GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Review of Survey activities 2004
No full textThe Review of Survey activities presents a selection of 18 papers reflecting the wide spectrum of activities of the Geological Survey of Denmark and Greenland, from the microbial to the plate tectonic level.Activities in Denmark: The Survey\u27s activities in Denmark are documented by 11 papers. The main themes are petroleum- and groundwater-related topics and Quaternary geology but neotectonics of the Baltic Shield and new methods in provenance studies of sandstones are also touched upon.Activities in Greenland: The Survey\u27s activities in Greenland and the North Atlantic are covered by six articles focusing on climate research, the mineral potential of the Precambrian basement terranes in West Greenland and on the possibility of exploiting dimension stones.Other countries: During 2004, the Survey carried out work in more than 20 countries outside Denmark, Greenland and the Faroe Islands. In this report a project on developing small-scale mining in Mongolia and Kyrgyzstan is described
Steam treatment of contaminated groundwater aquifers – development of pathogenic micro-organisms in soil
No full textSteam treatment of contaminated soil and aquifer sediment is a promising method of cleaning soil. The treatment is based on steam injection into a water saturated porous aquifer (Gudbjerg et al. 2004), by which the heat transfers the contaminants into the vapour phase, allowing entrapment in an active carbon filter connected to a large vacuum suction device. The treatment is effective against several important groundwater contaminants, including pentachlorophenole and perchloroethylene, typically found in association with industrial processes or dry cleaning facilities. Furthermore, as an example of removal of non-aqueous phase liquids (NAPLs) large amounts of creosote have been recovered after steam injection in a deep aquifer (Kuhlmann 2002; Tse & Lo 2002). Steam treatment is dependent on the complete heating of the soil volume under treatment. The steam has a strongly adverse impact on trees and other plants with deep root systems within the soil, but no other visible effects have been reported. The aim of the activities undertaken during collaborative projects carried out by the Geological Survey of Denmark and Greenland (GEUS) and the Danish Institute of Agricultural Sciences (DJF) for the Danish Environmental Protection Agency and the local authorities in Copenhagen (Københavns Amt) was to establish to what extent the microbial community was affected by the steam treatment of the soil. A few results from the literature indicate that the microbial activity increases in steam treated soil (Richardson et al. 2002), probably due to microbial degradation of the soil contaminants in combination with microbial utilisation of heatkilled organisms. It is, however, not known whether this increased microbial activity is associated with the development of pathogenic micro-organisms; these are typically able to grow at higher temperatures than the general microbial community in soil
Late Quaternary environmental changes recorded in the Danish marine molluscan faunas
No full textLate Quaternary, marine deposits in Denmark have yielded 247 subfossil species of molluscs. The sites are presented, and comparisons are made between the subfossil mollusc assemblages and the 278 shell-bearing mollusc species presently living in the Danish seas. 184 species are common to the two groups. The 63 species no longer occurring around Denmark are used as indicators of changing environmental conditions, including temperature, salinity and depth, throughout the last 130 000 years. Seven modern faunal regional units are defined and considered: the Bælt, the Baltic, the Kattegat, the Limfjord, the North Sea and the Vendsyssel regions, and the Skagen area based on the Skagen III Well DGU File No. 1.287. The Late Quaternary, marine, shell-bearing molluscs, comprising 341 subfossil and recent species, are characterised from the point of view of climatic (i.e. Arctic, Subarctic, Boreal and Lusitanian) affinities and animal–sediment relationships. On this background the faunal and environmental evolution recorded in the 217 m long Skagen Well core is analysed and described. The mollusc assemblages in the Skagen sequence indicate a deeper-water facies during the Eemian, the Weichselian and the older Holocene in contrast to what hitherto was known in other parts of the Danish area during the Late Quaternary. For the Skagen Well the chronozones Preboreal/Boreal, Atlantic, Subboreal and Subatlantic can be identified by 14C dating. The environmental changes within the seven regions through the Late Quaternary are evaluated by depicting the molluscan communities encountered in the seven Late Quaternary stages together with remarks on studies of the neighbouring areas. By following the marine communities through the Late Quaternary in the light of the classical bottom communities sensu C.G.J. Petersen, it is demonstrated how facies have changed both through time and space within the Danish marine realm. The well-established, more temperate Eemian marine fauna was closely associated with shallow-water environments. The inferred climatic changes reflect an interglacial–glacial cycle. However, the climatically induced changes during the Holocene in the marine environment were small and overshadowed by the facies changes. Out of the 341 species recorded in this study, 140 occur in the Eemian, 36 in the Early/Middle Weichselian and 41 in the Late Weichselian. The Holocene fauna is represented by 183 species of shell-bearing molluscs, of which the first recorded occurrence of 148 species has been radiocarbon-dated
The Billund delta: a possible new giant aquifer in central and western Jutland
No full textThe search for new, deep-seated drinking water resources in Denmark has increased significantly during the past five years as a result of the discovery of excessive amounts of nitrate, pesticides and other pollutants in shallow groundwater boreholes (e.g. Nygaard et al. 2004, this volume). To find and map these aquifers, a multidisciplinary sequence stratigraphic approach has successfully been applied to the Miocene deposits of southern Jutland, where especially the Odderup and Ribe Formations are known as a main aquifer for drinking water from several test wells (Rasmussen et al. 2002). Recently, a more systematic study of the Miocene succession in central and western Jutland has been initiated by the Geological Survey of Denmark and Greenland (GEUS) under contract with local authorities. It includes detailed sedimentological descriptions of outcrops, sedimentological and log-interpretations of new stratigraphic boreholes and interpretation of new high-resolution seismic data (Fig. 1). A number of outcrops and wells have been studied palynologically, resulting in a detailed dinoflagellate cyst stratigraphy and in palynofacies interpretations. The results of these studies have been integrated in the regional geological and stratigraphic model (Fig. 2). Two new aquifers have been discovered: the Bastrup sand and the Billund sand. The Bastrup sand has already been exploited as a main aquifer in central and southern Jutland, and has been referred to either the Ribe or Odderup Formations. However, new stratigraphic results reveal that the Bastrup sand is a separate unit in the Miocene succession. The Billund sand is a deep-seated aquifer located more than 100 m and often more than 150 m deep, and is therefore not penetrated by standard water supply wells which rarely reach c. 100 m. The Billund sand was first revealed by multichannel seismic data deriving from former oil-exploration carried out in the Billund area (Fig. 3A). The resolution of these seismic data is very poor, but one interpretation of the dipping reflectors (clinoforms) seen in Fig. 3A was of a delta complex. This agrees with outcrop studies along the fjords of eastern Jutland which suggest that a spit complex was deposited in this area during the Early Miocene. The Billund sand was tested by the Vandel Mark well in 2001, which penetrated c. 40 m of sand at a depth of 200 m. The presence of a regional major sand body was later confirmed by new high-resolution seismic data and by the Billund and Løvlund wells in 2002. The Billund well penetrated 50 m of medium- to coarse-grained sand, and chemical tests of the water quality were good. However, a water supply well at Fjand in western Jutland has had problems with so-called ‘brown water’ – water enriched in organic matter (humus). Saline water may also be expected close to older deep-seated faults. This paper summarises the results of a mapping programme of the Billund sand initiated in the summer of 2003
Investigating the diamond potential of southern West Greenland
No full textSouthern West Greenland hosts a province of ultramafic alkaline rocks, including swarms of dykes traditionally described as kimberlites and lamproites (Larsen 1991; Jensen et al. 2002). Since the mid-1990s, commercial diamond exploration has been focused on the Sarfartoq region and the region south-east of Maniitsoq (Fig. 1), and has resulted in numerous reports of diamond-favourable indicator minerals from till sampling, finds of kimberlitic dykes, and recovery of diamonds from kimberlitic rocks. A new digital compilation of company data released from confidential status (Jensen et al. 2003a) presents a comprehensive overview of exploration activities and results that have emerged since the Survey’s first compilation of occurrences of kimberlitic and related rocks (Larsen 1991). The new compilation in a GIS (geographic information system) environment allows for refined assessment of the distribution, structural control and possible spatial and petrogenetic relationships that characterise the kimberlitic occurrences. In 2003, the Geological Survey of Denmark and Greenland (GEUS) and the Government of Greenland’s Bureau of Minerals and Petroleum (BMP) went further than has been customary in investigating the economic potential of specific sites. Four areas were temporarily closed to application for exploration licences, pending sampling and testing for diamond content of large samples of more than one tonne each from significant kimberlitic occurrences. Additional characterisation and research initiated on these and other occurrences include magnetic mapping, detailed petrography and studies of mantle xenoliths, as well as indicator mineral chemistry. An extensive programme to determine the ages of kimberlitic and related rocks was also initiated in 2003
Towards an assessment of the balance state of the Greenland Ice Sheet
No full textThe climate of Europe is strongly influenced by heat transport by ocean currents flowing from equatorial regions towards the Arctic (Clark et al. 2002). During recent years, research has been increasingly focused on factors affecting this circulation, e.g. the freshwater budget of the Arctic which is influenced by glacial meltwater from North and East Greenland outlet glaciers (Linthout et al. 2000, Mayer et al. 2000). Furthermore, the climate is affected by snow cover that, apart from its contribution to the freshwater budget, provides feedback effects in that it reflects most of the solar radiation. Apart from Arctic sea-ice cover, the Greenland Ice Sheet is the largest permanent ice- and snow-covered area in the northern hemisphere, with an area of 1.67 ×106 km2 and by far the largest storage of ice with a volume of 2.93 × 106 km3 (Bamber et al. 2001). Most of the mass loss from the Greenland Ice Sheet (the least known mass-balance parameter) occurs in the marginal region of the ice sheet, which is also the area where the largest changes in albedo occur. The Geological Survey of Denmark and Greenland (GEUS) has for many years carried out research along the Greenland Ice Sheet margin to monitor changes of mass balance and melt conditions