| 1. |
- Bahroudi, A, et al.
(författare)
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Effect of ductile and frictional decollements on style of extension
- 2003
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Ingår i: Journal of Structural Geology. - 0191-8141 .- 1873-1201. ; 25:9, s. 1401-1423
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Tidskriftsartikel (refereegranskat)abstract
- Scaled analogue models were used to study the effect of frictional and ductile detachments on thin-skinned extension. Models consisted of two halves; one half is the ductile and the other has a frictional detachment. Extension occurred above two different basal configurations: a stretchable rubber sheet and a folded, banded sheet intended to produce homogeneous and heterogeneous extension, respectively. Model parameters varied systematically and included the brittle/ductile thickness ratio, rheologies, and bulk strain. Structures in the two halves are compared in profiles and plan views. A series of graben developed above both halves of models extended above a banded sheet, although there were differences in style, propagation rate and width of the deformation zone between the two halves. Different rates of propagation of structures in the two halves led to the formation of an accommodation or transfer zone parallel to the extension direction. Most relay ramps and inflection of normal faults in this zone indicate differential extension between the two halves.In contrast, in models extended above a stretchable rubber sheet, extensional structures such as horst and graben developed only above the ductile detachment. Model results indicate that heterogeneous mechanical stratigraphy and displacement rate have no effect on extensional structure above a rubber sheet. However, above 20% bulk extension, deformation becomes heterogeneous along multiple sets of conjugate faults oblique to the extension direction.
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| 2. |
- Harris, Lyal, et al.
(författare)
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Centrifuge modelling of folding in high grade rocks during rifting
- 2003
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Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 25:2, s. 291-305
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Tidskriftsartikel (refereegranskat)abstract
- Centrifuge modelling is used to simulate the progressive development of structures in a simplified crustal profile during rifting. This paper focuses on folding of ductile layers representing the middle to lower crust. Displacement along a pre-existing cut in the layer representing mantle lithosphere creates a broad shear zone in overlying ductile layers and an asymmetric rift in upper layers. The footwall of the ‘mantle lithosphere’ layer and overlying shear zone are rotated to sub-horizontal during rise of the basal ductile layer (representing asthenosphere) as an isostatic response to thinning in the extended model. Synthetic and antithetic faults develop in models with thicker ductile ‘crustal’ layers. Although upper, semi-brittle layers, representing upper crust constitute a simple fault-bounded or sag ‘basin’, the underlying ductile layers are complexly folded. Open, upright folds developed over the crest of the footwall ‘mantle lithosphere’ layer are tightened and increased in amplitude as they progressively rotate to a recumbent attitude. Refolding occurs during rise of the basal ductile material representing asthenosphere and from boudinage of overlying competent layers. This study suggests that regional-scale folds in some high-grade terrains previously interpreted as evolving in a convergent margin tectonic setting may instead be produced as a result of flow of the ductile crust during rifting.
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| 3. |
- Koyi, Hemin A.
(författare)
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Estimation of salt thickness and restoration of cross-sections with diapiric structures : a few critical comments on two powerful methods
- 1994
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 16:8, s. 1121-1128
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Tidskriftsartikel (refereegranskat)abstract
- Estimation of the initial thickness of a salt layer that has produced diapirs in a sedimentary basin provides information about basin history and evolution of the resulting salt structures. In many cases quantifying sedimentation and deformation history assists the understanding of hydrocarbon entrapment by salt structures. Limitations of the methods that are used to estimate salt thickness and restoration of profiles with salt structures may cause great error in thickness calculation or interpretation of deformation history. These limitations also cause confusion if they are not explained clearly during presentation of results.Restoration of profiles of extension areas where salt structures are present could give erroneous results when the regional extension and the flow of salt in and out of the profile along strike and within the profile are not incorporated in the restoration. Scaled analogues demonstrate that restored profiles of diapiric structures may show incorrect evolution history of salt structure and initial salt thickness.
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| 4. |
- Ali, Moamen, et al.
(författare)
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Geometry and kinematics of the Middle to Late Miocene salt tectonics, central Egyptian Red Sea margin
- 2023
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Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 176
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Tidskriftsartikel (refereegranskat)abstract
- The Red Sea basin includes a thick Middle to Late Miocene evaporitic succession that underwent halokinesis and caused intensive reshaping of the seafloor and the development of salt-tectonic structures. However, the ge-ometry and kinematics of these structures are still poorly understood. This study uses 2D and 3D seismic surveys and well data of the northern Egyptian Red Sea to systematically describe the distribution and morphology of salt structures, discuss their initiation, and construct a kinematic model for their origin. Our results indicate that the massive salt layer developed into five major NW-SE to NNE-SSW trending salt walls, characterized by relatively irregular crests and moderately dipping flanks. In addition, several symmetrical and asymmetrical folds and two categories of normal faults (subsalt and suprasalt) have been recognized. Based on our observations, salt mobilization in the study area started in the Late Miocene, during the precipitation of layered evaporites, and continued until the present day. In the northern Egyptian Red Sea, seismic interpretation indicates that hal-okinesis was triggered by a combination of thin-and thick-skinned systems, where the latter played a major role. The salt layer was welded during the Quaternary as several sags and grabens developed above the salt diapirs. Thick-skinned physical models are compatible with our observations, supporting the impact of basement faulting on Red Sea diapirism.
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| 5. |
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| 6. |
- Amri, Zayneb, et al.
(författare)
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Mechanical relationship between strike-slip faulting and salt tectonics in the Northern Tunisian Atlas : The Bir-El-Afou salt structure
- 2022
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Ingår i: Journal of Structural Geology. - : Elsevier. - 0191-8141 .- 1873-1201. ; 154
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Tidskriftsartikel (refereegranskat)abstract
- Wide variety of salt structures -from typical diapirs to large allochthonous salt sheets- are recognized in the Northern Tunisian Atlas. In this study, we present for the first time the presence of a diapiric structure, Bir-ElAfou Salt Structure (BEASS), which has formed in response to strike-slip tectonics. Structural mapping, mesoscale field observations, fault kinematic analysis, and interpretation of gravity data are used to interpret BEASS, which is currently associated with a restraining bend. The present-day NNE- trending restraining stepover is formed as a result of E-W dextral fault system. We assume that the restraining stepover is a product of the inversion of a pre-existing pull-apart basin that formed during the Cretaceous South Tethyan extension. Tectono-sedimentary relationship is used to argue for an early Cretaceous NW-SE regional extension and local transtension. During the opening of the pull-apart basin, salt movement took place in the southwestern corner of the basin which must have thinned due to its extension facilitating diapiric emplacement. Diapir growth during Aptian was followed by brief salt flow from the diapir crest towards the basin forming a salt sheet. A period of Tertiary contraction resulted in the inversion of the pull-apart basin and consequently, squeezing of BEASS.
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| 7. |
- Bertrand, Lionel, et al.
(författare)
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A multiscale analysis of a fracture pattern in granite : A case study of the Tamariu granite, Catalunya, Spain
- 2015
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 78, s. 52-66
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Tidskriftsartikel (refereegranskat)abstract
- The in-depth investigation of fractured reservoirs is mainly limited to geophysical data that is in 3D and mostly on the scale of hundred meters to several kilometers or boreholes data that is in 1D and at meter to lower scale. The study of outcropping analogues of buried reservoirs is therefore a key tool for the characterization of the fault and fracture network at the reservoir scale. Tamariu granite has been the subject of this study with the aim to analyse faults and fractures from seismic to borehole scale. With the combination of satellite picture at different resolution and field study, we perform a statistical analysis focused of the length and orientation from infra centimeter crack to hundred kilometer length fault. On the whole range of scale studied, i.e. on 7 orders of magnitude, we have defined a length distribution following a power-law with an exponent a = -2. On the contrary to the length that can be modelled with a unique law, the orientation data shows a variation depending on the scale of observation: as the fault and fracture sets are suitable from the regional faults to the centimeter crack, the proportion of the sets varies at each scale of observation.
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| 8. |
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| 9. |
- Borthwick, V.E., et al.
(författare)
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Complex temperature dependent behaviour revealed by in-situ heating experiments on single crystals of deformed halite: New ways to recognize and evaluate annealing in geological materials
- 2010
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 32:7, s. 982-996
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of substructures, which encompass all structures present at the subgrain-scale, were investigated by static, in-situ annealingexperiments. Deformed, single crystalhalite was annealed inside a scanning electron microscope at temperatures between 280 and 470 °C. Electron backscatter diffraction maps provided detailed information about crystallographic orientation changes. Three temperature dependent regimes were distinguished based on boundary misorientation changes. In regime I (280–300 °C) some low angle boundaries (LABs), i.e. with 1°–15° misorientation, increase in misorientation angle, while others decrease. In regime II (∼300 °C) all LABs undergo a decrease in misorientation angle. Regime III (>300 °C) is defined by enhancement of the subgrain structure as remaining LABs increase and some undergo a rotation axis change. Throughout regimes I and II, new LABs develop, subdividing subgrains. LABs could be divided into four categories based on annealingbehaviour, orientation and morphology. We suggest that these observations can be directly related to the mobility and activation temperature of climb of two dislocation groups introduced during deformation. Therefore, with in-depth investigation of a substructure with known deformation geometry, we can infer ratios of dislocation types and their post-deformation and post-annealing location. These can potentially be used to estimate the post-deformational annealing temperature in crystalline materials.
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| 10. |
- Borthwick, Verity, 1983-, et al.
(författare)
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Post-deformational annealing at the subgrain scale : Temperature dependent behaviour revealed by in-situ heating experiments on deformed single crystal halite
- 2010
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 32:7, s. 982-996
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of substructures, which encompass all structures present at the subgrain-scale, were investigated by static, in-situ annealing experiments. Deformed, single crystal halite was annealed inside a scanning electron microscope at temperatures between 280-470 ºC. Electron backscatter diffraction maps provided detailed information about crystallographic orientation changes. Three temperature dependent regimes were distinguished based on boundary misorientation changes. In regime I (280-300 ºC) some low angle boundaries (LABs), i.e. with 1º-15º misorientation, increase in misorientation angle, while others decrease. In regime II (~300 ºC) all LABs undergo a decrease in misorientation angle. Regime III (>300 ºC) is defined by enhancement of the subgrain structure as remaining LABs increase and some undergo a rotation axis change. Throughout regimes I and II, new LABs develop, subdividing subgrains. LABs could be divided into four categories based on annealing behaviour, orientation and morphology. We suggest that these observations can be directly related to the mobility and activation temperature of climb of two dislocation groups introduced during deformation. Therefore, with in-depth investigation of a substructure with known deformation geometry, we can infer ratios of dislocation types and their post-deformation and post-annealing location. These can potentially be used to estimate the post-deformational annealing temperature in crystalline materials.
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