Bulletin of the Geological Society of Denmark • Volume 49/1
 | Contents Obst, K., Böhnke, A., Katzung, G. & Maletz, J.:
Pb-Pb zircon dating of tuff horizons inthe Cyrtograptus Shale (Wenlock, Silurian) of Bornholm
Pålsson, C.:
Upper Ordovician graptolites and biostratigraphy of the Röstånga 1 core,Scania, S. Sweden.
Kilda, L. & Friis, H.:
The key factors controlling reservoir quality of the Middle CambrianDeimena Group sandstone in West Lithuania
Bergström, S. M., Larsson, K., Pålsson, C. & Ahlberg, P.:
The Almelund Shale, a replacement name for the Upper Didymograptus Shale and the Lower Dicellograptus Shale in the lithostratigraphical classification of the Ordovician succession in Scania, Southern Sweden
Machalski, M.:
Danian ammonites: A discussion.
Walaszczyk, I., Cobban, W.A. & Odin, G.S.:
The inoceramid succession across the Campanian – Maastrichtian boundary
Madirazza, I.:
The influence of tectonics on the land forms in west Jutland, Denmark
Gregersen, S.:
Earthquakes and change of stress since the ice age in Scandinavia
Krissek, L.A. & St.John, K.E.K.:
Pleistocene iceberg production from East Greenland: Synchronous between source areas, but distinct from global ice volume
Book reviews:
Mortimore, R.N., Wood, C.J. & Gallois, R.W. 2001: British Upper Cretaceous Stratigraphy. Geological Conservation Review Series 23, xx + 558 pp. Joint Nature Conservation Committee, Peterborough.
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Baldschuhn, R., Binot, F., Fleig, S. & Kockel, F. (compilers) 2001: Geotektonischer Atlas von Nordwest-Deutschland und dem deutschen Nordsee-Sektor. Geologisches Jahrbuch A153, 88 pages and 3 CD-ROMs. By commission: E Schweizerbart’sche Verlagsbuchhandlung (Nägele u. Obermiller), Johannesstraße 3 A, D-70176 Stuttgart.
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Pb-Pb zircon dating of tuff horizons inthe Cyrtograptus Shale (Wenlock, Silurian) of Bornholm Obst, K., Böhnke, A., Katzung, G. & Maletz, J.: Pb-Pb zircon dating of tuff horizons inthe Cyrtograptus Shale (Wenlock, Silurian) of Bornholm, Denmark. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 1–8, Copenhagen.
Waterlain fallout ashes are interbedded in the upper part of the Cyrtograptus Shale of Bornholm, theyoungest preserved member of the Lower Palaeozoic sequence at the southern coast of the island.Graptolite faunas indicate that these tuffaceous sediments belong to the Cyrtograptus lundgreni Zonedeposited during Late Wenlock. A 207Pb/206Pb mean age of 430 ± 1.9 Ma obtained by evaporation of idiomorphic single zircons from the tuff layers supports this observation. Geochemical studies of the pyroclastic rocks point to an explosive, calc-alkaline magmatic arc volcanism which probably occurred along or slightly south of the Tornquist-Teisseyre Lineament, and could have been induced by the collision of Avalonia with the southern margin of Baltica during the Silurian. This assumption is supported by the contemporaneous deposition of bentonites on the Swedish island of Gotland which might represent a distal facies of these fallouts. Further, the subduction-related volcanic activity is interpreted as a fingerprint for closing of the Tornquist Ocean during the Caledonian orogeny.
Key words: Bornholm, Tornquist Ocean, Wenlock, Silurian, tuff, graptolites, Pb-Pb isotopes, singlezircon evaporation.
Karsten Obst [
], Gerhard Katzung & Jörg Maletz, Institut für GeologischeWissenschaften, Ernst-Moritz-Arndt-Universität Greifswald, Friedrich-Ludwig-Jahn-Str. 17a, D-17489Greifswald, Germany. Antje Böhnke [e-mail: aboehnke@rz.uni-leipzig.de], Institut für Geophysik und Geologie,Universität Leipzig, Talstr. 35, D-04103 Leipzig, Germany. 6 June 2000.
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Upper Ordovician graptolites and biostratigraphy of the Röstånga 1 core,Scania, S. SwedenPålsson, C.: Upper Ordovician graptolites and biostratigraphy of the Röstånga 1 core, Scania, S. Sweden. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 9–23, Copenhagen.
A core drilling at Röstånga in 1997, referred to as Röstånga 1, penetrated a significant portion of the Upper Ordovician-Lower Silurian succession in this classical Lower Palaeozoic outcrop area in W central Scania. In descending order the Upper Ordovician of the core embraces the following units (stratigraphic thickness in parenthesis): Lindegård Mudstone (27.8 m), Fjäcka Shale (13.6 m), Mossen Formation (0.6 m), Skagen Formation (0.8 m), and Sularp Formation (19.9 m+). Graptolites are described from the Lindegård Mudstone, the Fjäcka Shale, and the Mossen Formation. The graptolites are classified into 12 taxa, among which 9 are identified to species. Graptolites are very rare in the Mossen Formation, which has yielded only two specimens of Pseudoclimacograptus scharenbergi.The Fjäcka Shale yielded a fairly diverse graptolite fauna, indicative of the Pleurograptus linearis Zone.This zone is succeeded by the Dicellograptus complanatus Zone, with the zonal index appearing in the lower part of the Lindegård Mudstone immediately above graptolites indicative of the P. linearisZone. No graptolites were recovered from the Skagen Formation and the Sularp Formation.
Keywords: Upper Ordovician, Pleurograptus linearis Zone, Dicellograptus complanatus Zone, graptolites,taxonomy, biostratigraphy, Röstånga, Scania, S. Sweden.
C. Pålsson [
], Department of Geology, Historical Geology and Palaeontology,Sölvegatan 13, SE-223 62 Lund, Sweden. 17 May 2001.
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The key factors controlling reservoir quality of the Middle CambrianDeimena Group sandstone in West LithuaniaKilda, L. & Friis, H.: The key factors controlling reservoir quality of the Middle CambrianDeimena Group sandstone in West Lithuania. Bulletin of the Geological Society of Denmark, Vol. 49, pp.25–39, Copenhagen.
Sandstones of the Middle Cambrian Deimena Group are commercially important as they make up the largest part of the hydrocarbon-bearing reservoir in 15 oil fields discovered in West Lithuania. However, the sandstones are characterised by a very complicated spatial distribution of reservoir quality. In order to better understand the distribution of reservoir properties and their controlling parameters, eighty-two sandstone samples from twenty-one boreholes were studied by means of thin section description, scanning electron microscopy, using backscattered and cathodoluminescence modes and clay fraction analyses. Generally, the sandstones are strongly cemented by quartz, resulting in almost total destruction of porosity but porous domains with preserved early stage quartz cement occur in a complex pattern. The close location of the early and late stage overgrowth types indicates that some sandstone parts were preserved from intense authigenic quartz precipitation. We believe that early carbonate cement was such an inhibitor. Detrital quartz grains in carbonate cemented domains are mostly free of authigenic quartz and as a rule show weakly compacted fabric as compared to the quartz cemented parts. Moreover, large secondary pores are located close to the carbonate cemented domains and indicate that some carbonate cement eventually dissolved. Apparently, the best reservoir properties within the generally strongly quartz cemented Deimena Groupsandstones are found in domains where dissolution of the early carbonate cement took place.
Key words: Deimena Group, sandstone, porosity, quartz overgrowths, authigenic quartz, early carbonatecement.
Linas Kilda [
] Geological Institute of Lithuania, T. Šev…enkos 13, LT-2600, Vilnius, Lithuania.Henrik Friis [
] Department of Earth Sciences, University of Aarhus, C.F. Møllers Allé120, DK-8000, Århus C, Denmark. 16. April 2002.
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The Almelund Shale, a replacementname for the Upper Didymograptus Shale and the Lower Dicellograptus Shale in the lithostratigraphical classification of the Ordovician succession in Scania, Southern Sweden
Bergström, S. M., Larsson, K., Pålsson, C. & Ahlberg, P.: The Almelund Shale, a replacement name for the Upper Didymograptus Shale and the Lower Dicellograptus Shale in the lithostratigraphical classification of the Ordovician succession in Scania, Southern Sweden. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 41–47. Copenhagen.
The formation name Almelund Shale is proposed for a lithostratigraphically defined unit to replace the outdated chronostratigraphical designations Upper Didymograptus Shale and Dicellograptus Shalein the Middle and lowermost Upper Ordovician succession in Scania. The Almelund Shale is a lithologically uniform unit of dark-grey to black shales with rare carbonate interbeds between the Komstad Limestone and the Sularp Shale. Apart from a diverse graptolite fauna it yields a few shelly fossils (mostly lingulate brachiopods) and biostratigraphically diagnostic conodonts and chitinozoans. In the type sections of the Almelund Shale along the Sularp Brook in the Fågelsång area, W-central Scania, the top of the unit is taken to be the base of the Fågelsång Phosphorite, and its basal contact is at the top of the underlying Komstad Limestone. Its total thickness in the Fågelsång drill-core is 28.32 m. The unit is widely distributed in the subsurface in a SE-NW belt across Scania.
Key words: Ordovician, graptolite biostratigraphy, lithostratigraphy, Scania, Sweden.
S.M. Bergström [
], Department of Geological Sciences, 155 S. Oval Mall, The Ohio State University, Columbus, Ohio 43210, USA. K. Larsson, C. Pålsson & P. Ahlberg, Department ofGeology, Division of Historical Geology and Palaeontology, Lund University, Sölvegatan 13, SE-223 62 Lund, Sweden. 20 August 2001.
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Danian ammonites: A discussion
Machalski, M.: Danian ammonites: A discussion. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 49–52, Copenhagen.
Possible ammonite survivors reported from the lowermost Danian deposits of Denmark (Stevns Klint) and The Netherlands (Curfs-Ankerpoort quarry) are questioned. Some of the specimens from Denmark are almost certainly reworked from the uppermost Maastrichtian deposits. As concerns the remainder of the reported material, reworking is also possible, at least theoretically. On the basis of Ockham’s Razor, the hypothesis that all specimens are reworked from the Maastrichtian strata must be preferred until compelling evidence for Danian survivors is proven. Such evidence may be potentially provided by articulated ammonite aptychi located in Danian deposits or by aptychi revealing Danian isotopic signals.
Key words: K-Pg boundary, extinction, survival, ammonites, aptychi, reworking, hardgrounds, Danian, Maastrichtian, Denmark, Netherlands.
Marcin Machalski [
] Instytut Paleobiologii PAN, ul. Twarda 51/55, PL - 00-818 Warszawa, Poland. 12 March 2002.
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The inoceramid succession across the Campanian – Maastrichtian boundary
Walaszczyk, I., Cobban, W.A. & Odin, G.S.: The inoceramid succession across the Campanian – Maastrichtian boundary. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 53–60. Copenhagen.
Recent study revealed a high correlation potential of inoceramid bivalves across the Campanian – Maastrichtian (Upper Cretaceous) boundary within the Euroamerican biogeographical region. In inoceramid terms the Campanian/Maastricthian boundary, as currently defined, lies in the topmost part of the “Inoceramus” redbirdensis Zone, close to the base of the Endocostea typica Zone. Both zones, as well as the whole late Campanian and early Maastrichtian inoceramid succession is well recognisable across the European sections and across the Atlantic to the US Western Interior succession.
Key words: Inoceramid zonation, Campanian – Maastrichtian boundary, Euramerican biogeographical region, correlations.
Ireneusz Walaszczyk [
] , Institute of Geology, University of Warsaw, Al. Zwirki i Wigury 93, PL-02-089 Warszawa, Poland. William A. Cobban, 70 Estes Street, Lakewood, Colorado 80226, USA. Gilles S. Odin, Université P. & M. Curie, Unité de Géochronologie et Sédimentologie Océanique; 4, Place Jussieu, Case 119 A, F75252, Paris Cedex 05, France. 13 May 2002.
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The influence of tectonics on the land forms in west Jutland, Denmark
Madirazza, I.: The influence of tectonics on the land forms in west Jutland, Denmark. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 63–72, Copenhagen.
The structural development and its influence on the present land forms is discussed on the basis of the reflection seismic and gravity data. The study area covers the western part of Jutland which was not glaciated during the Weichselian and is delimited by two Weichsel main stationary lines: the line extending from west to east and the line extending from north to south (these two lines join at Dollerup). The southern border of the study area corresponds approximately to the northern limit of the buried Ringkøbing-Fyn High. In this part of west Jutland the base Zechstein faults can be traced to the surface where they control the drainage system. The faults are mainly NW-SE trending strike slip faults which are active also at the present time. Zechstein evaporates are present in the entire area discussed here.
Key words: gravity, seismics, strike slip faulting, neotectonics.
Ivan Madirazza, Department of Earth Sciences, Laboratory of Geophysics, University of Aarhus, Finlandsgade 6, DK-8200 Aarhus N, Denmark. 18 December 2001.
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Earthquakes and change of stress since the ice age in Scandinavia
Gregersen, S.: Earthquakes and change of stress since the ice age in Scandinavia. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 73–78. Copenhagen.
In a small, northern part of Scandinavia, where the present earthquake activity is not significantly different from its surroundings, large surface faults have been interpreted to show the occurrence of large earthquakes about 9,000 years ago. Signs of this are coincident landslides as well as liquefaction in loose sediments, which are very well dated through varv-counting. The interpretation is that the cause is stress release related to the final deglaciation after the last Ice Age. In contrast, the present dominating stress field in Scandinavia as a whole follows the pattern of the World Stress Map Project, namely compression along the absolute plate motion. This compression, NW-SE in Scandinavia, shows little influence of the deglaciation rebound, which is delineated by the area of the present-day lithospheric uplift. Through these observations change of dominating stress is clearly indicated during the last 9,000 years. And the modern earthquake activity of Scandinavia is not concentrated near the old, large earthquake faults. All these arguments influence the modern evaluation of earthquake hazard. This must be based on the present stress field, and not on that of 9000 years ago. The expectation of a large “10,000-year-earthquake” one of these days is zero, with the small uncertainty that such an earthquake could occur unexpected anywhere in a stable continental region.
Key words: Stress in Scandinavia, earthquakes in Scandinavia, seismicity in Scandinavia, earthquake hazard, stress from deglaciation, stress from plate motion.
Søren Gregersen [
], National Survey and Cadastre, Denmark, Rentemestervej 8, DK-2400 Copenhagen NV, Denmark. 17 December 2001.
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Pleistocene iceberg production from East Greenland: Synchronous between source areas, but distinct from global ice volume
Krissek, L.A. & St.John, K.E.K.: Pleistocene iceberg production from East Greenland: Synchronous between source areas, but distinct from global ice volume. Bulletin of the Geological Society of Denmark, Vol. 49, pp. 79–89. Copenhagen.
A 1 m.y. ice-rafted debris record (IRD) was developed for Ocean Drilling Program site 919, located in the western Irminger Basin. Compositional analyses of the IRD indicate that the major source regions for IRD found off SE Greenland were the Precambrian igneous and meta-igneous crystalline basement (predominantly gneiss and granite) of southeast Greenland and the Tertiary flood basalts located further north along the East Greenland coast. Temporal covariations in the IRD mass accumulation rates (MARs) of provenance-distinctive grain types suggest that these source areas experienced similar iceberg release histories during the Pleistocene. In contrast, no distinct relationship can be drawn between peaks in the IRD MAR record and oxygen-isotope defined glacial-interglacial cycles, suggesting that the history of IRD input off SE Greenland since 1 Ma was dominated by local, rather than global, climatic and distributional controls.
Key words: Ice-rafted debris, Greenland, Pleistocene, Irminger Basin.
L.A. Krissek [
], Department of Geological Sciences, Ohio State University, Colombus, Ohio 43210, USA. K.E.K. St.John [
], Department of Geology, Appalachian State University, Boone, NC 28608, USA. 13 June 2001.
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