Time Domain Electromagnetic (TEM) Measurements on a Buried Subglacial Valley in Northern Germany

Tezkan, B.; Mufor, H.; Helwig, Stefan L.; Bergers, R.

doi:10.3997/2214-4609.20146560

Cited by 2 publications

(2 citation statements)

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“…Loncarevic et al 1992;Bradwell et al 2008) and airborne or land electromagnetic surveys (e.g. Jørgensen & Sandersen 2006;Bosch et al 2009;Tezkan et al 2009) have been used to outline the distribution and infill of tunnel valleys in both on-and off-shore areas. In most cases, Pleistocene valleys are covered by interglacial sediments, making sections through tunnel-valley fills relatively rare and the outcrops often only reveal the uppermost part of the buried tunnel-valley infill (Eyles & McCabe 1989;Mooers 1989;Martini & Brookfield 1995;Clayton et al 1999;Piotrowski et al 1999;Russell et al 2003).…”

Section: Pleistocene Tunnel Valleysmentioning

confidence: 99%

Tunnel valleys: current knowledge and future perspectives

2012

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Tunnel valleys are elongated incisions that are commonly interpreted as being the result of erosional processes by subglacial meltwater occurring under continental ice sheets. The abundance, size and the primarily coarse-grained infill of these features have made tunnel valleys important hydrocarbon and groundwater reservoirs. Although numerous tunnel valleys have been described over the last century, their formation and infill remain poorly understood. This review summarizes and discusses the current knowledge of tunnel valleys, providing an overview of the observations around the world. Morphological aspects that separate tunnel valleys from other landforms are discussed, as well as the wide variety of sedimentary environments found to contribute to the infilling of these features. The depth of the incision and the character of ice retreat significantly determine the final infill architecture. The formational hypotheses proposed in the literature are assessed to test their wider applicability to all other tunnel valleys in order to find a generic model that helps in the prediction of the morphology and infilling of both Pleistocene and pre-Pleistocene age. A quasi-steady-state model, with small meltwater outbursts that erode tunnel valleys near the ice margin, seems compatible with most of the known valleys. Other proposed models require specific geographical or climatic conditions

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Section: Pleistocene Tunnel Valleysmentioning

confidence: 99%

Tunnel valleys: current knowledge and future perspectives

2012

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“…1C and D). Most of the data sets were acquired between 2000 and 2005 by the BurVal project (Blindow & Balke, 2005;Wiederhold et al, 2005a,b;BurVal Working Group, 2009;Tezkan et al, 2009).…”

Section: Databasementioning

confidence: 99%

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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Time Domain Electromagnetic (TEM) Measurements on a Buried Subglacial Valley in Northern Germany

Cited by 2 publications

References 0 publications

Tunnel valleys: current knowledge and future perspectives

Tunnel valleys: current knowledge and future perspectives

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

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