GEUS Bulletin (Geological Survey of Denmark and Greenland)
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P–T history of kimberlite-hosted garnet lherzolites from South-West Greenland
No full textExploration for diamonds in West Greenland has experienced a major boost within the last decade following the establishment of world-class diamond mines within the nearby Slave Province of the Canadian Arctic. Numerous companies have active programmes of diamond exploration and increasingly larger diamonds have been discovered, notably a 2.392 carat dodecahedral stone recovered by the Canadian exploration company Hudson Resources Inc. in January 2007. The Geological Survey of Denmark and Greenland (GEUS) is currently carrying out several studies aimed at understanding the petrogenesis of diamondiferous kimberlites in Greenland and the physical and chemical properties of their associated mantle source regions (e.g. Hutchison 2005; Nielsen & Jensen 2005). 
Offshore and onshore lithostratigraphic nomenclature: Paleocene, Eocene, Oligocene and Miocene
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Bayesian belief networks as a tool for participatory integrated assessment and adaptive groundwater management: the Upper Guadiana Basin, Spain
No full textLas Tablas de Daimiel, together with other wetlands in La Mancha, Spain, situated in the Upper Guadiana Basin (Fig. 1), has been catalogued as a Biosphere Reserve Area since 1981 as part of the UNESCO Man and the Biosphere programme. Between the mid-1970s and late 1980s, over 150 000 hectares of new irrigation areas were established, mainly as a result of private initiative. The average recharge rate of groundwater in the western La Mancha aquifer in the Upper Guadiana Basin is estimated to be between 200 and 500 million m3 per year, in dry and wet years respectively. Recharge also depends on the depth of the water table (Martínez-Cortina & Cruces 2003). Abstraction reached 600 million m3 per year by the end of the 1980s. Up to this time a total of 3000–5000 million m3 of the Upper Guadiana Basin aquifer’s water reserves was withdrawn (Bromley et al. 2000; Lopéz-Geta et al. 2006). The intensive use of groundwater has been a main factor for the improvement of the social and economic situation in this region, with a population of about half a million people, and where the agricultural sector is very important (Llamas et al. 2006). Water-table drawdown due to the intensive abstraction of groundwater for irrigation has caused severe negative impacts on wetlands, streams and rivers, and has resulted in a lowering of groundwater levels by up to 50 m. The main conflicts in the area are between farmers and conservationists, between central, regional and local government water agencies, and between small farmers and big farmers. The conflicts began about three decades ago (Llamas 1988) and have not yet been settled. In 2001 the Spanish Parliament asked the Government to present a hydrological plan for the Upper Guadiana Basin within one year. More than 20 draft proposals have been presented, the last one in 2006 with a budget of almost four billion Euros. This proposal has been met with strong opposition from most farmer lobbies. The Guadiana Basin is one of seven trans-boundary case studies of the EU NeWater research project (New Approaches for Adaptive Water Management under Uncertainty). The principal water-management issues in the project are addressed by adaptive and integrated water-resource manage ment. This includes uncertainty and risk mitigation, governance, crosssectoral integration, scale analysis, information management, stakeholder participation, financial aspects, system resilience and vulnerability. One work block in the NeWater project has the task of translating research outputs into tools for practitioners and end-users. As part of this effort, Bayesian belief networks (Bns) were selected as one possible tool to be developed as an aid to stakeholder participation in integrated assessment of gaps, being a suitable tool for dialogue in order to identify gaps in water-resource management functions, gaps to meet the goals of the EU Water Framework Directive and to analyse management potentials and constraints. The purpose of this paper is to describe the testing of Bns as a tool for participatory integrated assessment and adaptive and integrated water-resource management in the Upper Guadiana Basin
Colophon, contents, abstract, introduction, geological setting, previous work and material and methods
No full textAs a result of a lithological, sedimentological and biostratigraphic study of well sections from the Danish sector of the North Sea, including some recently drilled exploration wells on the Ringkøbing–Fyn High, the lithostratigraphic framework for the siliciclastic Palaeogene to Lower Neogene sediments of the Danish sector of the North Sea is revised. The sediment package from the top of the Chalk Group to the base of the Nordland Group is subdivided into seven formations containing eleven new members. The existing Våle, Lista, Sele, Fur, Balder, Horda and Lark Formations of previously published lithostratigraphic schemes are adequate for a subdivision of the Danish sector at formation level. Bor is a new sandstone member of the Våle Formation. The Lista Formation is subdivided into three new mudstone members: Vile, Ve and Bue, and three new sandstone members: Tyr, Idun and Rind. Kolga is a new sandstone member of the Sele Formation. Hefring is a new sandstone member of the Horda Formation. Freja and Dufa are two new sandstone members of the Lark Formation. Danish reference sections are established for the formations, and the descriptions of their lithology, biostratigraphy, age and palaeoenvironmental setting are updated.
 
Prediction of reservoir sand in Miocene deltaic deposits in Denmark based on high-resolution seismic data
No full textIntense investigations of deep aquifers in Jylland, western Denmark, during the last seven years have resulted in detailed mapping of Miocene sand-rich deposits laid down in fluvial channels, delta lobes, shoreface and spit complexes (Fig. 1; Rasmussen 2004). Detailed sedimentological and palynological studies of outcrops and cores, and interpretation of high-resolution seismic data, have resulted in a well-founded sequence-stratigraphic and lithostratigraphic scheme (Fig. 1) suitable for prediction of the distribution of sand. The Miocene succession onshore Denmark is divided into three sand-rich deltaic units: the Ribe and Bastrup sands and the Odderup Formation (Fig. 2). Prodeltaic clayey deposits of the Vejle Fjord and Arnum Formations interfinger with the sand-rich deposits. Most of the middle and upper Miocene in Denmark is composed of clayey sediments referred to the Hodde and Gram Formations (Fig. 2). This paper presents examples of seismic reflection patterns that have proved to correlate with sand-rich deposits from lower Miocene deltaic deposits and that could be applied in future exploration for aquifers and as analogues for oil- and gas-bearing sands in wave-dominated deltas
Lithostratigraphy of the Palaeogene – Lower Neogene succession of the Danish North Sea
No full textAs a result of a lithological, sedimentological and biostratigraphic study of well sections from the Danish sector of the North Sea, including some recently drilled exploration wells on the Ringkøbing–Fyn High, the lithostratigraphic framework for the siliciclastic Palaeogene to Lower Neogene sediments of the Danish sector of the North Sea is revised. The sediment package from the top of the Chalk Group to the base of the Nordland Group is subdivided into seven formations containing eleven new members. The existing Våle, Lista, Sele, Fur, Balder, Horda and Lark Formations of previously published lithostratigraphic schemes are adequate for a subdivision of the Danish sector at formation level. Bor is a new sandstone member of the Våle Formation. The Lista Formation is subdivided into three new mudstone members: Vile, Ve and Bue, and three new sandstone members: Tyr, Idun and Rind. Kolga is a new sandstone member of the Sele Formation. Hefring is a new sandstone member of the Horda Formation. Freja and Dufa are two new sandstone members of the Lark Formation. Danish reference sections are established for the formations, and the descriptions of their lithology, biostratigraphy, age and palaeoenvironmental setting are updated
Petroleum geochemistry of the deepened Lopra-1/1A re-entry well, Faroe Islands
No full textThe Lopra-1/1A re-entry well was drilled as a stratigraphic test with no immediate exploration objectives. Hence, petroleum geochemical studies were of limited extent, and restricted to non-destructive analyses. The presence of natural petroleum hydrocarbons could not be confirmed with certainty, but hydrocarbons extracted from the hydrochloric acid solute of a calcite vug present in RSWC #1 (3543 m), may represent indigenous petroleum since hydrocarbon-bearing fluid inclusions have been reported from the same sample. These hydrocarbons show some similarities to petroleum generated from the Upper Jurassic – Lower Cretaceous Kimmeridge Clay type source rocks present in surrounding areas. Except for this sample, the results generally show the presence of a variety of contaminants of different origins such as ‘naturally greasy fingers’ (squalene and cholesterol), cosmetics such as chap stick or hand lotion (e.g. esters such as butyl-stearate, stearyl-palmitate, vitamin A), plasticisers (phthalates), diesel oil and ‘pipe dope’
The Tikiusaaq carbonatite: a new Mesozoic intrusive complex in southern West Greenland
No full textUltrabasic alkaline magmatic rocks are products of melts generated deep within or at the base of the lithospheric mantle. The magmas may reach the surface to form lavas and pyroclastic deposits; alternatively they crystallise at depth to form dykes or central complexes. The rocks are chemically distinct and may contain high concentrations of economically interesting minerals and chemical elements, such as diamonds, niobium, tantalum, rare earth elements, phosphorus, iron, uranium, thorium, and zirconium. Ultrabasic alkaline rocks are known from several provinces in Greenland, but extrusive facies have only been preserved at a few places; e.g. at Qassiarsuk in South Greenland where pyroclastic rocks occur, and in the Maniitsoq region, where a small volcanic breccia (‘Fossilik’) contains fragments of Palaeozoic limestone. Ultramafic lamprophyre and kimberlite are mainly emplaced as dykes, whereas carbonatite forms large intrusive bodies as well as dykes. The ultrabasic alkaline magmas that have been emplaced at certain times during the geological evolution of Greenland can be related to major episodes of continental break-up (Larsen & Rex 1992). The oldest are Archaean and the youngest dated so far are Palaeogene. Figure 1 shows the distribution of known ultrabasic alkaline rocks in West Greenland. The large and well-exposed bodies of alkaline rocks and carbonatites in the Gardar Province were discovered already in the early 1800s (Ussing 1912), while less conspicuous bodies were discovered much later during geological mapping and mineral exploration. Many alkaline rock bodies, particularly dykes, are difficult to identify in the field because they weather more extensively than the country rock gneisses and form vegetated depressions in the landscape. However, their distinct chemistry and mineralogy render alkaline rocks identifiable in geochemical and geophysical survey data. Thus, the Sarfartôq carbonatite complex was discovered during regional airborne gamma-spectrometric surveying owing to its elevated uranium and thorium contents (Secher 1986). The use of kimberlite indicator minerals has led to the discovery of alkaline rocks such as kimberlites and ultramafic lamprophyres that carry fragments of deep lithospheric mantle. Such rocks may also contain diamonds. Kimberlite indicator minerals are high-pressure varieties of minerals, such as garnet, clinopyroxene, chromite and ilmenite that were formed in the lithospheric mantle. Exploration companies have processed thousands of till samples from southern West Greenland for kimberlite indicator minerals and found many new dykes