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  • 1
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    Magnetic Susceptibility Application : A Window onto Ancient Environments and Climatic Variations (2015)
    London : The Geological Society
    Details
    Beschreibung / Inhaltsverzeichnis: Magnetic susceptibility (MS) is a tool frequently used by geologists on sediments or rocks to perform correlations and sea-level or climatic reconstructions. Applied measurements are made on unoriented, bulk samples and bulk MS is mostly influenced by the magnetic mineral content of the rock and often interpreted as influenced by detrital inputs. Magnetic data acquisition is fast and straightforward and this allows the high-resolution sampling needed for palaeoclimatic research (e.g. spectral analysis). However, the link with detrital inputs is not always preserved and the impact of diagenesis on the final MS signal can blur primary information. This volume includes contributions dealing with the origin of the magnetic minerals, and the application of MS as a palaeoenvironmental or palaeoclimatic proxy and also as a tool to provide astronomical calibration in order to improve the chronology of selected time intervals.
    ISBN: 9781862397217
    URL: http://sp.lyellcollection.org/content/414/1.toc
    Sprache: Englisch
    Standort Signatur Erwartet Verfügbarkeit
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    E-BOOK
  • 2
    Digitale Medien
    Digitale Medien
    Karst in granitic rocks, South Cameroon: cave genesis and silica and taranakite speleothems (2002)
    Oxford, UK : Blackwell Science Ltd
    Terra nova 14 (2002), S. 0 
    Details
    ISSN: 1365-3121
    Quelle: Blackwell Publishing Journal Backfiles 1879-2005
    Thema: Geologie und Paläontologie
    Notizen: A cave in granitic rocks was studied in Mezesse, South Cameroon. Coralloid speleothems, draperies and dissolution traces on the cave walls attest to its truly karstic nature. The speleothems consist of microlayers of opal and taranakite (K,NH4)Al3(PO4)3(OH).9H2O. They indicate a significant mobilization of silica, Al and K from granite during the formation of the cave. Identification of silicified bacteria in the speleothems layers suggests a possible role of these micro-organisms in silica deposition. The presence of taranakite and of silicified organic remains within the speleothems lead to a better understanding of the genesis of the cave.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1046/j.1365-3121.2002.00429.x
    Standort Signatur Erwartet Verfügbarkeit
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    Artikel (Nationallizenzen)
    Volltext
  • 3
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    Magnetic susceptibility application: a window onto ancient environments and climatic variations: foreword (2015)
    Geological Society (of London)
    Details
    Publikationsdatum: 2015-06-26
    Beschreibung: Magnetic susceptibility (MS) is a powerful tool, which is being applied increasingly on sedimentary rocks to constrain stratigraphic correlations, or as a palaeo-environmental or palaeo-climatic tool. The origin of the magnetic minerals responsible for the variations in MS can be linked to various phenomena such as detrital inputs, pedogenesis, bacterial precipitation or diagenesis. Therefore, it is critical to improve our knowledge of the origin of the MS signal in order to apply it for correlations or as a proxy. Here, we present a synthesis of the techniques that can be applied to get a better understanding of the origin of the MS signal, through comparison with other palaeo-environmental proxies, through magnetic measurements or through dissolution and direct observation of the extracted minerals. We also propose an overview of the different techniques applied in order to use MS as a correlation tool, and we show various examples of successful applications of MS as a recorder of change in past sea-level and climate. We also present the main results and activities of the IGCP-580 project ‘Application of magnetic susceptibility as a palaeo-climatic proxy on Palaeozoic sedimentary rocks and characterization of the magnetic signal’.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society (of London)
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
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    Lower Carboniferous ramp sedimentation of the Central Alborz Basin, northern Iran: integrated sedimentological and rock-magnetic studies (2015)
    Geological Society (of London)
    Details
    Publikationsdatum: 2015-05-28
    Beschreibung: The Lower Carboniferous Mobarak Formation in the Alborz Basin (northern Iran) was deposited along the northeastern margin of Gondwana in a carbonate ramp setting. This paper focuses on the Tournaisian stratigraphic interval of this formation that crops out at the Jaban section in the southwestern Central Alborz Basin. The following facies associations, representing different ramp palaeoenvironments, have been identified: (1) mudstone–wackestone outer-ramp facies; (2) crinoidal to skeletal grainstone–packstone mid-ramp facies; (3) peloidal to crinoidal grainstone–packstone inner-ramp facies; and (4) coastal facies, which include a variety of microbial laminated to oncoidal grainstones and mudstones with evaporitic pseudomorphs. This ramp profile was affected by frequent storms that were responsible for the formation of several skeletal to non-skeletal shoals in the distal mid-ramp to the most proximal inner-ramp areas. The development of the skeletal to non-skeletal shoals along the sea side of the ramp formed a semi-enclosed lagoon sensitive to the influence of both high tides and storm surges. The magnetic susceptibility ( in ) of all the samples was measured and compared with that of the facies from which the sample was taken. There is a clear link between in and the facies; the average in values were higher for the distal facies than for the proximal facies. The in profile of this Lower Carboniferous carbonate sequence reflects stratigraphic variations in response to relative changes in sea level and the input of detrital materials. In the context of the sequence stratigraphic framework, the average in values for lowstand and transgressive systems tract deposits are higher than for the highstand systems tract deposits. The clear link between in and facies indicates at least a partly preserved primary in signal related to the detrital inputs. However, to obtain a better understanding of the nature and origin of the minerals carrying the in , we performed hysteresis measurements on selected samples. It appears that the in signal is mainly carried by low-coercivity ferromagnetic minerals such as magnetite, with a mixture of relatively coarse grains (detrital fraction) and ultra-fine grains (probably formed during diagenesis).
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society (of London)
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
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    Late Devonian-Early Carboniferous miospores from the Menen Borehole, Namur Synclinorium, Belgium (1994)
    Elsevier
    Details
    Publikationsdatum: 1994-01-01
    Print ISSN: 0034-6667
    Digitale ISSN: 1879-0615
    Thema: Geologie und Paläontologie
    Publiziert von Elsevier
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
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    The astronomical calibration of the Givetian (Middle Devonian) timescale (Dinant Synclinorium, Belgium) (2014)
    Geological Society (of London)
    Details
    Publikationsdatum: 2014-11-24
    Beschreibung: Recent advances in radiometric dating result in significant improvements in the geological timescale and provide better insight into the timing of various processes and evolutions within the Earth's system. However, no radiometric ages are contained within the Givetian. Consequently, the absolute ages of the Givetian Stage boundaries, as well as the stage's duration, remain poorly constrained. As an alternative, the analysis of sedimentary cycles allows for the estimation of the duration of this stage. We examined the high-resolution magnetic susceptibility signals of four Givetian outcrops in the Givet area for a possible astronomical imprint, to fully understand the rates of evolutionary and environmental change. All four sections are firmly correlated and wavelet analyses of the magnetic susceptibility signals reveal the imprint of astronomical eccentricity forcing. The highly stable 405 kyr cycles constrain the duration of the Givetian Stage at 4.35±0.45 Myr, which is in good agreement with the International Chronostratigraphic Chart (5.0 Myr). The studied sections also exhibit an imprint of obliquity, suggesting a climatic teleconnection between low and high latitudes. The corresponding microfacies curves demonstrate similar astronomical imprint, and thereby indicate that the observed 10 5 year-scale cyclicity is the result of climatic and environmental change.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society (of London)
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  • 7
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    Sedimentary development and magnetic susceptibility evolution of the Frasnian in Western Belgium (Dinant Synclinorium, La Thure section) (2014)
    Geological Society (of London)
    Details
    Publikationsdatum: 2014-12-10
    Beschreibung: Recent opening of the La Thure quarry in Western Belgium allowed the collection of new data from a poorly outcropping area of the Belgian Frasnian platform. The studied section covers an interval extending from the falsiovalis to hassi s.l. Zones. Sedimentological analyses allowed the reconstruction of depositional settings in the northwestern part of the Dinant Synclinorium after the demise of the extended Givetian carbonate platform. Two depositional models are distinguished: (a) siliciclastic drowned platform during the Early Frasnian; and (b) a fore-reef depositional setting belonging to a rimmed shelf during the Middle Frasnian. Moreover, interpreted depositional settings in the northwestern part of the Dinant Synclinorium allowed to constraint the direction of the main facies belts for the Belgian Frasnian platform. Combination of MS and geochemistry demonstrates the inherent-parallel link existing between variation in MS values and proxy for terrestrial input (such as Si and Al). This observation means that, despite the remagnetization occurring within the Belgian Frasnian lithologies, the main trends in the MS signal from the La Thure section still reflect some syn-sedimentary conditions. The increase in MS and clastic input proxies recorded in distal fore-reef deposit within the punctata Zone are likely to be considered as enhanced by rapid and strong shallowing events recognized in the ‘ puncata Event’ interval.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society (of London)
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
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    Magnetic susceptibility and facies relationship in Bajocian-Bathonian carbonates from the Aze caves, southeastern Paris Basin, France (2015)
    Geological Society (of London)
    Details
    Publikationsdatum: 2015-03-25
    Beschreibung: This study focuses on three Bajocian and Bathonian carbonate sections from the southeastern part of the Paris Basin (Mâconnais area, in the east of France). The main goals of the study are to propose a palaeoenvironmental model, to get insight into vertical and lateral facies evolution, to improve correlations and to better understand the origin of the magnetic susceptibility (MS) signal in these deposits. The sedimentological setting corresponds to a ramp, with two types of geometries: (1) a homoclinal carbonate ramp with oolitic shoals; and (2) a multiple-slopes carbonate ramp with reef complexes. The MS signal appears to be influenced by facies and ramp geometry. The evolution of MS seems to be mainly related to changes in carbonate productivity and water agitation: oolitic facies and reef complexes, with high carbonate production show the lowest signal, while storm deposits are characterized by higher values. In addition, the MS signal from proximal tempestites have higher values than distal ones. MS appears to be a useful complementary proxy for palaeoenvironmental interpretations, correlations and sequential stratigraphy. The facies evolution, supported by MS curves, shows at least nine successive depositional sequences, which were inserted into the regional sequential canvas.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society (of London)
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
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    Sedimentology and magnetic susceptibility of recent sediments from New Caledonia (2015)
    Geological Society (of London)
    Details
    Publikationsdatum: 2015-02-08
    Beschreibung: The interpretation of the primary origin of the minerals carrying the magnetic susceptibility (MS) signal from ancient rocks suffers notably from the scarcity of studies on Recent sediments. To bring new data, a study of tropical coastal sediments of New Caledonia was undertaken. This island is surrounded by a nearly uninterrupted reef barrier, isolating a wide lagoon from the open ocean. The erosion of extremely varied rocks (from mantle rocks to laterites) produces different types of detrital sediments, which are mixed with the indigenous precipitated carbonates. This generates different types of coastal sediments, detrital- or carbonate-dominated or mixed. More than 300 samples were analysed for grain size, nature of sediment, MS and geochemistry (major elements). The first results show that: (a) carbonate sands and carbonate silts are characterized by lower MS than detrital sediments; (b) the MS signal of mixed sediments is mostly influenced by the proportion of detrital sediments; (c) MS is directly correlated with Mn and Fe content; (d) beachrocks are characterized by lower MS than equivalent loose sediment; (e) the MS signal of carbonate sediments is locally positively correlated with granulometry; (f) there is no MS change between surface and 20 cm deep samples; and (g) when the subsurface sediment is reducing, the MS is higher than that from surface sediment.
    Print ISSN: 0305-8719
    Digitale ISSN: 2041-4927
    Thema: Geologie und Paläontologie
    Publiziert von Geological Society (of London)
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
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    Reconstructing atoll-like mounds from the Frasnian of Belgium (2004)
    Springer
    Details
    Publikationsdatum: 2004-08-12
    Print ISSN: 0172-9179
    Digitale ISSN: 1612-4820
    Thema: Geographie , Geologie und Paläontologie
    Publiziert von Springer
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