Publikationer

Contents

Gregersen, U., Knutz, P.C., Nøhr-Hansen, H., Sheldon, E. & Hopper, J.R. 27-02-2019. Tectonostratigraphy and evolution of the West Greenland continental margin.

Peel, J.S. 27.09.19. Ordovician gastropods from pebbles in Cretaceous fluvial sandstones in south-east Disko, West Greenland 

Bjerager, M., Alsen, P., Hovikoski, J., Lindström, S., Pilgaard, A.S., Stemmerik, L. & Therkelsen, J. 11-10-2019. Triassic lithostratigraphy of the Wandel Sea Basin, North Greenland.

Holm, P.M. & Prægel, N-O. 24.10.2019. The importance of in situ crystallisation and loss of interstitial melt during formation of the Kærven Syenite Complex, Kangerlussuaq, East Greenland.

Tectonostratigraphy and evolution of the West Greenland continental margin.

Gregersen, U., Knutz, P.C., Nøhr-Hansen, H., Sheldon, E. & Hopper, J.R. 2019. Tectonostratigraphy and evolution of the West Greenland continental margin.

© 2019 by Bulletin of the Geological Society of Denmark, Vol. 67, pp. 1–21, ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).

https://doi.org/10.37570/bgsd-2019-67-01

Abstract:

Large structural highs and sedimentary basins are identified from mapping of the West Greenland continental margin from the Labrador Sea to the Baffin Bay. We present a new tectonic elements map and a map of thickness from the seabed to the basement of the entire West Greenland margin. In addition, a new stratigraphic scheme of the main lithologies and tectonostratigraphy based on ties to all offshore exploration wells is presented together with seven interpreted seismic sections. The work is based on interpretation of more than 135 000 km of 2D seismic reflection data supported by other geophysical data, including gravity- and magnetic data and selected 3D seismic data, and is constrained by correlation to wells and seabed samples. Eight seismic mega-units (A–H) from the seabed to the basement, related to distinct tectonostratigraphic phases, were mapped. The oldest units include pre-rift basins that contain Proterozoic and Palaeozoic successions. Cretaceous syn-rift phases are characterised by development of large extensional fault blocks and basins with wedge-shaped units. The basin strata include Cretaceous and Palaeogene claystones, sandstones and conglomerates. During the latest Cretaceous, Paleocene and Eocene, crustal extension followed by oceanic crust formation took place, causing separation of the continental margins of Greenland and Canada with north-east to northward movement of Greenland. From Paleocene to Eocene, volcanic rocks dominated the central West Greenland continental margin and covered the Cretaceous basins. Development of the oceanic crust is associated with compressional tectonics and the development of strike-slip and thrust faults, pull-apart basins and inversion structures, most pronounced in the Davis Strait and Baffin Bay regions. During the late Cenozoic, tectonism diminished, though some intra-plate vertical adjustments occurred. The latest basin development was characterised by formation of thick Neogene to Quaternary marine successions including contourite drifts and glacial related shelf progradation towards the west and south-west.

Keywords: West Greenland, tectonostratigraphy, structural elements map, seismic geo sections, rifted margin, Cretaceous and Cenozoic sedimentary basins.

Addresses: 

Ulrik Gregersen, Paul C. Knutz, Henrik Nøhr-Hansen, Emma Sheldon, John R. Hopper, all Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.

Schnetler, K.I. 2019. On the occurrence of Spinucella reimersi (von Koenen 1872) (Gastropoda: Muricidae) in the Late Miocene Gram Clay of Denmark, and an emended description of the species.

Abstract:

The very rare gastropod species Spinucella reimersi (von Koenen 1872) from the Gram Clay, southern Denmark, has for many years been more or less overlooked in the palaeontological literature. Schnetler (2005) monographed the mollusc fauna of the Gram Clay and gave a description and an illustration of the holotype, housed in the von Koenen collection in the Georg-August-University, Göttingen. In 2008 and 2011 two further specimens were found in the clay pit at Gram. The occurrence of the species is described. The new specimens have allowed an emended description of the species.

Keywords: Gastropoda, Muricidae, Spinucella reimersi, Gram Formation, Late Miocene, Denmark.

Addresses: 

Møller, I., Balling, N. & Ditlefsen, C. 2019. Shallow subsurface thermal structure onshore Denmark: temperature, thermal conductivity and heat flow.

Abstract:

Available measured temperatures and thermal conductivities covering Danish onshore areas to a depth of about 300 m have been compiled and analysed. Temperature data from 236 borehole sites, including 56 boreholes with detailed temperature profiles, are applied together with thermal conductivities mea- sured on samples collected at 34 well-characterised outcrops and on core material from 20 boreholes.
Significant thermal variations in the shallow subsurface are observed. At a depth of 50 m, a mean temperature of 8.9 ± 0.8°C is found, close to the mean annual surface temperature. Higher mean values of 9.7 ± 1.1°C found at 100 m and 11.6 ± 2.2°C at 200 m reflect a general increase of temperatures with depth. In contrast to the assumption commonly held, we observe significant lateral variations both lo- cally and regionally. At a depth of 100 m, temperatures vary between 7.3 and 13.0°C across Denmark, and at 250 m between 9.6 and 17.9°C.
Mean values of the thermal conductivities lie within a range of 0.6–6 W/(m·K) measured water- saturated at laboratory conditions. The majority of values are within the interval of 1–3 W/(m·K) and show a strong correlation with lithology. The content of quartz and the rock porosity (the content of water) are found to be two main factors controlling the observed variations. Characteristic temperature gradients are in the range 1–4°C/100 m. Following Fourier’s law of heat conduction, a clear correlation is observed between temperature gradients and thermal conductivities of different lithologies. Intervals of quartz-rich sand deposits with high thermal conductivity show low temperature gradients, chalk and limestone intervals with intermediate conductivity display intermediate gradients, while sections with fine grained clay deposits of low thermal conductivity show high gradient values. A correlation analysis provides an estimate of regional shallow heat flow of 37 ± 5 mW/m2, consistent with local, classically determined heat-flow values from shallow borehole data. However, it is significantly below deep background heat flow, and this is believed to be caused by long-term paleoclimatic effects.
The shallow subsurface thermal regime across the Danish area is largely controlled by thermal conduction. Only locally, and in rare cases, do we observe temperature perturbations due to ground- water migration. In addition to general geoscientific purposes, our results are important for several applications including exploitation of shallow geothermal energy and the use of the subsurface for heat storage and cooling purposes.

Keywords: Subsurface temperature, thermal conductivity, heat flow, Denmark, shallow depth.

Addresses: 

Development of the western Limfjord, Denmark, after the last deglaciation: a review with new data

Bennike, O., Nørgaard-Pedersen, N., Jensen, J.B., Andresen, K.J. & Seidenkrantz, M.-S. 07-09-2019. Development of the western Limfjord, Denmark, after the last deglaciation: a review with new data.

© 2019 by Bulletin of the Geological Society of Denmark, Vol. 67, pp. 53–73, ISSN 2245-7070.

(www.2dgf.dk/publikationer/bulletin).

https://doi.org/10.37570/bgsd-2019-67-04

Abstract:

This paper presents new marine evidence of Lateglacial and Holocene environmental changes in the western part of Limfjorden, and provides a review of the geological history/development of this part of northern Jylland, Denmark. Lateglacial clay without fossils is widespread in the region and is probably a glaciolacustrine deposit. Limfjorden began to form as a strait in the Early Holocene due to rising relative sea level and the oldest marine shells are dated to c. 9300 cal. years BP. We propose a new relative sealevel curve for the region based on new and published data, which appear to confirm that the relative sea-level change was not extremely rapid, which was suggested earlier. During the Mid-Holocene a wide connection existed from the western part of Limfjorden to the North Sea in the west and more narrow connections existed between Limfjorden and Skagerrak in the north. The marine fauna included several species that indicate warmer and more salty waters than at present. Gradually, the connections to the North Sea and Skagerrak closed due to long-shore sediment transport and deposition of aeolian sand combined with a fall in the relative sea level during the Middle- to Late Holocene. During the Viking Age, 800–1050 CE (Common Era), the western connection to the North Sea was still open, but around 1200 CE it was closed by a coastal sandy barrier and the western part of Limfjorden became brackish. The coastal barrier was flooded on several occasions but soon formed again. After 1825 CE the western connection from Limfjorden to the North Sea has been maintained artificially.

Keywords: Holocene, Lateglacial, relative sea-level changes, salinity changes, Limfjorden, Denmark.

Addresses: 

Ole Bennike, Niels Nørgaard-Pedersen, Jørn Bo Jensen, Geological Survey of Denmark and Greenland (GEUS), C.F. Møllers Allé 8, DK-8000 Aarhus C, Denmark. Katrine Juul Andresen, Marit-Solveig Seidenkrantz, Department of Geoscience, Aarhus University, Høegh-Guldbergs Gade 2, DK-8000 Aarhus C, Denmark.
Corresponding author: Ole Bennike.

Ordovician gastropods from pebbles in Cretaceous fluvial sandstones in south-east Disko, West Greenland.

Peel, J.S. Ordovician gastropods from pebbles in Cretaceous fluvial sandstones in south-east Disko, West Greenland.

© 2019 by Bulletin of the Geological Society of Denmark, Vol. 67, pp. 75–81. ISSN 2245-7070.

(www.2dgf.dk/publikationer/bulletin).

https://doi.org/10.37570/bgsd-2019-67-05

Abstract:

The gastropods Sinuopea sp. and Lecanospira cf. compacta (Salter 1859) of probable early Ordovician age are described from cherty limestone clasts within fluvial strata of the Cretaceous Atane Formation of south-east Disko, central West Greenland. The record of Sinuopea possibly suggests an earliest Ordovician (Tremadocian) age, slightly older than the Floian–Dapingian age suggested by the oldest known conodont assemblages described from West Greenland. The determinations provide supporting evidence for a former periodic cover of Ordovician strata in the Archaean terrane of south western Greenland, extending deep into the heart of the Laurentian landmass.

Keywords: Greenland, Disko, Cretaceous lags, Atane Formation, Ordovician gastropods.
Addresses: John S. Peel, Department of Earth Sciences (Palaeobiology), Uppsala University,
Villavägen 16, Uppsala SE-75236, Sweden.

Triassic lithostratigraphy of the Wandel Sea Basin, North Greenland

Bjerager, M., Alsen, P., Hovikoski, J., Lindström, S., Pilgaard, A.S., Stemmerik, L. & Therkelsen, J. 11-10-2019. Triassic lithostratigraphy of the Wandel Sea Basin, North Greenland.

© 2019 by Bulletin of the Geological Society of Denmark, Vol. 67, pp. 83–105, ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).

https://doi.org/10.37570/bgsd-2019-67-06

Abstract:

The Wandel Sea Basin in eastern North Greenland forms the northern continuation of the offshore Danmarkshavn Basin and the conjugate margin to the western Barents Shelf south of Spitsbergen. The Triassic succession of eastern North Greenland, up to 700 m thick, spans the Induan (Dienerian) – Norian. The Triassic sediments rest unconformably on Upper Carboniferous and Upper Permian sediments, and are unconformably overlain by Upper Jurassic – Lower Cretaceous deposits. Based on recent fieldwork in the Wandel Sea Basin, five new and revised Triassic formations are described and included in the Trolle Land Group (revised). The Lower Triassic (Induan) Parish Bjerg Formation (revised) consists of marine sandstones, fluvial conglomerates and sandstones, and muddy flood-plain deposits. It is conformably overlain by Lower Triassic (Dienerian – lower Spathian) offshore mudstones with minor sand-dominated intervals of the Ugleungernes Dal Formation (new). The upper Spathian to Ladinian Dunken Formation (revised) is represented mainly by marine sandstones. A marked erosional unconformity characterises the base of the overlying Upper Triassic (Carnian – Norian) Storekløft Formation (new) composed of marginal marine to marine, massive sandstones and conglomerates as well as cross-bedded and biomottled marine sandstones and minor mudstone units. The Isrand Formation (mainly Middle Triassic) consists of laminated mudstones with minor thin sandstone units that were deposited in slope and basin floor settings in the eastern deeper part of the Wandel Sea Basin in Kronprins Christian Land. The Triassic succession of the Wandel Sea Basin represents a well-constrained shallow shelf to deep shelf / basin floor transect and thus forms an excellent outcrop analogue to the time-equivalent intervals in the western Barents Sea basins and the Danmarkshavn Basin offshore North-East Greenland.

Keywords:Triassic, Arctic, Greenland, sedimentology, lithostratigraphy, palaeogeography, Peary Land, Kronprins Christian Land.

Addresses: 

Morten Bjerager, Peter Alsen, Jussi Hovikoski, Sofie Lindström, all Geological Survey of Denmark and Greenland (GEUS), Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. Lars Stemmerik, GEUS and The University Centre in
Svalbard (UNIS), N-9171 Longyearbyen, Norway. Anders Pilgaard, GEUS and Allerød Kommune, Natur og Miljø, Bjarkesvej 2, 3450 Allerød, Denmark. Jens Therkelsen, GEUS and MOE A/S, Næstvedvej 1, 4760 Vordingborg, Denmark

The importance of in situ crystallisation and loss of interstitial melt during formation of the Kærven Syenite Complex, Kangerlussuaq, East Greenland

Holm, P.M. & Prægel, N-O. 24.10.2019. The importance of in situ crystallisation and loss of interstitial
melt during formation of the Kærven Syenite Complex, Kangerlussuaq, East Greenland.

© 2019 by Bulletin of the Geological Society of Denmark, Vol. 67, pp. 107–146, ISSN 2245-7070. (www.2dgf.dk/publikationer/bulletin).

https://doi.org/10.37570/bgsd-2019-67-07

Abstract:

The Kærven Syenite Complex (KSC) is one of the oldest felsic intrusions in the Tertiary East Greenland province. Here we update our previous description of the KSC and supply a greatly expanded and comprehensive geochemical dataset. New data allow us to present a more detailed petrogenetic model for the evolution of the KSC and to investigate the geochemical characteristics of igneous cumulates subjected to loss and, occasionally, replacement of residual liquid. The KSC comprises eleven mappable units that generally young westwards. Rock types range from quartz syenite to quartz alkali feldspar syenite and alkali feldspar granite. Individual intrusive units are relatively narrow and steep-sided and are collectively suggested to represent a ring dyke complex. Basement gneiss and gabbro host rocks have locally contaminated the oldest quartz syenite KSC unit, but most of the main part of the complex escaped significant influence from host rocks. A late suite of E–W to NE–SW striking peralkaline dykes of trachytic to phonolitic compositions intrude the KSC. Compositions of the KSC rocks span a considerable range in SiO2, 59–73 wt%. Concentrations of several elements vary widely for a given SiO2 (especially at SiO2 < 66 wt%), and variation diagrams do not suggest a single model for the evolution of the units of the complex. A cumulative origin is envisaged for several KSC units. Geochemical modelling suggests that KSC magmas were derived from more than one primary magma, and that the complex evolved through a four-stage process: fractional crystallisation in precursory magma chambers was followed by final emplacement of each unit, establishment of a crystal/melt mush, expulsion of part of the residual melt and, finally, crystallisation of the remaining melt. Trace element disequilibria between alkali feldspar and host rocks in two closely associated quartz alkali feldspar syenite units indicate that highly evolved residual melt was replaced by a less evolved melt phase. Modelling of potential parent melt compositions to the Kærven magmas suggests an origin not in the Iceland plume asthenosphere, but rather in a moderately enriched source, possibly in the continental lithosphere. The course of melt evolution by fractional crystallisation is indicated to have taken place in magma chambers at depth, and repeated rise of magma into the upper crustal magma chambers and crystallisation there formed the KSC. Based on our survey of published geochemical data, the inferred parental magmas seem to have few equivalents in the North Atlantic Igneous Province and may have been generated mainly from melting of enriched dry lithospheric mantle of possibly Archaean age.

Keywords: Crystal–liquid separation; in situ crystallisation; cumulates; syenite; granite; North Atlantic Igneous Province; ring dyke complex; trace elements.
Addresses: Paul Martin Holm, Department of Geosciences and Natural Resource Management, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen, Denmark. Niels-Ole Prægel, Copenhagen University Library, Nørre Allé 49, DK-2200 Copenhagen, Denmark.