Using integrated near‐surface geophysical surveys to aid mapping and interpretation of geology in an alluvial landscape within a 3D soil‐geology framework

Abstract

An integrated geological, geophysical and remote sensing survey was undertaken as part of the construction of a high resolution 3D model of the shallow subsurface geology of part of the Trent Valley in Nottinghamshire, U.K. The 3D model was created using the GSI3D software package and geophysical techniques used included Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Automated Resistivity Profiling (ARP). In addition, the remote sensing techniques of Light Detection and Ranging (LIDAR) and Airborne Thematic Mapping (ATM) were used. The objective of the study was to assess the contribution of these techniques to improve the geological mapping and interpretation of terrace deposits and other geological features. The study site had an area of ~2 km 2 and consisted of a Triassic mudstone escarpment, overlain first by a sand and gravel river terrace that extended to the modern floodplain of the River Trent. ARP mapping proved to be the central tool in identifying and positioning geological features at a greater resolution than would be obtained through traditional geological mapping and borehole observation. These features included (i) a buried cliff delineating the south eastern limits of the incised Trent valley, (ii) siltstone beds within the Gunthorpe Member of the Mercia Mudstone Group and (iii) the variability of the sediments within the river terrace. A long ERT transect across the site successfully imaged the buried cliff and outcropping siltstone beds on the escarpment. Combined ERT and GPR transects revealed the depth of the sand and gravel deposits (Holme Pierrepont sands and gravels), whilst the GPR provided information about the depositional environment. Remote sensing using LIDAR proved essential in the original geological survey because it confirmed the absence of a second river terrace that had been previously thought to exist. This case study demonstrates the importance of combining geophysical techniques with traditional geological survey and borehole analysis, in order to create high-resolution 3D geological models, which are increasingly being used as a platform to understand and solve environmental problems.3

GPR 3d Profile of the Adequateness of Underground Dams in a Sub-Watershed of the Brazilian Semiarid

“…Although the GPR method has shown optimistic results for this type of application, it also presents some limitations. Tye et al (2011) also reported the importance of geophysical surveys for geological mapping of alluvial bodies and the development of the 3D geological models, which contribute to the knowledge of the complexity of sedimentary environments, such as alluvial deposits. Loperte et al (2011) demonstrated that GPR can be a useful tool for the non-intrusive diagnostics of dams and encouraged its use for other defect typologies affecting dams, such as waterproof layer fractures, detachment, and concentrated water infiltration zones.…”

Geophysical, geological, and hydrogeological characterization of a tributary buried bedrock valley in southern Ontario

“…In other words, the model that best matches the measured data is not necessarily an exact representation of the subsurface parameter distribution. Nevertheless, electrical imaging techniques using either induced or direct current sources have provided promising results for imaging valley morphology (e.g., Jørgensen et al 2003a;Ahmad et al 2009;Steuer et al 2009;Tye et al 2011), and in some cases, the infilled Quaternary sediment architecture (e.g., Baines et al 2002;Leopold et al 2013), particularly when combining multiple geophysical techniques with geological information (e.g., Greenhouse and Karrow 1994;Gabriel et al 2003;Jørgensen et al 2003b;Ahmad et al 2009). …”

“…Geophysical methods have the capacity to unravel complex geologic relationships and can play a critical role in advancing our understanding of shallow groundwater flow systems in these settings (van Dam 2012). Studies utilizing multiple geophysical methods combined with geologic and hydrogeologic data are particularly effective for 3D mapping of hydrostratigraphic units (e.g., Gabriel et al 2003;Jørgensen et al 2003aJørgensen et al , 2003bSteuer et al 2009; Stumpf and Ismail 2013;Cassidy et al 2014;Sapia et al 2014).…”

“…Alternatively, buried valleys can be infilled or covered by low-permeable Quaternary-age diamicton or a combination of sediment types with complex geometries and very different hydraulic properties (Jørgensen et al 2003a;Meyer and Eyles 2007;Cummings et al 2012), further complicating hydrogeologic conceptualizations (Cummings et al 2012;van der Kamp and Maathuis 2012). Therefore, these environments require more detailed characterization of both form and infill to ensure accurate quantitative analysis of local groundwater flow system geometries.…”

Combining ground-based and airborne EM through Artificial Neural Networks for modelling glacial till under saline groundwater conditions

“…Often the amount of drillings is not sufficient to create detailed models of the geological structure and lithological composition in the subsurface. Incorporation of 2-D and 3-D densely sampled ground-based and/or airborne geophysical data increases the amount of data for subsurface characterisation substantially (Hubbard and Rubin, 2000;Tye et al, 2011). Airborne geophysical techniques offer a quick way of collecting data over a large area in a cost-effective way.…”