Leibniz Institute For Angewandte Geophysik

Hannover, Germany

Leibniz Institute For Angewandte Geophysik

Hannover, Germany
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Karle M.,Niedersachsisches Institute For Historische Kustenforschung | Karle M.,Senckenberg Institute | Frechen M.,Leibniz Institute For Angewandte Geophysik | Wehrmann A.,Senckenberg Institute
Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften | Year: 2017

The climatic changes in the Late Quaternary have led to a series of environmental changes in the coastal area of the southern North Sea. The Pleistocene landscape around the Jade Bay was gradually inundated and covered with Holocene coastal deposits during sea-level rise after the Last Glacial Maximum (LGM). In this context, a data base of 827 core logs and 8 piston cores was interpreted with regard to lithological indicators of environmental changes south of the modern Jade Bay. By the sedimentological and stratigraphical analysis of ancient extended salt marsh belts, silting-up zones and tidal flat / tidal channel complexes, the position, internal structure and extension of the land-sea interface was reconstructed in detail giving insight into principle processes and interactions taking place in this highly sensitive zone during sea-level changes. The Holocene coastal sediment sequence in the Jade area consists of four distinct lithological units representing semiterrestrial, brackish-lagoonal and shallow marine sub-environments. With regard to small scale sea-level fluctuations in the latest phase of the Holocene transgression, distinct periods of stagnation or even regression occurred. In contrast to the typical internal composition of the Holocene deposits of the backbarrier coast with a multiple alternation of landward and seaward facies shifts, indicating repeated shoreline displacements, the Holocene sequence of the Jade Bay is characterised by only one landward-seaward facies shift. However, the sedimentary record is displayed in complex sequences of clastic deposits of tidal flat and brackish environments and intercalated beds of autochthonous fen and raised bog peat. From 11thcentury, onward increasing human activity has significantly influenced the development of the coastal landscape by dike construction, dewatering and land reclamation along the entire coastline. Consequently, the former swamptype characteristic of the extended lower supratidal zone has significantly changed into a narrow belt of salt marshes restricted by an artificially fixed coastline and the decoupling of marine-terrestrial processes. In the light of recent regional sea-level curve discussions, the presence of sea-level index points is critically discussed, due to the widespread existence of thick peat beds. © 2017 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.

Lysdahl A.K.,Norwegian Geotechnical Institute | Bazin S.,Norwegian Geotechnical Institute | Christensen C.,University of Calgary | Ahrens S.,Norwegian Maritime Museum | And 2 more authors.
Near Surface Geophysics | Year: 2017

Excavation and piling works related to seafront development in Oslo's historic harbour area need to mitigate the risk of damaging buried archaeological objects. In the Bjørvika harbour in Oslo, Norway, electrical resistivity tomography was performed to detect structures with potential archaeological value. A 2.5 dataset consisting of four equally spaced parallel lines was collected, trimmed, and systematically processed with both 2D and 3D inversion routines. The results were in good agreement with known underground features, and for the present dataset, an iteratively reweighted least squares 2D inversion was clearly preferable over a 3D inversion. This conclusion is based on differences in model resolution, data processing costs, and the value of the final product for engineering decision-making. © 2017 European Association of Geoscientists & Engineers.

Agemar T.,Leibniz Institute For Angewandte Geophysik | Hese F.,Landesamt fur Landwirtschaft | Moeck I.,Leibniz Institute For Angewandte Geophysik | Stober I.,Karlsruhe Institute of Technology
Zeitschrift der Deutschen Gesellschaft fur Geowissenschaften | Year: 2017

Disruptive deformations create deep subsurface faults, which may result in the formation of hydrothermal fluid pathways. Deep-reaching faults are promising targets for geothermal exploration. In Germany, the hydraulic properties of faults are usually not known when geothermal wells are planned. However, there are documented and plausible criteria to assess the geothermal potential of faults in advance. Experience gained from geologic exploration of faults confirms an empirical correlation between fault geometry and the distribution of geothermal resources. Geothermal surveys indicate that damage zones at fault terminations and interfering faults (e.g. relay ramps, crossing faults etc.) could represent favourable settings for exploration in critically stressed areas. Besides fault geometry and stress regime, additional criteria are outlined for the assessment of the geothermal potential of faults. © 2017 E. Schweizerbart’sche Verlagsbuchhandlung, Stuttgart, Germany.

Stokes M.,Drake University | Mather A.E.,Drake University | Belfoul M.,University Ibn Zohr | Faik F.,University Ibn Zohr | And 6 more authors.
Quaternary Science Reviews | Year: 2016

This study documents river terraces from upstream reaches of the Dadès River, a major fluvial system draining the south-central High Atlas Mountains. Terraces occur as straths with bedrock bases positioned at 10 m altitudinal intervals up to 40 m (T1-T5) above the valley floor, becoming less common between 50 and 140 m. The rock strength, stratigraphy and structure of the mountain belt influences terrace distribution. Terraces are absent in river gorges of structurally thickened limestone; whilst well-developed, laterally continuous terraces (T1-T4) form along wide valleys occupying syncline structures dominated by weaker interbedded limestone-mudstone. Terrace staircases develop in confined canyons associated with weaker lithologies and influence from structural dip and stratigraphic configuration.Terraces comprise a bedrock erosion surface overlain by fluvial conglomerates, rare overbank sands and colluvium. This sequence with some OSL/IRSL age control, suggests terrace formation over a 100 ka climate cycle with valley floor aggradation during full glacials and incision during glacial-interglacial transitions. This integrates with other archives (e.g. lakes, glaciers, dunes), appearing typical of landscape development along the NW Saharan margin south of the High Atlas, and similar to patterns in the western-southern Mediterranean. The 100 ka climate cycle relationship suggests that the terrace sequence documents Late-Middle Pleistocene landscape development.Consistent altitudinal spacing of terraces and their distribution throughout the orogen suggests sustained base-level lowering linked to uplift-exhumation of the High Atlas. Low incision rates (<0.2 mm a-1) and general absence of terrace deformation suggests dominance of isostatically driven base-level lowering with relief generation being Early Pleistocene or older. © 2017 Elsevier Ltd.

Diez A.,Alfred Wegener Institute for Polar and Marine Research | Diez A.,Karlsruhe Institute of Technology | Eisen O.,Alfred Wegener Institute for Polar and Marine Research | Eisen O.,University of Heidelberg | And 3 more authors.
Annals of Glaciology | Year: 2013

Two seismic surveys were carried out on the high-altitude glacier saddle, Colle Gnifetti, Monte Rosa, Italy/Switzerland. Explosive and vibroseismic sources were tested to explore the best way to generate seismic waves to deduce shallow and intermediate properties (<100 m) of firn and ice. The explosive source (SISSY) excites strong surface and diving waves, degrading data quality for processing; no englacial reflections besides the noisy bed reflector are visible. However, the strong diving waves are analyzed to derive the density distribution of the firn pack, yielding results similar to a nearby ice core. The vibrator source (ElViS), used in both P-and SH-wave modes, produces detectable laterally coherent reflections within the firn and ice column.We compare these with ice-core and radar data. The SH-wave data are particularly useful in providing detailed, high-resolution information on firn and ice stratigraphy. Our analyses demonstrate the potential of seismic methods to determine physical properties of firn and ice, particularly density and potentially also crystal-orientation fabric.

Agency: European Commission | Branch: FP7 | Program: CP | Phase: ENERGY.2008.5.2.4 | Award Amount: 10.56M | Year: 2009

The objectives of MUSTANG are to develop and disseminate a comprehensive set of methodologies and tools for the assessment and characterization of deep saline aquifers for CO2 storage, providing measures of performance and risk that are necessary for a cost-benefit analysis, ensuring public confidence and acceptance and promoting its deployment. Novel CO2 storage specific field investigation technologies and methodologies will be developed, allowing an improved determination of the relevant physical properties of the site and enabling short response times in the detection and monitoring of CO2 plumes during both the injection and storage phases. We also aim at an improved understanding of the processes of CO2 spreading by means of theoretical investigations, laboratory experiments, natural analogue studies and field scale injection tests, including those relevant to the 1) seal integrity; 2) the negative impact of possibly conductive faults; 3) formation heterogeneities; 4) CO2 trapping mechanisms; and 5) effective treatment for the wide span of spatial and temporal scales of the coupled thermo-hydro-mechanical-chemical processes. Based on the improved process models, conceptual and numerical models will be developed for analyzing CO2 injection and storage and implemented at six test sites representing different geological settings and geographical locations in Europe, also addressing the impact of the CO2 injection on seal integrity. The guidelines to be developed will be integrated into a decision support system, which will include a risk assessment component and liabilities consideration. The DSS will be tested and validated at the various project test sites. Special attention has been devoted to promote measures capable of enhancing public outreach and acceptance and dissemination of the methodologies and technologies to the wide public.

Weller A.,Clausthal University of Technology | Zhang Z.,Southwest Petroleum University | Slater L.,Rutgers University | Kruschwitz S.,BAM Federal Institute of Materials Research and Testing | Halisch M.,Leibniz Institute For Angewandte Geophysik
Geophysics | Year: 2016

Permeability estimation from induced polarization (IP) measurements is based on a fundamental premise that the characteristic relaxation time τ is related to the effective hydraulic radius reff controlling fluid flow. The approach requires a reliable estimate of the diffusion coefficient of the ions in the electrical double layer. Others have assumed a value for the diffusion coefficient, or postulated different values for clay versus clay-free rocks. We have examined the link between a widely used single estimate of τ and reff for an extensive database of sandstone samples, in which mercury porosimetry data confirm that reff is reliably determined from a modification of the Hagen-Poiseuille equation assuming that the electrical tortuosity is equal to the hydraulic tortuosity. Our database does not support the existence of one or two distinct representative diffusion coefficients but instead demonstrates strong evidence for six orders of magnitude of variation in an apparent diffusion coefficient that is well-correlated with reff and the specific surface area per unit pore volume Spor. Two scenarios can explain our findings: (1) the length scale defined by τ is not equal to reff and is likely much longer due to the control of pore-surface roughness or (2) the range of diffusion coefficients is large and likely determined by the relative proportions of the different minerals (e.g., silica and clays) making up the rock. In either case, the estimation of reff (and hence permeability) is inherently uncertain from a single characteristic IP relaxation time as considered in this study. © 2016 Society of Exploration Geophysicists.

Dahm T.,University of Hamburg | Kuhn D.,NORSAR | Ohrnberger M.,University of Potsdam | Kroger J.,Geologisches Landesamt Hamburg | And 4 more authors.
Geophysical Journal International | Year: 2010

Shallowly situated evaporites in built-up areas are of relevance for urban and cultural development and hydrological regulation. The hazard of sinkholes, subrosion depressions and gypsum karst is often difficult to evaluate and may quickly change with anthropogenic influence. The geophysical exploration of evaporites in metropolitan areas is often not feasible with active industrial techniques.We collect and combine different passive geophysical data as microgravity, ambient vibrations, deformation and hydrological information to study the roof morphology of shallow evaporites beneath Hamburg, Northern Germany. The application of a novel gravity inversion technique leads to a 3-D depth model of the salt diapir under study. We compare the gravity-based depth model to pseudo-depths from H/V measurements and depth estimates from small-scale seismological array data. While the general range and trend of the diapir roof is consistent, a few anomalous regions are identified where H/V pseudo-depths indicate shallower structures not observed in gravity or array data. These are interpreted by shallow residual caprock floaters and zones of increased porosity.The shallow salt structure clearly correlates with a relative subsidence in the order of 2 mm yr -1. The combined interpretation of roof morphology, yearly subsidence rates, chemical analyses of groundwater and of hydraulic head in aquifers indicates that the salt diapir beneath Hamburg is subject to significant ongoing dissolution that may possibly affect subrosion depressions, sinkhole distribution and land usage.The combined analysis of passive geophysical data may be exemplary for the study of shallow evaporites beneath other urban areas. © 2010 The Authors Journal compilation © 2010 RAS.

Hoecht G.,DMT Petrologic GmbH | Rost F.,DMT Petrologic GmbH | Luschen E.,Leibniz Institute For Angewandte Geophysik
76th European Association of Geoscientists and Engineers Conference and Exhibition 2014: Experience the Energy - Incorporating SPE EUROPEC 2014 | Year: 2014

In common-reflection-surface (CRS) imaging the data space is parameterized by operators that are expected to overlap in a continuous manner along events in the image space. These circumstances are employed in the operator-oriented scheme which integrates neighboring operators and, thereby, introduces multiple operators in the stacking process. Azimuth-dependant stacking velocities allow to account for a general type of model and are included in the hyperbolic CRS formula. We demonstrate the application of the operator-oriented CRS stacking method and the impact of azimuth-dependant stacking velocities in the context of a 3D WAZ land data set acquired over a crystalline basement.

Kuhn P.,University of Tübingen | Techmer A.,Leibniz Institute For Angewandte Geophysik | Weidenfeller M.,Landesamt fur Geologie und Bergbau Rheinland Pfalz
Quaternary Science Reviews | Year: 2013

Lower to middle Weichselian loess, loess derivatives and buried soils of the loess-paleosol sequence Alsheim (Central Europe) were characterised by particle size distribution, geochemical and micromorphological data. High rates of sedimentation with alternating phases of relocation are the main cause for a much less differentiation into Middle and Upper Weichselian loess-paleosol units of the Alsheim loess-paleosol sequence compared to other loess-paleosol sequences (e.g. Nussloch near Heidelberg), whereas the Lower Weichselian has distinct phases of pedogenesis resulting in Ah, Bw and Btw horizons.To distinguish between different loess deposits locally and intraregional, the degree of fineness is an easily applicable and suitable tool, though inappropriate for interregional comparisons. The chemical index of alteration (CIA) is low (<50=no weathering) for loess deposits in the Alsheim loess-paleosol sequence, which is in contrast to the worldwide compiled loess samples with CIA values ranging from >53 to <70 (Gallet etal., 1998). The highest weathering was detectable for Btw horizons with CIA values >70.A direct quantitative estimation of mean annual palaeotemperature and mean annual palaeoprecipitation can be provided by calculations based on geochemistry of soil horizons and sediments. The present mean annual precipitation (MAP) in the Mainz Basin is 789mm. In contrast, palaeoprecipitation data suggest a 150mm higher amount for the Last Interglacial (Btw horizon), a much lower amount of around 300-400mm MAPP (periods of loess and sandy loess deposition) and a MAPP of <500mm for Weichselian Interstadials (humus zones and Bw horizons). The calculated mean annual palaeotemperature (MAPT) for Interstadials with 8.9°C for Bw horizons or with 9.6°C for humus zones (or to 2K lower, considering the relation of the present MAT of the Mainz Basin with the MAT of Germany) seems to be a good approximation of the MAPT for Lower and Middle Weichselian Interstadials. A MAPT of 8.7°C (or 6.7°C) for Stadials (loess and sandy loess samples) is higher than other temperature estimations for Weichselian Stadials in Europe.Micromorphology shows compacted granular structure and moderately to strongly developed pedality as characteristic properties for aquatic loess, whereas channel microstructure with no pedality is typical for loess deposits. Spongy microstructure suggests a classification of the Lower Weichselian Mosbach Humus Zones as Chernozems. The Eemian paleosol (Btw horizon in Als III) has only weak clay illuviation, characteristic for drier regions in Europe.Palaeoclimate and soil formation of the Last Glacial-Interglacial cycle calculated from geochemistry and micromorphological data are in good accordance with other proxy data in Central Europe. This suggests that paleoclimate reconstruction based on palaeopedological analyses could be successfully implemented in Europe. Such data may provide a useful alternative to other proxies for correlating European records. © 2013 Elsevier Ltd.

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