Interaction between structural inheritance and extension direction during graben and depocentre formation: An experimental approach

Abstract : Analysis of structural rift architecture shows that the graben formation is commonly controlled by the contemporaneous activity of two fault trends with an angular obliquity of approximately 408. Inspection of the crustal basement and geophysical data reveals that these faults are parallel to inherited oblique crustal and lithospheric discrete fabrics, which are reactivated during the extension event. We conducted experiments at crustal scale to determine the role of the coeval reactivation of such oblique inherited fabrics in the graben and depocentre development. Experimentally the oblique inherited lithospheric faults were simulated by a basal discrete velocity discontinuity (VD) characterised by two different angles (a) with respect to the extension direction at the intersection of the VDs. Our models show that besides the extension direction which induces the formation of linear or independent en-echelon grabens, the intersection of the two oblique VD segments controls the location of the depocentre and concentrates subsidence. For different stretching direction values, the depocentre geometry varies from strongly asymmetric to symmetric when the stretching direction corresponds to the bisecting line of the two VD segments. Applied to the Upper Rhine graben (central segment of the West European rift), our models allow interpretation of the development of the Late Eocene–Oligocene depocentres at the intersection of two main oblique inherited structures, as the result of a constant NW–SE extension direction. Concerning the southern East African rift, the graben geometries and the evolution of the subsidence during the Mio-Pliocene period may be explained by the reactivation of two main Pan-African inherited shear zones with an E–W direction of extension. D 2005 Elsevier B.V. All rights reserved.
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Tectonophysics, Elsevier, 2005, 409, pp.125-146. 〈10.1016/j.tecto.2005.08.020〉
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Laurent Michon, Dimitrios Sokoutis. Interaction between structural inheritance and extension direction during graben and depocentre formation: An experimental approach. Tectonophysics, Elsevier, 2005, 409, pp.125-146. 〈10.1016/j.tecto.2005.08.020〉. 〈hal-01382027〉

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