Contents
Smith, A.S. 2007–01–10.
The back-to-front plesiosaur Cryptoclidus (Apractocleidus) aldingeri from the Kimmeridgian of Milne Land, Greenland
Houmark-Nielsen, M. 2007–02–23.
Extent and age of Middle and Late Pleistocene glaciations andperiglacial episodes in southern Jylland, Denmark.
Häggström, T. & Schmitz, B. 2007–03–11.
Distribution of extraterrestrial chromite in Middle Ordovician Komstad Limestone in the Killeröd quarry, Scania, Sweden
Lindow, B.E.K. & Dyke, G.J. 2007–03–12.
A small galliform bird from the Lower Eocene Fur Formation, north-western Denmark
Skaarup, N. & Pulvertaft, T.C.R. 2007–03–15.
Aspects of the structure on the coast of the West Greenland volcanic province revealed in seismic data.
Weidner, T. & Nielsen, A.T. 2007–09–10.
Linguagnostus groenwalli Kobayashi, 1939 (Trilobita, Middle Cambrian) from erratics in Denmark .
Noe-Nygaard, N., Milàn, J., Hede, M. U. & Holm, J. 2007–08–06.
A reindeer track from a drill core, and lake basin development of the Late Glacial Lille Slotseng kettle-hole basin, South-East Jylland, Denmark.
Fabricius, I. L. 2007–12–03.
Chalk: composition, diagenesis and physical properties. Bulletin of theGeological Society of Denmark .
The back-to-front plesiosaur Cryptoclidus (Apractocleidus) aldingeri from the Kimmeridgian of Milne Land, Greenland
Smith, A.S. 2007–01–10. The back-to-front plesiosaur Cryptoclidus (Apractocleidus) aldingeri from the Kimmeridgian of Milne Land, Greenland
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 1–7.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-01
Abstract: In 1935, von Huene identified the partial skeleton of a fossil reptile from the Kimmeridgian of Milne Land, Greenland, as part of a plesiosaur. This specimen was used as the holotype of Cryptoclidus (Apractoclidus) aldingeri, but was interpreted erroneously. The specimen is here reinterpreted and described as the pectoral region and posterior portion of the neck. The specimen is not diagnostic past the level of family, and is regarded as Cryptoclididae indet – the species aldingeri thereforebecomes a nomen dubium.
Keywords: Plesiosaur, Greenland, Cryptoclidus, von Huene, Jurassic.
Addresses:
Adam Stuart Smith , School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Ireland
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Extent and age of Middle and Late Pleistocene glaciations andperiglacial episodes in southern Jylland, Denmark
Houmark-Nielsen, M. 2007–02–23. Extent and age of Middle and Late Pleistocene glaciations andperiglacial episodes in southern Jylland, Denmark
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 9-35.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-02
Abstract: New evidence on distribution and chronology of glaciations in southern Jylland is presented. Ten stratigraphic units including four till-formations have been identified in Middle- and Late Pleistocene sediment successions.
The timing of successive glaciations and periglacial interludes based on luminescence dating is established for the past c. 200 kyr. The OSL-chronology predicts that deposition of Lillebælt Till (Late Saalian, Warthe Glaciation) occurred at 180-160 kyr. Deglaciation followed and barren periglacial environments existed until beginning of the Eemian. Periglacial conditions were restored c. 115 kyr ago and lasted well into the Middle Weichselian. Expansion of the Scandinavian Ice Sheet through the Baltic depression into southern Jylland caused deposition of Ristinge Klint Till (Ristinge Glaciation) c. 55–50 kyr ago. Glaciers flowed westwards beyond the Main Stationary Line (MSL) and may have terminated along ice showed ridges in the periglacially smoothed landscape east of the present North Sea coast.
This traditionally named “Old Baltic”glaciation is now recognized elsewhere in the circum Baltic region besides Denmark. Deglaciation was succeeded by periglacial environments with cryoturbation, ice wedge growth, formation of wind abrasion pavements and low arctic habitats.
Approaching the global glacio-eustatic low stand of the Last Glacial Maximum increased cooling and enhanced down slope creep caused widespread solifluction. In a sequence of Late Weichselian glacier advances, Mid Danish Till, East Jylland Till and Bælthav Till was deposited under progressing deglaciation between 25 and 18 kyr ago. Retarded melting of dead ice from the Ristinge Glaciation formed thermo karst depressions on the surfaceof outwash plains in front of MSL.
Keywords:Glacial and periglacial sediments, stratigraphy, OSL-dating, Middle and Late Pleistocene environments, Scandinavian Ice Sheet extent, Ice flow pattern, Baltic glaciers.
Addresses:
Michael Houmark-Nielsen, Institute of Geography & Geology, University of Copenhagen, Øster Voldgade 10, DK-1350, Copenhagen K.
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Distribution of extraterrestrial chromite in Middle Ordovician Komstad Limestone in the Killeröd quarry, Scania, Sweden
Häggström, T. & Schmitz, B. 2007–03–11. Distribution of extraterrestrial chromite in Middle Ordovician Komstad Limestone in the Killeröd quarry, Scania, Sweden
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 37-58.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-03
Abstract: Sediment-dispersed extraterrestrial chromite grains (63–355 µm) have been recovered in a sectionacross the Arenig-Llanvirn transition in the Killeröd quarry in southeastern Scania.
Previous studies of the same stratigraphic interval in the Orthoceratite Limestone at Kinnekulle, ca. 350 km to the north in Västergötland, have shown a two orders of magnitude increase in extraterrestrial chromite beginning close to the Arenig-Llanvirn boundary. The stratigraphic distribution and abundance trends of extraterrestrial chromite are essentially identical at Killeröd and Kinnekulle.
In the Killeröd section extraterrestrial chromite grains are extremely rare (2 grains/125 kg of rock) in the Arenig lower 8 m of the section (Megistaspis simon to Asaphus expansus trilobite zones) and abundant (326 grains/162 kg of rock) in the succeeding ca. 3 m of uppermost Arenig and lower Llanvirn (upper A. expansus and A. raniceps zones) section.
The extraterrestrial chromite grains at Killeröd and Kinnekulle are very similar in chemical composition, including characteristic elevated values and narrow ranges of V2O3 (0.6–0.9 wt%) and TiO2 (2.0–3.5 wt%). At Killeröd there is a small group (<4%) of chromite grains with relatively low TiO2 (1.5–2.0 wt%), but otherwise typical extraterrestrial compositions. These grains may reflect a somewhat more aggressive diagenetic environment at Killeröd than at Kinnekulle. As in previous studies, rare chrome spinel grains with terrestrial or uncertain origin have also been found in the limestone.
The results of this study support previous suggestions that after the disruption of the L chondrite parent body in the asteroid belt at ca. 470 Ma, the flux of extraterrestrial matter to Earth was enhanced by up to two orders of magnitude compared to the present. This is supported by finds in Sweden of abundant fossil meteorites in uppermost Arenig and lower Llanvirn sediments. Whether these conclusions can be put into a global context awaits further study of Middle Ordovician limestones from other continents.
Keywords: Komstad Limestone, chromite, chrome spinel, Middle Ordovician, Arenig-Llanvirn boundary, L chondrite, meteorite flux, fossil meteorites
Addresses:
Therese Häggström , Department of Marine Geology, Earth Sciences Centre, Göteborg University, SE-405 30 Göteborg, Sweden.
Birger Schmitz , Department of Geology, Lund University, SE-223 62 Lund, Sweden.
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A small galliform bird from the Lower Eocene Fur Formation, north-western Denmark
Lindow, B.E.K. & Dyke, G.J. 2007–03–12. A small galliform bird from the Lower Eocene Fur Formation, north-western Denmark
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 59-63.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-04
Abstract: A pair of fossilized imprints of feet represent the first published galliform (landfowl) specimenfrom the Lower Eocene Fur Formation of northwest Denmark. The specimen is referable to Galliformes due to the presence of a distinctly asymmetric trochlea metatarsi III. The specimen appears distinct from previously described Eocene Galliformes (e.g. Gallinuloididae, Quercymegapodiidae and Paraortygidae) and may represent a new taxon of Galliformes, increasing the diversity of this group in the Lower Eocene.
Keywords: Galliformes, Landfowl, Lower Eocene, Fur Formation.
Addresses:
Bent E. K. Lindow: School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Republic of Ireland & Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark;
Gareth J. Dyke : School of Biology and Environmental Science, University College Dublin, Belfield, Dublin 4, Republic of Ireland
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Aspects of the structure on the coast of the West Greenland volcanic province revealed in seismic data
Skaarup, N. & Pulvertaft, T.C.R. 2007–03–15. Aspects of the structure on the coast of the West Greenland volcanic province revealed in seismic data
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 65-80.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-05
Abstract: The coastal structure in central West Greenland is expressed by Palaeogene basalts which show pronounced seaward dip. Traced along strike the tilted basalts occur in two segments, separated by an area in which dips are low. Within these segments the lavas have been displaced by extensional faults with strike parallel to the strike of the lavas and dip and downthrow to the landward side.
This structural pattern bears many similarities to regional structural features in volcanic rifted margins in other parts of the world, although in West Greenland the continent-ocean boundary is situated more than 100 km west of the coast.
The structure has previously been studied onshore and has now been studied in high-resolution seismic data acquired both west of the coast and in the sounds between the Nuussuaq and Svartenhuk peninsulas. From the offshore data it can be seen that within the sections correlated with mid-Paleocene volcanic rocks onshore, the tilting of the lavas took place almost entirely after eruption, as there is little or no indication of any increase of dip towards the faults or of fan-shaped geometry in cross-section. However, southwest of Ubekendt Ejland and stratigraphically within Early Eocene lavas, dips can be seen to increase with depth in several fault blocks, indicating that tilting was active during eruption of these lavas. It is therefore concluded that tilting of the volcanic rocks in the coastal zone took place largely in the Eocene.
This conclusion is corroborated by the following onshore evidence:
Firstly, the angle of discordance between seaward-dipping Eocene lavas and the underlying tilted Paleocene lavas is small, where observed at all, so the mid-Paleocene lavas must owe their seaward dip largely to tilting during the Eocene.
Secondly, Early Eocene ages have been obtained from sequentially tilted dykes onshore. This tilting and concomitant extensional faulting was contemporaneous with the second phase of seafloor spreading in the Labrador Sea which took place during the Eocene. The first phase of seafloor spreading in this sea took place between magnetochrons 27r and 24r and was not accompanied by significant rifting of lavas in central West Greenland. It can also be seen from the seismic data that the tilted lavas level out less than 25 km from the coast. West of this, the volcanics generally show very low dips and thin gradually towards the continent-ocean boundary.
Keywords: West Greenland, coastal tilting, extensional faulting, Palaeogene basalts.
Addresses:
Skaarup, N . , Pulvertaft, T.C.R. , Geological Survey of Denmark and Greenland,
Øster Voldgade 10, DK-1350 Copenhagen K, Denmark
Linguagnostus groenwalli Kobayashi, 1939 (Trilobita, Middle Cambrian) from erratics in Denmark
Weidner, T. & Nielsen, A.T. 2007–09–10. Linguagnostus groenwalli Kobayashi, 1939 (Trilobita, Middle Cambrian) from erratics in Denmark
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 81-84.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-06
Abstract: Linguagnostus groenwalli Kobayashi, 1939 occurs very sparsely in the Middle Cambrian Ptychagnostus punctuosus Zone of Scandinavia and only six specimens have been described so far (three from in situ strata, three from erratic boulders). Additional well-preserved specimens found in two erratic boulders in Denmark are described; the material probably originates from the Bornholm area.
The new findings indicate that the species locally is more common than previously documented. A lectotype is designated and refigured.
Keywords: Trilobite, agnostid, Middle Cambrian, Denmark
Addresses:
Thomas Weidner, Ravnholtvej 23, Rårup, DK-7130 Juelsminde, Denmark.
Arne Thorshøj Nielsen, Geological Museum, University of Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K.
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A reindeer track from a drill core, and lake basin development of the Late Glacial Lille Slotseng kettle-hole basin, South-East Jylland, Denmark
Noe-Nygaard, N., Milàn, J., Hede, M. U. & Holm, J. 2007–08–06. A reindeer track from a drill core, and lake basin development of the Late Glacial Lille Slotseng kettle-hole basin, South-East Jylland, Denmark
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 85-95.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-07
Abstract: IA subfossil reindeer track is found in lake shore sediments in a drill core through the Late Glacial and Holocene lacustrine succession from the Lille Slotseng kettle-hole basin, located in the southeastern part of Jylland. The track is dated to 11,795 ± 80 14C yr BP or 13,635 cal. yr BP.
This is the first vertebrate track recognized from a soft sediment drill core. Hitherto, convincing vertebrate trace fossils have only been described from boreholes through lithified Triassic sediments. During a previous excavation at the site, skeletal remains of at least ten reindeer were recovered from the Bølling succession and a vertebra was dated to approximately 14,100 cal. yr BP.
The Lille Slotseng basin is semicircular with a maximum diameter of 23 m and the overall transgressive–regressive succession covers the time period from 16,000 to around 8,000 cal. yr BP. The oldest basin-fill sediments are melt-water deposits. They are overlain by a succession belonging to the Bølling Interstadial (GI 1-e), older Dryas (GI 1-d), Allerød, (GI 1-c, 1-b, 1-a), and Younger Dryas (GS 1), which terminates the Late Glacial succession. Then follows Preboreal algal gyttja and nearshore woody peat from the Boreal and Early Atlantic times, filling the basin.
Keywords: Lacustrine sedimentation, Late Glacial, Bølling/Allerød, drill core, footprint, artiodactyl track, slumped lake-margin.
Addresses:
Nanna Noe-Nygaard , Jesper Milán and Mikkel Ulfeldt Hede, Department of Geography and Geology – Geology Section, University of Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark.
Jørgen Holm, Haderslev Museum, Dalgade 7, DK-6100 Haderslev, Denmark.
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Chalk: composition, diagenesis and physical properties
Fabricius, I. L. 2007–12–03. Chalk: composition, diagenesis and physical properties
©2007 by Bulletin of the Geological Society of Denmark, Vol. 55, pp. 97-128.
ISSN 0011–6297. (www.2dgf.dk/publikationer/bulletin).
https://doi.org/10.37570/bgsd-2007-55-08
Download file replaced 2020-07-21: Erroneous formulas 8, 9 and 11 in the original publication are now correct.
Link to original download version of publication: bull55-97-128wmf.pdf
Abstract: Chalk is a sedimentary rock of unusually high homogeneity on the scale where physical propertiesare measured, but the properties fall in wide ranges. Chalk may thus be seen as the ideal starting point for a physical understanding of rocks in general.
Properties as porosity, permeability, capillary entry pressure, and elastic moduli are consequences of primary sediment composition and ofsubsequent diagenetic history as caused by microbial action, burial stress, temperature, and porepressure.
Porosity is a main determining factor for other properties. For a given porosity, the specific surface of the sediment controls permeability and capillary entry pressure. As diagenesis progresses, the specific surface is less and less due to the calcite component and more and more due to the fine-grained silicates, as a reflection of the coarsening and cementation of the calcite crystals.
The elastic moduli, which define sonic velocity, are for a given porosity mainly controlled be the degree of pore-stiffening cementation, which may be quantified by effective medium modeling. Diagenetic processes include mechanical compaction, pore-stiffening cementation, dissolution,and pore-filling cementation.
Processes involving clay, silica, and calcite are interlinked, but progress differently in different localities. This partly depends on primary sediment composition, including organic content, which may induce the formation of concretions by microbial action. The diagenetic processes also depend on water depth, rate of burial, and over-pressuring. These factors cause the stress, temperature and pore-pressure to increase at different rates during burial in different localities.
Keywords: Chalk, diagenesis, physical properties, elasticity, porosity, permeability, capillary entrypressure
Addresses:
Ida L. Fabricius , Technical University of Denmark, Institute of Environment and Resources,Bygningstorvet 115, DTU, DK-2800 Kgs. Lyngby, Denmark.