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  • 1
    Digitale Medien
    Digitale Medien
    Springer
    Environmental geology 26 (1995), S. 269-277 
    ISSN: 1432-0495
    Schlagwort(e): Glaciation ; Buried channels ; Canada ; Joints ; Contaminant migration
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Geologie und Paläontologie
    Notizen: Abstract The bedrock surface of many glaciated areas is obscured by thick drift deposits. In southern Ontario, Canada, the buried bedrock surface is dissected by channels, infilled with glacial deposits as much as 150 m thick, that are part of a wider mid-continent “preglacial” fluvial system that predates formation of the modern Great Lake basins. The infills of bedrock channels form major groundwater aquifers, influence regional groundwater flows and contaminant migration to Lake Ontario, and may localize the release of thermogenic methane and radon within heavily urbanized surface environments. A quantitative comparison of the regional pattern of bedrock joints and the orientation pattern of buried bedrock channels and modern river valleys shows that all these orientation patterns are virtually coincident. Buried bedrock channels in south-central Ontario are not part of a simple antecedent drainage system but were likely “predesigned” by bedrock joint patterns that have subsequently been propagated upward into overlying Pleistocene sediments. Joints in sediments are of considerable environmental significance (for example, subsurface contaminant and gas migration in fine-grained clayey sediments) and of many origins (stress release, desiccation, etc.) but are widely assumed to be a predominantly surface-related phenomena; the existence of deeper joints has been noted by some authors but their origin is obscure. Data presented herein from south-central Ontario confirm that, in addition to surface-related joints, a second population of bedrock-related joints, reflecting the upward propagation of bedrock fractures, is present in Pleistocene sediments of south-central Ontario.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Publikationsdatum: 2011-08-12
    Beschreibung: Geosyncline formation in earth crust by deposition of sediments in shallow water
    Schlagwort(e): GEOPHYSICS
    Format: text
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    facet.materialart.
    Unbekannt
    Publikationsdatum: 2019-11-04
    Beschreibung: A study is made of the orientations (strikes/trends) of joints, valleys, ridges and lineaments, i.e. of the (potentially) morphotectonic features, of the Mascarene Islands (Reunion, Mauritius and Rodrigues) in the Indian Ocean. It turns out that a connection exists between these features on all islands. For the joints alone, the results for Mauritius as a whole agree closely with those for Rodrigues as a whole, and also partially with those of Reunion. Inasmuch as the trends of the valleys, ridges and lineaments are related to the trends (strikes) of the joints, a common morphotectonic predesign seems to be present for all features studied. The morphotectonic orientations on the island also agree closely with the trends of fracture zones, ridges and trenches in the nearby ocean bottom; which has had a bearing on the theories of the origin of the Mascarene Islands. Generally, a hot-spot origin is preferred for Reunion, and may be for Mauritius as well, although differing opinions have also been voiced. The dynamics of a hot-spot is hard to reconcile with the close fit of the joint strikes in Réunion with the trends of the Madagascar and Rodrigues fracture zones. The closely agreeing joint maxima in Mauritius and Rodrigues í across the deep Mauritius trench í also agree with the trend of that trench and with the trend of the Rodrigues fracture zone. Thus, it would appear as most likely that the trends of joints and of fracture zones are all part of the same pattern and are due to the same cause: viz. to action of the neotectonic stress field.
    Beschreibung: JCR Journal
    Beschreibung: open
    Schlagwort(e): Mascarenes ; Indian Ocean floor ; neotectonics ; hot spots ; oceanic islands ; 04. Solid Earth::04.07. Tectonophysics::04.07.08. Volcanic arcs
    Repository-Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Materialart: article
    Format: 5060730 bytes
    Format: application/pdf
    Standort Signatur Erwartet Verfügbarkeit
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