3D Subsurface Modeling based on Ground Penetrating Radar Survey of Glaciomarine Deposits – Hagadrag Aquifer, Norway. A sedimentological, hydrogeological and geophysical study
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Despite abundant surface water in Norway, groundwater can be a better resource for drinking water due to the good natural protection and filtration properties of the groundwater aquifer. In Norway, 70 % of the groundwater is found in unconsolidated aquifers, hence it is fundamental to understand the sedimentary characteristics of these aquifers if one want to utilize the groundwater as a drinking water supply. The connection between groundwater and sedimentology can be referred to as aquifer sedimentology. Bø municipality uses groundwater as their main water supply, serving drinking water to approximately 4900 inhabitants. The water wells are placed in Hagadrag aquifer, in Bø Valley-fill deposits from the Quaternary time period. The Quaternary history for Bø Valley has been said to contain a glacier front terminating in a former fjord, and stagnating in a narrow part of the valley. Because of this, the area of interest is anticipated to contain large successions of glaciomarine deposits, of which this paper has analyzed. This thesis comprises a survey executed to generate a 3D subsurface model for better understanding of the sedimentary characteristics of Hagadrag aquifer. The main method used is a Ground Penetrating Radar, collecting radargrams of the subsurface from the floor of Verpe gravel pit. The radargrams were interpreted with radar stratigraphic analysis, highlighting radar sequences/packages and their radar facies, and suggesting a depositional history with corresponding depositional environments for the analyzed sedimentary successions (lithofacies). A geodatabase was put together to aid interpretation of what grain sizes the identified subsurface packages may consist of. The geodatabase includes data from several previous drilling surveys done in and around the study area, and yields important geological information for this thesis. A 3D model of the subsurface sedimentary packages and their bounding surfaces has been generated in Voxler and ArcScene. A bedrock grounding-line zone for a preexisting glacier was identified, together with several deposits derived from this grounding-line zone as glacial outwash material; stratified tills, gravity flow deposits, subaquatic grounding-line fan, scour pool infill deposits, and an ice-contact ridge (moraine ridge) on top of the bedrock threshold. The 3D subsurface model from this survey can be further used as a model for hydrogeological prospecting and groundwater modeling.