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  • 1
    Electronic Resource
    Electronic Resource
    An ocean-facing Aptian–Albian carbonate margin, Oman (2001)
    Oxford UK : Blackwell Science Ltd
    Sedimentology 48 (2001), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: A high-energy Aptian–Albian platform margin in northern Oman fronted onto an open oceanic basin, making the area a valuable analogue for coeval guyot margins. Most similar aged carbonate margins described in the literature faced either intracratonic or minor oceanic basins. The studied margin is characterized by a stabilized outer rim, which, although it did not rise discernibly above the adjacent lagoonal deposits, flanked a steep upper slope (32–40°) basinwards with a relief of at least 30 m. Two main facies provided the rigidity of the outer margin: Lithocodium boundstones that constituted up to 50% of the rock volume; and marine fibrous cements that occluded up to 35% of primary pore space. In contrast, coral–rudist patches and other shelly sessile benthos were distributed irregularly, and the rudist bioherms of the outer margin were often disrupted, with shells being transported and redeposited. The inner margin is characterized by wedge-shaped storm layers that radiate from the platform top lagoonwards, where they interdigitate with carbonate sands and small rudist bioherms. Polygenetic discontinuity surfaces that bear evidence of both marine hardground and subaerial exposure stages are prominent features of the margin. Throughout the latest Aptian to Middle Albian, the platform succession recorded some 30 relative sea-level falls, of which seven reached amplitudes of many tens of metres. These seven high-amplitude falls in sea level are recorded across the entire south-eastern portion of the Arabian craton and are probably of eustatic origin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-3091.2001.00416.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Calciturbidite composition related to exposure and flooding of a carbonate platform (Triassic, Eastern Alps) (1991)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 38 (1991), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: The compositional variation of calciturbidites (Pedata/Pötschen Formation), deposited adjacent to the Dachstein Formation carbonate platform in the Triassic Hallstatt Basin, was analysed using detailed field measurements and point-counting of thin sections. The 35 m long section is located in the Northern Calcareous Alps of Austria. Six point-count groups were distinguished separating basinal from platform-derived input. Summary statistics, cluster and correspondence analysis of the point-count data reveals a close relationship between the biota present on the Dachstein carbonate platform and the calciturbidite composition. The variations in turbidite composition are attributed to fluctuations in sea level and resulting flooding and exposure of the platform, which alternately created and destroyed shallow-water habitats on the platform top.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1991.tb00371.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Low-magnesian calcite limestones forming at the deep-sea floor, Tongue of the Ocean, Bahamas (1978)
    Oxford, UK : Blackwell Publishing Ltd
    Sedimentology 25 (1978), S. 0 
    Details
    ISSN: 1365-3091
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Carbonate ooze in the deep troughs between the Bahama Banks is a mixture of pelagic and bank-derived material. It consists of aragonite, calcite and magnesium calcite in a ratio of about 3:2:1. Where exposed in erosional cuts at the sea floor, this ooze lithifies within 100,000 years and is transformed into calcite micrite of only 3.5-5 mol % MgCO3. Where buried, the ooze maintains its original composition for at least 200,000-400,000 years and remains unlithified for tens of millions of years.Quite unexpectedly, the path of sea-floor diagenesis of peri-platform ooze was found to be the same as that of freshwater diagenesis. Most of the aragonite is leached, pteropod shells often leaving cement-lined moulds behind; magnesian calcite recrystallizes and loses magnesium; polyhedral calcite of 2-4 μm size appears as cement. The setting and the carbon-oxygen isotope ratios rule out any freshwater influence. Carbon isotope ratios remain heavy, oxygen ratios shift towards equilibrium with the cold bottom water.The calcite cement has 3.5-5 mol % MgCO3 and can be interpreted as the least soluble form of calcite emerging from alteration at the sea floor or, alternatively, as a direct precipitate from cold sea water. The change in the composition of calcite cements with water depth supports the second interpretation. In the Bahamas and elsewhere in the world ocean, magnesium in calcite cements decreases from the warm surface waters down to 700-1200 m, i.e. the boundary between intermediate and cold deep-water masses. Below this level, calcite prevails and magnesian calcite and aragonite cements are restricted to semi-enclosed seas with exceptionally warm bottom waters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-3091.1978.tb00325.x
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  • 4
    Electronic Resource
    Electronic Resource
    Pseudo-unconformities in seismic models of large outcrops (1995)
    Springer
    International journal of earth sciences 84 (1995), S. 761-769 
    Details
    ISSN: 1437-3262
    Keywords: Seismic modeling ; Seismic interpretation ; Sequence-stratigraphy ; Unconformities ; Carbonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract Traditionally, seismic modeling has concentrated on one-dimensional borehole modeling and two-dimensional forward modeling of basic structural-stratigraphic schemes, which are directly compared with real seismic data. Two-dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines. Examples include the Dolomites (North Italy), the Vercors (SE France), and the High Atlas (Morocco). The seismic models are generally constructed using the following procedure: (a) construction of a detailed lithologic model based on direct outcrop observations; (b) division of the lithologic model into lithostratigraphic units; (c) assignment of petrophysical properties to these lithostratigraphic units; (d) ray tracing to compute time- or depth sections of reflectivity; (e) convolution of the reflectivity sections with source wavelets of different frequencies. The lithologic detail modeled in the case studies led to some striking results, particularly the discovery of pseudo-unconformities. Pseudo-unconformities are unconformities in seismics, but correspond to rapid changes of dip and facies in outcrop. None of the outcrop geometries studied were correctly portrayed seismically at 25-Hz peak frequency. However, in some instances the true relationship would gradually emerge at peak frequencies of 50–100 Hz. The examples given in this study demonstrate that detailed, outcrop-derived, seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less-ideal conditions, and what pitfalls may befall the interpreter of real seismic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240566
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Professor Dr. Alfred G. Fischer für wegweisende Erkenntnisse über die Rhythmen des Lebens und des Klimas der Erde (1994)
    Springer
    International journal of earth sciences 83 (1994), S. 3-4 
    Details
    ISSN: 1437-3262
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211890
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Sedimentation Rates, Observation Span, and the Problem of Spurious Correlation (1998)
    Springer
    Mathematical geology 30 (1998), S. 547-556 
    Details
    ISSN: 1573-8868
    Keywords: part-and-whole correlation ; ratio correlation ; regression ; Cantor function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract Plots of sedimentation rates vs. time span of observation are routinely used to demonstrate that sedimentation rates decrease if one averages over longer time spans. However, these plots are suspect because they plot a variable, time, against its inverse. It has been shown that even random numbers may yield correlation coefficients of 0.7 or higher under these circumstances. We have circumvented this problem by splitting observed sedimentation rates into time classes and performing regression on the primary variables, thickness and time, separately in each class. An alternative is weighted regression that corrects for the effect of spurious correlation. Regression on the primary variables has been performed on real data from siliciclastic and carbonate rocks. Data were sorted into time classes of 10 −1–10 2 yr, 10 2–10 5 yr, and 10 5–10 8 yr. Sedimentation rates decrease systematically as the time windows increase. The experiment indicates that the decrease of sedimentation rates with increase of time is not simply an effect of the mathematical transformation. It is a physical phenomenon, probably related to the fact that sedimentation is an episodic process and that the sediment record is riddled with hiatuses on all scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1021742228242
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  • 7
    Electronic Resource
    Electronic Resource
    Pseudo-unconformities in seismic models of large outcrops (1995)
    Springer
    Geologische Rundschau 84 (1995), S. 761-769 
    Details
    ISSN: 0016-7835
    Keywords: Key words: Seismic modeling ; Seismic interpretation ; Sequence-stratigraphy ; Unconformities ; Carbonates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: Abstract  Traditionally, seismic modeling has concentrated on one-dimensional borehole modeling and two-dimensional forward modeling of basic structural–stratigraphic schemes, which are directly compared with real seismic data. Two-dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines. Examples include the Dolomites (North Italy), the Vercors (SE France), and the High Atlas (Morocco). The seismic models are generally constructed using the following procedure: (a) construction of a detailed lithologic model based on direct outcrop observations; (b) division of the lithologic model into lithostratigraphic units; (c) assignment of petrophysical properties to these lithostratigraphic units; (d) ray tracing to compute time- or depth sections of reflectivity; (e) convolution of the reflectivity sections with source wavelets of different frequencies. The lithologic detail modeled in the case studies led to some striking results, particularly the discovery of pseudo-unconformities. Pseudo-unconformities are unconformities in seismics, but correspond to rapid changes of dip and facies in outcrop. None of the outcrop geometries studied were correctly portrayed seismically at 25-Hz peak frequency. However, in some instances the true relationship would gradually emerge at peak frequencies of 50–100 Hz. The examples given in this study demonstrate that detailed, outcrop-derived, seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less-ideal conditions, and what pitfalls may befall the interpreter of real seismic data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00240566
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    Paper (German National Licenses)
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  • 8
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    3-D Seismic Characterization of Submarine Landslides on a Miocene Carbonate Platform (Luconia Province, Malaysia) (2004)
    SEPM
    In:  Journal of Sedimentary Research, 74 (6). pp. 817-830.
    Details
    Publication Date: 2016-05-04
    Description: 3-D seismic reflection data and a variance cube are used to determine the architecture and investigate the triggering processes of submarine landslides affecting the flanks of a Miocene carbonate platform in the Luconia Province, Malaysia. The slide masses exhibit, in time-slice displays, chaotic, patchy seismic patterns, in otherwise smooth reflections. They lie basinward of the slide scar, tend to widen in the transport direction, and end in indistinct lobes. Slide scars appear as crescent-shaped embayments in otherwise straight or oval platform-edge contours. However, slide scars show planar morphology where they coincide with a fault zone. In vertical sections, the basal surfaces of the slides are steep concave slope segments (slide scar) that rapidly flatten where they dip under the slide masses. Slide masses appear as zones of discontinuous wavy reflections that wedge out in both upslope and downslope directions, extend for 1.5 km into the basin, and have a maximum thickness of 130 m. The slide deposit on the western flank is the result of at least two individual sliding events. Two seismically chaotic bodies are separated by a smooth reflection interpreted as an intercalation of hemipelagic mud between carbonaterich slide masses. Syndepositional faulting affects the geometry of the platform and the platform margins, particularly at the time of slope failure. We suggest that the slides were generated by the interplay of steep-slope progradation and faulting accompanied by seismic shocks.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1306/040604740817
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 9
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    Quantification of input and compositional variations of calciturbidites in a Middle Triassic pelagic succession (Seceda, Western Dolomites, Southern Alps) (2003)
    Springer
    In:  International Journal of Earth Sciences, 92 (4). pp. 593-609.
    Details
    Publication Date: 2018-05-30
    Description: Triassic calciturbidites were studied in a 100-m long core and nearby outcrops of the basinal Buchenstein Formation to determine composition and thickness variations. The quantity of recognized turbidite sediment relative to background sediment changes from 15% (by volume) in the lower part to 60% in the upper part, reflecting the steady progradation of nearby platforms. The composition of the sand fraction of 214 turbidites was point-counted in thin sections. Micrite peloids (average 23%) and lithoclasts (16%) are by far the most dominant constituents. They are interpreted as two different varieties of in-situ precipitated micrite (automicrite), which probably formed under the influence of microbes and constitute the principal building material of the adjacent platforms. Platform-derived skeletal grains amount to only 0.5%. Variations in turbidite composition were quantified using Spearman's rank correlation and cluster analysis. The most significant compositional variations seem to be related to hydrodynamic sorting in the turbidity currents and to the gradual shift from distal to more proximal turbidites in the core as the platforms prograded basinward. Cluster analysis of the 214 samples shows a major subdivision into micrite and sparite dominated turbidites. Clusters associated with micrite-dominated turbidites are enriched in Radiolaria and thin-shelled bivalves, whereas the clusters related to sparite-dominated turbidites show an abundance of lithoclasts. This subdivision seems strongly related to sorting effects in a turbidity current. Point-counting of turbidites in nearby outcrops revealed a lateral variation in composition. Proximal turbidites are sparite-dominated and enriched in lithoclasts, distal portions are chiefly micrite with an open-ocean biota (thin-shelled bivalves, Radiolaria). This differentiation resembles the vertical change in composition of thick turbidite beds, and is attributed to different settling rates of the various grains in the turbidity current. There is no indication that turbidite composition fluctuated significantly under the influence of sea-level fluctuations. This is not surprising because the dominant automicrite facies of the platforms only migrates laterally, but does not change much during sea-level cycles.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-002-0301-z
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 10
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    Ocean Drilling Program: Rise and fall of carbonate platforms in the Bahamas (1985)
    In:  EPIC3Nature, 315(6021), pp. 632-633, ISSN: 0028-0836
    Details
    Publication Date: 2018-08-10
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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