GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Tectonic control on the formation of Roskilde Fjord, central Sjælland, Denmark
No full textRoskilde Fjord is a characteristic N–S-trending geomorphological element in north-east Sjælland (Fig. 1). The eastern coastline of the fjord forms a nearly straight, SSE– NNW-trending lineament from the town of Roskilde to the coastal areas at Kattegat. Due to the records from wells, it has long been known that a fault zone has to be present along this lineament (Bondesen 1979). The fault is named after the fjord: the Roskilde Fjord Fault (Fig. 2). However, a detailed analysis of the well data in the Roskilde area has shown that a number of minor faults are present, superposed by various landscape elements. These are the inner fjord and valley distributary at Roskilde, the Kornerup Å valley, the inlet of Lejre Vig and its contributory, and the peninsula of Bognæs (Figs 1, 2). In this paper we propose a lithostratigraphic division of the Cenozoic deposits and their dynamic development in the Roskilde area. A distribution of the faults with estimated maximum displacements is presented, and their relations to the geomorphological features are outlined. The description is based on several years’ studies of the Roskilde Fjord fault complex and presented here due to the recent interest in neotectonics in Denmark and environmental considerations focused on Roskilde Fjord (Gravesen & Pedersen 2005)
New zircon U-Pb and Hf isotopic constraints on the crustal evolution of the Skjoldungen region, South-East Greenland
No full textWe report new zircon U-Pb and Hf isotopic data from the Skjoldungen region between c. 62°30´ and 63°40´N in South-East Greenland. The work was carried out under the South-East Greenland Mineral Endowment Task (SEGMENT); a joint project between the Geological Survey of Denmark and Greenland (GEUS) and the Ministry of Mineral Resources (MMR) in Greenland to assess the mineral endowment and update the geological knowledge of the region using modern petrological, geochemical and geochronological tools. This paper presents new zircon U-Pb and Hf isotopic data from a range of different Archaean rocks in the Skjoldungen region, which greatly improve the understanding of the history of crustal growth
In situ fractionation and inward migration of the solidification front in the Skaergaard intrusion, East Greenland
No full textFor more than 80 years the Skaergaard intrusion, 68°N in southern East Greenland, has been a foremost natural laboratory for the study of the crystallisation and fractionation of basaltic magma. This process has been of prime importance in the evolution of the Earth and other stony planets. Models that have been developed and refined during numerous studies of this particular intrusion have been part of the foundation for petrogenetic modelling for decades. In later years, vast amounts of new data have been added, due to systematic sampling in the field and from analysis of exploration drill cores. Methods for the study on grain-size scale have advanced, and the quest for a wellsupported genetic model for the PGE-Au mineralisation of the intrusion has intensified. The new data and insight question the applicability of conventional petrogenetic modelling, and as a consequence, increasing importance is placed on in situ crystallisation and fractionation in mush zones at the roof, walls and floor of the intrusion
Geochemistry of the Maastrichtian Rørdal Member, Jylland, Denmark: Ce anomaly as a palaeo-redox proxy
No full textThe chemical composition of chalk and marl reflects the mixture of carbonate particles and clastic input deposited on the seabed together with growth of authigenic minerals and diagenesis. The Rørdal quarry in Jylland (Fig. 1) is known for its alternating chalk–marl succession (Surlyk et al. 2010) and the aim of this article is to investigate how this cyclicity is reflected in the geochemical signature of the sequence and test if this has implications for the interpretation of the depositional environment as well as the chemostratigraphy in the chalk
Mapping of the CO2 storage potential in the Nordic region
No full textThe concept of utilising available pore space in deep saline sandstone aquifers for storage of CO2 was recognised in the late 1980s. In 1996, the first commercial CO2 storage project began with injection into sandstones of the Utsira Formation in Norway. The formation is located above the Sleipner Formation from where the Sleipner field produces natural gas. The project was initiated due to a high CO2 content of the natural gas, which was subjected to a Norwegian offshore carbon tax. The natural gas is produced on the Sleipner platform where the CO2 is separated, captured and reinjected from a neighbouring platform. The potential for using the technology to reduce CO2 emissions from large stationary point sources initiated many research projects aimed at mapping areas with potential CO2 storage capacity around the world
Biostratigraphic correlation of the western and eastern margins of the Labrador–Baffin Seaway and implications for the regional geology
No full textNew analyses of the palynological assemblages in 13 offshore wells on the Canadian margin and six on the West Greenland Margin, in conjunction with onshore data, have led to a new biostratigraphic framework for the Cretaceous–Cenozoic strata of the Labrador Sea – Davis Strait – Baffin Bay (Labrador–Baffin Seaway) region and the first broad biostratigraphic correlation of the Canadian and Greenland margins. This framework is based on 167 last occurrences and 18 local/regional peak/common-occurrence events for dinocysts, miospores, fungal spores and Azolla. Detailed biostratigraphic evidence has confirmed the following hiatuses: pre-Aptian in the Hopedale Basin; pre-Albian in the Saglek Basin; Albian–Turonian in some wells of the Hopedale Basin; Turonian–Santonian/Campanian in some areas; pre-Campanian and late Campanian – Thanetian on the Greenland Margin; late Maastrichtian and Danian in some wells of the Hopedale Basin and in the Saglek Basin; Selandian in part of the Hopedale Basin, in all the Saglek Basin wells and in two wells on the West Greenland Margin; late Ypresian and/or Lutetian on both sides; Oligocene to middle Miocene of considerable variability on both margins, with all of the Oligocene and the lower Miocene missing in all the West Greenland Margin wells; and middle to late Miocene on the western side. On the Canadian margin, the hiatuses can be partially matched with the five previously recognised regional unconformities; on the Greenland margin, however, the relationship to the five unconformities is more tenuous. Palynomorph assemblages show that most Aptian to Albian sediments were deposited in generally non-marine to marginal marine settings, interrupted by a short-lived shallow marine episode in the Aptian. A marine transgression started in the Cenomanian–Turonian and led to the most open-marine, oceanic conditions in the Campanian–Lutetian; shallowing probably started in the late Lutetian and continued into the Rupelian, when inner neritic and marginal marine palaeoenvironments predominated. Throughout the rest of the Cenozoic, inner neritic palaeoenvironments alternated with marginal marine conditions on the margins of the Labrador–Baffin Seaway. These observations broadly reflect the tectonic evolution of the seaway, with rift conditions prevailing from Aptian to Danian times, followed by drift through much of the Paleocene and Eocene, and post-drift from Oligocene to the present. Dinocysts indicate that climatic conditions in the Labrador–Baffin Seaway region were relatively temperate in the Cretaceous, but varied dramatically through the Cenozoic. The Danian was a time of increasingly warmer climate, a thermal maximum being reached around the Paleocene–Eocene boundary reflecting the global thermal event at this time. Warm to hot conditions prevailed throughout the Ypresian, but the climate began to cool in the Lutetian, a trend that accelerated through the Priabonian and Rupelian. Throughout the Neogene, temperatures generally declined, culminating in the Quaternary
Colophon, contents, preface
No full textThis issue of Review of Survey Activities presents a selection of 24 papers reflecting the wide spectrum of current activities of the Geological Survey of Denmark and Greenland, from the microscopic to the plate-tectonic level. The Survey’s activities in Denmark are illustrated by 11 papers covering widely different subjects including groundwater management, pesticide monitoring, 3D urban geology, the regional Danish potential for geothermal energy, Palaeozoic stratigraphy from borehole logs, enhancement of oil production by injection of ‘smart’ water and glacial geology. Activities in Greenland are illustrated by eight papers on Precambrian crustal evolution and mineralisation processes in South-East and northern West Greenland, fundamental magma processes in the Skaergaard intrusion, onshore and offshore seismological studies, and on long-term monitoring of the Greenland ice sheet and sea-ice variability.
International studies by the Survey are represented by two papers describing a large Nordic CO2-storage project and a pilot study of burial and exhumation along the eastern passive margin of Labrador and Newfoundland using apatite fission track analysis. Finally, three papers describe new developments in the digital access to, and handling of Greenland-related geodata and presentation of a new smartphone- and tablet-based app for effective handling of geological and sample data during field work
jAgeDisplay: software for evaluation of data distributions in U-Th-Pb geochronology
No full textDuring the past 10–15 years, analytical innovations in geochronology have greatly enhanced the application of geochronological data to geological problems. The advances are mainly driven by developments in laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) which allows for rapid determination of U-Th-Pb ages of mineral grains in large sample sets. LA-ICPMS has now become the most common tool in the application of zircon geochronology to a host of different geological problems
Greenland ice sheet melt area from MODIS (2000–2014)
No full textThe Greenland ice sheet is an excellent observatory for global climate change. Meltwater from the 1.8 million km2 large ice sheet influences oceanic temperature and salinity, nutrient fluxes and global sea level (IPCC 2013). Surface reflectivity is a key driver of surface melt rates (Box et al. 2012). Mapping of different ice-sheet surface types provides a clear indicator of where changes in ice-sheet surface reflectivity are most prominent. Here, we present an updated version of a surface classification algorithm that utilises NASA’s Moderate resolution Imaging Spectroradiometer (MODIS) sensor on the Terra satellite to systematically monitor ice-sheet surface melt (Fausto et al. 2007). Our aim is to determine the areal extent of three surface types over the 2000–2014 period: glacier ice, melting snow (including percolation areas) and dry snow (Cuffey & Paterson 2010). Monthly 1 km2 resolution surface-type grids can be downloaded via the CryoClim internet portal (www.cryoclim.net). In this report, we briefly describe the updated classification algorithm, validation of surface types and inter-annual variability in surface types
Investigations of detrital zircon, rutile and titanite from present-day Labrador drainage basins: fingerprinting the Grenvillean front
No full textA multidisciplinary provenance study was conducted on stream sediment samples from major rivers in the eastern part of Labrador, Canada (Fig. 1). The purpose was to fingerprint the sources that deliver material to the stream sediments and to the reservoir sand units deposited off shore in the sedimentary basins in the Labrador Sea. We used a multimineral U-Pb geochronological approach employing rutile and titanite in addition to zircon to obtain unbiased age data. The purpose of this was to characterise the different igneous and metamorphic episodes that occurred in Labrador, which is an area with highly variable geology characterised by the Palaeoproterozoic south-eastern Churchill province in the north-west, the Archaean Nain plutonic suite in the north-east, the Palaeoproterozoic Makkovik province in the east and the Mesoproterozoic Grenville Province to the south. The field work was carried out in 2012 and 2013 and the study is a collaborative project between the Geological Survey of Denmark and Greenland and the Geological Survey of Newfoundland and Labrador. In this paper we focus on three samples from the southern part of the study area where two parts of the Grenville orogeny are found (Fig. 1)