Geological Survey of Denmark and Greenland Bulletin最新文献

{"title":"Radical past climatic changes in the Arctic Ocean and a geophysical signature of the Lomonosov Ridge north of Greenland","authors":"N. Mikkelsen, N. Nørgaard‐Pedersen, Y. Kristoffersen, S. Lassen, E. Sheldon","doi":"10.34194/GEUSB.V10.4911","DOIUrl":"https://doi.org/10.34194/GEUSB.V10.4911","url":null,"abstract":"The Arctic Ocean is a landlocked basin, at present covered by perennial sea ice. During the past few decades a significant thinning and shrinking of the sea ice has been observed, and modelling studies indicate that the Arctic Ocean ice cover could, by the end of this century, almost disappear from most parts of the Arctic Ocean during peak summer seasons. It remains uncertain, however, whether the environmental changes are an enhanced greenhouse-warming signal or a result of natural (long-term) variability, but palaeoceanographic studies can contribute to our understanding of the natural variability of environmental parameters, e.g. sea-ice cover and oceanographic changes on time-scales of centuries to millennia. As part of the multidisciplinary EU project Greenland Arctic Shelf Ice and Climate Experiment (GreenICE), sediment coring and seismic reflection measurements have been undertaken in a hitherto unexplored part of the Arctic Ocean, the margin of the Lomonosov Ridge in the Lincoln Sea (Fig. 1). The aim of the project was to study the structure and dynamics of the sea-ice cover and attempt to relate these to longer-term records of climate variability retrieved from sediment cores. The main field work was carried out in May 2004 from an ice camp established by a Twin Otter aircraft on drifting sea ice at 85°N, 65°W, c. 170 km north of Alert, Arctic Canada. The camp was deployed over the shallowest part of the Lomonosov Ridge off the northern Greenland/Canada continental margin (Fig. 1). The sea-ice drift would normally be between east and south, but persistent easterly winds resulted in a fast drift trajectory towards the WSW, such that the camp drifted a distance of approximately 62 km during the two weeks camp period. At present the study area is heavily ice covered, and forecast models of future shrinking Arctic sea-ice cover suggest that this area is one of the least sensitive to warming in the Arctic. The results obtained from the GreenICE project challenge this view.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"37 1","pages":"61-64"},"PeriodicalIF":0.0,"publicationDate":"2006-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74441198","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Gold in central West Greenland - known and prospective occurrences","authors":"A. Steenfelt, H. Stendal, B. Nielsen, T. Rasmussen","doi":"10.34194/GEUSB.V4.4787","DOIUrl":"https://doi.org/10.34194/GEUSB.V4.4787","url":null,"abstract":"In 2003, the Geological Survey of Denmark and Greenland (GEUS) completed a four-year project aimed at assessing the mineral potential of the Precambrian region of West Greenland between latitudes 66° and 70°15´N. The project was part of a contract between GEUS and the Ministry of the Environment, and involved compilation of existing geoscientific data, new geological mapping, field examinations of known and potential mineral occurrences, new chemical and isotope analyses, and data interpretation. The data compilation, available on a DVD (Schjoth et al. 2004), comprises regional, systematically acquired data sets presented in a Geographic Information System environment. Aeromagnetic, aeroradiometric, stream sediment and rock geochemical and gravity data, a digital elevation model and a satellite image are included, plus descriptions of 60 mineral occurrences. Evaluation of the mineral potential is based on interpretations of the compiled information as well as on earlier investigations by the Survey, the University of Copenhagen and commercial companies (see e.g. Stendal & Schonwandt 2003; Stendal et al. 2004). From an economic point of view, the potential for gold and diamonds is the most interesting in the investigated area. This paper summarises the evaluation of the gold potential; results of diamond-related investigations are reported separately (Jensen & Secher 2004, this volume).","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"15 1","pages":"65-68"},"PeriodicalIF":0.0,"publicationDate":"2004-07-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73801267","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Jurassic of Skåne, Southern Sweden","authors":"A. Ahlberg, U. Sivhed, M. Erlström","doi":"10.34194/GEUSB.V1.4682","DOIUrl":"https://doi.org/10.34194/GEUSB.V1.4682","url":null,"abstract":"In Sweden, Jurassic strata are restricted to Skane and adjacent offshore areas. Jurassic sedimentary rocks predominantly comprise sandy to muddy siliciclastics, with subordinate coal beds and few carbonate-rich beds. During Mesozoic times, block-faulting took place in the Sorgenfrei‐ Tornquist Zone, a tectonic zone which transects Skane in a NW‐SE direction. The Jurassic depositional environments in Skane were thus strongly influenced by uplift and downfaulting, and to some extent by volcanism. Consequently, the sedimentary record reveals evidence of numerous transgressions, regressions and breaks in sedimentation. Relative sea-level changes played a significant role in controlling the facies distribution, as deposition mainly took place in coastal plain to shallow shelf environments. The alluvial deposits in Skane include floodplain palaeosols, autochthonous coals, overbank sandstones, and stream channel pebbly sandstones. Restricted marine strata comprise intertidal heteroliths with mixed freshwater and marine trace fossil assemblages, and intertidal delta distributary channel sandstones. Shallow marine sediments encompass subtidal and shoreface sandstones with herringbone structures, and bioturbated mudstones with tempestite sandstones. Offshore deposits typically comprise extensively bioturbated muddy sandstones. Floral remains, palaeopedology, clay mineralogy and arenite maturity indicate a warm and humid climate in Skane throughout the Jurassic, possibly with slightly increasing aridity towards the end of the period. Most Jurassic strata in Skane have been subjected to mild burial diagenesis, and the petroleum generative window has rarely been reached.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"47 1","pages":"527-541"},"PeriodicalIF":0.0,"publicationDate":"2003-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87597461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ablation observations for 2008-2011 from the Programme for Monitoring of the Greenland Ice Sheet (PROMICE)","authors":"R. Fausto, D. As, A. Ahlstrøm, S. Andersen, M. L. Andersen, M. Citterio, K. Edelvang, S. H. Larsen, H. Machguth, S. Nielsen, A. Weidick","doi":"10.34194/GEUSB.V26.4765","DOIUrl":"https://doi.org/10.34194/GEUSB.V26.4765","url":null,"abstract":"Recent 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 robustness of mass-balance predictions relies heavily on observational data from the Greenland ice sheet and in recent years the need for frequent, reliable surface mass-balance measurements has increased (IPCC 2007; Dahl-Jensen et al. 2009). In anticipation of this need, the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) was initiated in 2007, delivering in situ data from a network of automatic weather stations (AWS) covering eight different regions of the ice sheet (Fig. 1; van As et al. 2011). Apart from the direct insight into the surface mass balance provided by these stations, the in situ data are also valuable for calibrating and validating melt estimates from remote sensors and surface mass-balance models (Dahl-Jensen et al. 2009). In this paper, we present the ablation records for the PROMICE AWSs for 2008–2011, and the impact of the extraordinary atmospheric conditions on ablation in 2010 (Tedesco et al. 2011) are compared to the other years.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"6 1","pages":"73-76"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74873153","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Review of Survey activities 2015: Pre-Quaternary rocks and sediments with a high level of radioactivity in Denmark","authors":"P. Gravesen, P. Jakobsen","doi":"10.34194/geusb.v35.4903","DOIUrl":"https://doi.org/10.34194/geusb.v35.4903","url":null,"abstract":"© 2016 GEUS. Geological Survey of Denmark and Greenland Bulletin 35, 31–34. Open access: www.geus.dk/publications/bull The pre-Quaternary sediments and rocks in Denmark generally have a low content of radioactive minerals and elements. Uranium, thorium and radium are built into mineral structures or are, for example, adsorbed on the surface of clay minerals, Fe-minerals or organic material. Radon (222Rn) is a radioactive noble insoluble gas with a half-life of 3.8 days. It belongs to the uranium (238U) decay chain where radon is formed from radium (226Ra). When Rn is formed by radioactive decay from Ra, the emanation process sends part of the radon produced into the pore spaces of rocks and soils. From here, the radon can enter and accumulate in buildings. The source of the radioactive materials in Danish sediments and rocks is primarily from weathered Precambrian crystalline rocks from Norway, Sweden, Finland and the Danish island of Bornholm. Physical and chemical weathering disintegrates these rocks and rivers transport the material into the Danish–Norwegian and Danish–Polish sedimentary basins. Several studies have analysed and described the radioactive content of Danish sediments and crystalline rocks (e.g. Damkjær & Korsbech 1985, 1988; Gravesen et al. 1996, 1999; Gravesen & Jakobsen 2010) and investigations have demonstrated a relationship between sediments and rocks and Rn levels in Danish buildings (Andersen et al. 2001). This paper addresses the radioactive content of sediments and rocks with the highest radioactive levels in Denmark and the highest recorded radon emanations: Precambrian crystalline rocks on Bornholm and Late Paleocene clays in north-western Jylland (Fig 1). The data were collected by Gravesen et al. (1999) at the Geological Survey of Denmark and Greenland (GEUS) with the aim of characterising and mapping Rn in Danish rocks and sediments.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"70 3 1","pages":"31-34"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82281408","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Programme for Monitoring of the Greenland Ice Sheet (PROMICE): first temperature and ablation record","authors":"D. As, R. Fausto, A. Ahlstrøm, S. Andersen, M. Andersen, M. Citterio, K. Edelvang, P. Gravesen, H. Machguth, F. Nick, S. Nielsen, A. Weidick","doi":"10.34194/GEUSB.V23.4876","DOIUrl":"https://doi.org/10.34194/GEUSB.V23.4876","url":null,"abstract":"The Greenland ice sheet is reacting to climate change. Yet, mass-budget estimates differ considerably, partly due to climatic variability and partly to uncertainties in the techniques of assessing mass change (IPCC 2007). Nevertheless, all recent estimates agree that the ice sheet is losing mass (e.g. 286 Gt/yr; Velicogna 2009) at an accelerating rate (Rignot et al. 2011). On top of this, the area with a negative mass budget is expanding rapidly (Khan et al. 2010). The mass loss is attributed equally to increases in both iceberg production and melting of the ice sheet (Van den Broeke et al. 2009). The increasing mass loss in recent years has caught public attention and given rise to concern worldwide due to its potential impact on sea level. In the light of this, the Programme for Monitoring of the Greenland Ice Sheet (PROMICE) was initiated in 2007 (Ahlstrom & PROMICE project team 2008), lead by the Geological Survey of Denmark and Greenland (GEUS). PROMICE undertakes surface mass-budget measurements using automatic weather stations, quantifies the mass loss by iceberg calving using remotely sensed data from satellites and airborne surveys and tracks changes in the extent of glaciers. In this paper, we focus on weather station measurements, which are crucial in calculating the energy exchange between the atmosphere and the ice sheet, and in validating model calculations of the surface mass budget. In particular, we present the observed temperatures and investigate how their high 2010 values affected ablation in southern Greenland.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"45 1","pages":"73-76"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87759939","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geological observations in the southern West Greenland basement from Ameralik to Frederikshåb Isblink in 2008","authors":"Nynke Keulen, A. Schersten, J. Schumacher, T. Næraa, B. Windley","doi":"10.34194/GEUSB.V17.5012","DOIUrl":"https://doi.org/10.34194/GEUSB.V17.5012","url":null,"abstract":"began a project in collaboration with the Bureau of Minerals and Petroleum of Greenland with the aim to publish a webbased, seamless digital map of the Precambrian bedrock between 61°30 and 64°N in southern West Greenland. Such a map will be helpful for the mineral exploration industry and for basic research. Producing an updated digital map requires additional field work revisiting key localities to collect samples for geochemistry, geochronology and metamorphic petrology. The new data will help us to test and refine existing models and improve general understanding of the geological evolution of the area. Here we summarise some results from the 2008 field activities between Ame ralik in the north and Frederikshab Is blink in the south (Fig. 1). The area was mapped in the 1960s and 1970s, and although the 1:100 000-scale maps are of excellent quality, they do not include more recent developments in geochro nology, thermobarometry and geochemistry. A notable exception is the Fiske naesset complex (Fig. 1), which has re ceived considerable attention after it was first mapped (Ellitsgaard-Ras mus sen & Mouritzen 1954; Wind ley et al., 1973; Windley & Smith, 1974; Myers 1985). New tectonic models have been developed since the original 1:100 000 maps were produced, and the tectonic evolution has been com monly ex plained in terms of terrane accretion (Friend et al. 1996). Friend’s model de fines a number of boundaries that separate terranes of different age and origin and which might have contrasting tectono-metamorphic histories prior to terrane accretion. The current project area includes the northern part and proposed boundary of the Tasiusarsuaq terrane, which was amalgamated with the terranes to the north at 2.72 Ga, when regional metamorphism affected the region (Friend et al. 1996). In addition, Windley & Garde","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"1 1","pages":"49-52"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83132631","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Thrust-fault architecture of glaciotectonic complexes in Denmark","authors":"S. Pedersen, L. O. Boldreel","doi":"10.34194/geusb.v33.4479","DOIUrl":"https://doi.org/10.34194/geusb.v33.4479","url":null,"abstract":"Cross sections of glaciotectonic complexes are exposed in coastal cliff s in Denmark, which allow structural studies of the architecture of thin-skinned thrust-fault deformation (Pedersen 2014). However, the basal part of the thrust-fault complex is never exposed, because it is located 50 to 100 m below sea level. It is in the basal part the most important structure – the décollement zone – of the complex is found. Th e décollement zone constitutes the more or less horizontal surface that separates undeformed bedrock from the displaced thrust-sheet units along the décollement level. One of the most famous exposures of glaciotectonic deformations in Denmark is the Møns Klint Glaciotectonic Complex. Th e structures above sea level are well documented, whereas the structures below sea level down to the décollement level are poorly known. Modelling of deep structures was carried out by Pedersen (2000) but still needs documentation. A glaciotectonic c omplex aff ecting comparable rock units, such as the chalk at Møns Klint, was recently recognised in seismic sections from Jammerbugten in the North Sea (Fig. 1). Th ese sections provide an excellent opportunity for comparable studies of the upper and lower structural levels in thin-skinned thrust-fault deformation, which is discussed in this paper with examples from three major glaciotectonic complexes.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"17 1","pages":"17-20"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90786071","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Consistency of postglacial geodynamics for the Kattegat region, southern Scandinavia, based on seismological, geological and geodetic data","authors":"S. Gregersen, P. Voss","doi":"10.34194/geusb.v33.4480","DOIUrl":"https://doi.org/10.34194/geusb.v33.4480","url":null,"abstract":"Th e earthquake map of Denmark is constantly being improved. Together with data from western Sweden and southern Norway it shows more and more convincingly a gradual, scattered earthquake activity across the Kattegat region from low activity in the Precambrian basement of Scandinavia to lack of earthquakes in south-western Denmark and northern Germany. Th e activity is only partly connected with mapped geological features. Th e three most recently felt earthquakes in Denmark augment and support this pattern with two or three activity concentrations in the seas around Denmark (Fig. 1). Th e smoothness and irregularities of this picture must in some way be related to the geological structure as well as to the geodynamic pattern of postglacial uplift mapped from geology and geodesy. Since the dominant stress fi eld, from the lithospheric plate motion is smooth (Gregersen & Voss 2010), a natural question is whether the picture","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"11 1","pages":"21-24"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78582888","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Review of Survey activities 2014: A hydrological early warning system for Denmark based on the national model","authors":"H. J. Henriksen, S. Stisen, Xin He, Marianne B. Wiese","doi":"10.34194/geusb.v33.4482","DOIUrl":"https://doi.org/10.34194/geusb.v33.4482","url":null,"abstract":"The rapidly increasing impacts of climate change are likely to require changes in relevant institutions (IPCC 2012). An example is the growing need for immediate information on the entire water cycle (Fig. 1), with quantitative assessments of critical hydrological variables and flow interactions between different domains, e.g. atmosphere, plant-soil, surface water, groundwater and the sea, as they take place.","PeriodicalId":49199,"journal":{"name":"Geological Survey of Denmark and Greenland Bulletin","volume":"83 1","pages":"29-32"},"PeriodicalIF":0.0,"publicationDate":"1969-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72745793","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}