GEUS Bulletin (Geological Survey of Denmark and Greenland)
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No full textReview of Survey activities 2005
Adam A. GardeChief editor
The present volume is the third issue of Review of Survey activities (RoSa). It contains 15 four-page contributions that cover a wide range of the current activities at the Geological Survey of Denmark and Greenland (GEUS). Thirteen of these are short scientific papers dealing with ongoing research by the Survey and its external partners. For the first time the research-based papers in the Review are now externally peer reviewed. A new standing panel of reviewers for RoSa has been established to ensure that the contributions are of general interest to a wide readership and that, within the limitations of space, they maintain the normal scientific standards of the Survey\u27s publications. All articles are planned to be easily readable by non-specialists, and since this is a Review of Survey activities, it should be borne in mind that many papers are first accounts of ongoing research.
The fact that almost all contributions in the current volume are scientific in nature implies that while providing a timely panorama of current research at the Survey, they are far from embracing all projects undertaken by the Survey in Denmark, Greenland and other countries in 2005. A factual overview of the activities of GEUS as a whole can be obtained at GEUS\u27 website.
In the present volume three papers deal with Cretaceous–Holocene onshore and offshore stratigraphy, sedimentology and palaeoceanography in Denmark, in part related to hydrocarbon exploration. A fourth paper from Denmark, that illustrates just one of the broad spectrum of the Survey\u27s routine responsibilities undertaken on behalf of the state, addresses construction of 3D geological models to characterise the migration of point-source pollution in groundwater reservoirs.
Projects related to Greenland and the Arctic in general are represented in this volume by a group of ten papers. The first is a methodology paper describing advanced in situ geochronological and trace element microanalysis by laser ablation techniques, a now routine analytical tool at the Survey that has provided data for several of the subsequent articles, including a study of sediment provenance in the East Greenland – Faroe Islands – Shetland region, and an account of zircon geochronology applied to Archaean geological studies in southern West Greenland. Within the same region, a new method of integrative and quantitative assessment of the gold potential is presented, and two papers deal with newly discovered kimberlites and carbonatites and their potential economic significance. One paper describes five profiles through basalts and sedimentary rocks in the Nuussuaq Basin in West Greenland, constructed using geological photogrammetrical techniques along coastal cliffs and steep valley sides. Another paper presents new evidence for the presence of continental crust in the Davis Strait obtained from seabed sampling; this is an important new contribution to the long-standing debate of the nature of the crust under the Labrador Sea and Davis Strait and its stratigraphy. A report on ongoing studies of the deep crustal structure of Greenland using earthquake seismology is presented, and a last paper concerning the Arctic region describes radical former climatic changes in the Arctic Ocean and the geophysical signature of the Lomonosov Ridge north of Greenland, and discusses the sensitivity of the sea-ice cover to global warming.
The final paper in the present volume describes the development of an environmental sensitivity atlas for coastal areas of Kenya. This project is just one of several current GEUS projects where the Survey\u27s broad technical and managing expertise is put to use in developing countries
Zircon geochronology from the Kangaatsiaq–Qasigiannguit region, the northern part of the 1.9–1.8 Ga Nagssugtoqidian orogen, West Greenland
No full textThe Kangaatsiaq–Qasigiannguit region in the northern part of the Palaeoproterozoic Nagssugtoqidian orogen of West Greenland consists of poly-deformed orthogneisses and minor occurrences of interleaved, discontinuous supracrustal belts. Laser ablation ICP-MS 207Pb/206Pb analyses of detrital zircons from four metasedimentary rocks (supplemented by ion probe analysis of one sample) and igneous zircons from six granitoid rocks cutting metasedimentary units indicate that the supracrustal rocks in the Kangaatsiaq–Qasigiannguit (Christianshåb) region are predominantly Archaean in age. Four occurrences of metasedimentary rocks are clearly Archaean, two have equivocal ages, and only one metasedimentary unit, from within the Naternaq (Lersletten) supracrustal belt, is demonstrably Palaeoproterozoic and readily defines a large fold complex of this age at Naternaq. The 2.9–2.8 Ga ages of detrital Archaean grains are compatible with derivation from the local basement orthogneisses within the Nagssugtoqidian orogen. The detrital age patterns are similar to those of metasediments within the central Nagssugtoqidian orogen but distinct from age patterns in metasediments of the Rinkian belt to the north, where there is an additional component of pre-2.9 Ga zircons. Synkinematic intrusive granitoid rocks constrain the ages of some Archaean deformation at 2748 ± 19 Ma and some Palaeoproterozoic deformation at 1837 ± 12 Ma
Five slices through the Nuussuaq Basin, West Greenland
No full textIn 2006 an important milestone will be reached in the study of the three-dimensional structure and architecture of the Nuussuaq Basin in West Greenland. The fifth and last of a series of detailed geological profiles through the sedimentary and volcanic rocks of the Nuussuaq Basin on Disko and Nuussuaq will be published (Fig. 1). At the same time, the last geological map at scale 1:100 000 of the basin area will be completed. These studies have been carried out over more than two decades by a group of scientists within Geocenter Copenhagen and the Technical University of Denmark. The five geological profiles are at scale 1:20 000 and have been published as coloured plates in the same format as the geological maps (Pedersen et al. 1993, 2002a, 2003, 2005, 2006). In total, the profiles cover about 500 km of cross-sections through a classic sedimentary-volcanic basin and its crystalline basement. This is one of the best exposed basins of its kind on Earth, and it serves as a reference area for studies of similar basins on the continental shelves of Greenland, north-western Europe and elsewhere
Magnetic anomalies and metamorphic boundaries in the southern Nagssugtoqidian orogen, West Greenland
No full textWithin the southern Nagssugtoqidian orogen in West Greenland metamorphic terrains of both Archaean and Palaeoproterozoic ages occur with metamorphic grade varying from low amphibolite facies to granulite facies. The determination of the relative ages of the different metamorphic terrains is greatly aided by the intrusion of the 2 Ga Kangâmiut dyke swarm along a NNE trend. In Archaean areas dykes cross-cut gneiss structures, and the host gneisses are in amphibolite to granulite facies. Along Itilleq strong shearing in an E–W-oriented zone caused retrogression of surrounding gneisses to low amphibolite facies. Within this Itivdleq shear zone Kangâmiut dykes follow the E–W shear fabrics giving the impression that dykes were reoriented by the shearing. However, the dykes remain largely undeformed and unmetamorphosed, indicating that the shear zone was established prior to dyke emplacement and that the orientation of the dykes here was governed by the shear fabric. Metamorphism and deformation north of Itilleq involve both dykes and host gneisses, and the metamorphic grade is amphibolite facies increasing to granulite facies at the northern boundary of the southern Nagssugtoqidian orogen. Here a zone of strong deformation, the Ikertôq thrust zone, coincides roughly with the amphibolite–granulite facies transition. Total magnetic field intensity anomalies from aeromagnetic data coincide spectacularly with metamorphic boundaries and reflect changes in content of the magnetic minerals at facies transitions. Even the nature of facies transitions is apparent. Static metamorphic boundaries are gradual whereas dynamic boundaries along deformation zones are abrupt
Construction of 3D geological models in glacial deposits to characterise migration of pollution
No full textThe National geological database at the Geological Survey of Denmark and Greenland (GEUS) is based on an extensive well database Jupiter, a geophysical database Gerda (Tulstrup 2003) and a recently established database for various types of geological models. These databases are integrated in a GIS system. The integration of this data enables new possibilities of constructing improved geological models. GIS systems offer a powerful tool for the geologist not only in combining multiple data, but also in visualising the model and hence presenting the final product in a simple and understandable way. 3D geological models will become increasingly important for the execution of improved cost-benefit analysis and risk assessment of contaminated sites, as well as strategic evaluation of groundwater and raw material resources in general. The possibility of storing such models on a public platform will be a major advance for future users of geological databases. The primary goal of this paper is to demonstrate the potential of an integrated GIS system, with an example of how traditional geological information may be combined in new ways in order to improve the correlation of well data in multiple directions. The application is demonstrated for a highly contaminated industrial site in the town of Ringe, Denmark (Fig. 1)
East Greenland and Faroe–Shetland sediment provenance and Palaeogene sand dispersal systems
No full textThe sedimentation and basin evolution of the Kangerlussuaq Basin, southern East Greenland has gained renewed interest with the licensing rounds offshore the Faroe Islands in 2000 and 2005, as it forms an important analogy to the Faroese geological setting. The Faroes frontier area is in part covered by basalts and is a high-risk area with poorly known plays and sedimentary basins. It is therefore essential to obtain as much information as possible on the evolution of sedimentary basins on the rifted volcanic margins closest to the Faroese Islands margin. Plate reconstructions of the North Atlantic region indicate the former close proximity of East Greenland to the Faroe Islands region (Fig. 1), and the Kangerlussuaq Basin thus constitutes the most important field analogue with respect to stratigraphy, major unconformities and basin evolution. The study of the sedimentary succession in the Kangerlussuaq Basin, and the provenance of the sandstones in particular, will provide constraints on exploration models and may help to predict the distribution of potential reservoir sandstones in the Faroese offshore basins, and eventually lead to development of play types that are new to this frontier region.This paper presents the main conclusions from two research projects: Stratigraphy of the pre-basaltic sedimentary succession of the Kangerlussuaq Basin Volcanic basin of the North Atlantic and An innovative sedimentary provenance analysis, jointly undertaken by the Geological Survey of Denmark and Greenland (GEUS) and CASP (formerly Cambridge Arctic Shelf Programme). Both projects were initiated in October 2002 and concluded in September 2005. They form part of Future Exploration Issues Programme of the Faroese Continental Shelf (SINDRI programme), established by the Faroese Ministry of Petroleum and financed by the partners of the Sindri Group (see Acknowledgements)
KenSea – development of an environmental sensitivity atlas for coastal areas of Kenya
No full textThe Kenya coastline extends 600 km from the border of Tanzania in the south to the border of Somalia in the north (Fig. 1). The Kenyan coast features a diverse marine environment, including estuaries, mangroves, sea grass beds and intertidal reef platforms and coral reefs, which are vital for the reproduction of marine organisms. These coastal ecosystems are regarded as some of the most valuable in Kenya but face serious threats from the ever increasing human pressure of tourism, industrial pollution, destructive fishing, mangrove logging and other unsustainable uses of marine resources. Another serious threat is the maritime transportation activities along the coast and at the ports. It is estimated that at any given time more than 50 ships operate in the major shipping lanes off the Kenyan coast, of which about nine are oil tankers with capacities ranging from 50 000 to 250 000 tonnes. Furthermore, the harbour of Mombasa serves as the major port for countries in East Africa. In recognition of the risks posed by oil pollution the government of Kenya and the commercial petroleum industry agreed to develop a National Oil Spill Response Contingency Plan (NOSRCP) with the purpose of enabling a speedy and effective response to any oil spill within the territorial waters of Kenya. An important element of this plan was the mapping of the coastal resources and the development of an environmental sensitivity atlas showing the vulnerability of the coast to marine oil spills. In 2004, the Government of Kenya approached the United Nations Development Program (UNDP) in Kenya for financial support to develop an environmental sensitivity atlas. The project was approved and forwarded for funding by the Danish Consultancy Trust Fund administrated by United Nations Operational Program (UNOPS) in Copenhagen. The project was announced in Denmark, and the KenSea group headed by the Geological Survey of Denmark and Greenland (GEUS) was awarded the contract. The project comprises four phases: (1) data compilation and development of the KenSea database, (2) development of a coastal classification for Kenya, (3) development of the sensitivity index jointly with a group of stakeholders, and (4) compilation of the KenSea environmental sensitivity atlas (Tychsen 2006)
Presentation and interpretation of structural data from the Nagssugtoqidian orogen using a GIS platform: general trends and features
No full textIn this contribution we present data collected by more than 50 international geologists involved in geological mapping and research projects in the Nagssugtoqidian orogen of West Greenland, organised by the Geological Survey of Denmark and Greenland and the Danish Lithosphere Centre. Using a geographical information system (GIS) as a framework for visualisation and analysis of structural and lithological data, it is now possible to give a unique overview of thousands of data points, employed here within a study area of approximately 160 × 180 km in the central and northern Nagssugtoqidian orogen. The GIS methodology allows comparison, integration and analysis of datasets in terms of subject, space, and scale. This is extremely helpful in the recognition of geological patterns, such as terrain or domain boundaries and map-scale structures. Analysis of the available structural data shows clear differences in deformation patterns between the core and the northern segment of the Nagssugtoqidian orogen. One of the most prominent features is the ENE-striking Nordre Strømfjord shear zone, which transects the orogen from the coast to the Inland Ice. The data also clearly document a change from predominantly steeply dipping, ENE–WSW-trending fabrics and large, elongate structural domains in the core of the orogen, to large, open fold patterns and moderately to shallowly dipping fabrics in smaller structural domains in the north
Precambrian mineralising events in central West Greenland (66°–70°15´N)
No full textDuring the past decade the Geological Survey of Denmark and Greenland (GEUS) has carried out two major resource evaluations in the Precambrian basement terranes of South and West Greenland in order to locate potential areas of mineral deposits (Steenfelt et al. 2000, 2004; Stendal & Schønwandt 2003; Stendal et al. 2004). Based on geological field work and geochemical and geophysical data, these evaluations have assessed the interplay between the magmatic, tectonic and metamorphic evolution in the study areas and their mineralising events. As a result of the second of these evaluations it is now possible to outline a succession of mineralising events in the northern part of the Nagssugtoqidian orogen and in the Disko Bugt area of central West Greenland (Fig. 1), and relate them to the general Archaean and Palaeoproterozoic geological evolution of this region. However, uncertainties still exist concerning the age and detailed setting of many epigenetic mineralisations
