基于改进IHS融合方法的冰川变化监测研究

随着卫星及传感器的发展,对地观测技术已广泛用于冰川变化监测中。针对多时相、同源遥感影像,提出了一种改进的IHS融合冰川变化监测方法。将不同时期影像进行改进IHS融合,使冰川变化区域突显出来,然后利用决策树分类方法对变化区域进行提取。利用两期LANDSAT影像进行基于改进IHS融合方法的冰川变化监测实验,并与常用于冰川变化监测研究的波段比值法进行比较,实验结果表明,该方法无论在定性分析还是定量分析上均优于波段比值法。     

The Azuara impact structure (Spain): new insights from geophysical and geological investigations

A progress report on geophysical and geological investigations in the 35–40 km diameter Azuara probable impact structure (northeast Spain) is given. The target is a 10 km thick sequence of Palaeozoic, Mesozoic, and Cenozoic sediments. Gravity measurements establish a negative residual anomaly of about 100m/s² and a mass deficiency of 1.24×10¹⁴ kg. They suggest the existence of a buried inner ring with half the size of the outer ring. The result of preliminary model calculations is compatible with the assumption of a flat structure only a few kilometers deep. Measurements of the total intensity of the Earth's magnetic field do not indicate causative bodies related to the structure. Geological mapping reveals a tectonic style which is characterized by folds and faults with radial and tangential elements and a strong horizontal component. Ejecta, abundant monomict and polymict breccias, dislocated megablocks, inverted stratigraphy, and a megabreccia up to 80 m thick in the outer ring are evidence for intense and violent deformation. Networks of typical breccia dikes well-known from many impact structure cut through nearly all stratigraphical units. Various types and generations of breccia dikes occur. In addition to previously described shock deformation in quartz and mica, we present further evidence of high-pressure and high-temperature signatures in rocks. The age of the impact is estimated to be Upper Eocene or Oligocene. We conclude that the formation of the Azuara structure is difficult to explain by mechanisms other than impact, and we discuss our observations within the scope of the contact/compression, excavation, and modification stages of impact cratering with special attention directed to the peculiarities of the Azuara sedimentary target.

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Zusammenfassung Es wird über geophysikalische und geologische Untersuchungen in der Struktur von Azuara berichtet. Sie liegt in Nordost-Spanien, ist nach der gängigen Klassifikation eine wahrscheinliche komplexe Impakt-Struktur, hat einen Durchmesser von 35–40 km und ist in etwa 10 km mächtigen Sedimenten angelegt. Schweremessungen erbringen eine Restfeld-Anomalie von etwa –100m/s² (–10 mgal) und ein Massendefizit von 1,24×10¹⁴ kg. Kleinräumige Anomalien können als Ausdruck eines inneren Ringes gedeutet werden; sein Durchmesser wäre grob halb so groß wie der des morphologischen Ringes. Einfache Modellrechnungen sind mit der Annahme einer sehr flachen Struktur anomaler Dichte verträglich. Messungen der Totalintensität des Erdmagnetfeldes geben keine Hinweise auf Störkörper, die mit der Entstehung der Struktur in Verbindung gebracht werden könnten. Nach Kartierungen und strukturgeologischen Untersuchungen ist ein tektonischer Stil gegeben, der radiale und tangentiale Elemente mit ausgeprägter horizontaler Komponente aufweist. Auswurfmassen, viele und verschiedenartige monomikte und polymikte Brekzien, dislozierte Schollen, inverse Stratigraphie und eine bis zu 80 m mächtige Megabrekzie im Bereich des morphologischen Ringes belegen ungewöhnliche und energiereiche Deformationen. Charakteristische Brekziengänge, die von vielen Impakt-Strukturen bekannt sind, durchschlagen nahezu alle stratigraphischen Einheiten. Verschiedenartige Typen und Mehrfach-Generationen von Brekziengängen treten auf. Früheren Beobachtungen von Schockeffekten in Mineralen werden neue Befunde zu Hochdruck- und Hochtemperatur-Einwirkungen hinzugefügt. Beim gegenwärtigen Stand der Kenntnisse ist es schwer, endogene Prozesse zur Entstehung der Azuara-Struktur heranzuziehen; die Annahme eines Impakts, der in das obere Eozän oder ins Oligozän datiert wird, ist zwingend. Die wesentlichen Phasen der Kraterbildung, soweit sie Lehrbuchwissen geworden sind, werden für die Azuara-Struktur erörtert.

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Resumen Se presenta un informe detallado sobre las investigaciones geofísicas y geológicas realizadas en la probable estructura de impacto (compleja) de Azuara, con un diåmetro de 35–40 Km. Las medidas gravimétricas establecen una anomalia residual de alrededor de –100 m/s² (–10 mgal) y una deficiencia de masa de 1.24×10¹⁴ Kg. Estas medidas sugieren la existencia de un anillo interno soterrado con un diámetro cuyo valor es la mitad del anillo externo. El resultado de los cálculos en un modelo preliminar es compatible con la admisión de una estructura plana de únicamente pocos kilómetros de profundidad. Las medidas de intensidad total de campo magnético terrestre descartan la presencia en profundidad de un cuerpo causante de la estructura. El mapa geológico revela un estilo tectónico caracterizado por pliegues y fallas con elementos radiales y tangenciales, y un fuerte componente horizontal. Ejecta, abundantes brechas monomícticas y polimícticas, megabloques dislocados, estratigrafia invertida, y una megabrecha de más de 80 m. de espesor loealizada en el anillo externo, constituyen evidencias de una deformación intensa y violenta. Redes de típicos diques de brecha, bien conocidos en otras estructuras de impacto, cortan casi todas las unidades estratigråficas. Pueden observarse varios tipos y generaciones de diques de brecha. Además de la previamente descrita deformación por efecto de choque en granos de cuarzo y mica, nosotros presentamos evidencias adicionales de efectos en las rocas generados a altas presiones y temperaturas. La edad de la estructura puede ser o Eoceno superior o Oligoceno. Concluimos que la formación de la estructura de Azuara es difícil de explicar por cualquier otro mecanismo que no sea un impacto, y discutimos nuestras observaciones dentro del ámbito de los estadios de contacto/compresión, excavación, y modificatión (presentes en la craterización por impacto), haciendo hincapié en las peculiaridades del objetivo sedimentario de Azuara.

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Overview of some recent geophysical investigations in Himalaya

Recent work on long-period surface wave dispersion investigations and other geophysical work have shown that in the Himalayan and Tibet Plateau region the crust is extremely thick and the velocities are low: However, the upper mantle below Tibet appears to have normal velocities. Seismic Research Observatories, being established in the vicinity of Himalaya, will be extremely useful for near-source investigations due to their digital data acquisition capabilities and much larger dynamic range. Quantitative seismicity maps prepared for the Himalayan region are useful in comprehending regional tectonics. With international collaboration, Deep Seismic Sounding surveys have been successfully carried out in western Himalaya. It is inferred that the northern boundary of the Indian Plate does not lie along the Main Central Himalayan Thrust or the Indus Suture line, but falls very much north of the combined Indo-Tibetan block. Focal mechanism studies are, by and large, consistent with the northward thrusting of the Indian Plate. Conflicting results regarding the prevalence of isostasy in the Himalayan region have been obtained from gravity surveys. Geophysical investigations and observational facilities need to be intensified for a better understanding of the tectonics.     

First geophysical and shallow ice core investigation of the Kazbek plateau glacier,Caucasus Mountains

First-ever ice core drilling at Mt. Kazbek (Caucasus Mountains) took place in the summer of 2014. A shallow ice core (18 m) was extracted from a plateau at ~4500 m a.s.l. in the vicinity of the Mt. Kazbek summit (5033 m a.s.l.). A detailed radar survey showed that the maximum ice thickness at this location is ~250 m. Borehole temperature of ?7 °C was measured at 10 m depth. The ice core was analyzed for oxygen and deuterium isotopes and dust concentration. From the observed seasonal cycle, it was determined that the ice core covers the time interval of 2009–2014, with a mean annual snow accumulation rate of 1800 mm w. eq. Multiple melt layers have been detected. δ¹⁸O values vary from ?25 to ?5‰. The dust content was determined using a particle sizing and counting analyzer. The dust layers were investigated using scanning electron microscopy and X-ray diffraction analysis. Dust can be separated into two categories by its origin: local and distant. Samples reflecting predominantly local origin consisted mainly of magmatic rocks, while clay minerals were a characteristic of dust carried over large distances, from the deserts of the Middle East and Sahara. The calculated average dust flux over three years at Kazbek was of 1.3 mg/cm² a^?1. Neither δ¹⁸O nor dust records appear to have been affected by summer melting. Overall, the conditions on Kazbek plateau and the available data suggest that the area offers good prospects of future deep drilling in order to obtain a unique environmental record.     

中国冰川变化对气候变化的响应程度研究

理清冰川变化对气候变化的响应程度、揭示响应度的空间变化规律,是开展冰川变化预估及其对社会经济影响程度量化研究的基础。使用1958-2010年西部地区150个气象站点的夏季平均气温和年降水量资料、中国第一、二次冰川编目数据,通过夏季平均气温和年降水量变化趋势值定量反映气候变化,以冰川面积变化率表征冰川变化,借助GIS技术平台,采用参照对比方法,从宏观层面研究了中国西部冰川变化对气候变化的响应程度。依据等分分类法（Equal Interval）,将响应程度分为极低度响应、低度响应、中度响应、高度响应、极高度响应5级。结果表明：中国冰川变化对气候变化的响应方式与程度不同,对夏季平均气温变化表现为正响应,而对年降水量变化主要表现为负响应,冰川分布区年降水量增加带来的冰川积累量增多不足以抵消因温度升高而增加的消融量,升温是中国西部冰川快速退缩的主导性因素。就整体而言,冰川变化对夏季平均气温变化的响应程度相对较低,但局部地区冰川变化对温度变化高度敏感,响应程度高与极高。不同类型冰川的变化对夏季平均气温变化的响应程度亦不同,海洋型冰川的变化以中高度响应为主,极大陆型冰川的变化主要呈现极低、低响应程度,而大陆型冰川变化的响应程度呈两级化。     

地质调查地球物理技术标准现状与发展趋势

经过近30年的发展,我国地质调查地球物理技术标准从无到有,从零散到成系列,逐步建立了重力勘查、磁力勘查、电法勘查、地震勘查、放射性勘查等系列化的标准体系,为我国地质调查地球物理技术方法规范化工作程序的建立和新方法新技术推广起到重要作用。随着我国地质调查的转型发展,目前已经形成的地球物理勘查技术标准体系不能完全适应当下地质调查的需求。本文总结了我国地质调查地球物理技术标准的发展现状,结合当前我国地质调查转型发展对地球物理方法技术的需求,研究探讨了地球物理勘查技术标准化工作的研究方向和发展趋势。     

天山冰川储量变化和面积变化关系分析研究

冰川储量的变化对海平面和区域水资源、生态环境以及社会经济等有重要影响,但是对大量冰川的储量变化很难通过实地观测获得。基于天山9条监测冰川储量变化的估算结果,通过统计分析,探讨冰川储量变化和面积变化的相互关系,以期通过测定冰川面积变化来估算冰川储量变化。结果表明：冰川储量变化与面积变化具有线性关系,其决定系数为0.67~0.70。加入其他山区冰川样本以后,决定系数并没有提高。其原因在于,一方面对冰川变化监测和冰川储量估算存在误差;另一方面,不同的冰川区由于冰川的类型、规模及区域气候特征的差异,冰川变化对气候变化响应的敏感程度不同。因此,未来不仅需要更多更准确的冰川储量估算,还需要按冰川形态类型和区域分别研究。     

Application of advanced borehole geophysical logging to managed aquifer recharge investigations

Communities and water utilities are increasingly being forced to implement more hydrogeologically complex alternative water supply and storage options to meet increasing freshwater demands. The performance of managed aquifer recharge projects, including aquifer storage and recovery, is controlled by the movement and mixing of stored freshwater and native groundwater, and fluid–rock interactions, which, in turn, are strongly influenced by aquifer heterogeneity. Advanced borehole geophysical logging techniques developed for the oil and gas industry such as neutron-gamma ray spectroscopy, microresistivity imaging, and nuclear magnetic resonance, can provide hitherto unavailable fine-scale data on porosity (total and effective), hydraulic conductivity, salinity, and the mineralogical composition of aquifers. Data on aquifer heterogeneity obtained from advanced borehole geophysics logs, combined with information on larger-scale aquifer hydraulics obtained from pumping tests, have the potential for improving aquifer characterization and modeling needed for feasibility assessments and the design and optimization of the operation of managed aquifer recharge systems.     

Till body morphology and structure related to glacier flow

Tills are described which occur in ridges and mounds arranged both parallel and transverse to the flow direction of the depositing glacier. Field localities are drawn from the English Midlands, Western Canada, and South Victoria Land, Antarctica. The tills retain textural and structural properties associated with glacial transport, and have suffered a minimum of redistribution suhsequent to their release from glacier ice. It is shown that ridges and mounds cannot he explained in terms of preferential till accretion. An alternative mechanism is presented in which form and structurc are a result of redistribution of debris in transport by secondary flows in ice.
Flutings are longitudinal forms which are related to helicoidal flow cells. Fabric distributions, patterns of till thickness, and internal structure support the helicoidal flow hypothesis.
Debris entrainment by Antarctic cold-based glaciers is explained by consideration of the morphology and sedimentology of the ice margin and the pattern of glacier flow. Deposition by sublimation and melt-out produces an upwards succession of (1) undisturbed proglacial deposits; (2) a complex of poorly sorted flow deposits intercalated with sorted and stratified water-lain deposits; (3) foliated till with sub-horizantal jointing and isolated clasts. A section shobbing this succession is described from Taylor Valley, Antarctica.
Transverse asymmetric ridges are related to till stacking by over-folding in the marginal compressive zone of cold-based glaciers. Plastic deformation of the debris-laden ice may be enhanced by incorporated salts. The folding process is illustrated by structures within Taylor glacier, and is used to explain Pleistocene landforms and structures in Shropshirc, England and Taylor Valley, Antarctica.     

Surface geophysical investigations of landslide at the Wiri area in southeastern Korea

A geophysical survey was undertaken at Wiri area of the Andong in southeastern Korea to delineate subsurface structure and to detect the fault zone, which affected the 1997 mountain–hill subsidence and subsequent road heaving initiated by the intense rainfall. Electrical resistivity methods of dipole–dipole array profiling and Schlumberger array sounding and seismic methods of refraction and reflection profiling were used to map a clay zone, which was regarded as the major factor for the landslide. The clay zone was identified in electrical resistivity and seismic sections as having low electrical resistivity (<100 Ωm) and low seismic velocity (<400 m/s), respectively. The clay zone detected by using geophysical methods is well correlated with its distribution from the trench and drill-core data. The results of the electrical and seismic surveys showed that slope subsidence was associated with the sliding of saturated clay along a fault plane trending NNW–SSE and dipping 10°–20° SW. However, the road heaving was caused by the slope movement of the saturated clay along a sub-vertical NNE-trending fault.     

Study of landslides at the archaeological site of Abakainon necropolis (NE Sicily) by geomorphological and geophysical investigations

This paper reports on the investigation of the old landslide body on which the necropolis of Abakainon, an Italian archaeological site, was built about 2400 years ago. This site is located in a geologically complex area of northeastern Sicily, where active tectonics has strongly modified the morphological landscape, as testified by the meandering path of watercourses, widespread presence of paleosurfaces, and deviations of crest line. Previous studies have hypothesized that the necropolis, suddenly destroyed by a catastrophic event in historical times, could have been built on an old landslide body. This represents the starting point of this paper, focused on geomorphological analysis and geophysical surveys, which allowed discovering peculiar elements in support of the landslide theory. In particular, the elaboration of a Digital Terrain Model allowed locating the main morphostructural elements, thus highlighting how the occurrence of landslides in the study area is strongly linked to recent tectonics. Passive seismic surveys, carried out through the acquisition of ambient noise, allowed detecting the presence of impedance contrasts, which were associated to peculiar features, such as the landslide body itself. Moreover, local strong directional effects testify the presence of faults, affecting even the necropolis area. Such results, further corroborated by the outcomes of an electrical resistivity survey, lay the foundations for interesting consideration on the possible cause of the destruction of this site, probably related to the occurrence of a historical earthquake in the first century AD.     

Electrical geophysical and hydrogeological investigations of groundwater aquifers in Ruseifa municipal landfill, Jordan

The effect of the Ruseifa municipal landfill on the shallow groundwater aquifers in the area was investigated in two separate sites. The first one was not used since 1994, whereas the other is still being used for dumping. Fourteen electrical resistivity soundings were performed to detect the leachate and its effect on the quality of the groundwater. Results indicated that the solid waste thickness of the landfill was ranged from 3 to 20 m with resistivity value less than 10 Ω m. Based on the resistivity decreases of values less than 5 Ω m, the leachate was detected in the landfill sites at depths ranged from 10 to 50 m. However, the flow direction of the leachate at depth ranging 10–20 m in the terminated site was toward north, whereas the flow direction of the leachate in the site still used for dumping was toward east–northeast which causes the major source of groundwater pollution.     

Palaeozoic amalgamation of Central Europe: new results from recent geological and geophysical investigations

Multidisciplinary studies of geotransects across the North European Plain and Southern North Sea, and geological reexamination of the Variscides of the North Bohemian Massif, permit a new 3-D reassessment of the relationships between the principal crustal blocks abutting Baltica along the Trans-European Suture Zone (TESZ). Accretion was in three stages: Cambrian accretion of the Bruno–Silesian, Lysogory and Malopolska terranes; end-Ordovician/early Silurian accretion of Avalonia; and early Carboniferous accretion of the Armorican Terrane Assemblage (ATA). Palaeozoic plume-influenced metabasite geochemistry in the Bohemian Massif explains the progressive rifting away of peri-Gondwanan crustal blocks before their accretion to Baltica. Geophysical data, faunal and provenance information from boreholes, and dated small inliers and cores confirm that Avalonian crust extends beyond the Anglo-Brabant Deformation Belt eastwards to northwest Poland. The location and dip of reflectors along the TESZ and beneath the North European Plain suggest that Avalonian crust overrode the Baltica passive margin, marked by a high-velocity lower crustal layer, on shallowly southwest-dipping thrust planes forming the Heligoland–Pomerania Deformation Belt. The “Variscan orocline” of southwest Poland masks two junctions between the Armorican Terrane Assemblage (ATA) and previously accreted crustal blocks. To the east is a dextrally transpressive contact with the Bruno–Silesian and Malopolska blocks, accreted in the Cambrian, while to the north is a thrust contact with easternmost Avalonia, deeply buried beneath younger sedimentary cover. In the northeast Bohemian and Rhenohercynian Massifs Devonian “early Variscide” deformation dominated by WNW and NW-directed thrusting, records closure of Ordovician–Devonian seaways between detached “islands” of the ATA and Avalonia.     

国内主要航空物探飞行平台特点及发展

航空物探是将航空地球物理勘探仪器搭载在不同飞行器上,通过特定的飞行作业方式开展的地球物理勘查技术。航空物探的勘查效果同时受物探仪器性能和所采用的飞行平台及其飞行控制效果的双重影响。根据不同的需求,合理地选择并运用飞行器,是开展航空物探测量工作需要解决的首要任务。笔者在回顾国内航空物探发展的基础上,将主要使用的航空物探飞行器分为固定翼、直升机、无人机及其他等四类,分析每类飞行器作为航空物探搭载平台的优缺点,从持续服务地质勘查的需要出发,展望了航空物探及搭载平台的主要发展方向。     

西藏班公湖-怒江缝合带--深部地球物理结构给出的启示

通过跨越缝合带的综合地球物理和地质调查研究,查明了地质上推测的“班公湖-怒江缝合带”的深部结构和构造,提出了下述观点现有资料尚不足以证明,“班公湖-怒江缝合带”是严格意义上的缝合带,而趋向表明是一个老的弧后拉张区,在后来的印度大陆与拉萨地块碰撞挤压过程中,先是沉积了巨厚的第三纪地层,仅在20Ma(?)以来才转变成挤压体制,形成多条逆冲断裂;纳木错-申扎逆冲的蛇绿岩片带代表着侏罗纪洋的主要缝合带位置,在其闭合过程中洋壳与陆壳一起向北发生俯冲,并形成班戈岩带所代表的岩浆弧,在岩浆弧后出现了拉张区;下地壳向北挤压增厚,物理性质不同的上、下地壳之间相互运动而形成了一条缓倾的剪切片理化带,南北长达300km,命名为主羌塘逆冲断裂带(MQT);并使班戈岩片整体向南逆推上去,致使地壳分层增厚;在拉张期伦坡拉小地块向下运动,20Ma以后转变成压缩体制后又开始向上逆推,再加上后期的剥蚀,致使班戈深成岩体出露于地表;唐古拉山、各拉丹冬等年轻的火山岩浆带与地表显示的构造活动无直接关系,推测应是地壳深层作用引起的构造岩浆活动的显示。     

Geological results of recent geophysical investigations in the Harz Mountains (Germany)

For the investigation of the tectonical situation of the Harz mountains various geophysical surveys were carried out during recent years. These included reflection seismic and refraction seismic lines crossing the Harz in NNE-SSW direction east of Clausthal-Zellerfeld. To complement this data magnetotelluric recordings were acquired in the same area, and a detailed gravity survey covered mainly the northern Harz margin. The investigations were directed primarily to test any evidence for overthrusting along the Harz margin with the possibility of less-consolidated sediments bearing hydrocarbon potential below the more-consolidated Harz sediments of mainly Lower Carboniferous or older age.The reflection seismic lines show mainly discontinuous reflections in several bands, but no single predominant reflection, similar e.g. to that of the Aachen — Faille du Midi overthrust in the western Rhenish Massif has been observed. As a main result of the refraction line the existence of a refracting horizon at a depth of less than 1 km in the NE (between Altenau and Bad Harzburg) has been shown dipping about 3 to 4 degrees to the SW to a depth of about 2500 m (near Herzberg) and continuing further to the south. The refraction velocity of 6250 m/s together with its geological setting favour an interpretation which associates this horizon with the top of the granitic intrusion of the Brocken pluton. It appears to underly the Harz and its southern foreland in great areal extent. No evidence for significant seismic inversion layers has been observed.The results of the magnetotelluric investigations are best explained by unconsolidated and electrically conductive sediments of the northern Harz foreland reaching south below the Harz paleozoic only about 2 km from the northern Harz margin.This agrees with the gravity field of the northern Harz margin which shows that the main increase of the Bouguer anomaly is within a zone of a few kilometers south of the boundary between mesozoic foreland sediments and the Harz paleozoic at the surface. Moreover, many tectonic details of the foreland and the internal tectonic units of the Harz show up on the map of the Bouguer anomaly.

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Zusammenfassung Zur Untersuchung der tektonischen Situation im Harz wurden in den vergangenen Jahren verschiedene geophysikalische Messungen durchgeführt. Dabei wurden reflektionsseismische Profile und eine refraktionsseismische Linie in NNE-SSW-Richtung quer zum Streichen des Harzes östlich von Clausthal-Zellerfeld vermessen. Zusätzlich wurden in diesem Gebiet magnetotellurische Messungen durchgeführt und der Harz und sein nördliches Vorland mit einem dichten Netz von Schwerestationen überdeckt. Diese Untersuchungen waren hauptsächlich darauf ausgerichtet, Anzeichen für Überschiebungen am Harzrand erkennen zu lassen. Unter einer solchen Überschiebung könnten sich möglicherweise weniger konsolidierte Sedimente mit Kohlenwasserstoff-Potential unter dem stärker konsolidierten Harz-Paläozoikum befinden.Die reflektionsseismischen Linien zeigen hauptsächlich diskontinuierliche Reflexionen in mehreren Bändern, aber keine einzelne dominierende Reflexion, welche vergleichbar wäre mit derjenigen der Aachener Überschiebung — Faille du Midi im westlichen Rheinischen Schiefergebirge.Als ein Hauptergebnis des Refraktionsprofiles konnte die Existenz eines Refraktionshorizontes in einer Teufe von weniger als 1 km nördlich von Altenau gezeigt werden, der etwa 3 bis 4 Grad nach SW einfällt, am Südrand des Harzes (bei Herzberg) in etwa 2500 m Tiefe liegt und sich weiter nach Süden fortsetzt. Die Refraktionsgeschwindigkeit von 6250 m/s und die geologische Situation deuten darauf hin, daß dieser Refraktor identisch ist mit der Oberfläche der granitischen Intrusion des Brocken-Plutons. Er scheint den Harz und sein südliches Vorland großflächig zu unterlagern. Anzeichen für Inversionen der seismischen Geschwindigkeit konnten nicht beobachtet werden.Die Ergebnisse der magnetotellurischen Untersuchungen lassen sich am besten deuten, wenn unkonsolidierte, leitfähige Sedimente des nördlichen Vorlandes nur etwa 2 km vom nördlichen Harzrand nach Süden unter das Paläozoikum des Harzes reichen.Dies stimmt überein mit den Ergebnissen des Schwerefelds am Harz-Nordrand, welches zeigt, daß die Hauptzunahme der Bouguer-Anomalie innerhalb einer wenige Kilometer breiten Zone südlich der Grenze zwischen den mesozoischen Vorlandsedimenten und dem Harz-Paläozoikum erfolgt. Viele tektonische Details aus dem Vorland und den internen Einheiten des Harzes lassen sich auf der Karte der Bouguer-Anomalie erkennen.

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Résumé Dans le cadre de l'investigation tectonique du massif du Harz, diverses missions géophysiques ont été effectuées ces dernières années. Elles comportaient des profils de sismiqueréflexion et un profil de réfraction NNE-SSW traversant le Harz à l'est de Clausthal-Zellerfeld. En complément de ces données, des enregistrements de courants magnéto-telluriques furent effectués dans la même région ainsi qu'un relevé gravimétrique par un réseau dense de stations couvrant la montagne du Harz et son avant-pays septentrional. Ces recherches ont été conduites principalement pour mettre en évidence un éventuel chevauchement le long de la bordure du Harz. Ceci aurait impliqué la possibilité de trouver sous les sédiments consolidés du Harz, appartenant en grande partie au Paléozoïque, des sédiments moins consolidés possédant un potentiel en hydrocarbures.Les réflexions observées sur les profils sismiques se répartissent en bandes généralement discontinues mais ne montrent aucun réflecteur prédominant semblable à celui d'Aachen-Faille du Midi dans la partie Ouest du Massif schisteux Rhénan. Le résultat principal de la sismique que-réfraction a été de mettre en évidence un horizon qui se trouve à une profondeur de moins de 1 km au NE — entre Altenau et Bad Harzburg — et qui plonge de 3 à 4 degrés vers le SW atteignant une profondeur de 2.5 km près de Herzberg, à la limite du Harz, et se poursuivant plus au sud. La vitesse de réfraction de 6250 m/s ainsi que la situation géologique permettent une interprétation selon laquelle cet horizon coïncide avec le toit du pluton granitique de Brocken. Celui-ci apparaît comme étant omniprésent sous le Harz et ses contreforts méridionaux. Aucune inversion des vitesses sismiques avec la profondeur n'a été observée.Les résultats des mesures magnéto-telluriques s'expliquent le mieux par la présence de sédiments non consolidés de bonne conductivité électrique s'enfonçant sous les roches paléozoïques du Harz, depuis la limite nord du massif, sur une distance d'environ 2 km.Ces résultats sont en accord avec ceux du levé gravimétrique de la limite nord du Harz, qui indiquent que l'augmentation la plus importante de l'anomalie de Bouguer a lieu dans une zone de quelques kilomètres de large, bordant au sud la limite entre les sédiments mésozoïques de l'avant-pays et le Paléozoïque du Harz. De plus, de nombreux éléments tectoniques de détail, tant à l'extérieur qu'à l'intérieur du massif, sont reconnaissables sur la carte de l'anomalie de Bouguer.

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Podzol development, vegetation change and glacier variations at Haugabreen, southern Norway

¹⁴C dating and pollen analysis of the surface organic (LFH) horizons of several humo-ferric podzol profiles forming a soil catena close to the 'Little Ice Agc' outer moraine ridge of Haugabreen, southern Norway, are used to examine the timing and nature of podzol development at the low-/sub-alpine margin of the Jostedalsbreen area. Comparison with results from a palaeosol buried beneath the outer moraine shows that FH horizon development began as early as 5,265 ± 65 B.P., but that it was not synehronous across the profiles, the latest profile having a date of 3,590 ± 65 B.P. It is argued that surface organic horizons developed as a response to a deterioration of climate and possibly the recrudescence of the Myklebustbreen ice cap at c . 5,000 B.P., and that the dates for horizon initiation vary according to local topographic and soil-hydrologic conditions. It is still uncertain whether the hump-ferric podzols were preceded by brown earths or weakly podzolised sub-alpine podzolic soils, but at all sites where pollen evidence is available it appears that FH initiation took place beneath Betula woodland.