Contents
Stein, M. 2008–01–03
Fritzolenellus lapworthi (Peach and Horne, 1892) from the lower Cambrian(Cambrian Series 2) Bastion Formation of North-East Greenland.
Beckmann, George, E.J. 2008–07–02:
Magnetic susceptibility ellipsoids in Nagssugtoqidian and Archaean rocks in South-East Greenland..
Larsen, T. B., Gregersen, S., Voss, P.H.1, Bidstrup, T., and Orozova-Bekkevold, V. 2008–26–11.
The earthquake that shook central Sjælland, Denmark, November 6, 2001
Sørensen, A. M., Håkansson, E. & Stemmerik, L. 2008–12–30.
Upper Permian bryozoans of central East Greenland
Fritzolenellus lapworthi (Peach and Horne, 1892) from the lower Cambrian(Cambrian Series 2) Bastion Formation of North-East Greenland.
Stein, M. 2008–01–03 Fritzolenellus lapworthi (Peach and Horne, 1892) from the lower Cambrian(Cambrian Series 2) Bastion Formation of North-East Greenland.
©2008 by Bulletin of the Geological Society of Denmark, Vol. 56, pp. 1-10.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2008-56-01
Abstract: Fossil collections from the lower Cambrian (Cambrian Series 2) Bastion Formation at Albert Heim Bjerge in North-East Greenland acquired during 1950 and 1951 contain some 60 specimens of olenellid trilobites.
Although morphologically variable, the material can be attributed to a single species, Fritzolenellus lapworthi (Peach and Horne, 1892), previously known from the ‘Fucoid’ Beds of north-west Scotland.
Immature specimens allow a first, limited, description of the ontogeny of Fritzolenellus. The presence of F. lapworthi in North-East Greenland offers an important tie point for correlation of Olenellus-bearing strata (Cambrian Series 2, Stage 4) across eastern Laurentia.
Keywords: Fritzolenellus lapworthi, Trilobita, Cambrian Series 2, Bastion Formation, Greenland
Addresses:
Martin Stein, Uppsala University, Department of Earth Sciences, Palaeobiology program, Villavägen 16, SE-752 36 Uppsala, Sweden.
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Magnetic susceptibility ellipsoids in Nagssugtoqidian and Archaean rocks in South-East Greenland.
Beckmann, George, E.J. 2008–07–02: Magnetic susceptibility ellipsoids in Nagssugtoqidian and Archaean rocks in South-East Greenland.
©2008 by Bulletin of the Geological Society of Denmark, Vol. 56, pp. 11-25.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2008-56-02
Abstract: Measurements of magnetic susceptibility have been carried out on Precambrian rocks in south-east Greenland in the Nagssugtoqidian mobile belt from Ammassalik northwards to its boundary with the Archaean craton, and slightly beyond.
Directions of maximum susceptibility are the best defined, and are as follows: Ammassalik: Declination = 3º, Inclination = 40º,α95 = 7º; Nagssugtoqidian/Archaean “boundary”: Declination = 311º, Inclination = 62º, α95 = 10º; area enclosing post-tectonic plutons: Declination = 194º, Inclination = 87º, α95 = 17º.
The boundary is invisible to the directions of maximum susceptibility. A shear zone near the boundary has been studied in detail. The maximum directions of the samples are tightly grouped and lie in the plane of the zone, whilst the intermediate directions rotate about the maximum direction as the zone is approached, until they lie in its plane.
Such rotation is widespread in the boundary area. A plate tectonic explanation for the maxima from the boundary and from Ammassalik is proposed as follows: the maximum direction from the boundary is attributed to subduction and collision of the Archaean plate arriving from the north-east, followed by a vertical component imprinted by the emplacement of the plutons.
The maximum direction at Ammassalik is due to overriding Archaean crust coming from the north. Anisotropy of magnetic susceptibility is useful in detecting shear zones and rock fabric when these are not apparent in the field or hand specimen.
Keywords: Greenland, Nagssugtoqidian, Archaean, Magnetic Anisotropy, Shear Zones collision.
Addresses:
George, E .J. Beckmann , Physics Centre, School of Natural Scinces, Newcastle University, Newcastle uponTyne, NE1 7RU, UK. Present Address: 22 Oak Avenue, Hampton, Middlesex, TW12 3NX.
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The earthquake that shook central Sjælland, Denmark, November 6, 2001
Larsen, T. B.1, Gregersen, S.1, Voss, P.H.1, Bidstrup, T.1, and Orozova-Bekkevold, V.1 2008–26–11. The earthquake that shook central Sjælland, Denmark, November 6, 2001
©2008 by Bulletin of the Geological Society of Denmark, Vol. 56, pp. 26-37.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2008-56-03
Abstract: Earthquakes on Sjælland are in general small and seldom felt. The largest earthquakes in the Danish region occur in Skagerrak and Kattegat, and they are felt in NW Jylland (Thy) and in North Sjælland on average several years apart. A small earthquake measuring just 2.8 on the Richter Scale was felt and heard over a surprisingly large area of Sjælland, Denmark on November 6, 2001.
The earthquake caused people to abruptly leave their houses near the epicenter, and minor damage to several buildings was observed. The felt area is oriented strongly asymmetrically with respect to the epicenter, but it correlates well with the local geology. Specifically the shaking was felt in a region where the depth to the Top Chalk surface is small, and the thickness of the Quaternary sediments is less than 50 m.
In 1869 an earthquake was felt strongly in the exact same area, and contours separating the felt area from the area where nothing was felt coincide almost exactly for the two earthquakes. This supports that geology and not human subjectivity is the determining factor in delineating the felt area for this earthquake.
Keywords: Earthquake; macroseismic data; seismicity.
Addresses:
1: Geological Survey of Denmark and Greenland [ T. B. Larsen ] Øster Voldgade 10, DK-1350 Copenhagen K,
Denmark.
2: DONG Energy A/S [ V. Orozova-Bekkevold ] Agern Alle 24-26, DK-2970 Hørsholm, Denmark.
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Upper Permian bryozoans of central East Greenland
Sørensen, A. M., Håkansson, E. & Stemmerik, L. 2008–12–30. Upper Permian bryozoans of central East Greenland
©2008 by Bulletin of the Geological Society of Denmark, Vol. 56, pp. 39-51.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2008-56-04
Abstract: The bryozoan fauna in the Upper Permian Wegener Halvø, Ravnefjeld and Schuchert Dal formations, central East Greenland is of modest diversity, with only 15 genera identified.
Bryozoans are most abundant in the Wegener Halvø Formation where they are important in the formation of carbonate buildups. Robust, rigidly erect colony types dominate in buildup cores whereas delicate erect types characterize the distal parts of the buildups. Cement-dominated bryozoan buildups are found in East Greenland and in the Zechstein Basin but are not known from the contemporaneous cool-water successions of North Greenland and Svalbard.
The buildups are probably formed by seawater chemistry facilitating syn-depositional cement rather than a difference in the composition of the bryozoan fauna.
Keywords: Bryozoans, Carbonate buildups, East Greenland, Permian
Addresses:
Anne M. Sørensen, Eckart Håkansson and Lars Stemmerik, Department of Geography and Geology, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.