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  • 1
    Electronic Resource
    Electronic Resource
    High-resolution sequence stratigraphy of a Hettangian-Sinemurian paralic succession, Bornholm, Denmark (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 42 (1995), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Sequence stratigraphic interpretation of paralic successions is complicated by the complex interfingering of marine and continental strata. The successions may also include terrestrial extensions of marine parasequences and completely independent lacustrine parasequence analogues. Failure in recognizing the possible interbeddding of these two independent parasequence types may lead to construction of sequence stratigraphic schemes based on incompatible data sets. We have studied a Lower Jurassic paralic section from the Baltic island of Bornholm, situated in the Tornquist Zone, which demarcates the transition from the stable Precambrian Baltic Shield to the subsiding Danish Basin and Danish-Polish Trough. The Hettangian-Sinemurian Sose Bugt Member (Rønne Formation) of Bornholm includes lacustrine, fluvial and restricted marine, estuarine deposits reflecting the basin-margin position. Biostatigraphic resolution is poor and a sequence stratigraphic interpretation of the paralic succession is far from straightforward. A multidisciplinary approach including facies analysis, recognition and lateral trading of key surfaces, palynostratigraphy, palynofacies, coal petrography, palaeopedology, clay mineralogy and source rock geochemistry is applied in order to obtain a high degree of precision in the interpretation of the paralic facies. In this way four sequences are recognized in the overall backstepping lacustrine to estuarine succession. Marine and marginal marine parasequences are distinguished from their purely lacustrine analogues, and an internally consistent sequence stratigraphic scheme is proposed. This is compared and tentatively correlated with fossiliferous marine sediments in the Danish Basin and with published eustatic cycle charts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1995.tb02105.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Jurassic basin evolution of East Greenland (1978)
    [s.l.] : Nature Publishing Group
    Nature 274 (1978), S. 130-133 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Jurassic basin of East Greenland was formed by rifting from south to north in a series of steps and was filled longitudinally from the north mainly by marine sediments. It may serve as a model for Jurassic graben formation and sedimentation in the areas surrounding the northern North Atlantic ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/274130a0
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    Paper (German National Licenses)
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  • 3
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    Ridge and valley systems in the Upper Cretaceous chalk of the Danish Basin: contourites in an epeiric sea (2007)
    In:  Geological Society Special Publication 276: 265-282.
    Details
    Publication Date: 2007-10-08
    Description: Extensive low-lying parts of the NW European craton were flooded during the Late Cretaceous transgression, creating a relatively deep epeiric sea with reduced supply of siliciclastic material and insignificant coastal upwelling. The chalk, essentially an oceanic sediment type, was deposited as a pelagic rain of mainly coccolith debris and with local redeposition along structural highs. The study area is located in the eastern part of the Danish Basin, where the bordering Ringkobing-Fyn High and the inverted Sorgenfrei-Tornquist Zone converge. Multichannel seismic reflection lines show the Chalk Group to be far from the expected flat-lying pelagic succession. A multitude of features of considerable relief, comprising an extensive unconformity, sediment waves, drifts and moats, are recognized. At least two episodes of widespread drift deposition are identified, one in the Santonian-Late Campanian and one in the Maastrichtian, separated by a Top Campanian Unconformity. The structures were formed by strong bottom currents flowing northwestward through the basin parallel to bathymetric contours. A lateral northeastward change, from more depositional to more erosional architecture, indicates a positive current velocity gradient towards the inversion zone, probably as a result of the Coriolis force. The strong similarity between the chalk drifts and modem contourite deposits supports the proposal that the oceanographic conditions linked to continental margins were extended into the Late Cretaceous epeiric sea of NW Europe.
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  • 4
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    Slope failure of chalk channel margins: implications of an Upper Cretaceous mass transport complex, southern England (2015)
    Geological Society of London
    Details
    Publication Date: 2015-10-29
    Description: The importance of mass transport and bottom currents is now widely recognized in the Upper Cretaceous Chalk Group of Northern Europe. The detailed dynamics and interaction of the two phenomena are difficult to study as most evidence is based on seismic data and drill core. Here, field observations provide evidence for recurring margin collapse of a long-lived Campanian channel. Compressionally deformed and thrust chalk hardgrounds are correlated to thicker, non-cemented chalk beds that form a broad, gentle anticline. These chalks represent a slump complex with a roll-over anticline of expanded, non-cemented chalk in the head region and a culmination of condensed hardgrounds in the toe region. Observations strongly suggest that the slumping represents collapse of a channel margin. Farther northwards, the contemporaneous succession shows evidence of small-scale penecontemporaneous normal faulting towards the south, here interpreted as gravitational settling of the chalk immediately adjacent to the channel margin. Detailed biostratigraphic studies and sedimentological observations provide evidence for at least two discrete collapse events and suggest the slumping to be the result of channel margin oversteepening rather than evidence for a regional tectonic phase. The described example thus serves as an analogue for processes commonly only inferred from subsurface data.
    Print ISSN: 0016-7649
    Topics: Geosciences
    Published by Geological Society of London
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  • 5
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    Deep-time evidence of a link between elevated CO2 concentrations and perturbations in the hydrological cycle via drop in plant transpiration (2012)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2012-09-01
    Description: The physiological effects of high CO 2 concentrations, i.e., [CO 2 ], on plant stomatal responses may be of major importance in understanding the consequences of climate change, by causing increases in runoff through suppression of plant transpiration. Radiative forcing by high [CO 2 ] has been the main consideration in models of global change to the exclusion of plant physiological forcing, but this potentially underestimates the effects on the hydrological cycle, and the consequences for ecosystems. We tested the physiological responses of fossil plants from the Triassic–Jurassic boundary transition (Tr–J) succession of East Greenland. This interval marks a major high CO 2 -driven environmental upheaval, with faunal mass extinctions and significant floral turnover. Our results show that both stomatal size (expressed in fossil material as SL, the length of the stomatal complex opening) and stomatal density (SD, the number of stomata per mm 2 ) decreased significantly during the Tr–J. We estimate, using a leaf gas-exchange model, that the decreases in SD and SL resulted in a 50%–60% drop in stomatal and canopy transpiration at the Tr–J. We also present new field evidence indicating simultaneous increases in runoff and erosion rates. We propose that the consequences of stomatal responses to elevated [CO 2 ] may lead to locally increased runoff and erosion, and may link terrestrial and marine biodiversity loss via the hydrological cycle.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 6
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    The influence of depositional processes on the porosity of chalk (2012)
    Geological Society of London
    Details
    Publication Date: 2012-05-12
    Description: Chalk constitutes challenging low-permeability reservoirs with porosity variations attributable to complex interactions between numerous processes. The influence of depositional processes, and thus the value of depositional models to predict porosity, is subject to continuing debate. In this study, a new approach is applied to investigate the influence of depositional and early post-depositional processes on chalk porosity, based on the 303 m thick Upper Cretaceous chalk succession in the Mona-1 core from the Danish North Sea. The influence of depositional processes on porosity is isolated by a mathematical correction of porosity data. Results confirm that mass-transport deposits are on average more porous than pelagites, whereas turbidites are less porous, given similar composition, burial history, and hydrocarbon migration history. The porosity variation between 12 chalk facies suggests that grain packing of the sediment in the consolidated state caused the facies-dependent porosity variation. Bioturbation caused a relatively tight grain packing compared with deposits that escaped bioturbation. Early plastic shear deformation of tightly packed bioturbated units resulted in dilative behaviour, which increased porosity, whereas more loosely packed units responded contractively, resulting in decreased porosity preservation. A firm understanding of chalk facies and thorough facies analyses are thus considered instrumental in chalk reservoir prediction.
    Print ISSN: 0016-7649
    Topics: Geosciences
    Published by Geological Society of London
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  • 7
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    Channelling versus inversion: origin of condensed Upper Cretaceous chalks, eastern Isle of Wight, UK (2013)
    Geological Society of London
    Details
    Publication Date: 2013-03-14
    Description: Evidence from regional stratigraphical patterns in Santonian–Campanian chalk is used to infer the presence of a very broad channel system (5 km across) with a depth of at least 50 m, running NNW–SSE across the eastern Isle of Wight; only the western part of the channel wall and fill is exposed. Within this channel were smaller erosional structures (〈10 m deep) that truncate originally horizontal bedding, are floored by hardgrounds, and locally have a basal fill of granular phosphorite. The entire channel system was progressively infilled by chalk, as demonstrated by the expanded succession of the lower Campanian Culver Chalk Formation. The beds of the channel fill are cut by small step faults, resulting from gravitational collapse. Complete burial had taken place by the base of the upper Campanian Portsdown Chalk Formation, which is of even thickness across the region. The structures are interpreted with reference to high-resolution seismic profiles through chalk channel systems described from the German sector of the North Sea, and the Santonian–Campanian of the eastern Paris Basin, and were formed by persistent bottom currents. Previous interpretations of the condensed Santonian–Campanian chalks in the eastern Isle of Wight, involving penecontemporaneous tectonic inversion of the underlying basement structure, are rejected.
    Print ISSN: 0016-7649
    Topics: Geosciences
    Published by Geological Society of London
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  • 8
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    Diagenesis of silica-rich mound-bedded chalk, the Coniacian Arnager Limestone, Denmark (2010)
    Elsevier
    Details
    Publication Date: 2010-01-01
    Print ISSN: 0037-0738
    Electronic ISSN: 1879-0968
    Topics: Geosciences
    Published by Elsevier
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  • 9
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    Upper Jurassic coal-bearing shoreline deposits, Hochstetter Forland, east Greenland (1976)
    Elsevier
    Details
    Publication Date: 1976-04-01
    Print ISSN: 0037-0738
    Electronic ISSN: 1879-0968
    Topics: Geosciences
    Published by Elsevier
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  • 10
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    The phytoplankton record of the end-Cretaceous warming in the Boreal realm and the Pacific Ocean (2009)
    Institute of Physics
    Details
    Publication Date: 2009-02-01
    Print ISSN: 1755-1307
    Electronic ISSN: 1755-1315
    Topics: Geography , Geosciences , Physics
    Published by Institute of Physics
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