Papers by Flemming Jørgensen
Large amounts of airborne electromagnetic data have been gathered in Denmark over the last 15 yea... more Large amounts of airborne electromagnetic data have been gathered in Denmark over the last 15 years in order to map groundwater resources. These data have been supplemented by high-resolution seismic data and many new drillings. The new data add considerably to the existing geological knowledge of the near-surface layers down to depths of 300 m. While detailed lithostratigraphic information can be drawn from the boreholes, the seismic data provide 2D structural information. The airborne data are utilized to extend the information into 3D. By analysing such data and setting up detailed 3D models for parts of southwest Jutland we have been able to study tunnel valleys and large-scale glaciotectonic complexes in detail. In one of the models we observe several generations of tunnel valleys and are able to constrain their ages to the Saalian and the Elsterian (or older). We find very deep (up to 470 m) and old valleys occasionally filled with interglacial marine sediments of Holsteinian ...
The mapping of buried valleys in Denmark has so far resulted in delineation of a large number of ... more The mapping of buried valleys in Denmark has so far resulted in delineation of a large number of valley segments with a total length of 3.523 km. The buried valleys are often arranged in separate generations showing preferred orientations. An analysis of the orientations of the mapped buried valleys reveals varying preferred orientations within geographically confined areas. Typically, each subarea shows one dominant and one to two sub-dominant orientations. Each preferred orientation often represents more than one generation of tunnel valleys and at several locations recurrent erosion of older valley-traces has taken place. The preferred orientations of the buried tunnel valleys have been compared with orientation analyses of 1) valley erosions in the present day terrain and 2) large scale faults in the pre-Zechstein basement. In the majority of the sub-areas we find a close correlation between the preferred orientations of the valley erosions in the terrain and in several instance...
Based on high-detail topographic data we observe that a Late Weichselian outwash plain above the ... more Based on high-detail topographic data we observe that a Late Weichselian outwash plain above the Tønder Graben structure in Denmark is deformed, and this has led us to conclude that deep-seated faults were reactivated after the formation of the outwash plain. Dating of borehole samples from an 8-m deep depression showed that sedimentation was not initiated before early Holocene, about 9,000 years after the ice sheet retreat. We interpret the tectonic deformations to be related to the deglaciation phase because the time-frame is concurrent with other observations of deglaciation phenomena in Scandinavia. As streams are diverted and show highly angular patterns we interpret the tectonic event to be a short-lived phenomenon. The tectonic event is interpreted as being the result of release of ambient tectonic stress (plate motion) suppressed by the weight of the ice sheet, and glacioisostatic recovery involving elastic flexing of the lithosphere and viscous flow in the mantle. Tectonic ...
The transient electromagnetic (TEM) method has proven to be a powerful tool for the delineation o... more The transient electromagnetic (TEM) method has proven to be a powerful tool for the delineation of water-bearing sand and gravel layers in hydrogeophysical investigations. Advancements in the technique include newly developed TEM systems—the Pulled Array TEM (PATEM) and the High Moment TEM (HiTEM) systems—along with innovations in data interpretation. The advanced methodology is illustrated in two case histories. The first,
71st EAGE Conference and Exhibition - Workshops and Fieldtrips, 2009
71st EAGE Conference and Exhibition - Workshops and Fieldtrips, 2009
Second International Conference on Engineering Geophysics, 2013
Extensive mapping with airborne EM has since 2003 revealed intricate patterns of buried tunnel va... more Extensive mapping with airborne EM has since 2003 revealed intricate patterns of buried tunnel valleys in the Danish subsurface. Several generations of cross-cutting valleys are found making up a highly complicated geological setting. The valleys play a vital role for the Danish water supply because they are assumed to host about 50 % of all extractable groundwater, but they are also important because they impose a significant impact on groundwater flow. Especially three properties of the valleys are essential to map: 1) their spatial extent, 2) their internal architecture, and 3) the lithology of the infill and surrounding environment. Borehole data constitute an insufficient basis for 1) and 2). Instead, techniques like the airborne SkyTEM system providing 3D data are required. Almost 20.000 km 2 have been mapped with the TEM method resulting in more than 5000 km mapped buried valleys. With the SkyTEM system full information about the spatial extent of the valleys (1) can normally be achieved, but also information about the internal architecture (2) and lithology is obtained to some extent. Collection of seismic data and borehole data provide supplementary information about (3) at selected sites.
Zeitschrift der Deutschen Gesellschaft für Geowissenschaften, 2009
... All borehole data are stored in the national database, Jupiter, hosted and maintained by the ... more ... All borehole data are stored in the national database, Jupiter, hosted and maintained by the Geological Survey of Denmark and Greenland (GEUS). ... Another method used for mapping of buried valleys is gravimetry (eg Wolfe & Richard 1996, Thomsen 1997, Gabriel 2006). ...
Second International Conference on Engineering Geophysics, 2013
ABSTRACT In many countries, United Arab Emirates and most of the Middle East countries included, ... more ABSTRACT In many countries, United Arab Emirates and most of the Middle East countries included, the need for groundwater has increased and/or is bound to in the upcoming years. The Danish Government has fully understood the importance to manage and preserve groundwater for current and future generations. In 1998 it began an ambitious nation-wide groundwater mapping programme, which will be completed by 2015, and having the purpose to get an accurate picture of Danish aquifers. Geophysics plays a fundamental role, through the use of Airborne EM (AEM) and ground-based methods. Another key feature is the use of rigorous data processing and protocols, together with the use of innovative 3D geological modelling. Building on this experience, the Danish Minister of Environment supported the Rethink Water project, a network of over 50 Danish companies, organisations and institutions able to join knowledge among industry, researchers and governmental bodies in order to improve water safety and efficiency. The aim is to use this experience to propose the same approach (as a whole, or using only some of its constituent blocks) to other countries all over the World, by promoting knowledge transfer to the local partners.
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Papers by Flemming Jørgensen