GEUS Bulletin (Geological Survey of Denmark and Greenland)
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Igneous intrusions in the cored Upper Jurassic succession of the Blokelv-1 borehole, Jameson Land Basin, East Greenland
No full textThe fully cored Upper Jurassic succession in the Blokelv-1 borehole in the Jameson Land Basin, East Greenland, is intersected by igneous intrusions at four levels; the intrusions comprise a c. 15 cm thick dyke and three sills with thicknesses of 0.7, 1.2 and 1.9 m. The sills consist of fine-grained, sparsely plagioclase-olivine-phyric basalt with chilled contacts to the sediments. Analyses of two sills gave very similar results. The sills are tholeiitic basalts with compositions similar to the main group of dykes and sills in the Jameson Land Basin, and the Blokelv-1 sills are thus considered to belong to this group which has been dated at c. 53 Ma. The intrusions form part of a 55–51 Ma suite of tholeiitic basalt intrusions that was emplaced over an area extending for over 500 km north-to-south within the sedimentary basins of East and North-East Greenland
Shale fabric and organic nanoporosity in lower Palaeozoic shales, Bornholm, Denmark
No full textIn organic-rich shales, pores form during oil and gas genesis within organic matter (OM) domains. The porosity thus differs markedly from that of conventional reservoir lithologies. Here we present the first description of shale fabric and pore types in the lower Palaeozoic shales on Bornholm, Denmark. The pores have been studied using the focused ion beam scanning electron microscope (FIB-SEM) technique, which allows for high resolution SEM images of ion polished surfaces. Shale porosity is influenced by many factors including depositional fabric, mineralogical composition, diagenesis and oil and gas generation (Schieber 2013). Here we discuss some of these factors based on a study of lower Palaeozoic shale samples from the Billegrav-2 borehole on Bornholm (Fig. 1) undertaken by Henningsen & Jensen (2017). The shales are dry gas-mature (2.3% graptolite reflectance; Petersen et al. 2013) and have been extensively used as analogies for the deeply buried Palaeozoic shales elsewhere in Denmark (Schovsbo et al. 2011; Gautier et al. 2014). The Danish lower Palaeozoic shale gas play was tested by the Vendsyssel-1 well drilled in northern Jylland in 2015. Gas was discovered within a c. 70 m thick gas-mature, organic rich succession (Ferrand et al. 2016). However, the licence was subsequently relinquished, due to a too low gas content. The present study confirms a close similarity of pore development between the shales on Bornholm and in the Vendsys sel-1 indicating a high porosity within this stratigraphic level throughout the subsurface of Denmark. However, the rather different development of porosity in the different shale units presents a hitherto neglected aspect of the Palaeozoic gas play in Denmark
Sedimentological and glaciotectonic interpretation of georadar data from the margin of the Vig ice-push ridge, NW Sjælland, Denmark
No full textGlaciotectonic deformations often result in a high degree of variability, including glaciotectonic and sedimentary variability. Redeposition of sediments during deformation increases the variability. Ground-penetrating radar (GPR) has proven to be a good method to determine sedimentary structures in glaciofluvial deposits (Olsen & Andreasen 1994; Van Overmeeren 1998) as well as glaciotectonic structures (Busby & Merrit 1999; Overgaard & Jakobsen 2001). Reflection facies analysis (radar facies) is a useful tool in the characterisation and interpretation of deformed sediments (Van Overmeeren 1998; Jakobsen & Overgaard 2002; Lerche et al. 2014). A GPR survey was carried out at Jyderup Skov in Odsherred in north-west Sjælland (Fig. 1). The presence of parallel ridges in the area indicates glaciotectonic deformation. The aim of the GPR study was to map the interior of the ridge complex and to interpret the genesis of the ridges
Potential for brine storage near the gas storage facility at Lille Torup, northern Jylland, Denmark
No full textThis study is based on a feasibility study for the Danish Energinet. dk to identify potential formations for brine storage near the gas storage facility at Lille Torup, northern Jylland, Denmark (Fig. 1; Hjuler et al. 2017). Located on top of a salt structure, the gas storage facility comprises seven caverns, which have been washed out by circulating water in the salt dome. One cavern contains c. 520.000 m3 of intrusive brine that must be disposed of in order to increase the storage volume for gas. One option is to inject the brine into the subsurface if a target with appropriate storage properties can be identified, but it is a prerequisite that the stored brine does not compromise freshwater reservoirs. Due to cost considerations, the brine storage should be situated within a radius of 50 km of the gas storage facility and at a depth not exceeding 2000 m. Based on the national geothermal research conducted during the last decade, a number of sandy formations are considered potential storage reservoirs (Fig. 2; e.g. Mathiesen et al. 2009; Vosgerau et al. 2016). Around Lille Torup, these include the Bunter Sandstone/Skagerrak, Gassum, Haldager Sand and Frederikshavn formations where the two former formations are discarded due to present-day burial depths exceeding 2000 m. In addition, the Chalk Group is considered a potential storage formation due to its importance as a hydrocarbon reservoir in the North Sea, however, due to risk of leakage to the younger sediments and risk of environmental issues, the chalk was discarded as potential storage zone
Colophon, contents, preface
No full textThis bulletin presents a series of nine papers dealing with the succession of Upper Jurassic – Lower Cretaceous sedimentary rocks penetrated by the fully cored Blokelv-1 borehole, drilled in western Jameson Land, central East Greenland in August 2008. The borehole was drilled as the first of three boreholes that in combination were designed to provide full coverage of the Upper Jurassic – Lower Cretaceous petroleum source-rock succession in eastern Greenland. The remaining two boreholes, Rødryggen-1 and Brorson Halvø-1, were drilled on Wollaston Forland in 2009 and 2010, respectively, and the results from these boreholes will be published in a companion volume. The objectives of the drilling campaign were fulfilled, demonstrating that continuous sedimentation of oil-prone petroleum source rocks took place in eastern Greenland over a period of c. 13 million years from the Oxfordian to the Ryazanian, with the Blokelv-1 succession representing the older, Oxfordian–Volgian part of this interval.
The drilling campaign was carried out as one of a number of projects within the framework of a multi-client collaborative programme between GEUS and a long list of petroleum companies entitled Petroleum Geological Studies, Services and Data in East and Northeast Greenland. This collaboration was initiated in 2007 and is ongoing at the time of writing with more than 20 participant companies, a subset of which sponsored the studies presented herein; for contractual reasons, these companies cannot be named. The GEUS–industry collaboration was initiated in recognition of the need for new and better data on many aspects of the petroleum geology of eastern Greenland prior to an anticipated licensing round of offshore North-East Greenland. The Circum-Arctic Resource Appraisal (CARA), undertaken by the United States Geological Survey (USGS), also played an important role in defining the priorities of the collaborative agreement by directing attention towards specific subjects in need of investigation. Licensing rounds in 2012 and 2013 resulted in the award of five licences.
Based on the results of these activities in eastern Greenland, a large number of scientific papers have been published since 2008, and more are expected as confidentiality clauses expire. This volume is, however, the first GEUS Bulletin to be published as a direct consequence of the GEUS–industry collaboration
Provenance of basinal sandstones in the Upper Jurassic Hareelv Formation, Jameson Land Basin, East Greenland
No full textZircon U–Pb geochronology and heavy mineral CCSEM analysis were used to interpret the provenance of Oxfordian–Volgian sandstones of the Hareelv Formation in East Greenland. Six samples were collected from the Blokelv-1 core drilled in southern Jameson Land, and the zircon age distributions and heavy-mineral assemblages are quite uniform. The samples contain a wide spectrum of Archaean to Palaeozoic zircon ages with peak ages at 2.71, 2.49, 1.95, 1.65, 1.49, 1.37, 1.10 and 0.43 Ga when combining all data. The heavy-mineral compositions show derivation from felsic source rocks, some of which were metamorphic. The results reveal that the sediment was derived from the Caledonides, and it is plausible that some or all of the material has experienced several cycles of sedimentation. Devonian and Carboniferous sediments preserved north of the area have zircon age distributions that correspond to those from the Hareelv Formation, and such rocks may have been reworked into the Jameson Land Basin. The provenance signature describes both the gravity-flow sandstones of the Hareelv Formation and the delta-edge sands that are inferred to have fed them. Lithological and provenance contrasts between the sandstones of the Sjællandselv Member and those of the Katedralen Member indicate a shorter transport distance, source to sink, suggestive of proximal topographic rejuvenation in the Volgian
Diagenesis of Upper Jurassic sandstones of the Blokelv-1 core in the Jameson Land Basin, East Greenland
No full textPetrographic analysis combined with X-ray diffraction are used to identify the diagenetic changes that have affected the porosity and permeability of gravity-flow sandstones of the Oxfordian–Volgian Hareelv Formation in the cored Blokelv-1 borehole in Jameson Land. Kaolinite replacement of albite grains probably occurred early after deposition and microquartz coatings formed under shallow burial. At deeper burial, illite and quartz formed from kaolinite and K-feldspar. Pervasive ankerite cement formed in the finest grained sandstones and may have formed at the expense of early calcite cement. Quartz overgrowths are volumetrically small, partly due to inhibition by microquartz coatings and partly due to limited residence time during deep burial. The succession reached the maximum burial depth of c. 2.8 km during the late Eocene. Basaltic material was intruded into the sediments during the early Eocene and the enhanced heat flow accelerated diagenesis in the close vicinity of the intrusions, which have thicknesses of up to 2 m. Most of the sandstones have porosities between 14.4 and 25.7% and permeabilities between 0.4 and 411.9 mD; this variation resulted from a combination of microquartz coatings and clay minerals. However, the intrusion-influenced sandstones and the ankerite-cemented sandstones have lower porosity and permeability
Lithostratigraphy, geology and geochemistry of the volcanic rocks of the Maligât Formation and associated intrusions on Disko and Nuussuaq, Paleocene of West Greenland
No full textThe Paleocene volcanic rocks in the Nuussuaq Basin on Disko and Nuussuaq comprise the picritic Vaigat Formation (c. 62–61 Ma) and the overlying basaltic Maligât Formation (c. 60 Ma). The Maligât Formation is up to 2000 m thick on western Disko where the top of the formation is least eroded. The formation is divided into four members, the Rinks Dal, Nordfjord, Niaqussat and Sapernuvik members, which are formally defined here. On central and eastern Disko and Nuussuaq the Maligât Formation lavas are interbedded with fluvial and lacustrine sandstones and mudstones of the Atanikerluk Formation.The Rinks Dal Member is the lowest member and originally constituted around 61% by volume of the formation. It is divided into 12 informal units based on chemically recognisable oscillations in the fractionation state of the basalts. The oldest units are present on central and south Disko close to the Disko Gneiss Ridge. The younger lavas spread farther to the east, north and west, filled the Assoq Lake basin east of the ridge and gradually onlapped the shield of the earlier Vaigat Formation that rose to the north. Only the lavas of the upper Rinks Dal Member reached far into Nuussuaq. The lavas are generally not crustally contaminated and comprise evolved basalts with 4.4–9.2 wt% MgO and a few picrites. The most evolved basalts with 3.2–4.8 wt% TiO2 occur in the middle part of the member where they form the Akuarut unit.
The Nordfjord Member originally constituted around 6% by volume of the formation. It is not subdivided because the lithological variability is local. The member is widespread but has its depocentre on north-western Disko where thicknesses reach 350 m and eruption sites, intermediate lavas and acid tuffs are present. Over most of the area the member consists of just a few lava flows with combined thicknesses of 30–100 m. The member has a very diverse lithology with rock types ranging from silicic basalt with 5.3–10.0 wt% MgO through magnesian basaltic andesite and andesite with 2.4–10.6 wt% MgO to dacite with 1.2–2.2 wt% MgO. Rhyolite with 0.2–1.2 wt% MgO and up to 77 wt% SiO2 occur in tuffs and conglomerate clasts. All rocks are crustally contaminated and some are native-iron-bearing.
The Niaqussat Member originally constituted around 33% by volume of the formation. It is subdivided into three informal units. The member is widespread, but much of it has been removed by erosion. Lithologies in the lower unit range from silicic picrite with up to 15 wt% MgO to basalt with 6–12 wt% MgO and a few basaltic andesite flows. The middle and upper parts of the Niaqussat Member comprise more evolved basalts with respectively 6.1–7.2 wt% MgO and 4.9–6.4 wt% MgO. All rocks are crustally contaminated and a few lava flows are native-iron-bearing.
The Sapernuvik Member comprises three uncontaminated basalt flows with 7.5–10.7 wt% MgO. It is only preserved in a small area on western Disko.
Dyke systems with up to 80 km long dykes and subvolcanic intrusions associated with the Nordfjord and Niaqussat members occur on western and north-eastern Disko. The rocks are crustally contaminated and range from silicic basalt with 4–13 wt% MgO to magnesian andesite with 3–10 wt% MgO. They commonly form composite intrusions, some of which contain accumulations of native iron and sulfides.
The contaminants are carbon- and sulfur-bearing sediments of the Nuussuaq Group. Major contamination mechanisms were mixing with partial melts from the sediment sidewall and xenoliths and selective exchange of some elements, including carbon and sulfur, between magma and sediment. Degrees of contamination vary from 2−5% in the basalts to 10−50% in the more silicic rocks. No rocks more evolved than basalt were produced by ordinary fractional crystallisation
Remote geological mapping using 3D photogrammetry: an example from Karrat, West Greenland
No full textThe geology of the Paleoproterozoic Karrat Group in West Greenland (71°–74°50´N) was investigated during the field seasons 2015–2017, using a combination of digital photogrammetry and traditional field work in a collaboration between the Geological Survey of Denmark and Greenland and the Ministry of Minerals Resources of Greenland. The area is characterised by steep alpine terrain with more than 2000 m of relief that in many places is completely inaccessible, which makes field work extremely difficult. Therefore 3D mapping using digital photogrammetry is an invaluable tool in the investigation of the region. Early geological investigations of the area involved the first use of photogrammetry in Greenland (Henderson & Pulvertaft 1987). This contribution serves as an example of the present-day use of photogrammetry in geological interpretation, following the workflow outlined in Sørensen & Dueholm (2018). During the last three years, more than 50 000 stereo images have been collected using handheld, calibrated digital cameras while conducting field work in the area (Rosa et al. 2016, 2017, 2018). The images, which cover large parts of the steep cliff sections in which the geology is superbly exposed, are essential to the ongoing revision of the geological map sheets covering the area. Here we present a small subset of the data from the island of Karrat (Fig. 1), showcasing the potential of 3D geological mapping in Greenland as well as presenting new insights into the geology of the Karrat Group
Biostratigraphy of the Hareelv Formation (Upper Jurassic) in the Blokelv-1 core, Jameson Land, central East Greenland
No full textThe Hareelv Formation in the Blokelv-1 core is biostratigraphically subdivided by means of ammonite and dinoflagellate cyst stratigraphy. The succession ranges from the Oxfordian C. densiplicatum Chronozone to the Volgian P. elegans Chronozone. The mudstones of the Blokelv-1 core are characterised by large amounts of amorphous organic matter. This hampers the preparation and identification of dinoflagellate cysts, which are also commonly degraded and corroded. Ammonites, on the other hand, are common and well-preserved in the core, contrasting with that observed in the equivalent facies and stratigraphic interval at outcrop. Integration of the ammonite and dinoflagellate cyst biostratigraphical data yields a robust chronostratigraphic subdivision of the middle Oxfordian – lowermost Volgian cored section