Building isopach layer

Cyril Galéra and Chakib Bennis and Isabelle Moretti. ( 2000 )
in: 20th gOcad Meeting, ASGA

Abstract

According to the classification of Ramsay and Huber (1987 [8]), various geological structures are characterized by a mode of deformation. Thus, a fold is similar if compatible with the simple shear deformation. In such a layer, the distance measured in a vertical or oblique direction (the direction of shear) between the top and the bottom of the formation is constant. A fold is concentric if compatible with the flexural slip deformation mode. In this case, the thickness remains the same during and after the deformation. If the thickness is constant, the layer is called isopach. This last mechanism, of shear parallel to the bed discontinuities, is the most common in competent layers and compressive contexts (Moretti et al., 1989 [7]). Like the simple shear, the flexural slip follows the law of material preservation established by Dahlstrom (1969 [2]) and implies a geometrical relationship between the top and the bottom. Thus, an easy way to build an isopach layer knowing one of its limits, the surface which models the top (or bottom), is first to duplicate the given surface and then to move the points of the surface following a direction given by the normal, and a distance given by the thickness. Nevertheless, when the distance is too great, some incoherencies may appear on the surface: it crosses itself (figure 1). So these incoherencies have to be detected and removed.

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    BibTeX Reference

    @inproceedings{GaleraRM2000,
     abstract = { According to the classification of Ramsay and Huber (1987 [8]), various geological structures are characterized by a mode of deformation. Thus, a fold is similar if compatible with the simple shear deformation. In such a layer, the distance measured in a vertical or oblique direction (the direction of shear) between the top and the bottom of the formation is constant. A fold is concentric if compatible with the flexural slip deformation mode. In this case, the thickness remains the same during and after the deformation. If the thickness is constant, the layer is called isopach. This last mechanism, of shear parallel to the bed discontinuities, is the most common in competent layers and compressive contexts (Moretti et al., 1989 [7]). Like the simple shear, the flexural slip follows the law of material preservation established by Dahlstrom (1969 [2]) and implies a geometrical relationship between the top and the bottom. Thus, an easy way to build an isopach layer knowing one of its limits, the surface which models the top (or bottom), is first to duplicate the given surface and then to move the points of the surface following a direction given by the normal, and a distance given by the thickness. Nevertheless, when the distance is too great, some incoherencies may appear on the surface: it crosses itself (figure 1). So these incoherencies have to be detected and removed. },
     author = { Galéra, Cyril AND Bennis, Chakib AND Moretti, Isabelle },
     booktitle = { 20th gOcad Meeting },
     month = { "june" },
     publisher = { ASGA },
     title = { Building isopach layer },
     year = { 2000 }
    }