Refine
Has Fulltext
- no (69)
Year of publication
- 2018 (69) (remove)
Document Type
- Article (69) (remove)
Language
- English (69) (remove)
Is part of the Bibliography
- yes (69)
Keywords
- Climate change (2)
- LiDAR (2)
- radiative forcing (2)
- seasonality (2)
- Acacia plantation (1)
- Adaptation (1)
- Algeria (1)
- Annaba (1)
- Archean spherule layers (1)
- Arctic (1)
- Arctic aerosol (1)
- Argentina (1)
- Arid Central Asia (1)
- Array Seismology (1)
- Array design (1)
- Athalassic subsaline lake (1)
- Austria (1)
- Barberton Greenstone Belt (1)
- Biogenic silica (1)
- Biome (1)
- Biosilicification (1)
- Black Sea (1)
- Blind thrust (1)
- Body waves (1)
- Bolivian tin belt (1)
- Bunker cave (1)
- CO2 emissions (1)
- COSMOS rover (1)
- Capital Approach Framework (CAF) (1)
- Carbon footprint (1)
- Catchment management (1)
- Central Asia (1)
- Centroid moment tensor of M approximate to 3 earthquakes (1)
- City benchmarking (1)
- Computational seismology (1)
- Conductive channel (1)
- Conservation agriculture (1)
- Content analysis (1)
- Correlation (1)
- Crop water use (1)
- Curvature (1)
- DEA (1)
- DTM comparison (1)
- DTM vertical accuracy (1)
- Dansgaard-Oeschger event (1)
- Decollement (1)
- Deep crustal intraplate seismicity (1)
- Digital terrain model (DTM) (1)
- Domuyo geothermal field (1)
- Drop fall velocity (1)
- Drop size distribution (1)
- Duplex (1)
- EU (1)
- Earthquake source observations (1)
- Earthquake swarm (1)
- East Antarctica (1)
- Eco-efficiency (1)
- Electrical conductivity (1)
- Endogenic carbonates (1)
- Engineering Strong Motion database (1)
- Eocene monsoon (1)
- Epithermal Ag-Sn deposits (1)
- Euglyphida (1)
- Europe (1)
- FAO56 (1)
- Fault reactivation (1)
- Flatfile (1)
- Flood defence measures (1)
- Flood risk (1)
- Fluid inclusions (1)
- Fluids (1)
- Fold and thrust belt (1)
- GMMs (1)
- Geomorphometry (1)
- Grassroots initiatives (1)
- Greenhouse gas emissions (1)
- Gullies (1)
- HRU customization (1)
- HRU fragmentation (1)
- High Asia (1)
- Himalaya (1)
- Ice volume (1)
- In situ silicon isotope ratio analysis (1)
- Indian Summer Monsoon (1)
- Inland salinization (1)
- Insurance (1)
- Irregular sampling (1)
- Irrigation requirements (1)
- Italian Alps (1)
- Kinematic analysis (1)
- Kizilirmak River (1)
- Kyoto (flexible) mechanisms (1)
- LC/MS (1)
- Lake level reconstruction (1)
- Lake number (1)
- Land use management (1)
- Landscape features (1)
- Low carbon economy (1)
- MIS (1)
- Maghreb (1)
- Magnetotellurics (1)
- Marine isotope stage 3 (1)
- Maritime Alps (1)
- Mediterranean catchments (1)
- Metadata (1)
- Micro-XRF (1)
- Multi-proxy approach (1)
- Noble gas (1)
- North Anatolian Fault Zone (1)
- OLS ranking (1)
- OSL dating (1)
- Observed and simulated ground motions (1)
- Operationalisation (1)
- Optical distrometer (1)
- Orogenic wedge (1)
- Ostracoda (1)
- PPGIS (1)
- Palaeoclimatology (1)
- Paratethys sea (1)
- Participatory mapping (1)
- Peatlands (1)
- Permafrost (1)
- Petrography (1)
- Pirquitas (1)
- Pleistocene (1)
- Plio-quaternary tectonic evolution (1)
- Pollen (1)
- Pontides (1)
- Pore-fluid conductivity (1)
- Pore-water hydrochemistry (1)
- Pothole (1)
- Provenance (1)
- Public perception (1)
- Public sector (1)
- QAToCA (1)
- Quaternary (1)
- Rainfall kinetic energy (1)
- Record of multiple impacts (1)
- Reflection seismics (1)
- Reflectivity method (1)
- Remote sensing analysis (1)
- Resampling methods (1)
- Risk governance (1)
- Risk reduction (1)
- Risk reduction partnerships (1)
- Rotational fault (1)
- SWAT (1)
- Schmidt stability (1)
- Sediment connectivity (1)
- Seismicity and tectonics (1)
- Seismicity modelling (1)
- Silicon cycling (1)
- Siwaliks (1)
- Soil erosion (1)
- Soil erosion modelling (1)
- Soil salinity dynamics (1)
- Solar insolation (1)
- South America (1)
- Southem Andes (1)
- Speleothems (1)
- Stakeholder involvement (1)
- Strong motion records (1)
- Subduction zone (1)
- Surface roughness (1)
- Sustainability transitions (1)
- Sustainable lifestyles (1)
- Sustainable urban development (1)
- Swiss Alps (1)
- Terrestrial biogeosystems (1)
- Time scale dependence (1)
- Time-series analysis (1)
- Traditional drainage systems (1)
- Transport sector (1)
- Turkey (1)
- U-Th series (1)
- Urban metabolism (1)
- Vogtland (1)
- Vulnerable communities (1)
- Water footprint (1)
- Water resource management (1)
- Water use change (1)
- West Bohemia (1)
- Westerlies (1)
- XRF scanning (1)
- Zambia (1)
- active stress (1)
- adaptation (1)
- aerosol (1)
- afecto (1)
- affect (1)
- ambiente (1)
- aridification (1)
- atmosphere (1)
- atmosphère (1)
- authigenic clay (1)
- beach sediments (1)
- biogenic silica (1)
- bivalves (1)
- carbon (1)
- carotenoids (1)
- climate change (1)
- cloud cover (1)
- conjugate fractures (1)
- corporalité (1)
- corporeality (1)
- corporeidad (1)
- cosmic ray neutrons (1)
- digital terrain models (1)
- drainage-based land use (1)
- elevation dependency (1)
- emoción (1)
- emotion (1)
- estadio (1)
- event recurrence predictability (1)
- fenomenología (1)
- field-scale (1)
- football (1)
- forced migrants (1)
- foreland basin (1)
- forest soils (1)
- fossil placer (1)
- fútbol (1)
- geochemistry (1)
- global warming potential (1)
- glucosinolates (1)
- heavy minerals (1)
- high-rate GPS (1)
- horsetail splays (1)
- hydrogeomorphological modelling (1)
- ice-albedo feedback (1)
- ice-shelf grounding (1)
- ice-shelf thickness (1)
- kinematic inversion (1)
- knickpoint (1)
- kyoto protocol (1)
- lake sediments (1)
- laser ablation inductively coupled plasma-mass spectrometry (1)
- lidar (1)
- lowland coasts (1)
- megathrust earthquakes (1)
- metabolite profiling (1)
- mobile survey (1)
- moorsh forming process (1)
- mountain climate (1)
- multi-scale analysis (1)
- non-compliance (1)
- oil palm plantation (1)
- orographic precipitation (1)
- pak choi (1)
- palynology (1)
- partial adoption (1)
- participatory research (1)
- permafrost (1)
- permafrost degradation (1)
- phenolic compounds (1)
- phenomenology (1)
- phytolith (1)
- phénoménologie (1)
- plant macrofossil analysis (1)
- policy effectiveness (1)
- polymictic lakes (1)
- public communication (1)
- public engagement (1)
- random forest (1)
- restoration (1)
- retrieval of aerosol properties (1)
- risk governance (1)
- river longitudinal profile (1)
- road effect (1)
- rock glacier (1)
- snow (1)
- soil moisture (1)
- soil organic matter decomposition (1)
- spatial modeling (1)
- spectral analysis (1)
- stable isotope (1)
- stade (1)
- stadium (1)
- stick-slip motion (1)
- strike-slip system (1)
- strong Motion (1)
- subduction segmentation (1)
- swamp forest (1)
- tectonic regime (1)
- temperature trend (1)
- tidally modulated cryogenic seismicity (1)
- tropical peatland (1)
- tundra vegetation (1)
- unsaturated hydraulic conductivity (1)
- variability (1)
- vegetation reconstruction (1)
- weather types (1)
- western Canadian Arctic (1)
- émotion (1)
Institute
- Institut für Umweltwissenschaften und Geographie (69) (remove)
Phytoplankton biomass and production regulates key aspects of freshwater ecosystems yet its variability and subsequent predictability is poorly understood. We estimated within-lake variation in biomass using high-frequency chlorophyll fluorescence data from 18 globally distributed lakes. We tested how variation in fluorescence at monthly, daily, and hourly scales was related to high-frequency variability of wind, water temperature, and radiation within lakes as well as productivity and physical attributes among lakes. Within lakes, monthly variation dominated, but combined daily and hourly variation were equivalent to that expressed monthly. Among lakes, biomass variability increased with trophic status while, within-lake biomass variation increased with increasing variability in wind speed. Our results highlight the benefits of high-frequency chlorophyll monitoring and suggest that predicted changes associated with climate, as well as ongoing cultural eutrophication, are likely to substantially increase the temporal variability of algal biomass and thus the predictability of the services it provides.
We present a pollen record for last 28 cal kyr BP from the eastern basin of Lake Karakul, the largest lake in Tajikistan, located in the eastern Pamir Mountains at 3915 m asl, a geographically complex region. The pollen record is dominated by Artemisia and Chenopodiaceae, while other taxa, apart from Poaceae, are present in low quantities and rarely exceed 5% in total. Arboreal pollen occur predominantly from similar to 28 to similar to 13 cal kyr BP, but as likely no trees occurred in the high mountain regions of the eastern Pamir during this time due to the high altitude and cold climate, arboreal taxa are attributed to long distance transport, probably by the Westerlies, the dominant atmospheric circulation. Tree pollen influx decreases strongly after similar to 13 cal kyr BP, allowing the pollen spectra to be interpreted as a regional vegetation signal. We infer that from 27.6 to 19.4 cal kyr BP the eastern Pamir was dominated by dry mountain steppe with low vegetation cover, while from 19.0 to 13.6 cal kyr BP Artemisia values increase and Chenopodiaceae, most herb taxa, and inferred far distant input from arboreal taxa decrease. Between 12.9 and 6.7 cal kyr BP open steppe vegetation dominated with maximum values in Ephedra, and while steppe taxa still dominated the spectra from 5.4 to 1 cal kyr BP, meadow taxa start to increase. During the last millennium, alpine steppe and alpine meadows expanded and a weak human influence can be ascertained from the increase of Asteraceae and the occurrence of Plantago pollen in the spectra.
The climate conditions during Marine Isotope Stage (MIS) 3 were similar to present-day conditions, but whether humidity then exceeded present levels is debated, and the driving mechanisms of palaeoclimate evolution since MIS 3 remain unclear. Here, we use pollen data from Wulagai Lake, Inner Mongolia, to reconstruct vegetation and climate changes since the middle MIS 3. The steppe biome is reconstructed as the first dominant biome and the desert biome as the second, and the results show that the vegetation was steppe over the last 43,800 years. Poaceae, Artemisia, Caryophyllaceae and Humulus were abundant from middle to late MIS 3, indicating humid climate conditions. As drought-tolerant species such as Hippophae, Nitraria and Chenopodiaceae spread during MIS 2, the climate became arid. The Holocene is characterized by the dominance of steppe with mixed coniferous-broadleaved forests in the Greater Hinggan Range, and the desert biome retains high affinity scores, indicating that the climate was semi-arid. The climate from middle to late MIS 3 was wetter than in the Holocene; this shift was related to changes in the Northern Hemisphere's solar insolation and ice volume. The humid conditions during MIS 3 were attributed to strong ice–albedo feedback, which led to evaporation that was less than the precipitation. The enhanced evaporation caused by increased solar insolation and decreased ice volume might have exceeded the precipitation during the Holocene and resulted in low effective humidity in the Wulagai Lake basin.
For bare soil conditions, the most important process driving and initiating splash and interrill erosion is the detachment of soil particles via raindrop impact. The kinetic energy of a rainfall event is controlled by the drop size and fall velocity distribution, which is often directly or indirectly implemented in erosion models. Therefore, numerous theoretical functions have been developed for the estimation of rainfall kinetic energy from available rainfall intensity measurements. The aim of this study is to assess differences inherent in a wide number of kinetic energy-rainfall intensity (KE-I) relations and their role in soil erosion modelling. Therefore, 32 KE-I relations are compared against measured rainfall energies based on optical distrometer measurements carried out at five stations of two substantially different rainfall regimes. These allow for continuous high-resolution (1-min) direct measurements of rainfall kinetic energies from a detailed spectrum of measured drop sizes and corresponding fall velocities. To quantify the effect of different KE-I relations on sediment delivery, we apply the erosion model WATEM/SEDEM in an experimental setup to four catchments of NE-Germany. The distrometer data shows substantial differences between measured and theoretical models of drop size and fall velocity distributions. For low intensities the number of small drops is overestimated by the Marshall and Palmer (1948; MP) drop size distribution, while for high intensities the proportion of large drops is overestimated by the MP distribution. The distrometer measurements show a considerable proportion of large drops falling at slower velocities than predicted by the Gunn and Kinzer (1949) terminal velocity model. For almost all rainfall events at all stations, the KE-I relations predicted higher cumulative kinetic energy sums compared to the direct measurements of the optical distrometers. The different KE-I relations show individual characteristics over the course of rainfall intensity levels. Our results indicate a high sensitivity (up to a range from 10 to 27 t ha(-1)) of the simulated sediment delivery related to different KE-I relations. Hence, the uncertainty associated with KE-I relations for soil erosion modelling is of critical importance.
Arctic tundra landscapes are composed of a complex mosaic of patterned ground features, varying in soil moisture, vegetation composition, and surface hydrology over small spatial scales (10-100 m). The importance of microtopography and associated geomorphic landforms in influencing ecosystem structure and function is well founded, however, spatial data products describing local to regional scale distribution of patterned ground or polygonal tundra geomorphology are largely unavailable. Thus, our understanding of local impacts on regional scale processes (e.g., carbon dynamics) may be limited. We produced two key spatiotemporal datasets spanning the Arctic Coastal Plain of northern Alaska (similar to 60,000 km(2)) to evaluate climate-geomorphological controls on arctic tundra productivity change, using (1) a novel 30m classification of polygonal tundra geomorphology and (2) decadal-trends in surface greenness using the Landsat archive (1999-2014). These datasets can be easily integrated and adapted in an array of local to regional applications such as (1) upscaling plot-level measurements (e.g., carbon/energy fluxes), (2) mapping of soils, vegetation, or permafrost, and/or (3) initializing ecosystem biogeochemistry, hydrology, and/or habitat modeling.
Peatlands represent large terrestrial carbon banks. Given that most peat accumulates in boreal regions, where low temperatures and water saturation preserve organic matter, the existence of peat in (sub)tropical regions remains enigmatic. Here we examined peat and plant chemistry across a latitudinal transect from the Arctic to the tropics. Near-surface low-latitude peat has lower carbohydrate and greater aromatic content than near-surface high-latitude peat, creating a reduced oxidation state and resulting recalcitrance. This recalcitrance allows peat to persist in the (sub)tropics despite warm temperatures. Because we observed similar declines in carbohydrate content with depth in high-latitude peat, our data explain recent field-scale deep peat warming experiments in which catotelm (deeper) peat remained stable despite temperature increases up to 9 degrees C. We suggest that high-latitude deep peat reservoirs may be stabilized in the face of climate change by their ultimately lower carbohydrate and higher aromatic composition, similar to tropical peats.
The Engineering Strong-Motion (ESM) flatfile is a parametric table which contains verified and reliable metadata and intensity measures of manually processed waveforms included in the ESM database. The flatfile has been developed within the Seismology Thematic Core Service of EPOS-IP (European Plate Observing System Implementation Phase) and it is disseminated throughout a web portal for research and technical purposes. The adopted criteria for flatfile compilation aim to collect strong motion data and related metadata in a uniform, updated, traceable and quality-checked way to develop Ground Motion Models (GMMs) for Probabilistic Seismic Hazard Assessment (PSHA) and engineering applications. In this paper, we present the characteristics of ESM flatfile in terms of recording, event and station distributions, and we discuss the most relevant features of the Intensity Measures (IMs) of engineering interest included in the table. The dataset for flatfile compilation includes 23,014 recordings from 2179 earthquakes and 2080 stations from Europe and Middle-East. The events are characterized by magnitudes in the range 3.5-8.0 and refer to different tectonics regimes, such as shallow active crustal and subduction zones. Intensity measures include peak and integral parameters and duration of each waveform. The spectral amplitudes of the (5% damping) acceleration and displacement response are provided for 36 periods, in the interval 0.01-10 s, as well as the 103 amplitudes of the Fourier spectrum for the frequency range 0.04-50 Hz. Several statistics are shown with reference to the most significant metadata for GMMs calibrations, such as moment magnitude, focal depth, several distance metrics, style of faulting and parameters for site characterization. Furthermore, we also compare and explain the most relevant differences between the metadata of ESM flatfile with those provided by the previous flatfile derived in RESORCE (Reference Database for Seismic Ground Motion in Europe) project.
We applied coarse spectral analysis to more than 2 decades of daily near-surface water temperature (WT) measurements from Muggelsee, a shallow polymictic lake in Germany, to systematically characterize patterns in WT variability from daily to yearly temporal scales. Comparison of WT with local air temperature indicates that the WT variability patterns are likely attributable to both meteorological forcing and internal lake dynamics. We identified seasonal patterns of WT variability and showed that WT variability increases with increasing Schmidt stability, decreasing Lake number and decreasing ice cover duration, and is higher near the shore than in open water. We introduced the slope of WT spectra as an indicator for the degree of lake mixing to help explain the identified temporal and spatial scales of WT variability. The explanatory power of this indicator in other lakes with different mixing regimes remains to be established.
The Kohat and Potwar fold thrust belts (KP-FTB) in Pakistan exhibit structural variations over 250 km along strike within the Himalayan fold and thrust system. Our 3D deformation model shows that Kohat surface structures evolved above an active roof thrust in Eocene evaporites. The ramp-forming duplexes in the Kohat were stacked and passively transported toward the foreland above new ramps, resulting in up to 5 km of thickening between the two decollements. Ramps from the Kohat extend into the Potwar as thrust tips of fault propagation folds. The basement slope changes from flat (beta < 1 degrees) below the northern part to north-dipping (beta > 1 degrees) below the southern part, corresponding to the change in structural style and complexity of the KP-FTB. The Kalabagh Fault Zone, linking the two belts, is interpreted as a zone of complex dextral strike-slip rotational faulting. Salt expulsed from the hanging walls of normal faults and under synclines in the Kalabagh Fault Zone moved toward the footwall of normal faults, accumulated in the cores of anticlines, and formed lobe structures at the deformation front. The fundamental reasons for the variable structural styles are changes in decollement strength, basement slope, preexisting normal faulting, presence of a secondary decollement and spatially-variable salt mobility and accumulation.
Geothermal fields in subduction-related orogens are closely linked to areas characterized by young magmatic and tectonic activity, both in arc- and back-arc settings. The spatio-temporal interaction of Quaternary volcanic complexes with regional extensional and transtensional structures might favor a hydrothermal circuit between meteoric water and magmatic fluids. This study encompasses a kinematic analysis of fault structures from the high-enthalpy system located at the western flank of the Domuyo volcano in Argentina. An analysis of remote sensing data was applied to detect regional lineaments, lineament density, and to identify fracture patterns possibly associated with the different deformational stages documented in the area. These results were combined with detailed fracture analysis and kinematic study of mesoscale faults, as well as existing geological, structural, and geophysical data. The integration suggests that the fluid dynamics of the Domuyo geothermal field are directly conditioned by pre-existing basement structures that were reactivated as normal faults during Pliocene to-Quaternary times. Furthermore, the intensely fracture late Triassic - early Jurassic units are interpreted as the potential level for the reservoir. The fault reactivation was likely associated with the accommodation of regional extension along pre-existing fault structures, and locally enhanced by hydrothermal effects of the Domuyo geothermal field.
On April 29, 2017 at 0:56 UTC (2:56 local time), an M (W) = 2.8 earthquake struck the metropolitan area between Leipzig and Halle, Germany, near the small town of Markranstadt. The earthquake was felt within 50 km from the epicenter and reached a local intensity of I (0) = IV. Already in 2015 and only 15 km northwest of the epicenter, a M (W) = 3.2 earthquake struck the area with a similar large felt radius and I (0) = IV. More than 1.1 million people live in the region, and the unusual occurrence of the two earthquakes led to public attention, because the tectonic activity is unclear and induced earthquakes have occurred in neighboring regions. Historical earthquakes south of Leipzig had estimated magnitudes up to M (W) ae 5 and coincide with NW-SE striking crustal basement faults. We use different seismological methods to analyze the two recent earthquakes and discuss them in the context of the known tectonic structures and historical seismicity. Novel stochastic full waveform simulation and inversion approaches are adapted for the application to weak, local earthquakes, to analyze mechanisms and ground motions and their relation to observed intensities. We find NW-SE striking normal faulting mechanisms for both earthquakes and centroid depths of 26 and 29 km. The earthquakes are located where faults with large vertical offsets of several hundred meters and Hercynian strike have developed since the Mesozoic. We use a stochastic full waveform simulation to explain the local peak ground velocities and calibrate the method to simulate intensities. Since the area is densely populated and has sensitive infrastructure, we simulate scenarios assuming that a 12-km long fault segment between the two recent earthquakes is ruptured and study the impact of rupture parameters on ground motions and expected damage.
Inland salt meadows are particularly valuable ecosystems, because they support a variety of salt-adapted species (halophytes). They can be found throughout Europe; including the peatlands of the glacial lowlands in northeast Germany. These German ecosystems have been seriously damaged through drainage. To assess and ultimately limit the damages, temporal monitoring of soil salinity is essential, which can be conducted by geoelectrical techniques that measure the soil electrical conductivity. However, there is limited knowledge on how to interpret electrical conductivity surveys of peaty salt meadows. In this study, temporal and spatial monitoring of dissolved salts was conducted in saline peatland soils using different geoelectrical techniques at different scales (1D: conductivity probe, 2D: conductivity cross-sections). Cores and soil samples were taken to validate the geoelectrical surveys. Although the influence of peat on bulk conductivity is large, the seasonal dynamics of dissolved salts within the soil profile could be monitored by repeated geoelectrical measurements. A close correlation is observed between conductivity (similar to salinity) at different depths and temperature, precipitation and corresponding groundwater level. The conductivity distribution between top- and subsoil during the growing season reflected the leaching of dissolved salts by precipitation and the capillary rise of dissolved salts by increasing temperature (similar to evaporation). Groundwater levels below 0.38 cm resulted in very low conductivities in the topsoil, which is presumably due to limited soil moisture and thus precipitation of salts. Therefore, to prevent the disappearance of dissolved salts from the rooting zone, which are essential for the halophytes, groundwater levels should be adjusted to maintain depths of between 20 and 35 cm. Lower groundwater levels will lead to the loss of dissolved salts from the rooting zone and higher levels to increasing dilution with fresh rainwater. The easy-to-handle conductivity probe is an appropriate tool for salinity monitoring. Using this probe with regressions adjusted for sandy and organic substrates (peat and organic gyttja) additional influences on bulk conductivity (e.g. cation exchange capacity, water content) can be compensated for and the correlation between salinity and electrical conductivity is high.
The transport sector is crucial for the functioning of modern societies and their economic welfares. However, it is vulnerable to natural hazards since damage and disturbances appear recurrently. Risk management of transport infrastructure is a complex task that usually involves various stakeholders from the public and private sector. Related scientific knowledge, however, is limited so far. Therefore, this paper presents detailed information on the risk management of the Austrian railway operator gathered through literature studies, in interviews, meetings and workshops. The findings reveal three decision making levels of risk reduction: 1) a superordinate level for the negotiation of frameworks and guidelines, 2) a regional to local level for the planning and implementation of structural measures and 3) a regional to local level for non-structural risk reduction measures and emergency management. On each of these levels, multi-sectoral partnerships exist that aim at reducing the risk to railway infrastructure. Chosen partnerships are evaluated applying the Capital Approach Framework and some collaborations are analyzed considering the flood and landslide events in June 2013. The evaluation reveals that the risk management of the railway operator and its partners has been successful, but there is still potential for enhancement. Difficulties are seen for instance in obtaining continuity of employees and organizational structures which can affect personal contacts and mutual trust and might hamper sharing data and experiences. Altogether, the case reveals the importance of multi-sectoral partnerships that are seen as a crucial element of risk management in the Sendai Framework for Disaster Risk Reduction 2015-2030.
The West Bohemia/Vogtland region, characterized by the intersection of the Eger (Ohre) Rift and the Marianske Lazne fault, is a geodynamically active area exhibiting repeated occurrence of earthquake swarms, massive CO2 emanations and mid Pleistocene volcanism. The Eger Rift is the only known intra-continental region in Europe where such deep seated, active lithospheric processes currently take place. We present an image of electrical resistivity obtained from two-dimensional inversion of magnetotelluric (MT) data acquired along a regional profile crossing the Eger Rift. At the near surface, the Cheb basin and the aquifer feeding the mofette fields of Bublak and Hartousov have been imaged as part of a region of very low resistivity. The most striking resistivity feature, however, is a deep reaching conductive channel which extends from the surface into the lower crust spatially correlated with the hypocentres of the seismic events of the Novy Kostel Focal Zone. This channel has been interpreted as imaging a pathway from a possible mid-crustal fluid reservoir to the surface. The resistivity model reinforces the relation between the fluid circulation along deep-reaching faults and the generation of the earthquakes. Additionally, a further conductive channel has been revealed to the south of the profile. This other feature could be associated to fossil hydrothermal alteration related to Mytina and/or Neualbenreuth Maar structures or alternatively could be the signature of a structure associated to the suture between the Saxo-Thuringian and Tepla-Barrandian zones, whose surface expression is located only a few kilometres away.
Thermokarst lakes cover nearly one fourth of ice-rich permafrost lowlands in the Arctic. Sediments from an athalassic subsaline thermokarst lake on Herschel Island (69°36′N; 139°04′W, Canadian Arctic) were used to understand regional changes in climate and in sediment transport, hydrology, nutrient availability and permafrost disturbance. The sediment record spans the last ~ 11,700 years and the basal date is in good agreement with the Holocene onset of thermokarst initiation in the region. Electrical conductivity in pore water continuously decreases, thus indicating desalinization and continuous increase of lake size and water level. The inc/coh ratio of XRF scans provides a high-resolution organic-carbon proxy which correlates with TOC measurements. XRF-derived Mn/Fe ratios indicate aerobic versus anaerobic conditions which moderate the preservation potential of organic matter in lake sediments. The coexistence of marine, brackish and freshwater ostracods and foraminifera is explained by (1) oligohaline to mesohaline water chemistry of the past lake and (2) redeposition of Pleistocene specimens found within upthrusted marine sediments around the lake. Episodes of catchment disturbance are identified when calcareous fossils and allochthonous material were transported into the lake by thermokarst processes such as active-layer detachments, slumping and erosion of ice-rich shores. The pollen record does not show major variations and the pollen-based climate record does not match well with other summer air temperature reconstructions from this region. Local vegetation patterns in small catchments are strongly linked to morphology and sub-surface permafrost conditions rather than to climate. Multidisciplinary studies can identify the onset and life cycle of thermokarst lakes as they play a crucial role in Arctic freshwater ecosystems and in the global carbon cycle of the past, present and future.
Active source near-vertical reflection (NVR) data from the interdisciplinary project TIPTEQ were used to image and identify structural and petrophysical properties within the Chilean subduction zone at 38.25 degrees S, where in 1960 the largest earthquake ever recorded (M-w 9.5) occurred. Reflection seismic images of the subduction zone were obtained using the post-stack depth migration technique to process the three components of the NVR data, allowing to present P- and S-stacked time sections and depth-migrated seismic reflection images. Next, the reflectivity method allowed to model traveltimes and amplitude ratios of pairs of reflections for two 1D profiles along the studied transect. The 1D seismic velocities that produced the synthetic seismograms with amplitudes and traveltimes that fit the observed ones were used to infer the rock composition of the different layers in each 1D profile. Finally, an image of the subduction zone is given. The Chilean subduction zone at 38.25 degrees S underlies a continental crust with highly reflective horizontal, as well as dipping events. Among them, the Lanalhue Fault Zone (LFZ), interpreted to be east-dipping, is imaged to very shallow depths for the first time. In terms of seismic velocities, the inferred composition of the continental crust is in agreement with field geology observations at the surface along the profile. Furthermore, no measurable amounts of fluids above the plate interface in the continental crust in this part of the Chilean subduction zone are necessary to explain the results. A large-scale anisotropy in the continental crust and upper mantle is qualitatively proposed. However, quantitative studies on this topic in the continental crust of the Chilean subduction zone at 38.25 degrees S do not exist to date.
We analysed the interplay between coastal uplift, sea level change in the Black Sea, and incision of the Kizilirmak River in northern Turkey. These processes have created multiple co-genetic fluvial and marine terrace sequences that serve as excellent strain markers to assess the ongoing evolution of the Pontide orogenic wedge and the growth of the northern margin of the Central Anatolian Plateau. We used high-resolution topographic data, OSL ages, and published information on past sea levels to analyse the spatiotemporal evolution of these terraces; we derived a regional uplift model for the northward advancing orogenic wedge that supports the notion of laterally variable uplift rates along the flanks of the Pontides. The best-fit uplift model defines a constant long-term uplift rate of 0.28 +/- 0.07 m/ka for the last 545 ka. This model explains the evolution of the terrace sequence in light of active tectonic processes and superposed cycles of climate-controlled sea-level change. Our new data reveal regional uplift characteristics that are comparable to the inner sectors of the Central Pontides; accordingly, the rate of uplift diminishes with increasing distance from the main strand of the restraining bend of the North Anatolian Fault Zone (NAFZ). This spatial relationship between the regional impact of the restraining bend of the NAFZ and uplift of the Pontide wedge thus suggests a strong link between the activity of the NAFZ, deformation and uplift in the Pontide orogenic wedge, and the sustained lateral growth of the Central Anatolian Plateau flank. (C) 2018 Elsevier Ltd. All rights reserved.
The paper presents the first study of heavy-mineral sand beaches from the Mediterranean coast of Annaba/Algeria. The studied beaches run along the basement outcrops of the Edough massif, which are mainly composed by micaschists, tourmaline-rich quartzo-feldspathic veins, gneisses, skarns and marbles. Sand samples were taken from three localities (Ain Achir, Plage-Militaire and El Nasr). The heavy-mineral fraction comprises between 74 and 91 vol%. The garnets of the beaches are almandine rich and tourmalines vary with respect to their location from schorl to dravite. Tourmaline at Ain Achir and the Plage-Militaire is schorlits, while at El Nasr beach dravite is ubiquitous. The World Shale Average normalised REE of the sands and the basement outcrops reveal: (i) Ain Achir beach: REE pattern of sand and the coastal rocks from the studied beaches reflects a multiple sources; (ii) Plage-Militaire: the sand and the coastal outcrops show similar LREE and a strong enrichment in HREE, suggesting the presence HREE-rich phases found as inclusions in staurolite; (iii) El Nasr: two types of sand patterns are found: one with flat REE pattern similar to the proximal rocks and other one enriched in HREE suggesting a mixed source.
The physical and hydrological properties of peat from seven peatlands in northern Maputaland (South Africa) were investigated and related to the degradation processes of peatlands in different hydrogeomorphic settings. The selected peatlands are representative of typical hydrogeomorphic settings and different stages of human modification from natural to severely degraded. Nineteen transects (141 soil corings in total) were examined in order to describe peat properties typical of the distinct hydrogeomorphic settings. We studied degree of decomposition, organic matter content, bulk density, water retention, saturated hydraulic conductivity and hydrophobicity of the peats. From these properties we derived pore size distribution, unsaturated hydraulic conductivity and maximum capillary rise. We found that, after drainage, degradation advances faster in peatlands containing wood peat than in peatlands containing radicell peat. Eucalyptus plantations in catchment areas are especially threatening to peatlands in seeps, interdune depressions and unchannelled valley bottoms. All peatlands and their recharge areas require wise management, especially valley-bottom peatlands with swamp forest vegetation. Blocking drainage ditches is indispensable as a first step towards achieving the restoration of drained peatland areas, and further measures may be necessary to enhance the distribution of water. The sensitive swamp forest ecosystems should be given conservation priority.
The Archean spherule layers (SLs) of the Barberton Greenstone Belt (BGB, South Africa) and Pilbara Craton (Australia) are the only known evidence of early, large impact events on Earth. Spherules in these layers have been, alternatively, interpreted as molten impact ejecta, condensation products from an impact vapor cloud, or ejecta from impact craters melted during atmospheric re-entry. Recently, a new exploration drill core (CT3) from the northern BGB revealed 17 SL intersections. Spherules are densely packed, sand-sized, and variably rounded or deformed. The CT3 SLs are intercalated with black and brown shale, and laminated chert. The determination of the original number of impact events that are represented by these multiple SLs is central to the present paper. A comprehensive study of the sedimentary and petrographic characteristics of these SLs involved the determination of the size, shape and types of individual spherules, as well as their mineralogy. CT3 SLs consist of K-feldspar, phyllosilicate, siderite, dolomite, quartz, Ti- and Fe-oxides, as well as apatite. In addition, small amounts of carbonaceous, presumably organic material are observed in several spherules at 145 and 149 m depth. Only Ni-rich Cr-spinel (up to 11 wt% NiO) crystals, rare zircon grains, and alloys of platinum group elements ± Fe or Ni represent primary phases in these thoroughly altered strata. The 0.3 to 2.6-mm-sized spherules can be classified into four types: 1. Spherules crystallized completely with secondary K-feldspar (subtype 1A) or phyllosilicate (subtype 1B); spherules completely filled with Ti- and Fe-oxides (subtype 1C); spherules containing disordered or radially oriented, fibrous and lath-shaped K-feldspar textures (subtype 1D); or subtype 1B spherules that contain significant Cr-spinel (subtype 1E); 2. zoned compositions with these types 1A and/or 1B minerals (subtype 2A); spherules that contain central or marginal vesicles (subtype 2B); subtype 1B spherules whose rims consist of Ti and Fe-oxides (subtype 2C); 3. deformed spherules (subtype 3A) - of all types; (B) subtype 1B spherules are assimilated into groundmass; (C) open spherules or spherules with collapsed rims; and 4. interconnected spherules of type 1A.
A few spherules show botryoidal devitrification textures interpreted to result from rapid cooling/devitrification of former melt droplets. SL 15 at a depth of 145 m is unique in being the only grain-size sorted SL; this bed may have been deposited by fallout through a water column. The SL and their host rocks can be easily distinguished by their significant differences in micro-XRF elemental distribution maps. Depending on which aspects of the SLs are primarily considered (such as similar geochemistry, similar layering, SL occurrences abundant at three different depth intervals), the 17 CT3 SLs can be assigned to three or up to 13 individual impact events. Uncertainty about the actual number of impact events represented remains, however, due to the complex folding deformation observed throughout the drill core.