550 Geowissenschaften
Refine
Has Fulltext
- yes (108)
Is part of the Bibliography
- yes (108)
Year of publication
Document Type
- Journal article (108) (remove)
Keywords
- remote sensing (15)
- Geographie (8)
- climate change (6)
- time series (6)
- Niger (5)
- earth observation (5)
- forest (5)
- review (5)
- MODIS (4)
- Sentinel-1 (4)
- drought (4)
- machine learning (4)
- Earth Observation (3)
- Earth observation (3)
- Landsat (3)
- South Africa (3)
- dynamics (3)
- land cover (3)
- permafrost (3)
- Antarctic ice sheet (2)
- Antarctica (2)
- Geologie (2)
- Germany (2)
- Google Earth Engine (2)
- Kilombero (2)
- NDVI (2)
- SAR (2)
- Sahara (2)
- Sentinel-2 (2)
- TanDEM-X (2)
- biodiversity (2)
- change detection (2)
- deep learning (2)
- forecast (2)
- forest ecology (2)
- geomorphology (2)
- glaciers (2)
- global change (2)
- hydrology (2)
- land use (2)
- movement ecology (2)
- object-based classification (2)
- optical remote sensing (2)
- probability (2)
- random forest (2)
- satellite data (2)
- supraglacial lakes (2)
- time series analysis (2)
- wetland (2)
- 3D (1)
- 3D remote sensing (1)
- 3‐D electrical resistivity imaging (1)
- AVHRR (1)
- Aggeneys (1)
- Alps (1)
- Analyse (1)
- Angola (1)
- Animal Tracking (1)
- Antarktis (1)
- Asia (1)
- Bavaria (1)
- Bilma <Region> (1)
- Biostratigraphy (1)
- Blue Spot Analysis (1)
- Broken Hill (1)
- CORDEX Africa (1)
- Cambrian (1)
- Covid‐19 (1)
- DEM (1)
- DEUQUA (1)
- DInSAR (1)
- DSM (1)
- Dongting Lake (1)
- ERT (1)
- Einzelhandel (1)
- El Niño (1)
- Elissen-Palm flux (1)
- Erbendorf (1)
- Erholungsplanung (1)
- Europe (1)
- Extreme flows (1)
- Eyjafjallajökull 2010 (1)
- Fractional cover analysis (1)
- Fulgurite (1)
- GEDI (1)
- GPS-Tracking (1)
- GSV (1)
- Gamsberg (1)
- Ghana (1)
- GlobALS (1)
- Global Ecosystem Dynamics Investigation (1)
- Google Earth Engine (GEE) (1)
- Greenland ice sheet (1)
- Herodotus (1)
- Himalaya Karakoram (1)
- Holocene (1)
- Holozän (1)
- Hunsrueck (1)
- InSAR (1)
- InSAR height (1)
- Indus-Ganges-Brahmaputra-Meghna (1)
- Isheru (1)
- Karst (1)
- Karstverfüllungen (1)
- Kontinentales Tiefbohrprogramm der Bundesrepublik Deutschland (1)
- Kunduz River Basin (1)
- LST (1)
- Land Change Modeler (1)
- Landsat archive (1)
- Landsat time series (1)
- Lantana camara (1)
- LiDAR (1)
- MODIS time-series (1)
- Mann-Kendall test (1)
- Markov chains (1)
- Mekong (1)
- Mikrosonde (1)
- Mineralogie (1)
- Morocco (1)
- NDVI thresholds (1)
- Nachhaltigkeitstransformation (1)
- Namibia (1)
- Neolithic (1)
- Niger <Ost> (1)
- Nile delta (1)
- Nile flow (1)
- Nordvictorialand (1)
- Oman (1)
- Oshana (1)
- Ostniger (1)
- PEST (1)
- Pakistan (1)
- Paläoklima (1)
- PlanetScope (1)
- Pleistozän (1)
- R (1)
- Ramsar Convention on Wetlands (1)
- RapidEye (1)
- Reliefgeschichte (1)
- SBAS (1)
- SDG 11.3.1 (1)
- SOC content prediction (1)
- SPOT-6 (1)
- SWAT (1)
- SWAT model (1)
- Sahel (1)
- Sandstein (1)
- Scenario analysis (1)
- Schmuckperle (1)
- Sebennitic (1)
- Sentine-1 (1)
- Sentinel–1 (1)
- Silicate (1)
- Snow Line Elevation (1)
- Soil and Water Assessment Tool (SWAT) (1)
- Southeast Asia (1)
- Swabian Alb (1)
- Systematics (1)
- Sápmi (1)
- TIMELINE (1)
- Tanzania (1)
- Tell Basta (1)
- Tepl-Taus (1)
- Tian Shan (1)
- Trilobita (1)
- UAV (1)
- Uzbekistan (1)
- Vohenstrauß (1)
- WaSiM-ETH (1)
- West Africa (1)
- West Gondwana (1)
- Western Cape (1)
- Western Europe (1)
- Wilson Terrane (1)
- Wilson Terrane ; intrusions ; mafic composition ; relative age ; petrographic analysis ; gabbroic composition ; subduction zones (1)
- Zambia (1)
- accuracy (1)
- agricultural drought (1)
- agricultural mapping (1)
- agriculture (1)
- air quality (1)
- alpha diversity (1)
- ancient Egypt (1)
- anthroposphere (1)
- aquaculture (1)
- atmospheric circulation (1)
- atmospheric correction (1)
- atmospheric waves (1)
- automatic processing (1)
- base metal deposit (1)
- beech (1)
- beta diversity (1)
- big earth data (1)
- biosphere (1)
- black carbon AOD (1)
- boreholes (1)
- burned area (1)
- calc-silicate rocks; fluid behaviour; P-T path; reaction textures; Variscan basement; very high-pressure metamorphism (1)
- canopy height (1)
- causal networks (1)
- change vector analysis (1)
- circulation patterns (1)
- circulation type (1)
- circum-Arctic (1)
- class homogeneity (1)
- climate extremes (1)
- climate related trends (1)
- climate scenarios (1)
- climatic change (1)
- coal (1)
- coal fire (1)
- coal mining area (1)
- coastal erosion (1)
- coastal zone (1)
- coastline dynamics (1)
- composition (1)
- conservation (1)
- consumptive water use (1)
- convolutional neural network (1)
- crop statistics (1)
- cryosphere (1)
- culturable command area (1)
- damage assessment disaster (1)
- database (1)
- debris-covered glaciers (1)
- digitalisation initiative (1)
- disaster (1)
- distributary (1)
- diurnal (1)
- drainage ratio (1)
- drilling (1)
- driving forces (1)
- drought impact (1)
- drought stress indicators (1)
- eCognition (1)
- earthquake (1)
- electrical resistivity tomography (1)
- emissivity (1)
- energy (1)
- entrainment (1)
- environmental justice (1)
- environmental modeling (1)
- error estimation (1)
- eruption rate (1)
- evapotranspiration (1)
- explosive volcanism (1)
- e‐commerce (1)
- feature tracking (1)
- fire (1)
- flood (1)
- floodpath lake (1)
- food production (1)
- forest disturbances (1)
- forest hydrology (1)
- forest monitoring (1)
- forest resources inventory (1)
- forest structure Germany (1)
- framing (1)
- fulgurites (1)
- function (1)
- galamsey (1)
- gamma diversity (1)
- general circulation model (1)
- geoarchaeology (1)
- geomorphologie (1)
- gis (1)
- global (1)
- global warming (1)
- grassland (1)
- ground penetrating radar (1)
- groundwater (1)
- ground‐penetrating radar (1)
- harmonization (1)
- hazard maps (1)
- heat wave (1)
- historical (1)
- hotspot analysis (1)
- human disturbance (1)
- human pressure (1)
- hydrological drought (1)
- hydrological modelling (1)
- hydrological regime (1)
- ice sheet dynamics (1)
- ice sheet hydrology (1)
- image (1)
- image artifacts (1)
- impervious surface (1)
- indicator importance assessment (1)
- infrasound (1)
- integration (1)
- intercomparison (1)
- interferometry (1)
- interpolation (1)
- inundation (1)
- inverse parameterization (1)
- irrigated agriculture (1)
- irrigation (1)
- irrigation pricing (1)
- jet stream (1)
- jets (1)
- karst siliceux (1)
- land cover change (1)
- land surface (1)
- land surface temperature (1)
- land surface temperature (LST) (1)
- land use change (1)
- land use/cover pattern (LUCP) (1)
- land-use/land-cover change (1)
- landcover changes (1)
- landsat (1)
- landscape metrics (1)
- landslides (1)
- large‐scale atmospheric circulation modes (1)
- lava (1)
- letzte Meile (1)
- lightning (1)
- loess plateau (1)
- lokaler Onlinemarktplatz (1)
- loss (1)
- low-cost applications (1)
- management (1)
- mass (1)
- metamorphic sulfidation (1)
- meteorological drought (1)
- mineralization (1)
- mining (1)
- modeling (1)
- models (1)
- mountains (1)
- multi-sensor (1)
- multi-spectral (1)
- multispectral VNIR (1)
- multitemporal metrics (1)
- multi‐model ensemble (1)
- nature conservation (1)
- near-field monitoring (1)
- near-surface geophysics (1)
- networking (1)
- nu SVR (1)
- object-based image analysis (1)
- oil spill (1)
- optical diversity (1)
- optimization (1)
- palaeoclimatology (1)
- palaeontology (1)
- palaeosols (1)
- paleoclimate (1)
- paleoenvironment (1)
- palsa development (1)
- paléoclimat (1)
- pan (1)
- partial correlation (1)
- peatland (1)
- penetration bias (1)
- performance assessment (1)
- periglacial (1)
- periurban (1)
- phenology (1)
- pilot-point-approach (1)
- platform economy (1)
- plumes (1)
- polarimetery (1)
- pollution (1)
- ponds (1)
- population change (1)
- post-classification comparison (1)
- predictive performance (1)
- preface (1)
- protection status (1)
- pulsating explosive eruptions (1)
- radar (1)
- random forest regression (1)
- regional climate model (1)
- reliability (1)
- renewable energy (1)
- resource mapping (1)
- resource suitability (1)
- retrogressive thaw slump (1)
- river discharge (1)
- robust change vector analysis (1)
- rock glaciers (1)
- sacred lakes (1)
- sar (1)
- satellite remote sensing (1)
- scenario analysis (1)
- seasonal (1)
- seasonal dynamics (1)
- seasonality (1)
- sedimentology (1)
- segmentation (1)
- semantic segmentation (1)
- sensitivity analysis (1)
- sentinel (1)
- sentinel-2 (1)
- silicate karst (1)
- slope bogs (1)
- snow cover area (1)
- snow hydrology (1)
- snow parameters (1)
- snow variability (1)
- snowmelt runoff model (1)
- soil matric potential (1)
- source parameters (1)
- southern annular mode (1)
- spatial analysis (1)
- spatial scale (1)
- spatial water balance (1)
- spatiotemporal slump development (1)
- species (1)
- spectral diversity (1)
- spectral variation hypothesis (1)
- spring flood (1)
- statistical modeling (1)
- storage volume (1)
- stream flow (1)
- structure (1)
- sub-pixel coastline extraction (1)
- subpixel (1)
- subsidence (1)
- subsurface hydrology (1)
- sulfide inclusions (1)
- surface melt (1)
- surface reflectances (1)
- surface urban heat island (SUHI) (1)
- surface water (1)
- surface water area (1)
- sustainable irrigation system (1)
- synthetic aperture RADAR (1)
- tasselled cap (1)
- temperature (1)
- thermal infrared (1)
- thunderstorms (1)
- tikhonov regularization (1)
- time-series features (1)
- training sample migration (1)
- trend analysis (1)
- trends (1)
- two‐sided markets (1)
- uncertainties (1)
- uncertainty (1)
- uneven-aged mountainous (1)
- urban climate (1)
- urban environments (1)
- urbane Logistik (1)
- vDEUQUA2021 (1)
- validation (1)
- value of water (1)
- variability (1)
- vegetation indices (1)
- vegetation restoration (1)
- volcano (1)
- volcanoes (1)
- water (1)
- water balance (1)
- water dynamics (1)
- water management (1)
- water retention (1)
- water yield (1)
- wetland mapping (1)
- wind speed (1)
Institute
EU-Project number / Contract (GA) number
- 20-3044-2-11 (1)
- 308377 (1)
- 776019 (1)
The new ellipsocephaloid trilobite species Kingaspidoides spinirecurvatus has a spectacular morphology because of a unique set of two long and anteriorly recurved spines on the occipital ring and the axial ring of thoracic segment 8. Together with the long genal spines this whimsical dorsally directed spine arrangement is thought to act as a non-standard protective device against predators. This is illustrated by the body posture during different stages of enrolment, contrasting with the more sophisticated spinosities seen in later trilobites, which are discussed in brief. Kingaspidoides spinirecurvatus from the lower–middle Cambrian boundary interval of the eastern Anti-Atlas in Morocco has been known for about two decades, with specimens handled as precious objects on the fossil market. Similar, but far less spectacular, spine arrangements on the thoracic axial rings are known from other ellipsocephaloid trilobites from the Anti-Atlas of Morocco and the Franconian Forest region of Germany. This suggests that an experimental phase of spine development took place within the Kingaspi-doides clade during the early–middle Cambrian boundary interval.
In recent years, the midlatitudes are characterized by more intense heatwaves in summer and sometimes severe cold spells in winter that might emanate from changes in atmospheric circulation, including synoptic‐scale and planetary wave activity in the midlatitudes. In this study, we investigate the heat and momentum exchange between the mean flow and atmospheric waves in the North Atlantic sector and adjacent continents by means of the physically consistent Eliassen–Palm flux diagnostics applied to reanalysis and forced climate model data. In the long‐term mean, momentum is transferred from the mean flow to atmospheric waves in the northwest Atlantic region, where cyclogenesis prevails. Further downstream over Europe, eddy fluxes return momentum to the mean flow, sustaining the jet stream against friction. A global climate model is able to reproduce this pattern with high accuracy. Atmospheric variability related to atmospheric wave activity is much more expressed at the intraseasonal rather than the interannual time‐scale. Over the last 40 years, reanalyses reveal a northward shift of the jet stream and a weakening of intraseasonal weather variability related to synoptic‐scale and planetary wave activity. This pertains to the winter and summer seasons, especially over central Europe, and correlates with changes in the North Atlantic Oscillation as well as regional temperature and precipitation. A very similar phenomenon is found in a climate model simulation with business‐as‐usual scenario, suggesting an anthropogenic trigger in the weakening of intraseasonal weather variability in the midlatitudes.
The heavily debris-covered Inylchek glaciers in the central Tian Shan are the largest glacier system in the Tarim catchment. It is assumed that almost 50% of the discharge of Tarim River are provided by glaciers. For this reason, climatic changes, and thus changes in glacier mass balance and glacier discharge are of high impact for the whole region. In this study, a conceptual hydrological model able to incorporate discharge from debris-covered glacier areas is presented. To simulate glacier melt and subsequent runoff in the past (1970/1971–1999/2000) and future (2070/2071–2099/2100), meteorological input data were generated based on ECHAM5/MPI-OM1 global climate model projections. The hydrological model HBV-LMU was calibrated by an automatic calibration algorithm using runoff and snow cover information as objective functions. Manual fine-tuning was performed to avoid unrealistic results for glacier mass balance. The simulations show that annual runoff sums will increase significantly under future climate conditions. A sensitivity analysis revealed that total runoff does not decrease until the glacier area is reduced by 43%. Ice melt is the major runoff source in the recent past, and its contribution will even increase in the coming decades. Seasonal changes reveal a trend towards enhanced melt in spring, but a change from a glacial-nival to a nival-pluvial runoff regime will not be reached until the end of this century.
Peatlands located on slopes (herein called slope bogs) are typical landscape units in the Hunsrueck, a low mountain range in Southwestern Germany. The pathways of the water feeding the slope bogs have not yet been documented and analyzed. The identification of the different mechanisms allowing these peatlands to originate and survive requires a better understanding of the subsurface lithology and hydrogeology. Hence, we applied a multi-method approach to two case study sites in order to characterize the subsurface lithology and to image the variable spatio-temporal hydrological conditions. The combination of Electrical Resistivity Tomography (ERT) and an ERT-Monitoring and Ground Penetrating Radar (GPR), in conjunction with direct methods and data (borehole drilling and meteorological data), allowed us to gain deeper insights into the subsurface characteristics and dynamics of the peatlands and their catchment area. The precipitation influences the hydrology of the peatlands as well as the interflow in the subsurface. Especially, the geoelectrical monitoring data, in combination with the precipitation and temperature data, indicate that there are several forces driving the hydrology and hydrogeology of the peatlands. While the water content of the uppermost layers changes with the weather conditions, the bottom layer seems to be more stable and changes to a lesser extent. At the selected case study sites, small differences in subsurface properties can have a huge impact on the subsurface hydrogeology and the water paths. Based on the collected data, conceptual models have been deduced for the two case study sites.
The use of inverse methods allow efficient model calibration. This study employs PEST to calibrate a large catchment scale transient flow model. Results are demonstrated by comparing manually calibrated approaches with the automated approach. An advanced Tikhonov regularization algorithm was employed for carrying out the automated pilot point (PP) method. The results indicate that automated PP is more flexible and robust as compared to other approaches. Different statistical indicators show that this method yields reliable calibration as values of coefficient of determination (R-2) range from 0.98 to 0.99, Nash Sutcliffe efficiency (ME) range from 0.964 to 0.976, and root mean square errors (RMSE) range from 1.68 m to 1.23 m, for manual and automated approaches, respectively. Validation results of automated PP show ME as 0.969 and RMSE as 1.31 m. The results of output sensitivity suggest that hydraulic conductivity is a more influential parameter. Considering the limitations of the current study, it is recommended to perform global sensitivity and linear uncertainty analysis for the better estimation of the modelling results.
Estimating flood risks and managing disasters combines knowledge in climatology, meteorology, hydrology, hydraulic engineering, statistics, planning and geography - thus a complex multi-faceted problem. This study focuses on the capabilities of multi-source remote sensing data to support decision-making before, during and after a flood event. With our focus on urbanized areas, sample methods and applications show multi-scale products from the hazard and vulnerability perspective of the risk framework. From the hazard side, we present capabilities with which to assess flood-prone areas before an expected disaster. Then we map the spatial impact during or after a flood and finally, we analyze damage grades after a flood disaster. From the vulnerability side, we monitor urbanization over time on an urban footprint level, classify urban structures on an individual building level, assess building stability and quantify probably affected people. The results show a large database for sustainable development and for developing mitigation strategies, ad-hoc coordination of relief measures and organizing rehabilitation.
The 2010 eruption of Eyjafjallajokull volcano was characterized by pulsating activity. Discrete ash bursts merged at higher altitude and formed a sustained quasi-continuous eruption column. High-resolution near-field videos were recorded on 8-10 May, during the second explosive phase of the eruption, and supplemented by contemporary aerial observations. In the observed period, pulses occurred at intervals of 0.8 to 23.4 s (average, 4.2 s). On the basis of video analysis, the pulse volume and the velocity of the reversely buoyant jets that initiated each pulse were determined. The expansion history of jets was tracked until the pulses reached the height of transition from a negatively buoyant jet to a convective buoyant plume about 100 m above the vent. Based on the assumption that the density of the gas-solid mixture making up the pulse approximates that of the surrounding air at the level of transition from the jet to the plume, a mass flux ranging between 2.2 and 3.5 . 10\(^4\) kg/s was calculated. This mass eruption rate is in good agreement with results obtained with simple models relating plume height with mass discharge at the vent. Our findings indicate that near-field measurements of eruption source parameters in a pulsating eruption may prove to be an effective monitoring tool. A comparison of the observed pulses with those generated in calibrated large-scale experiments reveals very similar characteristics and suggests that the analysis of near-field sensors could in the future help to constrain the triggering mechanism of explosive eruptions.
No abstract available.
Dans le Niger oriental, des phénomenes karstiques sont fréquents dans les roches siliceuses: gres, silcretes, croûtes ferrugineuses, roches cristallines. A partir des études géomorphologiques et micromorphologiques, on peut conclure a une kartsification, au sense de production de formes par dissolution. Les résultats permettent de dater du Tertiaire inférieur la principale période de karstification. La répartition régionale des formes induites par cette karstification indique une dépendance probable des conditions paléoclimatiques. Actuellement le karst influe encore sur le développement des autres formes de relief.
A 42 m drilling was pertormed in the depresalon of Bilma, Xawar, NE-Niger. The sediment and pollen records show that after an initial deposition of dune sands there were repeated lake phases which terminated by desiccation and consolidation of spring mounds. The pollen record indicates a continuous presence of savanna vegetation. The record probably covers the period between the Upper Pleistocene and the Late Holocene. The climate was characterised by a monssonal summer rain regime giving effective rain fall of about 450-500 mm per year. Groundwater recharge was possible but estimates of the amount of water resources are difficult because of the karstic system of the escarpment and the nearly unknown hydrogeological situation.
No abstract available
no abstract available
no abstract available
The overarching goal of this research was to explore accurate methods of mapping irrigated crops, where digital cadastre information is unavailable: (a) Boundary separation by object-oriented image segmentation using very high spatial resolution (2.5–5 m) data was followed by (b) identification of crops and crop rotations by means of phenology, tasselled cap, and rule-based classification using high resolution (15–30 m) bi-temporal data. The extensive irrigated cotton production system of the Khorezm province in Uzbekistan, Central Asia, was selected as a study region. Image segmentation was carried out on pan-sharpened SPOT data. Varying combinations of segmentation parameters (shape, compactness, and color) were tested for optimized boundary separation. The resulting geometry was validated against polygons digitized from the data and cadastre maps, analysing similarity (size, shape) and congruence. The parameters shape and compactness were decisive for segmentation accuracy. Differences between crop phenologies were analyzed at field level using bi-temporal ASTER data. A rule set based on the tasselled cap indices greenness and brightness allowed for classifying crop rotations of cotton, winter-wheat and rice, resulting in an overall accuracy of 80 %. The proposed field-based crop classification method can be an important tool for use in water demand estimations, crop yield simulations, or economic models in agricultural systems similar to Khorezm.
Wetlands in West Africa are among the most vulnerable ecosystems to climate change. West African wetlands are often freshwater transfer mechanisms from wetter climate regions to dryer areas, providing an array of ecosystem services and functions. Often wetland-specific data in Africa is only available on a per country basis or as point data. Since wetlands are challenging to map, their accuracies are not well considered in global land cover products. In this paper we describe a methodology to map wetlands using well-corrected 250-meter MODIS time-series data for the year 2002 and over a 360,000 km2 large study area in western Burkina Faso and southern Mali (West Africa). A MODIS-based spectral index table is used to map basic wetland morphology classes. The index uses the wet season near infrared (NIR) metrics as a surrogate for flooding, as a function of the dry season chlorophyll activity metrics (as NDVI). Topographic features such as sinks and streamline areas were used to mask areas where wetlands can potentially occur, and minimize spectral confusion. 30-m Landsat trajectories from the same year, over two reference sites, were used for accuracy assessment, which considered the area-proportion of each class mapped in Landsat for every MODIS cell. We were able to map a total of five wetland categories. Aerial extend of all mapped wetlands (class “Wetland”) is 9,350 km2, corresponding to 4.3% of the total study area size. The classes “No wetland”/“Wetland” could be separated with very high certainty; the overall agreement (KHAT) was 84.2% (0.67) and 97.9% (0.59) for the two reference sites, respectively. The methodology described herein can be employed to render wide area base line information on wetland distributions in semi-arid West Africa, as a data-scarce region. The results can provide (spatially) interoperable information feeds for inter-zonal as well as local scale water assessments.
The mineralogical and chemical characteristics of fulgurites ( = natural glasses forrned by lightning strikes to the ground) from the southern Centrat Sahara (Niger) are presented. The fulgurites are indicators of thunderstorms. The northernmost important fulgurite formation in the study area reached up to about l8°N, with decreasing fulgurite concentration from south to north. Their distribution pattern and the relative dating of their formation in relation to Iandscape history from the Late Pleistocene onwards (e.g., palaeolakes, palaeosols), and to Neolithic settlement reveals their value as palaeoenvironmental indicators. They indicate: (1) local palaeoenvironmental conditions depending on the topographical situation in a complex dune relief; (2) climatic change during the mid-Holocene from northerly rains to southerly rains; and (3) the northernmost Iimit of important thunderstorrns and rainfall activity since this time in the southern Centrat Sahara.
Die Arbeit beschreibt im ersten Teil die Auswirkung der Sandstein- und Eisenkrustenverkarstung auf das Plateaurelief des östlichen Niger. Angesprochen werden die abflußlosen Karstdepressionen auf den Plateaudachflächen, die Rolle intensiver Verkarstung bei der Herauspräparierung von Sandsteinsäulen an Hängen, von Plateauspornen und Inselbergen, die Mitwirkung bei der Talbildung sowie Einsturzdolinen an Hängen. Im zweiten Teil wird die Mikromorphologie von Karsthöhlenüberzügen aus der Endphase der phreatischen Karstlösung beschrieben. Oberflächennahe Körner weisen starke Korrosion auf. Phosphor in der wiederausgefällten Matrix und eingekieselte Bakterien deuten auf eine organische Komponente bei der Ausbildung des tertiären Silikatkarsts.
Vorgestellt werden Lösungsformen in karbonatfreien Sandsteinen und Eisenkrusten der östlichen Republik Niger. Diese Formen haben eine außerordentlich weite Verbreitung und sind wesentliche Elemente der Landschaft. Beschrieben werden sowohl auf den Dachflächen der südsaharisch/sahelischen Schichtstufen entwickelte Depressionen mit subterraner Entwässerung als auch an Wadi hängen und steilen Stufenabschnitten gekappte, horizontal bis schräg verlaufende Höhlen und Röhren. Viele dieser Lösungsformen sind zumindest in Resten noch von einer Eisen- oder Kieselkruste ausgekleidet, die u.a. als Indiz für eine Entstehung der Formen im Grundwasserbereich angesehen werden kann. Die Anlage der Karstformen wäre demnach noch vor die Herauspräparierung der Stufen und Inselberge im ausgehenden Tertiär zu stellen. Die Karstformen in nichtkarbonatischen Gesteinen gleichen bis ins Detail denen des Karbonatkarstes. Eine initiale Formung durch äolische oder fluviatile Prozesse oder durch Piping kann ausgeschlossen werden.
Der größte Teil des zentralsaharischen Reliefs ist unter dem Einfluß nicht-arider Klimate gebildet worden. Andererseits gab es im Pleistozän äolisch geprägte aride Phasen, die extremer als heutige gewesen sind. Der Kenntnisstand zur Reliefgeschichte erlaubt es, daraus die Grundzüge der Klimageschichte eines großen Teils der südlich-zentralen Sahara abzuleiten.
Die Karstdepressionen auf den Dachflächen der Schichtstufen in Sahara und Sahel sind im allgemeinen von allochthonen quartären Lockermaterialien verfüllt. Die tieferen Verfüllungsschichten zeigen eine von Norden nach Süden zunehmende Überprägung durch Verwitterungs- und Bodenbildungsprozesse. Die obersten ca. 10 cm der Verfüllungen sind dagegen im ganzen Untersuchungsgebiet relativ uniform ausgebildet. Sie repräsentieren die äolischen Ablagerungen seit der mittelholozänen Aridisierung. Drei Verfiillungsprofile (Seggedim, Termit-Dougoule und Koutous) werden vorgestellt und hinsichtlich ihrer paläoklimatischen Aussagekraft überprüft.
Silicate and iron crust karst pits and sinkholes in eastern Niger are filled with reworked lateritic sediments or with unconsolidated palaeosoils and aeolian deposits. The fillings facies depend on the environmental conditions during deposition. Geomorphological and sedimentological studies on the karst fillings and the interpretation of various karst/filling associations allow an approach to the chronology of landscape development in eastern Niger plateaus.
Der vorliegende Beitrag faßt den derzeitigen Stand der Untersuchungen von Hangrutschungen im Bereich der Frankenhöhe, die im Rahmen des EPOCH-Programmes durchgeführt wurden, zusammen. Nach einer Inventarisierung der regionalen Rutschungsereignisse wird die Rutschung bei Obergailnau in einer geomorphologischen Detailkartierung vorgestellt. Für die Auslösung der Rutschung kommen mehrere Faktoren in Betracht: neben einer erhöhten Rutschungsanfälligkeit aufgrund der geologisch-tektonischen Verhältnisse muß v.a. auch eine Einflußnahme durch die Landnutzung mit berücksichtigt werden. Dazu zählen Steinbrucharbeiten in unmittelbarer Nähe der Rutschung, aber auch Wasserbaumaßnahmen am Schloßberg. In diesem potentielllabilisierten Gebiet kam es nach überdurchschnittlichen Niederschlägen Anfang 1958 zu einer Überschreitung der Belastungsgrenze des Hanges, die sich in einer großflächigen Rutschung äußerte. Die weiteren Untersuchungen sollen zeigen, ob sich die für Obergailnau herausgestellten Faktorenkomplexe im regionalen Rahmen verifizieren lassen.
Am Beispiel von vier Koris l) (Téloua, Barghot, Tazolé, Oufaguédout) des südlichen Air-Vorlandes werden Beobachtungen zum aktuellen morphodynamischen Geschehen dieser Region vorgestellt. Durch die regionalen Unterschiede der durchschnittlichen jährlichen Niederschlagshöhen und durch unterschiedliche Charakteristika ihrer Einzugsgebiete können diese vier Koris als typische Vertreter verschiedener fluviatil/äolischer Formungsgruppen angesehen werden. Der Übergang von vorherrschend fluviatiler zu vorherrschend äolischer Formung liegt dabei im Bereich des Kori Oufaguédout, im östlichen Teil des Untersuchungsraumes. Hier konnte durch mehrere Schürfe auch der zeitliche Übergang zwischen beiden Formungskreisen in der jüngeren Reliefgeschichte nachgewiesen werden.
Calc-silicate rocks occur as elliptical bands and boudins intimately interlayered with eclogites and high-pressure gneisses in the Munchberg gneiss complex of NE Bavaria. Core assemblages of the boudins consist of grossular-rich garnet, diopside, quartz, zoisite, clinozoisite, calcite, rutile and titanite. The polygonal granoblastic texture commonly displays mineral relics and reaction textures such as postkinematic grossular-rich garnet coronas. Reactions between these mineral phases have been modelled in the CaO-Al203-Si02-C02-H2 0 system with an internally consistent thermodynamic data base. High-pressure metamorphism in the calc-silicate rocks has been estimated at a minimum pressure of 31 kbar at a temperature of 630°C with X^oSQ.Gi. Small volumes of a C02-N2-rich fluid whose composition was buffered on a local scale were present at peak-metamorphic conditions. The P-T conditions for the onset of the amphibolite facies overprint are about 10 kbar at the same temperature. A'co., of the H20-rich fluid phase is regarded to have been <0.03 during amphibolite facies conditions. These P-T estimates are interpreted as representing different stages of recrystallization during isothermal decompression. The presence of multiple generations of mineral phases and the preservation of very high-pressure relics in single thin sections preclude pervasive post-peak metamorphic fluid flow as a cause of a re-equilibration within the calc-silicates. The preservation of eclogite facies, very high-pressure relics as well as amphibolite facies reactions textures in the presence of a fluid phase is in agreement with fast, tectonically driven unroofing of these rocks.
No abstract available
An Metabasiten der Zone Erbendorf-Vohenstrauß, der Erbendorfer Grünschieferzone und der Zone Tirschenreuth-Mähring wurden petrographische, geochemische und phasenpetrologische Untersuchungen sowie K-Ar-Mineraldatierungen durchgeführt. In der Zone Erbendorf-Vohenstrauß treten in regionaler Abhängigkeit drei Haupttypen von Metabasiten auf: 1. Flaseramphibolite mit der Paragenese Hornblende + Oligoklas/ Andesin + Granat ± Salit und mit Plagioklas- und / oder Kalksilikat-reichen Flasern findet man hauptsächlich im nördlichen und zentralen Teil der Zone Erbendorf-Vohenstrauß. Geochemisch zeigen sie eine deutliche Anreicherung der inkompatiblen Elemente und der leichten Seltenerdelemente und sind vergleichbar mit modernen Tholeiiten von ozeanischen Inseln oder anomalen Abschnitten mittelozeanischer Rükken. Ein kontinentaler Intraplatten-Charakter scheint nicht gegeben. In der Kontaktaureole von Windisch-Eschenbach wurde ein Teil der Flaseramphibolite kontaktmetamorph überprägt. 2. Schiefrige, teils streifige Amphibolite mit der Paragenese Hornblende + Andesin / Labrador ± Salit dominieren im Süd teil der Zone Erbendorf-Vohenstrauß, erscheinen aber in einzelnen Ausstrichen auch im Norden. Die Streifung entsteht durch Plagioklas- und / oder Kalksilikat-reiche Zwischenlagen. Geochemisch sind diese Amphibolite bei flachen Spurenelement- und Seltenerdelement- Mustern vergleichbar mit modernen Tholeiiten von normalen Abschnitten mittelozeanischer Rücken. Sowohl Flaseramphibolite als auch schiefrige, teils streifige Amphibolite zeigen Übergänge zu massigen, homogenen Amphiboliten. 3. Metagabbros mit der Paragenese Hornblende + Plagioklas ± Biotit und einer grobkörnigen, gabbro iden Textur treten hauptsächlich im Bereich der Schuppenzone Michldorf-Kaimling (VOLL 1960) auf. Geochemisch nehmen sie bei einer schwachen Anreicherung der inkompatiblen Elemente eine Zwischenstellung zwischen Flaseramphiboliten und schiefrigen, teils streifigen Amphiboliten ein. In der Erbendorfer Grünschieferzone treten Metagabbros und schiefrige, teils gestreifte Amphibolite mit der Paragenese Hornblende + Oligoklas ± Epidot ± Chlorit auf. Die Amphibolite wurden z. T. stark retrograd überprägt und dabei auch deformiert. Dies wird auf größere, post-regionalmetamorphe, tektonische Bewegungen, möglicherweise Deckenüberschiebungen zurückgeführt. Geochemisch sind die Metabasite der Erbendorfer Grünschieferzone mit modernen tholeiitischen bis kalkalkalischen, subduktionsgebundenen Basalten vergleichbar. Sie unterscheiden sich damit völlig von den südlich angrenzenden Flaseramphiboliten der Zone Erbendorf-Vohenstrauß und den nördlich benachbarten Amphiboliten des Fichtelgebirges. Dies unterstreicht die Stellung der Erbendorfer Grünschieferzone als eigenständige tektonische Einheit. Im Vergleich mit dem Münchberger Komplex zeigt die Erbendorfer Grünschieferzone große Ähnlichkeit mit der Prasinit-Phyllit-Serie hinsichtlich der tektonischen Stellung, der Lithologie und insbesondere des geochemischen Charakters der Metabasite. Zwischen der Zone Erbendorf-Vohen-strauß und den Münchberger Serien konnten bezüglich der Metabasite dagegen keine Parallelen festgestellt werden. Schiefrige, teils streifige Amphibolite der Zone Tirschenreuth-Mähring mit der Paragenese Hornblende + Andesin ± Salit (± Granat) und hellen Plagioklas- oder Kalksilikat-reichen Lagen sind geochemisch mit modernen Basalten normaler mittel ozeanischer Rücken vergleichbar. Die untersuchten Metabasite dürften die Zusammensetzung des basaltischen Ausgangsmaterials zumindest annähernd wiedergeben. In einigen Fällen wurde jedoch eine sekundäre Mobilisation von Elementen festgestellt: Die kontaktmetamorphe Überprägung eines Teils der Flaseramphibolite in der Kontaktaureole von Windisch-Eschenbach führte zu einer deutlichen Anreicherung von Rb, Li und K und zu einer Abreicherung von Ca, Sr und V, insbesondere aber von Cr und Ni. Die sog. immobilen Elemente Nb, Ce, (P), Zr, Ti, Y, Sc streuen in einem deutlich breiteren Bereich als bei den nicht kontaktmetamorphen Flaseramphiboliten. In einer Probe sind die Seltenerdelemente insgesamt angereichert. Eine Mobilisation von P20 S und den leichten Seltenerdelementen in einigen schiefrigen, teils streifigen Amphiboliten der Zone Erbendorf-Vohenstrauß und in einigen kontaktmetamorphen Flaseramphiboliten wird auf einen Abbau von Apatit im Zuge einer post-regionalmetamorphen, möglicherweise postgranitischen, hydrothermalen Überprägung zurückgeführt. Mineralchemische Untersuchungen ergaben für die Zusammensetzung der Hornblenden aus Amphiboliten der Zone Erbendorf-Vohenstrauß deutliche regionale Unterschiede, die weitgehend unabhängig von der regionalen Verteilung der einzelnen Metabasit-Haupttypen sind. Vergleichende Untersuchungen an Granat untermauern eine vermutete, frühere, eklogitfazielle Überprägung eines Granatamphibolits vom Nordrand der Zone Erbendorf-Vohenstrauß bei Hauxdorf. K-Ar-Altersdatierungen an Hornblende- und Glimmerkonzentraten belegen, daß das letzte, (Mitteldruck-) metamorphe Ereignis im Westteil der Zone Erbendorf-Vohenstrauß vor etwa 380 Ma beendet war. Dieses Alter wird korreliert mit einer letzten Metamorphose der höhermetamorphen Serien des Münchberger Komplexes zur gleichen Zeit. Im Ostteil der Zone Erbendorf-Vohenstrauß treten jüngere Altersdaten mit einem Schwerpunkt bei 324 Ma auf, die entweder auf einen Einfluß der etwa gleichalten Niederdruck-Metamorphose im unmittelbar benachbarten Moldanubikum i. e. S. oder auf die Intrusion des 324 Ma alten (KÖHLER et al. 1974) Leuchtenberger Granits zurückzuführen sind. Im Übergangsbereich vom Saxothuringikum zum Moldanubikum bei Mähring zeigen Altersdaten um 320Ma das Ende der letzten (Niederdruck-)Metamorphose an.
The Ringgold Knoll pegmatite, a late-stage member of the Granite Harbour Intrusives, crosscuts high-grade Wilson gneisses of the Oates Coast, which forms the westernmost part of the Wilson Terrane at the Pacific end of the Cambro-Ordovician Ross orogenic belt in West Antarctica. The pegmatite mineral assemblage consists of K-feldspar, plagioclase, quartz, garnet (almandinespessartine-pyrope), dark tourmaline (schorl-dravite), muscovite, apatite, monazite, zircon, blue AI-rich tourmaline and dumortierite in order of decreasing abundances. Major, minor and rare earth elements are reported for the greater part of the mineral assemblage. The time of pegmatite emplacement is constrained by Rb-Sr and Sm-Nd isochron ages of 492 ± 8 (2a) Ma and 500 ± 40 (2a) Ma, respectively. High initial 87Sr/86Sr of 0.7315 ± 0.0003 and low E Nd,t of -8.7 ± 1.2 strongly support an origin of the magma from highly evolved crustal source rocks. K-Ar and Ar-Ar model ages of about 470 to 475 Ma for igneous muscovite indicate that the pegmatite together with its wall rocks spent a prolonged period at elevated temperatures before final cooling below about 350 °C. The muscovite dates may give an estimate for the time of exhumation of the Oates Coast crystalline basement along two major late Ross orogenic detachment zones within the Wilson Terrane i.e. the Wilson and the Exiles thrusts (c.f. FLÖTTMANN and KLEINSCHMIDT, 1991).
Die Kupfer-Zink-Lagerstätte von Kupferberg-Neufang im Bereich der Münchberger Deckenstruktur besteht aus einem etwa 4 km langen Zug einzelner stratiformer Vererzungslinsen, der in NW-SE-Richtung vom anchimetamorphen Paläozoikum "Bayerischer" Faziesentwicklung in die Prasinit-Phyllit-Serie hinüberzieht. Bisherige lagerstättenkundliche Untersuchimgen interpretierten die gesamte Lagerstätte als einheitliche, submarin-exhalativ entstandene stratiforme Bildung in Zusammenhang mit ordovizischem basischem Vulkanismus, der in den Rahmengesteinen der Lagerstätte durch die Diabase der anchimetamorphen Randschieferserie bzw. die Prasinite der Prasinit-Phyllit-Serie dokumentiert ist. Diese Vorstellung steht jedoch in deutlichem Widerspruch zu den Ergebnissen neuerer geochemischer und biostratigraphischer Untersuchungen, die für die Diabase und Prasinite eine völlig unterschiedliche Zusammensetzung ergaben und die zeigten, daß die Prasinit-Phyllit-Serie schon im Oberproterozoikum, die erzführenden Schichten im anchimetamorphen Paläozoikum aber erst im Unterdevon sedimentiert wurden. Für eine Klärung der Situation sind weitere Untersuchungen im Bereich der Lagerstätte erforderlich.
No abstract available