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  • Articles  (45)
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  • 1
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Physics Edition 14 (1976), S. 643-650 
    ISSN: 0098-1273
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Depolarization ratios ρ of the Raman bands due to CH3 stretching at 2907 cm-1 and the Si—O skeletal mode at 491 cm-1 have been measured in polydimethylsiloxane gum as a function of temperature from 100°C to -45°C. Below 0°C the changes in p have been interpreted in terms of the formation of helical regions in the gum. The enthalpy of helix formation ΔH has been determined as 3200 ± 600 cal/mole. An upper limit on the entropy change, ΔS, of 16 ± 3 e.u./mole and minimum values of helix content at different temperatures have been found. The Raman spectrum of crystalline polydimethylsiloxane is presented.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2015-08-22
    Description: Extract The early discovery of the Arbroath Field in 1969, and the Montrose and giant Forties fields in 1970, initiated intensive exploration of the Tertiary deep-marine play in the North Sea region. Numerous subsequent discoveries (Fig. 1), including Frigg (in 1971), Maureen (in 1973), Gannet (in 1973), Andrew (in 1974), Pierce (in 1976), Everest (in 1982), Alba (in 1984), Gryphon (in 1987), Nelson (in 1988), Harding (in 1988), Jotun (in 1994), Siri (in 1995) and Merganser (in 1995), demonstrate the success of this play and the geological diversity of Paleocene and Eocene systems present within the region. Although the North Sea Basin is now considered mature, with Cenozoic reservoirs well along their creaming curve (Vining et al. 2005), recent discoveries (e.g. the Catcher Field in 2010) highlight that potential still remains within intensively explored areas such as the Central North Sea, as well as in the less explored regions such as the Atlantic margin and the Norwegian Sea. The importance of these reservoirs is demonstrated by the large proportion of UK production to which they contribute, amounting to approximately 25% of all production from UK oil fields since 1975 on a barrel of oil equivalent (BOE) basis (Fig. 2). Indeed, over time that proportion has increased from 20% of production in the 1970s and 1980s to 30% from the 1990s. ... This 250-word extract was created in the absence of an abstract.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 3
    Publication Date: 2015-06-02
    Description: :  Recent analysis of modern aggradational continental sedimentary basins reveals that sedimentation patterns are dominated by distributive fluvial systems (DFSs). The Salt Wash Member of the Late Jurassic Morrison Formation has previously been described as a fan-shaped fluvial system. This study characterizes facies variations across the Salt Wash DFS to quantitatively test predicted trends in conceptual DFS models. Notable proximal-to-distal trends include a change in total thickness of the fluvial succession from 174 m to 40 m, and an average grain size from coarse sand to silt, while the percentage of sand decreased from 70% in the proximal region to 8% in the distal region. The proportion of amalgamated channel-belt deposits decreased from 67% to 0%, while floodplain facies and lacustrine deposits increase (38% to 94% and 0.1% to 7% respectively). A downstream decrease in average channel-belt thickness (15 m to 3.8 m, from thickest to thinnest) and average story thickness (7.7 m to 2.3 m, from thickest to thinnest) is also recorded. Significant downstream changes in deposit architecture were also noted, with proximal regions dominated by stacked channel-belt deposits with a high degree of amalgamation. Distal deposits are dominated by floodplain muds and sheet sandstones and sparse ribbon channels, with little to no amalgamation of channel deposits. This study provides quantified information for an ancient DFSs with the aim of providing a dataset that can be used for objective comparison between different DFSs, as well as providing numerical data to aid resource exploration and modelling efforts.
    Print ISSN: 1527-1404
    Topics: Geosciences
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  • 4
    Publication Date: 2015-07-30
    Description: Meandering fluvial channels and their meander belts are common in modern continental sedimentary basins, yet compose a minor constituent of the reported fluvial rock record. Here we document exhumed amalgamated meander belt deposits from the upper Jurassic Morrison Formation, Utah (United States). The size of the amalgamated meander belt (9000 km 2 ) is significantly larger than any documented previously and comparable in size to those from modern sedimentary basins. We describe a representative outcrop of sandy point bar deposits that shows features considered characteristic of both braided and meandering fluvial systems. Lateral accretion sets compose 〈5% of the outcrop area, yet point bar morphology is clearly visible in plan view. We suggest that difficulties in the identification of sandy, amalgamated meander belt deposits indicate that they have gone largely unrecognized in the rock record. Their recognition has important implications for basin-scale reconstructions of fluvial systems and interpretation of tectonic setting.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 5
    Publication Date: 2016-07-05
    Description: We infer system-scale fluid flow in the Late Jurassic Salt Wash fluvial succession (SW USA) by plotting uranium deposit distribution against sedimentological data, using uranium distribution as a proxy for subsurface fluid flow. More than 90% of uranium deposits in the Salt Wash occur where sandstone forms 40–55% and sand-rich channel-belts form 20–50% of the succession, which coincides with changes in channel-belt connectivity and gross-scale architecture. The paucity of uranium below these cut-off values suggests that fluid flow is related directly to predictable downstream fining and facies variations in distributive fluvial systems. Supplementary material: A summary table of location data, key trends and the amalgamation ratio method is available at https://doi.org/10.6084/m9.figshare.c.2849581 .
    Print ISSN: 0016-7649
    Topics: Geosciences
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  • 6
    Publication Date: 2016-09-17
    Description: Distinguishing axial and lateral sedimentary systems in rift basins is crucial for predicting reservoir distribution and quality, particularly where synrift strata are interrupted by mass transport complexes (MTCs). Upper Jurassic deep-marine synrift successions in the central North Sea have been studied to assess the temporal and spatial relationships of sediments and controls on reservoir quality. In the Late Jurassic, the central graben experienced erosion at rift margins, whereas adjacent grabens were starved and underfilled with marine sediments, supplied by axial and transverse systems. This study focused on sediments adjacent to a major intrabasinal high, the Josephine ridge. Data included seismic, wireline logs from 16 wells, and biostratigraphic and sedimentological analysis of 144 m (472 ft) of core. Synrift strata are dominated by mudstones but include MTCs interbedded with coarse sandstones at the rift margin and fine-grained turbidite sandstones in basinal depocenters. Petrographic and heavy mineral data indicate different provenance between MTCs and basinal turbidites. Turbidites correlate with periods of lowered relative sea level, during the initial rift phase, and record axial sediment supply. The composition of the MTCs corresponds to in situ strata on the adjacent Jade and Judy horsts. The distribution of MTCs implies formation by crestal collapse horsts during the rift climax and represents a transverse system, with no genetic relationship to axial turbidites. In starved deep-marine basins, fine-grained, well-sorted axial systems may provide the most extensive reservoirs. Transverse systems derived from isolated horsts are typically coarse-grained, poorly sorted, and spatially restricted, being unlikely to provide significant reservoir material.
    Print ISSN: 0149-1423
    Electronic ISSN: 0149-1423
    Topics: Geosciences
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  • 7
    Publication Date: 2014-04-26
    Description: Understanding the controls on the size and shape of sandstone bodies deposited by fluvial systems is important in the reconstruction of ancient fluvial deposits and construction of quantitative reservoir models. Measurements and analyses of sandbodies from remotely sensed imagery have allowed quantification of width and length ratios of barforms in modern fluvial systems. For bank-attached bars the width:length ratios range between 0.12 and 0.47 (arithmetic mean: 0.25), for lateral bars between 0.19 and 0.42 (arithmetic mean: 0.30), for mid-channel bars between 0.09 and 0.49 (arithmetic mean: 0.28), and for point bars between 0.14 and 0.50 (arithmetic mean: 0.30). The majority of width:length ratios for all bar types range between 0.15 and 0.35. Examination of other parameters such as basin type, planform geometry, apparent stream width, river length, gradient over the investigated area, aggradational or degradational system, tectonic setting and climate do not significantly affect the width:length ratio. Therefore, the bar planform shape, the width:length ratio, can be considered to be scale invariant. The recognition that bar planform shape in fluvial systems is scale invariant will be useful in the construction of subsurface three-dimensional models of fluvial deposits with variable dimensions. Supplementary material: Data tables with information obtained for all of the rivers studied are available at http://www.geolsoc.org.uk/SUP18745 .
    Print ISSN: 1354-0793
    Topics: Chemistry and Pharmacology , Geosciences
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  • 8
    Publication Date: 2015-03-11
    Description: The relationship between movement on the Highland Boundary Fault and deposition of the Lower Old Red Sandstone in the Midland Valley Basin of Scotland is controversial. Most models favour mid-Silurian to early Devonian sinistral movement on the Highland Boundary Fault and development of a transtensional Midland Valley Basin. To constrain Highland Boundary Fault movement during the late Silurian, we examine the basal Lower Old Red Sandstone alluvial succession exposed adjacent to the Highland Boundary Fault. A lack of synsedimentary fault movement indicators, coupled with an increase in stratal thickness across the fault, indicates that the Highland Boundary Fault was not active during Lower Old Red Sandstone sedimentation. A transtensional basin model cannot be sustained.
    Print ISSN: 0016-7649
    Topics: Geosciences
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  • 9
    Publication Date: 2014-04-19
    Description: A seismic stratigraphic analysis constrained by well and wireline log data has been undertaken on the Paleocene and earliest Eocene succession of the South Buchan Graben (Quadrants 20 and 21), Outer Moray Firth Basin (OMFB). Two principal sequences have been described relating to two regressive/transgressive second-order cycles of relative sea-level change. The Maureen, Andrew, Glamis Tuff and Balmoral sandstone members are expressed as a stacked set of lowstand basin floor fans separated by mudstone intervals representing four cycles of third-order relative sea-level change. The Sele and Balder formations contain both basinal and shelfal packages as an expression of two cycles of third-order relative sea-level change. The Forties Sandstone Member is deposited within highly mounded, levee-confined channels downlapped by a prograding slope succession with well-defined clinoforms and deltaic topsets attributed to the Dornoch and Beauly formations. The individual parasequences of the prograding wedge are related to higher-order eustatic fluctuations with incision and slope fans, attributed to the Cromarty Sandstone Member, deposited during periods of relative sea-level lowstand. It is demonstrated that through the integration of lithostratigraphic, seismic geomorphological and sequence stratigraphic analyses an understanding of depositional environments and the distribution of facies within them can be obtained. The identification of basinal and slope features with reservoir potential, along with an understanding of their chronostratigraphic relationship to sealing facies, play an important role in regional play fairway mapping and risk analysis in this area and beyond. Future prospectivity within mature basins, such as the OMFB, relies on subtle stratigraphic traps typical of lowstand systems tracts, where the main risk is associated with reservoir quality and containment.
    Print ISSN: 0305-8719
    Electronic ISSN: 2041-4927
    Topics: Geosciences
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  • 10
    Publication Date: 2014-11-22
    Description: A bstract :  Regression relationships are derived relating the areal extent of large distributive fluvial systems (DFSs) (〉 30 km in length) formed in endorheic basins to contributing drainage area. The resulting correlation coefficients vary between 79% and 98%. Derived correlation values are strikingly similar when stratified by climate, large-scale tectonic regime, and basin context. Regression-equation exponent values range from 0.41 to 0.75, indicating a strong positive relationship between drainage area and DFS area, while coefficients account for the influence of external parameters on the derived relationships. Analysis of the dataset using planform morphology and drainage-basin slope as additional variables reveals that regressions for braided bifurcating DFS produce a highly significant relationship. The relationship suggests that drainage-basin relief influences sediment supply to the sedimentary basin in terms of volume or caliber, which in turn affects the depositional gradient of the DFS surface and resultant channel planform. An evaluation of the predictive capability of the regression equations reveals that the relationships derived from braided bifurcating DFSs perform best, with 80% of the predicted values falling within ± 25% of the measured DFS area value, with a third of the predicted values within ± 10% of the measured DFS area value. Application of the regression relationships derived here to rock-record examples of fluvial deposits interpreted as large DFSs show that DFS area can be used as a proxy to predict the surface area of fluvially transported sediment deposited in a sedimentary basin from the contributing drainage-basin area. The regression relationships for modern drainage areas and corresponding DFS areas from a range of tectonic and climatic settings suggest a measurable link between source and sink in the sedimentary rock record. The results provide a potential tool for more accurate reconstruction and prediction of preserved fluvial deposits and basin-fill architecture within basin-scale climatic and tectonic contexts.
    Print ISSN: 1527-1404
    Topics: Geosciences
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