GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Water budget of Skærsø, a lake in south-east Jylland, Denmark: exchange between groundwater and lake water
No full textThe European Union’s Water Frame - work Directive aims to achieve a ‘good’ ecological status for groundwater bodies, for groundwater-dependent terrestrial ecosystems, and for aquatic surface water bodies by the year 2015. In Denmark, this goal will most likely not be fulfilled within such a short time frame due to the current poor ecological condition of Danish lakes (Søndergaard et al. 2008). However, public concern about the protection of aquatic environments has increased, and so has interest in improving lake water quality by reducing nutrient loading. Effective and sustainable lake restoration and conservation depend on the ability to (1) point out sensitive catchment areas for the lake, (2) estimate its total water and nutrient budgets and (3) relate observed differences in seepage rates to the abundance and distribution of macrophytes in the lake and to the topography and land-use of the surrounding terrain. In seepage lakes, i.e. lakes without inlets or outlets, the influence of the surrounding terrain, regional hydrogeology and lake geometry on the overall lake water budget has been studied in some detail (Krabbenhoft et al. 1990; Anderson & Cheng 1993; Cheng & Anderson, 1994; Kratz et al. 1997; Winter 1999; Townley & Trefry 2000). However, little efforthas been made to understand and quantify how riparian zones (wetlands) surrounding lakes may control the water flow and nutrient transport to the lakes. Although groundwater inflow to seepage lakes is suspected to be smaller than inflow from drainage ditches, it may still account for a significant nutrient influx
Glaciological investigations at the Malmbjerg mining prospect, central East Greenland
No full textMeeting the technical challenges posed by the Arctic environment is a key issue in the development of Greenland’s economy, particularly in the light of increasing interest in developing Greenland’s mineral resources both on- and offshore. This paper describes some results of the glaciological investigations carried out at Malmbjerg
Fracture valleys in central Jylland – a neotectonic feature
No full textGeomorphological indications of tectonic activity in the Danish glacial landscape were pointed out already by Milthers (1916, 1948). He described a conspicuous system of N–S-trending, narrow valleys in central Jylland and interpreted them as fault-generated features (fracture valleys). The valleys occur in the area between Ulstrup and Hammel and in a smaller area near Skjød (Fig. 1). The most significant valley system is found near Hvorslev, and it is here referred to as the Hvorslev lineaments (Fig. 1)
Greenland from Archaean to Quaternary. Descriptive text to the 1995 Geological map of Greenland, 1:2 500 000. 2nd edition
No full textThe geological development of Greenland spans a period of nearly 4 Ga, from Eoarchaean to the Quaternary. Greenland is the largest island on Earth with a total area of 2 166 000 km2, but only c. 410 000 km2 are exposed bedrock, the remaining part being covered by a major ice sheet (the Inland Ice) reaching over 3 km in thickness. The adjacent offshore areas underlain by continental crust have an area of c. 825 000 km2.
Greenland is dominated by crystalline rocks of the Precambrian shield, which formed during a succession of Archaean and Palaeoproterozoic orogenic events and stabilised as a part of the Laurentian shield about 1600 Ma ago. The shield area can be divided into three distinct types of basement provinces: (1) Archaean rocks (3200–2600 Ma old, with local older units up to> 3800 Ma) that were almost unaffected by Proterozoic or later orogenic activity; (2) Archaean terrains reworked during the Palaeoproterozoic around 1900–1750 Ma ago; and (3) terrains mainly composed of juvenile Palaeoproterozoic rocks (2000–1750 Ma in age). Subsequent geological developments mainly took place along the margins of the shield. During the Proterozoic and throughout the Phanerozoic major sedimentary basins formed, notably in North and North-East Greenland, in which sedimentary successions locally reaching 18 km in thickness were deposited. Palaeozoic orogenic activity affected parts of these successions in the Ellesmerian fold belt of North Greenland and the East Greenland Caledonides; the latter also incorporates reworked Precambrian crystalline basement complexes.
Late Palaeozoic and Mesozoic sedimentary basins developed along the continent–ocean margins in North, East and West Greenland and are now preserved both onshore and offshore. Their development was closely related to continental break-up with formation of rift basins. Initial rifting in East Greenland in latest Devonian to earliest Carboniferous time and succeeding phases culminated with the opening of the North Atlantic Ocean in the late Paleocene. Sea-floor spreading was accompanied by extrusion of Palaeogene (early Tertiary) plateau basalts in both central West and central–southern East Greenland.
During the Quaternary Greenland was almost completely covered by ice, and the present day Inland Ice is a relic from the Pleistocene ice ages. Vast amounts of glacially eroded detritus were deposited on the continental shelves around Greenland.
Mineral exploitation in Greenland has so far encompassed cryolite, lead-zinc, gold, olivine and coal. Current prospecting activities in Greenland are concentrated on gold, base metals, platinum group elements, molybdenum, iron ore, diamonds and lead-zinc. Hydrocarbon potential is confined to the major Phanerozoic sedimentary basins, notably the large basins offshore North-East and West Greenland. While reserves of oil or gas have yet to be found, geophysical data combined with discoveries of oil seeps onshore have revealed a considerable potential for offshore oil and gas
Diamonds and lithospheric mantle properties in the Neoproterozoic igneous province of southern West Greenland
No full textThe search for diamonds in Greenland has resulted in the discovery of many new dykes of kimberlite and ultramafic lamprophyre and, most importantly, in the acquisition of a wealth of chemical data on rocks and minerals representing mantle material entrained by the dyke magmas. The discovery of a diamondiferous sheet at Garnet Lake in southern West Greenland stimulated the research (Hutchison 2005). Over the past five to ten years, the Geological Survey of Denmark and Greenland together with the Bureau of Minerals and Petroleum in Greenland and international research groups have acquired, processed and interpreted data with the objective of identifying diamond-favourable regimes within the lithospheric mantle below the Archaean craton in West Greenland. Here we present mineral data from drift samples that allow us to identify where mantle conditions in terms of lithology and depth may be favourable for the occurrence of diamonds
Holocene climate variability in southern Greenland: results from the Galathea 3 expedition
No full textThe third Galathea expedition (Galathea 3) left Copenhagen in August 2006 for a circumnavigation of the globe with the aim of conducting more than 70 scientific programmes en route. The first geological programme took place in South Greenland and included sampling of sediment cores and seismic profiling. The aim of the study is to obtain detailed knowledge about Holocene climate changes and the glacio-marine history
Post-rift landscape development of north-east Brazil
No full textThe evolution of the landscape of north-east Brazil in relation to the burial and exhumation history of both onshore and offshore areas is the focus of a research project carried out for StatoilHydrodo Brasil and Petrobras from 2007 to 2009 by the Geological Survey of Denmark and Greenland in collaboration with Geotrack International. In hydrocarbon exploration it is important to understand the regional tectonic framework and thus also to consider the volumes of rocks that may have been present and then removed during the geological past. For example, the timing of hydrocarbon generation and changes in migration routes can be assessed when the timing and magnitude of uplift and erosion is known. Studies in West Greenland have demonstrated the usefulness of large-scale, low-relief, high-level landscapes as markers of uplift events, and in particular the strength of combining the denudation history from landscape analysis with the cooling history from apatite fission-track analysis (AFTA) data and the stratigraphic record (Bonow et al. 2006, 2007; Japsen et al. 2006, 2009). In the study area, there are two plateaux with elevations up to c. 1300 m above sea level (a.s.l.). The plateaux are currently being dissected by deeply incised fluvial valleys, and escarpments separate the two plateaux. The lowlands cut across Early Cretaceous rift systems along the Atlantic margin, including the intracontinental Recôncavo–Tucano–Jatobá (RTJ) Rift and also the Camamu Basin, of which the western margin is exposed onshore (Fig. 1). The RTJ Rift is a mature hydrocarbon province, whereas the deep-water parts of the Camamu Basin are the target of frontier exploration (e.g. Magnavita et al. 1994; Davison 1999; Cobbold et al. 2008). The post-rift sequence in the RTJ Rift and the inshore Camamu Basin is thin or absent. However, it has been estimated that up to 2000 m of sedimentary cover once was present, but has now been removed (Magnavita et al. 1994)
A new Neogene biostratigraphy for Denmark
No full textIn Denmark most of the water used in private households, in the industry and for irrigation in agriculture comes from subsurface aquifers. Some of the most important aquifers in Jylland, western Denmark, are sand layers deposited from 23 to 15 Ma ago, in the Early Neogene (Early to Middle Miocene). About 23 Ma ago, in the Early Miocene, the coastline ran NW–SE across present-day Jylland (Rasmussen 2004). Global climatic variations led to major sea-level changes (Zachos et al. 2001), which in combination with increased sediment transport from the north (the present Norway) resulted in deposition of several huge, fluvio-deltaic sand systems intercalated with marine clay (e.g. Rasmussen 1961; Rasmussen 2004; Rasmussen & Dybkjær 2005). The Geological Survey of Denmark and Greenland (GEUS) and the regional Environment Centres (the former counties (amter)) in Jylland are working in close cooperation to study the Early Neogene succession; the main purposes are: (1) to find new aquifers, (2) to map the extent of known aquifers and clarify their mutual relationships, in order to evaluate the size of the water resources and optimise production, and (3) to protect the aquifers from pollution due to leaching from the surface. In order to map the complex sedimentary succession, it has been necessary to combine several geological disciplines, including seismic interpretation, sedimentology, correlation of geophysical logs, and biostratigraphy (e.g. Dybkjær 2004; Rasmussen 2004; Rasmussen et al. 2004; Piasecki 2005; Rasmussen & Dybkjær 2005; Dybkjær & Rasmussen 2007). This article shows some results of a detailed dinoflagellate cyst stratigraphy, which is based on an extensive database (Fig. 1). We present here for the first time a dinoflagellate cyst zonation for the complete Neogene succession in the Danish area
From science to practice in implementing the European Union’s Water Framework Directive
No full textThe Water Framework Directive (WFD) of the European Union aims to achieve a ‘good’ status for all inland and coastal waters by the year 2015 (EC 2000). The directive defines how this should be achieved through the establishment of environmental objectives and ecological targets. Successful implementation of the WFD requires integration into already existing national legislation and a sound combination of issues on technical feasibility, scientific knowledge and socio-economic aspects requiring intensive stakeholder involvement. This calls for appropriate tools such as models to support management of technical and social aspects of different phases of the implementation (Rekolainen et al. 2003; Quevauviller et al. 2005). It is therefore necessary to provide an overview of already existing methods and tools and develop new ones. Research programmes funded by the European Commission (EC) often address issues of current interest for practitioners, such as the Fifth Framework Programme, where a number of research projects to support the practical implementation of the WFD were initiated under the theme ‘Energy, Environment and Sustainable Development’. The funding part (the Directorate-General for Research, DG Research) and the responsible authority for the WFD at European level (Directorate-General of Environment) saw the need to cluster these research projects and related activities, and initiated the Harmoni-CA project, a socalled ‘Concerted Action’ (i.e. Harmonised Modelling Tools for Integrated River Basin Management). The objectives of this paper are (a) to briefly describe the overall purpose of the Harmoni-CA project and some of its overarching outputs, and (b) to further illustrate how the implementation of the WFD can be enhanced by combining monitoring and modelling disciplines and by bringing practitioners and researchers together
Palaeogene diatomite deposits in Denmark: geological investigations and applied aspects
No full textThe Danish term ‘moler’ is the name for a special and unique marine deposit of Lower Eocene age found in the northern part of Denmark and the Danish North Sea. In the literature it is often referred to as mo-clay, the English translation of ‘moler’ – a whitish, powdery sediment that lithologically is a clayey diatomite. The deposit, which is defined as the Fur Formation, is also well known for its 180 volcanic ash beds, increasing in number towards the top of the formation (Pedersen & Surlyk 1983). Due to Pleistocene glaciotectonic deformations the diatomite deposits crop out at the surface in the Limfjorden area (Gry 1940; Klint & Pedersen 1995; Pedersen 1996, 2000). Prior to the deformations the Fur Formation was situated at about 50–100 m below sea level, but during the deformations the diatomite was displaced upwards into glaciotectonic complexes. The complexes form elongate parallel hills up to 80 m a.s.l. in the western Lim fjord region (Fig. 1). The clayey diatomite attracts attention because it is a valuable raw material for production of insulation bricks and absorbing granulates, which are mainly used as cat litter. In addition, the exposed Fur Formation is a unique reference for investigations of the Palaeogene stratigraphy in the North Sea, where mudstones and shales with ash layers are known as the Sele and Balder Formations (Schiøler et al. 2007). In a tectonic framework the ash layers provide a unique addition to the understanding of the development of the North Atlantic igneous province at the time when Greenland and Norway began to drift away from each other (Larsen et al. 2003). Moreover, the Fur Formation is especially noted for its rich fossil fauna, which comprises remarkably well-preserved specimens of birds, fish and insects. Due to the public interest two museum exhibitions have been established, on Mors and Fur, and the geological features are so evident that numerous geological field trips have benefited from the success of well-displayed geology seen in exposures along the coastal cliffs and in the mo-clay pits. At present a Norwegian drilling company is planning to use the Fur Formation outcrops at Skarrehage for testing before applying their new drilling method offshore. In 2007, GEUS has continued many years of mo-clay investigations, and this paper presents some results from the 2007 activities, in addition to a review on the geology of the mo-clay