

Specific features of the formation and distribution of periglacial loess association in the Volga region are discussed. Based on generalization of the results of the systematic paleogeographic analysis, the paper presents a comprehensive characteristic of the polygenetic and polychronous loess rocks. The results show regional specifics in the structure and composition of loess rock horizons confined to different-aged paleogeographic zones of the Russian Plain. Provincial discrepancies in the distribution and thickness of loess rocks are demonstrated in the summary map. Comparison of the complex characteristics of the loess rocks provides insight into the general trend of spatiotemporal variability of their structure and composition. Latitudinal zonation is manifested in the thickening of loess rock sequences along the distal direction of the paleoglacial zone (on the average, from 1.3 m to 5–10 m or more) and is usually accompanied by increase in contents of the silty material and carbonates and degree of sagging. Moreover, the stratigraphic structure of sections becomes more complicated with increase of the age interval of loess–soil series. The spatiotemporal trends, which are revealed in the development and periodicity of loess formation, have a great significance for the reconstruction of paleogeographic events in the Neopleistocene.