GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Borehole logs from the Precambrian basement on Bornholm, eastern Denmark: geology and groundwater flow
No full textBornholm is situated in the Sorgenfrei–Tornquist Zone that separates the North-West European Craton from the Baltic Shield and the East European Platform (Fig.1). The Precambrian basement of northern and eastern Bornholm consists of different granitic and gneissic Mesoproterozoic rocks that are dated to c. 1455 Ma (Waight et al. 2012). It appears from the age data that granitic magmatism, deformation and metamorphism occurred over a relatively short time period. The rocks contain abundant pegmatite and aplite bodies. More than 250 mafic dykes occur. The dykes were intruded during three Precambrian events at c. 1326 Ma, 1220 Ma, 950 Ma and during a Permian event at c. 300 Ma (Holm et al. 2010)
Seismic stratigraphy and sedimentary architecture of the Chalk Group in south-west Denmark
No full textThe Chalk Group is ubiquitous in the subsurface of the Danish Basin and its upper levels are exposed locally onshore, most notably in eastern Denmark. Although many subsurface studies have been made of the group in the Danish Basin, most of these have been in the eastern part of Denmark (e.g. Esmerode et al. 2007; Surlyk & Lykke-Andersen 2007) whereas the stratigraphy and character of the Chalk Group in the western onshore region is less well-known. The work described here was undertaken as a BSc project at the Department of Geosciences and Natural Resource Mangement at the University of Copenhagen by the first author as part of regional seismic mapping work contributing to an evaluation of the geothermal energy potential in Denmark. The aim of this paper is to present a summary of the key results of the study. We have subdivided and mapped the distribution of the Chalk Group in the northern North German Basin and the south-western Danish Basin based on digital reflection seismic profiles. We also highlight seismic architectural features that testify to periods of active bottom currents
A novel technique for obtaining representative water samples during CO2 core-flooding experiments on chalk at reservoir conditions
No full textThere is a huge potential for using CO2 gas to recover additional oil after water flooding in reservoir chalk. However, the injection of CO2 into chalk reservoirs will disturb the chemical equilibrium between formation water, injection water and chalk. A proper understanding of these CO2-induced interactions and the resulting changes in the physical properties at representative reservoir conditions is required. Unfortunately, reliable chemical data are rare because data cannot be acquired directly at reservoir conditions with present-day techniques. In published experiments, water samples are in many cases obtained at atmospheric conditions with the aid of a back-pressure regulator. Thus, water samples are not representative of in situ reservoir conditions and if proper care is not taken, the collected data cannot be used to judge the magnitude of the chemical reactions taking place at reservoir conditions. However, in some cases water obtained at laboratory conditions can give information on in situ reservoir conditions by using geochemical speciation models to account for dissolved gases that are lost from the effluents during sampling (Bachu & Adams 2003)
Calcareous nannofossil and foraminifer biostratigraphy of the Campanian–Maastrichtian chalk of the Femern Bælt (Denmark–Germany)
No full textA new study based on calcareous nannofossil and benthic and planktonic foraminifer biostratigraphy is presented for the upper Campanian – Maastrichtian chalk of the Femern Bælt (Denmark and Germany; Fig.1). The results are consistent with recent studies of the Danish chalk for this interval, allowing correlation across the Danish Basin and forming the basis for correlation further afield within the Boreal Realm. Numerous studies have been carried out recently on the upper Campanian – Maastrichtian chalk of the Danish Basin, covering aspects such as sedimentology, depositional environment, macrofossil biostratigraphy, carbon isotope stratigraphy as well as nannofossil and dinoflagellate biostratigraphy. However, very few published studies on foraminifers exist across this interval in this area. The 09.A.006, 09.A.007 and 09.A.008 boreholes (Fig. 2) were drilled in 2009 in preparation for construction of a fixed link across the Femern Bælt, which will connect Denmark to Germany (Rambøll Arup JV 2011). The boreholes penetrated glacial till, Paleocene– Eocene clay and chalk (Sheldon et al. 2012). Here, for the first time, the Boreal foraminifer biostratigraphy of the late Campanian – Maastrichtian interval is investigated and presented alongside nannofossil biostratigraphy
Aeromagnetic survey in south-eastern Greenland: project Aeromag 2013
No full textAeromagnetic surveys are nowadays used at a wide range of scales and purposes. In frontier and under-explored areas, where data are otherwise sparse or non-existent, aeromagnetic acquisition remains the cheapest and easiest way to obtain or refine a picture of the structural setting. Aeromagnetic data are also useful for strategic planning of geological mapping campaigns and detailed geophysical data acquisition. Moreover, aeromagnetic data are of importance for prospecting, helping to define prospects. Large aeromagnetic surveys can be carried out efficiently and safely almost everywhere, in a short period of time and at reasonable cost
Palynological and microfossil biostratigraphy and palaeoecology over the Paleocene–Eocene transition, Femern Bælt, northern Germany
No full textA palynological and micropalaeontological biostratigraphic and palaeoecological investigation has been carried out on the Paleocene–Eocene transition of core 10.A.057 from the Femern Bælt (Fig. 1). Initial investigations of boreholes from the Femern Bælt indicated that core 10.A.057 included a thick succession of Upper Paleocene – Lower Eocene clay (Sheldon & Nøhr Hansen 2010; Rambøll Arup JV 2011; Fig 2). Complete Paleocene–Eocene sections have been described from Jylland and the Storebælt (Heilmann-Clausen 1985, Laursen & Andersen 1997; Laursen & King 2000, Nielsen et al. 1986), but no detailed studies have been published on these successions from the Femern Bælt. Boreholes were drilled on Lolland in Denmark, under the Femern Bælt and on Fehmarn island, Germany from 2009 to 2011 as part of geological and geophysical investigations performed in preparation for the construction of a fixed road and rail link connecting Denmark and Germany. The boreholes penetrated Campanian – Upper Eocene strata, overlain by Quaternary deposits. Borehole 10.A.057 is located in the southern part of the Femern Bælt (Figs 1, 2)
Stormwater management: methods for measuring near-surface infiltration capacity in clayey till
No full textGlacial till forms a major proportion of the surface deposits in Northern Europe, and in Denmark more than 40% of the land surface is covered by clayey till. At the same time the majority of densely populated areas are situated on this fertile sediment type. In urban areas, one of the major tools in adaptation to climate change are sustainable drainage systems (SuDS). Their function is to manage the increasing amounts of stormwater on site, often by direct infiltration into the sediment. Accordingly, a realistic estimate of nearsurface hydraulic properties is required when dimensioning SuDS for infiltration
Combining exploration and multivariate techniques to detect the Bjørnesund West gold occurrence, southern West Greenland
No full textGold exploration in the Bjørnesund region has been carried out since the early 1990s, and gold was found in the central part of the Bjørnesund East area by NunaOil and the Geological Survey of Denmark and Greenland (GEUS). Records of stream sediment samples with elevated gold concentrations up to several hundred parts per billion led to the recognition that amphibolites in the central part of the Bjørnesund East could be a promising target and work in 1996 led to the discovery of hydrothermally altered amphibolites with up to several hundred ppb gold. However, exploration work was limited to grassroots prospecting and none of the targets were drilled
Mass loss from an ice-sheet drainage basin in West Greenland
No full textThe Greenland ice sheet is losing mass to the ocean at an increasing rate (Thomas et al. 2006). During the 1980s the ice sheet was believed to be in near-equilibrium (van den Broeke et al. 2009). Within the first decade of the 21st century, however, a net negative balance was observed. Greenland’s present rate of ice loss is c. 250 Gt yr–1, equivalent to a sea-level rise contribution of c. 0.69 mm yr–1. The rate of ice loss has increased over the post 1992 observation period (Shepherd et al. 2012)
To what extent is Denmark vulnerable to mineral supply shortage?
No full textMineral resources are building blocks of modern society and essential for progress and prosperity. Mankind has always depended on access to mineral raw materials, which have been a key factor for wealth, culture and development. Modern societies are characterised by a rapidly increasing demand for specialised mineral raw materials, determined by their stage of technological development, the number of consumers, and their standard of living. Generally, the availability of mineral raw materials has not, until recently, been considered an issue by the average consumer or by companies in the downstream end of the value chains, and mineral resources have not been part of the political agenda. In this context China’s control over rare-earth elements (REE) has been an eye opener to both industry and politicians worldwide, and has subsequently led to discussions about the possible exhaustion of finite resources and potential threats to the availability of raw materials caused by geopolitical tension and market restrictions