Local winds in the upper Rhone Valley

Balloon soundings during July and August 1979, 1981 and 1982 showed the vertical structure of the flow in the upper Rhone Valley. Between the low level winds up to a height of about 2000 m a s l and the gradient winds above 3000 m a s l, in 73 % of the 107 ascents, a counterflow was detected. It appeared more often in connection with down-valley flow (89 %) than with up-valley flow (38 %) above the ground. This flow pattern was found to be almost unaffected by the upper winds. The horizontal structure of the wind was studied with 3 ground weather stations that were separated 2 and 5 km along the valley axis. Up-valley winds occur in the average of 32 fair weather days only around noon. During the time of strongest up-slope winds, the valley wind is down-valley. That was already found in the climatic mean by Yoshino (1964) with wind shaped trees. As the wind recordings show, the down-valley flow develops first at the end of the valley and the resulting convergence zone moves down with about 2 m/s until it stops above a characteristic step near Fiesch (Fig 6). An explanation can be given by differential heating within the Rhone Valley itself and due to neighbouring valleys. The measured differences in the diurnal pressure changes of 5 stations is consistent with that hypothesis.     

Local winds in the upper Rhone Valley

Balloon soundings during July and August 1979, 1981 and 1982 showed the vertical structure of the flow in the upper Rhone Valley. Between the low level winds up to a height of about 2000 m a s l and the gradient winds above 3000 m a s l, in 73 % of the 107 ascents, a counterflow was detected. It appeared more often in connection with down-valley flow (89 %) than with up-valley flow (38 %) above the ground. This flow pattern was found to be almost unaffected by the upper winds.The horizontal structure of the wind was studied with 3 ground weather stations that were separated 2 and 5 km along the valley axis. Up-valley winds occur in the average of 32 fair weather days only around noon. During the time of strongest up-slope winds, the valley wind is down-valley. That was already found in the climatic mean by Yoshino (1964) with wind shaped trees.As the wind recordings show, the down-valley flow develops first at the end of the valley and the resulting convergence zone moves down with about 2 m/s until it stops above a characteristic step near Fiesch (Fig 6).An explanation can be given by differential heating within the Rhone Valley itself and due to neighbouring valleys. The measured differences in the diurnal pressure changes of 5 stations is consistent with that hypothesis.     

Recognition of two contrasting structural-and mineralogical-gold mineral systems in the Youjiang basin,China-Vietnam:Orogenic gold in the south and Carlin-type in the north

The gold deposits in the Youjiang basin,totaling 25 Moz gold,have traditionally been thought to be of Carlintype,particularly those with extensional structural geometries in the northern basin dominated by platform sedimentary sequences.However,the structural geometries,mineralization styles and alteration types for the Jinya,Gaolong and Nakuang gold deposits in the south-central part of the basin are remarkably similar to those of unequivocal orogenic gold deposits.Structural studies show that gold mineralization in the three gold deposits was controlled by tight "locked-up"anticlines with NW—SE-to E-W-trending and/or concomitant thrusts and/or shear zones,which resulted from NE-SW-to N-S-trending compression or transpression following the Early Triassic closure of the Paleo-Tethyan Ocean.Alteration zones in these deposits are dominated by silicification(quartz),sericitization,sulfidation and carbonation.Zoned pyrites in these deposits comprise Au-poor cores and invisible Au-bearing rims with minor external free gold.Euhedral to subhedral auriferous arsenopyrites also contribute to the gold budget.These features indicate that the three gold deposits are sediment-hosted orogenic gold deposits that contrast markedly with the Carlin-type gold deposits in the northern part of the Youjiang basin in terms of structural geometry and timing,mineralization style and nature of associated alteration.Although additional reliable ages using robust methodologies are still required,the older isotopic ages of the gold deposits in the south-central Youjiang basin are also consistent with earlier formation during transpression that predated extension during orogenic collapse,the period of formation of the Carlin-type gold deposits in the northern Youjiang basin.     

Characterisation and spatial distribution of gravitational slope deformation in the Upper Rhone catchment (Western Swiss Alps)

The influence of gravitational slope deformation (GSD) on erosion rates and the shape of mountain belts has been identified worldwide, particularly in valleys affected by glacial retreat. However, due to a lack of understanding about the main predisposing factors influencing their spatial distribution, size and failure mechanisms, the effective impact of GSD on the evolution of the landscape remains difficult to quantify. This study presents the first detailed, regional-scale GSD inventory of the entire Upper Rhone catchment (western Switzerland). The detection and mapping of GSD are performed by combining different remote sensing approaches. Moreover, we propose a detailed characterisation of GSD, taking into account geometry, morphology and failure mechanisms. Based on these analyses, more than 300 GSD are identified, corresponding to 11 % of the entire study area. Spatial and statistical analyses indicate that GSD are not uniformly distributed across the study area: six GSD clusters are highlighted, containing more than 80 % of the GSD events detected. Our observations suggest that the distribution of GSDs is primarily related to coexisting active tectonic processes (including high uplift gradients and earthquake activity) and pre-existing regional-scale, tectonic weakness zones. The region’s lithological and structural conditions, on the other hand, appear largely to influence the failure mechanisms and the sizes of the GSD detected.     

Environment and landscape management during the Middle Neolithic in Southern France: Evidence for agro-sylvo-pastoral systems in the Middle Rhone Valley

Rescue excavations in the Middle Rhone Valley have provided opportunities to develop innovative strategies for the study of palaeoenvironments. These strategies involve sampling and analysis of botanical remains, recovered not only from archaeological sites but also in “off-site” pedosedimentary sequences thought to be poor in botanical remains. Thus, these remains (phytoliths, pedo-charcoal) give access to unexplored depositional contexts, such as alluvial plains. Moreover, off-site data are useful because they minimise the hazard of cultural bias (e.g., selection of species during wood gathering). Comparison of data collected in the alluvial plain with data obtained via anthracological analyses of karstic caves and rock-shelters in the hinterland suggests a complex agro-sylvo-pastoral management of the landscape during the Middle Neolithic. We propose a pattern that supposes considerable specialization in use of plains vs. slopes in the landscape, and a strong and continuous human pressure on the vegetation and soils between 4500 and 3500 cal BC. Nevertheless, these constraints are not sufficient to explain the persistence of such a system for more than a millennium. Favourable climatic conditions are thought to have been a determining factor in the persistence of an ecologically meta-stable relationship between human societies and their natural environment.     

Rhone River flood deposits in Lake Le Bourget: a proxy for Holocene environmental changes in the NW Alps, France

The Holocene evolution of Rhone River clastic sediment supply in Lake Le Bourget is documented by sub-bottom seismic profiling and multidisciplinary analysis of well-dated sediment cores. Six high-amplitude reflectors within the lacustrine drape can be correlated to periods of enhanced inter- and underflow deposition in sediment cores. Based on the synthesis of major environmental changes in the NW Alps and on the age-depth model covering the past 7500 years in Lake Le Bourget, periods of enhanced Rhone River flood events in the lake can be related to abrupt climate changes and/or to increasing land use since c. 2700 cal. yr BP. For example, significant land use under rather stable climate conditions during the Roman Empire may be responsible for large flood deposits in the northern part of Lake Le Bourget between AD 966 and 1093. However, during the Little Ice Age (LIA), well-documented major environmental changes in the catchment area essentially resulted from climate change and formed basin-wide major flood deposits in Lake Le Bourget. Up to five 'LIA-like' Holocene cold periods developing enhanced Rhone River flooding activity in Lake Le Bourget are documented at c. 7200, 5200, 2800, 1600 and 200 cal. yr BP. These abrupt climate changes were associated in the NW Alps with Mont Blanc glacier advances, enhanced glaciofluvial regimes and high lake levels. Correlations with European lake level fluctuations and winter precipitation regimes inferred from glacier fluctuations in western Norway suggest that these five Holocene cooling events at 45°N were associated with enhanced westerlies, possibly resulting from a persistent negative mode of the North Atlantic Oscillation.     

Deformation mechanisms and flow regimes in limestones from the Helvetic zone of the Swiss Alps

This paper is based on a combined field, transmission-electron (TEM) and transmission-optical (TOM) microscope study of limestones from the Helvetic zone (Swiss Alps) and discusses the deformation mechanisms and flow regimes that governed the deformation of these rocks.During pre-metamorphic regional ductile deformations the limestones deformed by power-law dislocation creep with differential stresses probably not exceeding 1 kbar. Dynamic recrystallization with grain-boundary sliding and grain-boundary migration allowed the grains to be less elliptical than the strain ellipse. A characteristic of the structure is the existence of dislocation-free subgrains. In the footwall of and approaching the Lochseiten calc-mylonite along the Glarus overthrust, grain-boundary sliding becomes more important (shift to diffusional creep or superplastic flow).During a syn- and post-metamorphic deformation, dynamic recovery seems to have become less competitive (no dislocation-free sub-grains), and along thrust faults twinning indicates a shift to higher differential stresses at the close of the deformation.It was not possible to separate these deformation phases on the basis of the dislocation debris. Sub-grain sizes as observed in TEM and TOM were identical.In limestones that underwent cataclastic deformation the rocks seem to have started breaking up along the grain boundaries. The new grain fragments are very small (0.1–0.3 μm) and are heavily twinned. In TEM the old large grains show very long straight glide dislocations, cleavage and, when shattered, ring patterns in diffraction.     

Thrust tectonics in the south central pyrenees

Surface structural data and published stratigraphies are combined to construct two balanced and restored sections through the Nogueras Zone of the south central Pyrenees. The allochthonous Nogueras Zone units are interpreted as the foreland-dipping margin of a major antiformal stack in the Palaeozoic rocks of the Pyrenean Axial Zone. Their structural evolution is summarized in a hangingwall sequence diagram. This reinterpretation of the Nogueras Zone is incorporated into a new NS balanced and restored section from the centre of the Pyrenean Axial Zone to the Ebro Basin. A classical ‘Rocky Mountains’ piggy-back thrust model is employed and the resulting section is a significant departure from those previously published. It is argued that ‘gravity gliding’ has never been an important mechanism in the Alpine Pyrenees. Section restoration casts doubt on the correlation of the surface expression of the North Pyrenean Fault and the seismically detected Moho step beneath it.     

The DAV and Periadriatic fault systems in the Eastern Alps south of the Tauern window

Alpine deformation of Austroalpine units south of the Tauern window is dominated by two kinematic regimes. Prior to intrusion of the main Periadriatic plutons at ~30 Ma, the shear sense was sinistral in the current orientation, with a minor north-side-up component. Sinistral shearing locally overprints contact metamorphic porphyroblasts and early Periadriatic dykes. Direct Rb-Sr dating of microsampled synkinematic muscovite gave ages in the range 33-30 Ma, whereas pseudotachylyte locally crosscutting the mylonitic foliation gave an interpreted ⁴⁰Ar-³⁹Ar age of ~46 Ma. The transition from sinistral to dextral (transpressive) kinematics related to the Periadriatic fault occurred rapidly, between solidification of the earlier dykes and of the main plutons. Subsequent brittle-ductile to brittle faults are compatible with N-S to NNW-SSE shortening and orogen-parallel extension. Antithetic Riedel shears are distinguished from the previous sinistral fabric by their fine-grained quartz microstructures, with local pseudotachylyte formation. One such pseudotachylyte from Speikboden gave a ⁴⁰Ar-³⁹Ar age of 20 Ma, consistent with pseudotachylyte ages related to the Periadriatic fault. The magnitude of dextral offset on the Periadriatic fault cannot be directly estimated. However, the jump in zircon and apatite fission-track ages establishes that the relative vertical displacement was ~4-5 km since 24 Ma, and that movement continued until at least 13 Ma.     

赣南-粤北中生代晚期火山岩系岩石地层划分

分析了赣南—粤北中生代晚期火山岩系划分的现状和存在的问题,提出以火山旋回、火山—沉积复合岩相为划分依据,划分为３ 群６ 组：形成于中侏罗世的下火山岩系称为余田群,下分水头迳组和菖蒲组;形成于晚侏罗世的中火山岩系称为莲花寨群,下分上丁组和鸡笼嶂组;形成于早白垩世—晚白垩世早期的上火山岩系称为版石群,下分合水组和优胜组。     

Hf isotope systematics in granitoids from the central and southern Alps

First initial-Hf isotopic compositions for samples from the Alpine domain are presented and discussed. The results are mainly based on zircons and a few whole rocks with ages between 30 and 450 Ma. Of those so far analyzed, the present-day Hf isotopic compositions of zircons from non-metamorphic and metamorphic granitoid rocks vary between 0.2824 and 0.2829. Zircon populations with concordant U-Pb ages have much higher initial ¹⁷⁶Hf/¹⁷⁷Hf than inversely discordant populations which have been contaminated with older zircons containing less radiogenic Hf. Correlated Nd-Hf crustal-residence ages have been found involving model parameters of Hf/Nd=f(Lu/Hf)/f(Sm/Nd) 1.6 for the depleted mantle and f(Lu/Hf)/f(Sm/Nd) 1.2 for elemental fractionations in the crust. The model implies ¹⁷⁶Lu/¹⁷⁷Hf of 0.017 for the bulk crust. It is suggested that the granitoid rocks are the result of mixing of subcontinental mantle-derived magmas with 1.7 Ga old recycled and partially molten crustal material. The continental/mantle component mass-ratio values for the granitoids range between 0.3 and 2.     

回采工作面地质构造精细化综合探测技术研究与应用

小型地质构造是造成煤与瓦斯突出事故的主要因素,小构造的精准探测是亟需解决的关键问题。煤岩界面高精度探测是查明小构造,实现透明工作面的基础。声波远探测技术具有探测范围大、分辨率高、可成像等优点,能够实现对煤岩界面的精准识别。为此,提出了基于穿层钻孔声波远探测的煤岩界面探测技术,通过在井下穿层钻孔内布置声波远探测仪,采集孔周煤岩分界面产生的阵列波形,并利用反射波信息反演获得煤岩界面成像图,进一步结合钻孔群,实现工作面的整体勘察。首先,利用COMSOL Multiphysics软件构建出煤系单极远探测数值模型;然后通过模型正演分析全波信号与波场快照的全时空变化规律;最后对远探测声波数据进行反演实现煤岩界面的偏移成像。正演结果表明：模型中煤层的纵波波速比顶底板岩层慢1.2 km/s左右,声波在煤层中传播时能量衰减得更快,同时声波穿过煤岩界面时会出现主频的漂移;当测点趋近于仪器从底板岩层向煤层过渡的位置时,直达波的变化特征为幅度的骤降与声时的增大,而界面反射波的特征为时间−深度域中倾斜同相轴的斜率改变。对采集到的波形数据进行滤波、波场分离、反射波增强、偏移成像四个步骤完成模型反演,成像结果与原始模型相似度高,煤岩界面倾角误差0.6°、煤厚误差0.212 m,穿层钻孔远探测声波有限元方法可以有效地反演出煤岩界面的位置和形态特征。该研究可为声波远探测技术应用于穿层钻孔煤岩界面识别提供基础理论支撑。

     

Active deformation in the eastern Swiss Alps: post-glacial faults, seismicity and surface uplift

Post-glacial tectonic faults in the eastern Swiss Alps occur as single lineaments, clusters of faults or extensive fault zones consisting of several individual faults aligned along the same trend. The orientation of the faults reflects the underlying lithology and the pre-existing structures (joints, pervasive foliations) within these lithologies. Most post-glacially formed faults in the area around Chur, which undergoes active surface uplift of 1.6 mm/year, trend E–W and cut across Alpine and glacial features such as active screes and moraines. Additionally, there are NNW and ENE striking faults reactivating pervasive Alpine foliations and shear zones. Based on a comparison with the nodal planes of recent earthquakes, E–W striking faults are interpreted as active faults. Because of very short rupture lengths and mismatches of fault location with earthquake distribution, magnitude and abundance, the faults are considered to be secondary faults due to earthquake shaking, cumulative deformation in post- or interseismic periods or creep, and not primary earthquake-related faults. The maximum of recent surface uplift rates coincides with the youngest cooling of the rocks according to apatite fission-track data and is therefore a long-lived feature that extends well into pre-glacial times. Isostatic rebound owing to overthickened crust or to melting of glacial overburden cannot explain the observed surface uplift pattern. Rather, the faults, earthquakes and surface uplift patterns suggest that the Alps are deforming under active compression and that the Aar massif basement uplift is still active in response to ongoing collision.     

Climate,hydrology, land use,and environmental degradation in the lower Rhone Valley during the Roman period

This paper's aims are three: firstly, to demonstrate the importance of a long-term perspective on socio-environmental dynamics; secondly, to show the relevance of archaeological data in constructing such a long-term history of such dynamics; thirdly, to illustrate with a case study how one may identify the component processes of environmental change from archaeological materials. Taking the Roman occupation of the middle and lower Rhone Valley as a point of departure, the paper identifies some of the processes of regional environmental change. Firstly, it demonstrates the existence of a regional phase of climate degradation during the 2nd century ad. It is in all probability of anthropogenic origin. This degradation seems to have been caused by widespread deforestation in preparation for intensive cultivation of cereals, wine and olives for export to other parts of the Roman Empire. Next, it isolates the principal interactions occurring between relief, soils, and water on the one hand, and the societal dynamics on the other. The location of each settlement is considered representative of an environmental choice, made by its founders at the time the settlement is initiated. These environmental choices, in turn, reflect the perception of the landscape and its resources by the settlers. The principal indicators at our disposal for this study are the relief, soil, and hydrological maps. They are used as a basis for the calculation of the altitude, slope, orientation, annual solar radiation, exposure to the prevailing winds, and fertility of the soil of all sites and their environment. Subsequently, preferences are calculated statistically based on the 1000-odd settlements concerned. The third part of the paper concerns the evolution of the sites. It turns out that the earlier ones are the most successful, in part because they occupied the best locations, but also because they structured the landscape and the territory to their advantage, determined the road network, and were the first to lay hands on localized resources. Eighty percent of the total number of sites is abandoned in less than 200 years. The reasons for that abandonment are not to be sought in any kind of environmental degradation, as the proportion of abandoned sites is about the same in all landscapes. Rather, they seem to have to do with a reorganization of the settlement pattern after some 100 years of increasingly intensive agro-industry. This reorganization is triggered by a combination of economic and political events that come close to destabilizing the Empire. Settlement size and accessibility are the main determinants of survival. The exact nature of the events leading up to this re-structuration differs from region to region. In the case of the Tricastin, the Emperor undertook a vast land reclamation project in the first century bc. He used it to retire soldiers from the many legions that were active around the time of the birth of Christ. However, the peace of the early decades of the first century ad abruptly reduced the number of soldiers to be retired. Hence, the orthogonal, Roman drainage system could no longer be maintained sufficiently well, to ensure that it functioned correctly. As a result, the surface available for cultivation, and the yield per hectare, fell drastically, and many farms were deserted. To cite this article: S.E. van der Leeuw, The ARCHAEOMEDES research team, C. R. Geoscience 337 (2005).     

Paleozoic swells in the north of central and western Siberia

The relationships between the main tectonic features in the north of central and western Siberia are analyzed on the basis of the available geologic and geophysical data. The chain of troughs and syneclises, including the Yenisei-Khatanga Foredeep, the Lena-Anabar Trough, and the Ust-Yenisei and Yamal-Gydan syneclises are bounded in the north and south by systems of swells of approximately the same size and age. It is suggested that these swells, having appeared simultaneously with the troughs, were eroded subsequently and then buried beneath the Mesozoic-Cenozoic sediments.     

Facies and tectonic significance of two contrasting Miocene basins in south coastal Turkey

Several Miocene basins are developed on a mosaic of deformed Mesozoic carbonate platforms and ophiolitic units in the Antalya region of south-west Turkey. Two of these, the Manavgat and Köprü basins, show contrasting orientations and stratigraphies. The Manavgat basin is orientated broadly SE-NW and contains a succession of shallow-water reef carbonates overlain by a thick sequence of deeper-water marls. The upper part of the succession consists of sandstones, siltstones and conglomerates, mainly deposited by gravity processes. The stratigraphy of the N-S Köprü basin can be subdivided into a western part, which consists of coarse fan delta-conglomerates with local patch reefs, and an eastern part with thinly bedded sandy turbidites. Tooi marks indicate north to south flow in the north of the basin, but a southeasterly direction in the area of intersection with the Manavgat basin in the south-east. In the light of alternative regional hypotheses, it is thought that early Miocene basin initiation is related to coeval southeastward thrusting of the Mesozoic Lycian Nappes. Flexural loading is inferred to have resulted in block faulting of the foreland and this exploited pre-existing lines of structural weakness, dating from early Mesozoic rifting. mid-Miocene relative sea- level rise may relate to global eustacy, and/or regional tectonic subsidence. Finally, late Miocene renewed coarse clastic input (locally very coarse) and basin infilling reflect tectonic uplift to the north, possibly related to continuing Africa-Eurasia convergence in the region.     

Regional lithofacies and pedofacies variations along a north to south climatic gradient during the Last Glacial period in the central Loess Plateau,China

Five lateral sand–loess–palaeosol continua occur within the last glacial sediments of the central Loess Plateau of China along a 500 km north to south climatic gradient. The continua shift southward or northward in concert with desert expansion or contraction, respectively. Lateral lithofacies (desert sand to loess) variations are evident at the north end of the gradient and follow Walther's Law of the correlation of facies. Lateral pedofacies (loess to palaeosol) variations are present near the south end of the gradient, where the climate was warmer and wetter. The lateral stratigraphic changes from sand to loess or loess to soil are driven by variations in the rate of sedimentation along a climatic gradient.Vertical stratigraphic profiles at the north end of the gradient reveal alternating sand and loess beds. In contrast, alternating loess and palaeosols occur within the same stratigraphic interval in the southern Loess Plateau, where dust accretion rates were lower. However, in high resolution studies of climate change vertical profiles of alternating loess and palaeosols (especially weak palaeosols) may not reflect regional or global climate change. Alternating loess and weak palaeosols may reflect local variations in the balance between the rates of dust accretion and pedogenesis. Local fluctuations in either of these rates could result in the presence of time equivalent loess and palaeosols at high resolutions. Thus, some of the high resolution loess-palaeosol alternations may reflect local climatic variation rather than global or hemispherical climate change.     

Relationships between glacier and rock glacier in the Maritime Alps, Schiantala Valley, Italy

In the Schiantala Valley of the Maritime Alps, the relationship between a till-like body and a contiguous rock glacier has been analyzed using geomorphologic, geoelectric and ice-petrographic methodologies. DC resistivity tomographies undertaken in the till and in the rock glacier show the presence of buried massive ice and ice-rich sediments, respectively. Ice samples from a massive ice outcrop show spherical gas inclusions and equidimensional ice crystals that are randomly orientated, confirming the typical petrographic characteristics of sedimentary ice. The rock glacier formation began after a phase of glacier expansion about 2550 ± 50 ¹⁴C yr BP. Further ice advance during the Little Ice Age (LIA) overrode the rock glacier root and caused partial shrinkage of the pre-existing permafrost. Finally, during the 19th and 20th centuries, the glacial surface became totally debris covered. Geomorphological and geophysical methods combined with analyses of ice structure and fabric can effectively interpret the genesis of landforms in an environment where glaciers and permafrost interact. Ice petrography proved especially useful for differentiating ice of past glaciers versus ice formed under permafrost conditions. These two mechanisms of ice formation are common in the Maritime Alps where many sites of modern rock glaciers were formerly occupied by LIA glaciers.