Three-dimensional mapping of Quaternary sediments improved by airborne electromagnetics in the case of the Quakenbrück Basin, Northern Germany

Klimke, Jennifer; Wiederhold, H.; Winsemann, Jutta; Ertl, Gabriele; Elbracht, Jörg

doi:10.1127/1860-1804/2013/0023

Cited by 4 publications

(6 citation statements)

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“…The 3D HFEM resistivity grid indicates that clay (grain-size class 1) has an average resistivity of 30 Ωm in the study area. This value corresponds to previous results of AEM data commonly reported in the literature for clay (Burschil et al, 2012b; Klimke et al, 2013). In comparison to borehole resistivity (commonly between 5 and 20 Ωm) the 3D HFEM resistivity value is slightly to high and may be caused (1) by a certain silt and sand content or (2) by the limited resolution of the HFEM method providing an over- or underestimated thickness or merging of lithological units.…”

Section: Resultssupporting

confidence: 92%

“…Our analysis shows that resistivity generally increases with grain size and permeability, as also shown by Burschil et al (2012b) and Klimke et al (2013) for HTEM data. However, there are substantial differences between the borehole lithology and resistivity values derived from the two interpolated 3D AEM resistivity grids (Fig.…”

Section: Resultssupporting

confidence: 89%

“…The larger overlaps of HTEM resistivity values can be explained as an effect of restricted HTEM data coverage and the projection of interpolated resistivity values onto the borehole locations. Similar HTEM resistivity values were found at the island of Föhr (Burschil et al, 2012a,b) and for the region of Quakenbrück, southwestern Lower Saxony (Klimke et al, 2013). Nonetheless, discrimination of different lithologies with a wide range of resistivity values is possible by integrating with other data sets, for example borehole or seismic reflection data.…”

Section: Resultssupporting

confidence: 69%

“…Our results show that AEM data provide excellent opportunities to map the subsurface geology as previously demonstrated by, for example, Newman et al (1986), Jordan & Siemon (2002), Danielsen et al (2003), Jørgensen et al (2003b, 2013), Auken & Christiansen (2004), Auken et al (2008), Viezzoli et al (2008), Bosch et al (2009), Christensen et al (2009), Klimke et al (2013) and Gunnink & Siemon (2014). A good relationship between resistivity values and lithology enables the 3D imaging of the subsurface architecture.…”

Section: Discussionmentioning

confidence: 71%

“…It has successfully been applied in various geological settings to analyse the depositional architecture (e.g. Jordan & Siemon, 2002; Huuse et al, 2003; Sandersen & Jørgensen, 2003; Paine & Minty, 2005; Jørgensen & Sandersen, 2006, 2009; Bosch et al, 2009; Steuer et al, 2009; Pryet et al, 2011; Burschil et al, 2012a,b; Klimke et al, 2013). AEM enables a fast geological overview mapping of subsurface structures and allows different lithologies and pore water conditions to be distinguished (Siemon, 2005; de Louw et al, 2011; Burschil et al, 2012a).…”

Section: Introductionmentioning

confidence: 99%

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Towards an improved geological interpretation of airborne electromagnetic data: a case study from the Cuxhaven tunnel valley and its Neogene host sediments (northwest Germany)

Steinmetz

Winsemann

Brandes

et al. 2014

Netherlands Journal of Geosciences

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Airborne electromagnetics (AEM) is an effective technique for geophysical investigations of the shallow subsurface and has successfully been applied in various geological settings to analyse the depositional architecture of sedimentary systems for groundwater and environmental purposes.However, interpretation of AEM data is often restricted to 1D inversion results imaged on resistivity maps and vertical resistivity sections. The integration of geophysical data based on AEM surveys with geological data is often missing and this deficiency can lead to uncertainties in the interpretation process. The aim of this study is to provide an improved methodology for the interpretation of AEM data and the construction of more realistic 3D geological subsurface models. This is achieved by the development of an integrated workflow and 3D modelling approaches based on combining different geophysical and geological data sets (frequency-domain helicopter-borne electromagnetic data (HFEM), time-domain helicopter-borne electromagnetic data (HTEM), three 2D reflection seismic sections and 488 borehole logs). We used 1D inversion results gained from both HFEM and HTEM surveys and applied a 3D resistivity gridding procedure based on geostatistical analyses and interpolation techniques to create continuous 3D resistivity grids. Subsequently, geological interpretations have been performed by combining with, and validation against, borehole and reflection seismic data. To verify the modelling results and to identify uncertainties of AEM inversions and interpretation, we compared the apparent resistivity values of the constructed 3D geological subsurface models with those of AEM field measurements. Our methodology is applied to a test site near Cuxhaven, northwest Germany, where Neogene sediments are incised by a Pleistocene tunnel valley. The Neogene succession is subdivided by four unconformities and consists of fine-grained shelf to marginal marine deposits. At the end of the Miocene an incised valley was formed and filled with Pliocene delta deposits, probably indicating a palaeo-course of the River Weser or Elbe. The Middle Pleistocene (Elsterian) tunnel valley is up to 350 m deep, 0.8-2 km wide, and incised into the Neogene succession. The unconsolidated fill of the Late Miocene to Pliocene incised valley probably formed a preferred pathway for the Pleistocene meltwater flows, favouring the incision. Based on the 3D AEM resistivity model the tunnel-valley fills could be imaged in high detail. They consist of a complex sedimentary succession with alternating fine-and coarse-grained Elsterian meltwater deposits, overlain by glaciolacustrine (Lauenburg Clay Complex) and marine Holsteinian interglacial deposits.The applied approaches and results show a reliable methodology, especially for future investigations of similar geological settings. The 3D resistivity models clearly allow a distinction to be made between different lithologies and enables the detection of major bounding surfaces and architectural elements.

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Section: Resultssupporting

confidence: 92%

Section: Resultssupporting

confidence: 89%

Section: Resultssupporting

confidence: 69%

Section: Discussionmentioning

confidence: 71%

Section: Introductionmentioning

confidence: 99%

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Towards an improved geological interpretation of airborne electromagnetic data: a case study from the Cuxhaven tunnel valley and its Neogene host sediments (northwest Germany)

Steinmetz

Winsemann

Brandes

et al. 2014

Netherlands Journal of Geosciences

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Towards an Integrative Inversion and Interpretation of Airborne and Terrestrial Data

Götze

Afanasjew

Alvers³

et al. 2014

Advanced Technologies in Earth Sciences

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Airborne and ground geophysical mapping of coastal clays in Eastern Friesland, Germany

et al. 2015

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Coastal areas such as the German Bight are at risk from storms and rising sea level that may affect the hydrogeologic setting. Because knowledge of the distribution of clayey sediments is important for understanding the current status of this dynamic setting, the German Federal Institute for Geosciences and Natural Resources (BGR) has focused on geophysical research projects on the North Sea coast applying airborne and ground geophysics. The airborne system operated by BGR was used to survey a 20- by 31-km large coastal area in Eastern Friesland, Germany, including the islands of Langeoog and Spiekeroog. Helicopter-borne electromagnetic (HEM) data were collected at six frequencies. In addition, the Leibniz Institute for Applied Geophysics commissioned a SkyTEM survey covering a 2-km-wide north–south strip. On the island of Langeoog, ground geophysical methods, such as transient electromagnetics (TEM) and magnetic resonance soundings (MRS) were used to investigate the hydrogeologic setting in greater detail. Onshore, the airborne electromagnetic results clearly outlined a complex electrically conductive pattern occurring at a shallow depth. Comparison with borehole results provided by the State Authority for Mining, Energy and Geology confirmed that these conductors were caused by clayey material, particularly down to an approximate 20-m depth. This pattern continues offshore, and it is likely that the saltwater is linked to stripes of clayey sediments and the fresh groundwater flows out to the Wadden Sea in between. On the islands, the HEM results revealed the freshwater lenses and showed some indications for clay layers within these freshwater lenses. The application of TEM and MRS helped to distinguish lithology from salinity and confirmed the existence of these clay layers. We demonstrated the usefulness of combining the spatial airborne data with geophysical and borehole data available at sparsely distributed sites on the ground to investigate hydrogeologic settings.

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Three-dimensional mapping of Quaternary sediments improved by airborne electromagnetics in the case of the Quakenbrück Basin, Northern Germany

Cited by 4 publications

References 0 publications

Towards an improved geological interpretation of airborne electromagnetic data: a case study from the Cuxhaven tunnel valley and its Neogene host sediments (northwest Germany)

Towards an improved geological interpretation of airborne electromagnetic data: a case study from the Cuxhaven tunnel valley and its Neogene host sediments (northwest Germany)

Towards an Integrative Inversion and Interpretation of Airborne and Terrestrial Data

Airborne and ground geophysical mapping of coastal clays in Eastern Friesland, Germany

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