The valley of Shimshal – a geographical portrait of a remote high mountain settlement and its pastures with reference to environmental habitat conditions in the North-West Karakorum (Pakistan)

This article presents observations on the natural hazard potential for permanent and seasonal mountain settlements and infrastructure such as routeways and irrigation canals in the North-West Karakorum. The remote high mountain settlement Shimshal (3080 m), located in the upper Shimshal valley and surrounded by three potential natural glacier dams, is of particular interest. The permanent settlement of Shimshal and its seasonal pasture settlements in the Shimshal Pamir at heights of 3200 and 4600 m respectively, reach the upper limits for permanent and temporary settlement. The choice of location for settlement and agricultural activities is already dictated by relief conditions. Primary settlement areas are the sediment accumulations in the valley floors. The wide distribution of unconsolidated screes in particular prevents settlement expansion upwards along the valley slopes. Glacial outburst floods as well as seasonal flooding events further reduce the scanty settlement area, as well as being among the most devastating sources of danger. The production of debris and the supply of loose material deposits induced in connection with the glaciation history of the area becomes a permanent source of danger for human settlement through resedimentation in the form of rockfall or mudflow. Furthermore, canal systems essential for the survival of oasis settlements suffer annual destruction through mass movements on the slopes, induced by the glacially pre-formed relief. Thus the adaptation of settlement locations to a glacially formed mountain relief will be examined in this study, with particular reference to the geomorphological landscape situation. What makes the Shimshal settlement particularly interesting is its very isolated location at a distance of 80 km from the Hunza valley which contains the main settlement concentration of the North-West Karakorum. Traditional ways of life can be expected to be well protected from outside influences. In the North-West Karakorum we find a debris landscape which differs greatly in its development and distribution from that of the Himalayas, influenced particularly in the lower valley locations between 1000 and 3000 m by the different climatic situation, and where therefore in comparison with the Himalayas a completely different pattern of natural hazards arises.     

The maximum Ice Age (LGM) glaciation of the Central- and South Karakorum: an investigation of the heights of its glacier levels and ice thicknesses as well as lowest prehistoric ice margin positions in the Hindukush, Himalaya and in East-Tibet on the Minya Konka-massif

A continuing prehistoric ice stream network between the Karakorum main crest and the Nanga Parbat massive has been evidenced, which, flowing down from the current Baltoro- and Chogolungma glaciers and filling the Shigar valley as well as the Skardu Basin, has flowed together with the Gilgit valley glacier to a joint Indus parent glacier through the Indus gorge. The ice stream network received an influx by a plateau glacier covering the Deosai plateau, which was connected through outlet glaciers to the ice filling of the Skardu Basin and the Astor glacier at the Nanga Parbat, as well as to the lower Indus glacier. The field observations introduced here in part confirm the results as to the Ice Age glacier surface area of Lydekker, Oestreich and Dainelli, but go beyond it. In additon, a reconstruction of the surface level of this ice stream network and its glacier thicknesses up to the highest regions of the present-day Karakorum valley glaciers has been carried out for the first time. In the area under investigation the Karakorum ice stream network showed three ice cupolas, culminating at an altitude of 6200–6400 m. Between the mountain groups towering 1000–2000 m higher up, they communicated with each other over the transfluence passes in a continuous glacier surface without breaks in slope. In the Braldu- and Basna valley ice thicknesses of 2400–2900 m have been reached. In the Skardu Basin, where the glacier thickness had decreased to c. 1500–1000 m, the ELA at an ice level of 3500-3200 m asl had fallen short to the extent that from here on down the Indus glacier a surface moraine cover has to be suggested. However, 80% of the surface of the ice stream network was devoid of debris and had an albedo of 75-90%. The lowest joint glacier terminus of the ice stream network was situated - as has already been published in 1988 – in the lower Indus valley at 850–800 m asl. The reconstructed maximum extension of the ice stream network has been classified as belonging to the LGM in the wider sense (60–18 Ka BP). Four Late Glacial glacier positions (I–IV), with a decreasing ice filling of the valleys, have been differentiated, which can be locally recognized through polish lines and lateral moraine ledges. The valley (trough-) flanks with their ground moraine covers, oversteepened by glacier abrasion, have been gravitationally destroyed by crumblings, slides and rock avalanches since the deglaciation, so that an interglacial fluvial-, i.e. V-shaped valley relief has been developed from the in part preserved glacial relief. The contrast of the current morphodynamics with regard to the preserved forms is seen as an indication of the prehistorically completely different - namely glacigenic – valley development and the obvious rapidity of this reshaping at still clearly preserved glacial forms provides evidence of their LGM-age. In an additional chapter the lowest ice margin positions, so far unpublished, are introduced, which have been reconstructed for the Hindukush, Central Himalaya and on the eastern margin of Tibet.     

Sedimentology of a debris‐rich,perhumid valley glacier margin in the Rakaia Valley,South Island,New Zealand

The sedimentology and stratigraphy of a multi‐phase glaciation sequence dating to Marine Isotope Stage 6 in the Rakaia Valley, South Island, New Zealand, is presented. This outcrop presents an example of the depositional signature of an end member of temperate valley glaciation, where voluminous sediment supply in a tectonically active setting combines with high annual temperatures and low seasonality to generate significant year‐round glacifluvial activity. Such glacial systems produce geological–climatic units that are dominated by thick sequences of aggradational gravels and proglacial lake sediments trapped behind outwash heads during deglaciation. At Bayfields Cliff, outwash sequences record an oscillating glacier margin marked by a sequence of glacier‐fed, Gilbert‐type deltas. The deltas are cut by numerous small‐scale, syndepositional, normal faults indicating both loss of glacier support and melt‐out of buried ice. A larger‐scale thrust fault system reflects late‐stage ice overrun. Braid plain gravels and chaotic disturbed glacial lake sediments are also recorded. A notable feature of these systems is the virtual absence of till in an environment with much other evidence for proximal ice. Cumulatively we regard these sediment–landform associations as diagnostic of debris‐laden, perhumid, temperate valley glacier systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Connectivity analyses of valley patterns indicate preservation of a preglacial fluvial valley system in the Dyfi basin, Wales

Coastal valleys in the west part of Mid-Wales, such as the Mawddach, Dysynni, Tal-y-llyn and Dyfi, acted as corridors for ice which drained the Welsh Ice Cap during the Devensian. Analyses of detailed digital elevation models, and interpretation of satellite images and aerial photographs, show the existence of large variations in the amount of glacial modification between these valleys. Although all the valleys are glacially over-deepened along late Caledonian fault lines, only the Dyfi basin exhibits a dendritic pattern, with V-shaped cross-profiles and valley spurs typical of valleys formed by fluvial processes. Connectivity analysis of the Dyfi basin shows that it exhibits an almost completely dendritic pattern with connectivity α and β values of 0.74 and 1.01, respectively, with little glacial modification of the preglacial fluvial valley pattern in the form of glacial valley breaching. Several examples of glacial meltwater incision into a well-developed pre-existing river valley system, causing river capture across watersheds, have been identified in the Dyfi basin. The degree of preservation of the preglacial fluvial valley system within the Dyfi basin indicates limited modification by glacial processes, despite the area being subjected to glacier activity during the Late Devensian at least. It is possible that major parts of the basin were covered by cold-based or slow-moving ice, close to, or under, a migrating ice-divide, with the major ice drainage occurring along the weaker zone of the Pennal Fault along which teh Dyfi valley is located, causing minor adjustments to the surrounding interfluves and uplands. It is proposed here that the general river valley morphology of the Dyfi basin is of a pre-Late Devensian age.     

西天山托木尔峰南麓大型山谷冰川冰舌区消融特征分析

基于对托木尔峰南麓托木尔型山谷冰川的野外考察和典型冰川的定位观测,对冰面被表碛广泛覆盖的所谓“托木尔型”冰川冰舌区表碛与冰面消融的关系进行了研究. 结果表明：表碛对冰面消融、冰川水文过程、冰川变化等均具有重要影响,当表碛厚度超过3 cm时,表碛对冰面消融就产生明显抑制作用,且随着厚度增加,冰面消融显明减弱. 科其喀尔冰川表面的观测表明,由末端向上,表碛厚度逐渐减薄. 受表碛影响,科其喀尔冰川区最大的消融量出现在海拔3 800~3 900 m之间、表碛物厚度小于10 cm的区域内;冰川消融强度由此向上随着海拔的升高而下降,向下随表碛厚度的增大而减弱. 冰面湖的发育是表碛覆盖冰川的又一主要特征,湖水对冰面的融蚀和快速排泄成为冰面产汇流的主要过程. 科其喀尔冰川研究表明,两三个冰面湖排泄形成的融蚀冰量就相当于冰川末端退缩造成的冰量损失. 因此,冰面湖等热喀斯特地形的形成、扩张融蚀、融穿排泄、形成湖区低地,这一周而复始的过程不仅是其主要消融方式之一,而且也强烈的影响着冰川水文及冰川变化. 托木尔峰南麓地区大型冰川变化主要以厚度减薄为主,而不是像大多数冰川显著的变化主要表现在末端和面积减少方面.     

Timing and extent of early marine oxygen isotope stage 2 alpine glaciation in Skagit Valley, Washington

Twenty-two new radiocarbon ages from Skagit valley provide a detailed chronology of alpine glaciation during the Evans Creek stade of the Fraser Glaciation (early marine oxygen isotope stage (MIS) 2) in the Cascade Range, Washington State. Sediments at sites near Concrete, Washington, record two advances of the Baker valley glacier between ca. 30.3 and 19.5 cal ka BP, with an intervening period of glacier recession about 24.9 cal ka BP. The Baker valley glacier dammed lower Skagit valley, creating glacial Lake Concrete, which discharged around the ice dam along Finney Creek, or south into the Sauk valley. Sediments along the shores of Ross Lake in upper Skagit valley accumulated in glacial Lake Skymo after ca. 28.7 cal ka BP behind a glacier flowing out of Big Beaver valley. Horizontally laminated silt and bedded sand and gravel up to 20 m thick record as much as 8000 yr of deposition in these glacially dammed lakes. The data indicate that alpine glaciers in Skagit valley were far less extensive than previously thought. Alpine glaciers remained in advanced positions for much of the Evans Creek stade, which may have ended as early as 20.8 cal ka BP.     

Lithostratigraphic development and neotectonic significance of the Quaternary sediments along the Kachchh Mainland Fault (KMF) zone,western India

The Kachchh Mainland Fault (KMF) is a major E–W trending seismically active fault of the Kachchh palaeorift basin whose neotectonic evolution is not known. The present study deals with the eastern part of the KMF zone where the fault is morphologically expressed as steep north facing scarps and is divisible into five morphotectonic segments. The Quaternary sediments occurring in a narrow zone between the E–W trending KMF scarps and the flat Banni plain to the north are documented. The sediments show considerable heterogeneity vertically as well as laterally along the KMF zone. (The Quaternary sediments for a northward sloping and are exposed along the north flowing streams which also show rapid decrease in the depth of incision in the same direction.) The deposits, in general, comprise coarse as well as finer gravelly deposits, sands and aeolian and fluvial miliolites. The Quaternary sediments of the KMF zone show three major aggradation phases. The oldest phase includes the colluvio-fluvial sediments occurring below the miliolites. These deposits are strikingly coarse grained and show poor sorting and large angular clasts of Mesozoic rocks. The sedimentary characteristics indicate deposition, dominantly by debris flows and sediment gravity flows, as small coalescing alluvial fans in front of the scarps. These deposits suggest pre-miliolite neotectonic activity along the KMF. The second aggradation phase comprises aeolian miliolites and fluvially reworked miliolites that have been previously dated from middle to late Pleistocene. The youngest phase is the post-miliolite phase that includes all deposits younger than miliolite. These are represented by comparatively finer sandy gravels, gravelly sands and sand. The sediment characteristics suggest deposition in shallow braided stream channels under reduced level of neotectonic activity along the KMF during post-miliolite time evidenced by vertical dips of miliolites and tilting of gravels near the scarps. The tectonically controlled incision and dissection of the Quaternary deposits is the result of neotectonic activity that continues at present day. The overall nature, sedimentary characteristics and geomorphic setting of the sediments suggest that the KMF remained neotectonically active throughout the Quaternary period.     

Basic tectonic features of the Knipovich Ridge (North Atlantic) and its neotectonic evolution

The geological and geophysical data primarily on the structure of the upper sedimentary sequence of the northern Knipovich Ridge (Norwegian-Greenland Basin) that were obtained during Cruise 24 of the R/V Akademik Nikolai Strakhov are considered. These data indicate that the recent kinematics of the northern Knipovich Ridge is determined by dextral strike-slip displacements along the Molloy Fracture Zone (315° NW). This stress field is superimposed by a system related to rifting and latitudinal opening of rifts belonging to the ridge proper. Thus, the structural elements formed under the effect of two stress fields are combined in this district. Several stages of tectonic movements are definable. The first stage (prior to 500 ka ago) is marked by the dominant normal faults, which are overlain by the lower and upper sedimentary sequences. The second stage (prior to 120–100 ka ago) is characterized by development of normal and reverse faults, which displace the lower sequence and are overlain by the upper sequence. Both younger and older structural features reveal peaks of tectonic activity separated by intermediate quiet periods 50–60 ka long. The stress field of the regional strike-slip faulting is realized in numerous oblique NE-trending normal and normal-strike-slip faults that divide the rift valley and its walls into the segments of different sizes. Their strike (20°–30° NE) is consistent with a system of secondary antithetic sinistral strike-slip faults. The system of depressions located 40 km west of the rift valley axis may be considered a paleorift zone that is conjugated at 78°07′ N and 5°20′ W with the NW-trending fault marked by the main dextral offset. The stress field that existed at this stage was identical to the recent one. The rift valley axis migrated eastward to its present-day position approximately 2 Ma ago (if the spreading rate of ～0.7 cm/yr is accepted). The obtained data substantially refine the understanding of the initial breakup of continents with the formation of oceanic structural elements. The neotectonic stage is characterized by combination of different stress fields that resulted in the formation of a complex system of tectonic structural units, including those located beyond the recent extension zone along the rift axis of the Knipovich Ridge. The tectonic deformations occurred throughout the neotectonic stage as discrete recurrent events.     

An outline of neotectonic structures and morphotectonics of the western and central Pannonian Basin

Neotectonic deformation in the western and central part of the Pannonian Basin was investigated by means of surface and subsurface structural analyses, and geomorphologic observations. The applied methodology includes the study of outcrops, industrial seismic profiles, digital elevation models, topographic maps, and borehole data. Observations suggest that most of the neotectonic structures in the Pannonian Basin are related to the inverse reactivation of earlier faults formed mainly during the Miocene syn- and post-rift phases. Typical structures are folds, blind reverse faults, and transpressional strike-slip faults, although normal or oblique-normal faults are also present. These structures significantly controlled the evolution of landforms and the drainage pattern by inducing surface upwarping and river deflections. Our analyses do not support the postulated tectonic origin of some landforms, particularly that of the radial valley system in the western Pannonian Basin. The most important neotectonic strike-slip faults are trending to east-northeast and have dextral to sinistral kinematics in the south-western and central-eastern part of the studied area, respectively. The suggested along-strike change of kinematics within the same shear zones is in agreement with the fan-shaped recent stress trajectories and with the present-day motion of crustal blocks derived from GPS data.     

山地冰川沉积相模式与特征

山地冰川沉积研究在中国有特殊重要性。因为欧、美对冰碛沉积研究多限于大陆冰盖,沉积环境比较单纯,冰水沉积比重很大,而中国山地冰川多限于山体内部,冰水沉积极不发育,且沉积环境很复杂,亚相变化也大。此外中国山地冰川多属大陆性,与欧、美海洋性冰川在物理性质和沉积特征上都有不同。如冰川磨蚀作用弱,冰碛中粉砂少,冰上融出碛发育而流碛和滞碛不发育,原生(同生)构造如粗糙斜层很发育等。这些都将丰富冰碛沉积学内容,并对科学地鉴别中国东部各种混杂堆积的成因有重要意义。如据现代冰川沉积指标庐山就没有任何冰川堆积。     

Neotectonic Characteristics of Central Anatolia

The Central Anatolian Crystalline Complex and its Tertiary cover have been highly dissected by neotectonic structures. The period of neotectonic activity is dominated by three main fault systems in Central Anatolia—the Tuzgolu fault zone, the Ecemis fault zone, and the Yozgat-Akdagmadeni-Bogazliyan fault system. The Tuzgolu fault zone, trending in a NW-SE direction, is located WSW of the Central Anatolian Crystalline Complex (CACC). This fault zone consists of parallel to subparallel, normal, and oblique right-lateral strike-slip faults displaying a step-like half-graben and horst-graben pattern. It controls the eastern margin of Tuzgolu, fault-parallel depressions, and the western margin of the Central Anatolian volcanic province. The Ecemis fault zone is located east of the CACC and is characterized by NE-SW-trending, left-lateral strike-slip faults controlling the eastern margin of the Central Anatolian volcanic province. The Yozgat-Akdagmadeni-Bogazliyan region is dominated by NW-SE- and NE-SW-trending conjugate faults. These three fault systems control the widely distributed Plio-Quaternary depressions, calc-alkaline-alkaline volcanic activity, and deposition of talus, alluvial fan, travertine, and terrace deposits. Alignment of hot springs, cinder cones, drainage offsets, and linear valleys are the characteristic features of strike-slip fault patterns observed in the region. Both morphotectonic features and recent earthquakes strongly suggest that most of the segments of these fault zones are stilt active.     

涟江源区河流地貌特征及其与构造的响应

通过对涟江源区河流地貌及地质构造的调查发现,区内河谷地貌平面展布形式有纵谷、横谷及斜向谷,纵断面形态主要为"V"型、次之为"U"型.支流与干流交汇处发育三处盆地,各盆地中均发育三级阶地,分别形成于距今56.7±3.6 Ka,24.2±2.4Ka,0.8±0.250 Ka.区内河谷地貌、阶地特征与新构造运动地壳间歇性抬升...     

The Glacial History of Landscape in the Batura Muztagh, NW Karakoram

The most recent glacial history of the Bar Valley on the Batura south side of the great Karakorum main ridge shows a marked retreat of the Kukuar and Baltar glaciers since 1915 by 8 km. This tendency is continuing. A great lateral moraine (GLM), which shows the latest, historical maximum postglacial stage, is accompanied by a higher level, which reflects a neoglacial glacier level whose ice margins no longer exist. An earth-pyramid moraine rising high above the glacier, as also occurs on the northern declivities of the Batura, does not mark a specific level, but bears witness to a valley-filling glacier, for which further indicators can be found along the valley flank. In the gorge-like narrow trough valley, the flanks of which are covered by steep debris cones originating from the postglacial, numerous former glacial characteristics contrast with the current glaciation of the far retreated Kukuar and Baltar glaciers. Moraine material found at the valley outlet at Chalt and also on the Talmutz pass demonstrates complete ice filling of the Bar valley, also supported by the Daintar glacier. From a glacial geomorphological perspective, this confirms a late to high glacial connection of the Bar glacier to a Hunza glacier, as postulated by Kuhle (2005).     

The glacial history of landscape in the Batura Muztagh, NW Karakoram

The most recent glacial history of the Bar Valley on the Batura south side of the great Karakorum main ridge shows a marked retreat of the Kukuar and Baltar glaciers since 1915 by 8 km. This tendency is continuing. A great lateral moraine (GLM), which shows the latest, historical maximum postglacial stage, is accompanied by a higher level, which reflects a neoglacial glacier level whose ice margins no longer exist. An earth-pyramid moraine rising high above the glacier, as also occurs on the northern declivities of the Batura, does not mark a specific level, but bears witness to a valley-filling glacier, for which further indicators can be found along the valley flank. In the gorge-like narrow trough valley, the flanks of which are covered by steep debris cones originating from the postglacial, numerous former glacial characteristics contrast with the current glaciation of the far retreated Kukuar and Baltar glaciers. Moraine material found at the valley outlet at Chalt and also on the Talmutz pass demonstrates complete ice filling of the Bar valley, also supported by the Daintar glacier. From a glacial geomorphological perspectives, this confirms a late to high glacial connection of the Bar glacier to a Hunza glacier, as postulated by Kuhle (2005).     

Morphology of the latest quaternary surface-faulting in the Gulf of Elat Region, eastern Sinai

A variety of morphotectonic features bear evidence of neotectonic activity along the Gulf of Elat. These include: stepped topography, deflected channels, fault-line grabens, sag-pond depressions, backtilted fan segments, faulted gravel bars and debris flow deposits. The age of the fault scarps is estimated on the basis of the extent of dissection, the amount of rounding of the crest of the scarps, the scarp gradient, the stage of clast weathering, the intensity of the micro-relief and the stage of soil and desert pavement development. The field data are interpreted and related to the geomorphic time curves suggested by Wallace, by Bucknam and Anderson and by Nash and the seismic hazard implications are discussed. Some criteria suggest a recent age, with 10,000 yrs B.P. as a frequently recurrent estimate. From the data it is concluded that the Gulf of Elat has definitely been tectonically highly active during the Holocene.     

Study of the Cuban fractures

With the help of aerial photographs, satellite photographs and imageries, contour maps, geological and geomorphological information (personal correspondence and unpublished works), geophysical regional data, and field work, it has been possible to map a network of fractures, alignments, and faults in 26 areas (distinguishing them quantitatively and hierarchically). Links with known regional structures were also studied. Interpretation of the linear relief elements confirms the very different density, dimensions, strikes, and function of the fracturation and also, from a microtectonic perspective, explains the activity of some active faults better. It has confirmed some previous results and improved on others; for example, the Oriente fault which is the most active in Cuba with two segments (Western: Cabo Cruz—Santiago de Cuba; Eastern: Santiago de Cuba—Punta de Maisí, the Western fault being the most active); the Nortecubana fault, forming the northern limit of the Cuban megablock, and divided into three segments; and the Cauto—Nipe fault, forming the limit of the neotectonic units, presenting two segments with three seismoactive knots.     

Late Quaternary deformation and slip rates in the northern San Andreas fault zone at Olema Valley, Marin County, California

Quaternary sedimentary deposits along the structural depression of the San Andreas fault (SAF) zone north of San Francisco in Marin County provide an excellent record of rates and styles of neotectonic deformation in a location near where the greatest amount of horizontal offset was measured after the great 1906 San Francisco earthquake. A high-resolution gravity survey in the Olema Valley was used to determine the depth to bedrock and the thickness of sediment fill along and across the SAF valley. In the gravity profile across the SAF zone, Quaternary deposits are offset across the 1906 fault trace and truncated by the Western and Eastern Boundary faults, whose youthful activity was previously unknown. The gravity profile parallel to the fault valley shows a basement surface that slopes northward toward an area of present-day subsidence near the head of Tomales Bay. Surface and subsurface investigations of the late Pleistocene Olema Creek Formation (Qoc) indicate that this area of subsidence was located further south during deposition of the Qoc and that it has migrated northward since then. Localized subsidence has been replaced by localized contraction that has produced folding and uplift of the Qoc. This apparent alternation between transtension and transpression may be the result of a northward-diverging fault geometry of fault strands that includes the valley-bounding faults as well as the 1906 SAF trace. The Vedanta marsh is a smaller example of localized subsidence in the fault zone, between the 1906 SAF trace and the Western Boundary fault. Analyses of Holocene marsh sediments in cores and a paleoseismic trench indicate thickening, and probably tilting, toward the 1906 trace, consistent with coseismic deformation observed at the site following the 1906 earthquake.New age data and offset sedimentary and geomorphic features were used to calculate four late Quaternary slip rate estimates for the SAF at this latitude. Luminescence dates of 112–186 ka for the middle part of the Olema Creek Formation (Qoc), the oldest Quaternary deposit in this part of the valley, suggest a late Pleistocene slip rate of 17–35 mm/year, which replaces the unit to a position adjacent to its sediment source area. A younger alluvial fan deposit (Qqf; basal age 30 ka) is exposed in a quarry along the medial ridge of the fault valley. This fan deposit has been truncated on its western side by dextral SAF movement, and west-side-down vertical movement that has created the Vedanta marsh. Paleocurrent measurements, clast compositions, sediment facies distributions, and soil characteristics show that the Bear Valley Creek drainage, now located northwest of the site, supplied sediment to the fan, which is now being eroded. Restoration of the drainage to its previous location provides an estimated slip rate of 25 mm/year. Furthermore, the Bear Valley Creek drainage probably created a water gap located north of the Qqf deposit during the last glacial maximum 18 ka. The amount of offset between the drainage and the water gap yields an average slip rate of 21–30 mm/year. Finally, displacement of a 1000-year-old debris lobe approximately 20 m from its hillside hollow along the medial ridge indicates a minimum late Holocene slip rate of 21–25 mm/year. Similarity of the late Pleistocene rates to the Holocene slip rate, and to previous rates obtained in paleoseismic trenches in the area, indicates that the rates may not have changed over the past 30 ka, and perhaps the past 200–400 ka. Stratigraphic and structural observations also indicate that valley-bounding faults were active in the late Pleistocene and suggest the need for further study to evaluate their continued seismic potential.     

中国公路泥石流研究

公路泥石流是指发育于公路沿线并对公路桥涵、路基路面及相应防护结构具有冲击毁损和淤埋破坏的病害类型。丰富的物源、具有焚风效应的气象条件以及泥石流沟轴线与区域新构造应力场主压应力方向一致等是形成大型泥石流的宏观背景。将泥石流概化为固、液两相流体,运用两相流理论、泥沙运动力学、Bingham流变方程和Bagnold颗粒相互作用试验结果等,初步建立了泥石流固-液分相流速计算方法、基于泥石流在防治结构表面及泥石流沟岸产生的冲击形迹建立的反求泥石流冲击力计算方法以及泥石流磨蚀力计算方法。开发了速流结构、泥石流隧道及翼型墩汇流结构等10余种防治技术,集成了拦-汇-排等多种综合治理模式。据此撰写了《公路泥石流防治工程设计、施工指南》。实施了60余个防治工程。效果显著。研究成果初步构建了公路泥石流理论及技术体系。     

Within-valley asymmetry and related problems of Neoglacial lateral moraine development at certain Jotunheimen glaciers, southern Norway

A difference in the size of Neoglacial lateral moraines on either side of a valley axis (within-valley asymmetry of lateral moraine development) is described. Analysis of clast roundness has revealed subangular material in latero-terminal and terminal moraines; lateral moraines, however, exhibit a compositional gradient of increasing angularity with distance from the former glacier snout. Comparisons with clasts of known origin suggest that this 'roundness gradient' may be explained with reference to either or both of two hypotheses: (1) a variable proportion of supraglacial (or englacial) to subglacial transported material; and (2) the variable composition of regolith incorporated by a push mechanism from the valley sides. Within-valley asymmetry is inferred to result where the supply of debris to lateral moraines from these sources is unequal either side of a valley axis. Both interpretations are also consistent with the relatively large size of latero-terminal sections of end moraines. In order to account for the discrepancy between moraine size and apparent debris supply rates, it is suggested that the largest lateral moraines may have been formed over a longer time scale than the 'Little Ice Age', and that reworking of deposits may have occurred. The supply of debris to the north-facing lateral moraine at Nordre Illåbreen has been so great that it has developed into a rock glacier; this suggests the possibility that subglacial material and valley-side regolith, as well as supraglacial material, contributes to the formation of ice-cored rock glaciers.     

Formation and disintegration of a high-arctic ice-cored moraine complex, Scott Turnerbreen, Svalbard

Englacial debris structures, morphology and sediment distribution at the frontal part and at the proglacial area of the Scott Turnerbreen glacier have been studied through fieldwork and aerial photograph interpretation. The main emphasis has been on processes controlling the morphological development of the proglacial area. Three types of supraglacial ridges have been related to different types of englacial debris bands. We suggest that the sediments were transported in thrusts, along flow lines and in englacial meltwater channels prior to, and during a surge in, the 1930s, before the glacier turned cold. Melting-out of englacial debris and debris that flows down the glacier front has formed an isolating debris cover on the glacier surface, preventing further melting. As the glacier wasted, the stagnant, debris-covered front became separated from the glacier and formed icecored moraine ridges. Three moraine ridges were formed outside the present ice-front. The further glacier wastage formed a low-relief proglacial area with debris-flow deposits resting directly on glacier ice. Melting of this buried ice initiated a second phase of slides and debris flows with a flow direction independent of the present glacier surface. The rapid disintegration of the proglacial morphology is mainly caused by slides and stream erosion that uncover buried ice and often cause sediments to be transported into the main river and out of the proglacial area. Inactive stream channels are probably one of the morphological elements that have the best potential for preservation in a wasting ice-cored moraine complex and may indicate former ice-front positions.