GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Geology, seismic activity and groundwater conditions at six potential disposal sites for radioactive waste from Risø, Denmark
No full textIn 2003 it was decided by the Danish Parliament that low and intermediate-level radioactive waste from the Danish nuclear research facility, Risø, is to be stored at a permanent disposal site (Ministeriet for Sundhed og Forebyggelse 2008; Gravesen et al. 2012a). Both the issue of storage and the selection of potential sites have caused considerable public debate. In this paper we report on the most recent geological investigations intended to further improve the database for the selection and decision process, although no conclusions have been drawn at this stage
Terrain subsidence detected by satellite radar scanning of the Copenhagen area, Denmark, and its relation to the tectonic framework
No full textIn the European Union (EU) project Terrafirma, which is supported by the European Space Agency to stimulate the Global Monitoring Environment System, we are using the latest technology to measure terrain motion on the basis of satellite radar data. The technique we employ is known as persistent scatterer interferometry (PSI); in Denmark, it was previously used to map areas of subsidence susceptible to flooding in the Danish part of the Wadden Sea (Vadehavet) area (Pedersen et al. 2011). That study was part of the flooding risk theme under the TerraFirma Extension project. Another coastal protection monitoring activity in the EU seventh framework project SubCoast followed, in which the low-lying south coast of Lolland, prone to flooding, was studied. The Geological Survey of Denmark and Greenland (GEUS) is also involved in the three-year EU collaborative project PanGeo in which GEUS is one of 27 EU national geological surveys. The objective of PanGeo is to provide free and open access to geohazard information in support of the Global Monitoring Environment System. This will be achieved by providing a free, online geohazard information service for the two largest cities in each EU country, i.e. 52 towns throughout Europe with c. 13% of EU’s population
Geochemistry and petrology of gold-bearing hydrothermal alteration zones on Qilanngaarsuit, southern West Greenland
No full textDuring field work in 2008, the Geological Survey of Denmark and Greenland investigated the gold potential of hydrothermal vein systems in the Nuuk region of the Archaean North Atlantic craton. A new gold occurrence was discovered on the island of Qilanngaarsuit, 35 km south of Nuuk. Two cross sections through hydrothermal alteration zones, that locally contain up to 672 ppb Au, were mapped and sampled in detail. In this study, we present petrological and geochemical data in order to constrain the conditions for ore formation and transport of elements during fluid–rock interaction
A new seamless digital 1:500 000 scale geological map of Greenland
No full textFor around 40 years, the Geological Survey of Greenland (GGU) and later the Geological Survey of Denmark and Greenland (GEUS) conducted systematic geological overview mapping of Greenland, leading to the production of 14 printed map sheets on a scale of 1:500 000 which covers the entire country (Fig. 1). The mapping was completed in 1999 and the map sheets were published between 1971 and 2004. Revised 2nd editions of two of the sheets have been published (Table 1). As a result of the development of the Internet, the publi-cation platform for geological maps has increasingly moved from traditional paper sheets to digital publications for most geological surveys worldwide. This tendency has changed the requirements to the underlying production, storage and publication platforms for map data. For the same reason, it has over the past decade been a strategy of GEUS to bring the 1:500 000 geological maps of Greenland together as a seamless, digital product with a homogeneous legend. This has been further motivated by the increasing number of Geo-graphic Information System (GIS) and web applications to which such a map would provide a valuable background, as well as to many international projects such as OneGeology. The harmonisation of the geological maps was carried out by a project team at GEUS comprising both geological and GIS expertise. The first version of the new seamless map was finished in 2012 and will be released in various web applications in 2013
Methane distribution in Holocene marine sediments in the Bornholm Basin, southern Scandinavia
No full textThe Baltic Sea is an ideal natural laboratory to study the methane cycle in the framework of diagenetic processes. In this paper we present preliminary geological mapping results from project Baltic Gas, a research project with the overall aim to contribute to the development of a scientific basis for long term sustainable use and protection of the Baltic Sea ecosystem. The Baltic Sea is a marginal sea with a strong permanent haline stratification, which leads to oxygen-poor bottom waters, and which is sometimes interrupted by oxygen-rich saltwater flowing in from the North Sea. The history of the Baltic Sea has resulted in deposition of organic-rich Holocene marine sediments that overlie glacial, late-glacial and early Holocene organic-poor sediments
Results of monitoring groundwater above the natural gas underground storage at Stenlille, Denmark
No full textGroundwater in the Stenlille area is regularly analysed for light hydrocarbons after a natural gas underground storage facility was established there in 1989. The monitoring is carried out by the Geological Survey of Denmark and Greenland and is part of the authorities’ requirements for the environmental approval of the natural gas storage run by the state-owned Danish Oil and Gas company DONG A/S. Groundwater from observation wells and water wells in the area was analysed every month during the first year of operation and four times a year in the following years. More frequent analyses are undertaken on special occasions
Ablation observations for 2008–2011 from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE)
No full textRecent estimates from the glaciological community agree that the Greenland ice sheet is losing mass at an accelerated pace due to climate change (Velicogna 2009; Khan et al. 2010; Rignot et al. 2011). This has caught the attention of the public and policy makers due to the potential impact on sea-level rise (Dahl-Jensen et al. 2009). The mass loss can be attributed approximately equally to increases in meltwater runoff from surface melt and iceberg production (van den Broeke et al. 2009)
The Cenozoic Song Hong and Beibuwan Basins, Vietnam
No full textThe Vietnamese offshore margin holds a substantially underexplored petroleum potential. The key to unravelling this potential lies in understanding the tectono-stratigraphic framework of the region including the Cenozoic mechanisms governing syn-rift and source rock deposition. This is essential for prediction of, for instance the presence and nature of source rocks in South-East Asia and possible reservoir intervals in the syn-rift packages. The Vietnamese part of the Song Hong and Beibuwan Basins (Fig. 1) differs from other basins along the western margin of the South China Sea in that the Palaeogene syn-rift succession is sporadically exposed due to uplift and inversion. These exposures provide a unique glimpse into the Cenozoic syn-rift succession of the basin
Neoglacial and historical glacier changes around Kangersuneq fjord in southern West Greenland
No full textThe Nuup Kangerlua region in southern West Greenland became deglaciated in the early Holocene and by the mid-Holocene, the margin of the Inland Ice was located east of its present position. Discussion of late Holocene changes in the frontal positions of outlets relies on descriptions, paintings, photographs, maps, data from investigations of Norse ruins, aerial photographs and satellite images.
The Kangiata Nunaata Sermia glacier system has receded over 20 km during the last two centuries, indicating a marked response to climatic fluctuations during and since the Little Ice Age (LIA). A large advance between 1700 and 1800 was followed by rapid recession in the first half of the 1800s. Limited data from c. 1850–1920 indicate that although the long-term position of the glacier front remained c. 10–12 km behind the LIA maximum, the late 1800s and the early 1900s may have seen a recession followed by an advance that resulted in a pronounced moraine system. The ice-dammed lake Isvand formed during the LIA maximum when meltwater from the western side of Kangiata Nunaata Sermia drained to the Ameralla fjord in the west. This is in contrast to the drainage pattern before the 1700s, when water probably drained to Kangersuneq in the north. Thinning of Kangiata Nunaata Sermia resulted in total drainage of Isvand between 2000 and 2010 and the discharge of water through Austmannadalen has now returned to the same level as that in medieval times.
Other outlets in the region, such as Akullersuup Sermia and Qamanaarsuup Sermia have varied in phase with Kangiata Nunaata Sermia, but with amplitudes of only a few kilometres. In contrast, Narsap Sermia has been nearly stationary and Kangilinnguata Sermia may have advanced until the middle of the 1900s.
Lowland marine outlets in south-western Greenland were characterised by large amplitude changes during the Neoglacial. Extreme examples, in addition to Kangiata Nunaata Sermia, are Eqalorutsit Killiit Sermiat at the head of Nordre Sermilik fjord in southern Greenland and Jakobshavn Isbræ in Disko Bugt, central West Greenland. The Neoglacial advances appear to have occurred at different times, although this may in part reflect the limited information about fluctuations prior to the 1930s. The differences could also reflect variations in mass balance of different sectors of the ice sheet, different subglacial dynamics or topographical factors. The lowland areas are separated by uplands and highlands that extend below the marginal part of the Inland Ice; in such areas, the outlets have been advancing almost up to the present, so that the position of the glacier front around AD 2000 broadly coincides with the LIA maximum. Charting the fluctuations of the outlets thus illustrates the large variability of the glaciers\u27 response to changing climate but it is notable that the number of advancing outlets has decreased markedly in recent years
Methane and possible gas hydrates in the Disko Bugt region, central West Greenland
No full textCurrent climate models predict an annual temperature increase in the Arctic between 4° and 6°C by the end of the 21st century with widespread impact on the Arctic environment. Warming will lead to thawing of the widespread, permanently frozen, high-latitude peat-lands and to degradation of marine gas hydrates, both of which may increase the rate of methane release to the atmosphere. This will influence global climate as methane is a potent greenhouse gas with a large global warming potential. Marine gas hydrates are found worldwide on continental margins and frequently occur in the Arctic. Interpretation of seismic profiles has also indicated their presence in the Disko Bugt region in western Greenland