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Etude de la déformation récente et actuelle a l'apex des diapirs salifères

Abstract : Present-day deformation in the tops of salt plugs has been studied in two different settings: the post-extensional Alsace rift in NE France and the foreland of the Zagros belt in southern Iran. In the Rhine graben, using levelling survey data collected between 1924 and 1994, vertical movement rates above salt ridges have been estimated to be up to 1 mm.y-1. Rates above longitudinal (N-S) salt ridges (0.5 mm.y-1) are less than above transverse (NW-SE) ridges (1 mmy-1)* Salt uplift above transverse salt ridges was facilitated by their being perpendicular to the minimum horizontal stress axis of the present-day regional stress field . In the second area (eastern Zagros Mountains, north of Bandar Abbas), we have examined seven sites, four in detail. By studying drainage networks, digital elevation models, stereoscopic SPOT images, the dispersion of earthquakes and, using a new method, the alignment of salt diapirs, a series of structural lineaments has been identified. Two N 10°E-N30°E and N140°E-N160°E families correspond to recent conjugate surface faults, one N40°E-N70°E family to crustal sinistral faults, and one N80°E-N100°E family parallels the trends of folds . One N110°E-N140°E family could not be associated with any discontinuity. Several phenomena associated with salt diapirism that could help find unknown diapiric sites have also been identified in the Zagros Mountains, namely inflation, collapse, deflation, plunge cut, watershed change and alluvial cone tilt. The relationship between salt plug outcrops and recent alluvium in the Bandar Abbas area shows that the active salt diapirs were unroofed between 4,000 and 30,000 years ago. The irregularity of alluvium on salt outcrops shows that salt uplift rates vary between 2 cm.y-1 and about 1 cm.y-1, the present-day rate bring ten times that in the southern Rhine graben. Alluvial cones in contact with salt plugs have been tilted more than distant cones in the Zagros Mountains. This difference (1.5° to 2.5°) is due to salt uplift, the rate of diapiric tilting being 0.5° per 1000 years
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Submitted on : Monday, July 16, 2012 - 11:47:17 AM
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  • HAL Id : tel-00718123, version 1

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Ciroos Liaghat. Etude de la déformation récente et actuelle a l'apex des diapirs salifères. Tectonique. Université de Savoie, 1999. Français. ⟨tel-00718123⟩

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