| 1. |
- Carrillo, Emilio, et al.
(författare)
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Structural significance of an evaporite formation with lateral stratigraphic heterogeneities (Southeastern Pyrenean Basin, NE Spain)
- 2017
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Ingår i: Marine and Petroleum Geology. - : Elsevier. - 0264-8172 .- 1873-4073. ; 86, s. 1310-1326
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Tidskriftsartikel (refereegranskat)abstract
- We run a series of analogue models to study the effect of stratigraphic heterogeneities of an evaporite formation on thin-skinned deformation of the Southeastern Pyrenean Basin (SPB; NE Spain). This basin is characterized by the existence of evaporites, deposited during the Early-Middle Eocene with lateral variations in thickness and lithological composition. These evaporites are distributed in three lithostratigraphic units, known as Serrat Evaporites, Vallfogona and Beuda Gypsum formations and acted as decollement levels, during compressional deformation in the Lutetian. In addition to analogue modeling, we have used field data, detailed geological mapping and key cross-sections supported by seismic and well data to build a new structural interpretation for the SPB. In this interpretation, it is recognized that the basal and upper parts of the Serrat Evaporites acted as the main decollement levels of the so-called Cadi thrust sheet and Serrat unit. A balanced restoration of the basin indicates that thrust faults nucleated at the stratigraphic transition of the Serrat Evaporites (zone with lateral variations of thickness and lithological composition), characterized by a wedge of anhydrite and shale. The analogue models were setup based on information extracted from cross-sections, built in two sectors with different lithology and stratigraphy of the evaporites, and the restored section of the SPB. In these models, deformation preferentially concentrated in areas where thickness change, defined by wedges of the ductile materials, was inbuilt. Based on the structural interpretation and model results, a kinematic evolution of the SPB is proposed. The kinematic model is characterized by the generation of out-of-sequence structures developed due to lateral stratigraphic variations of the Serrat Evaporites. The present work shows a good example of the role of stratigraphic heterogeneities of an evaporite formation which acts as decollement level on structural deformation in a fold-thrust belt. The results of this work have implications for hydrocarbon exploration and are relevant for studying structural geometry and mechanics in shortened evaporite basins. (C) 2017 Elsevier Ltd. All rights reserved.
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| 2. |
- Hessami, Khaled, et al.
(författare)
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Active deformation within the Zagros Mountains deduced from GPS measurements
- 2006
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Ingår i: Journal of the Geological Society. - : Geological Society of London. - 0016-7649 .- 2041-479X. ; 163:1, s. 143-148
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Tidskriftsartikel (refereegranskat)abstract
- We present and interpret the results of Global Positioning System (GPS) measurements at 35 stations in and beside the Zagros Mountain belt, SW Iran, for three campaigns ending March 1998, December 1999 and June 2001. Preliminary motion estimates show clearly the change in character along the strike of the belt. Stations to the SE move at 13–22 ± 3 mm a–1 towards N 7 ± 5°E with respect to Eurasia. Most of the shortening indicated by the GPS velocities seems to occur in the SE Zagros along two major seismic zones and along the Zagros front. To the NW, stations move oblique to the trend of the belt towards N 12 ± 8°W, at 14–19 ± 3 mm a–1. Most of the shortening in the NW Zagros seems to occur along the Mountain Front Fault with its major earthquakes as well as along the Zagros front. The change in direction and magnitude of the velocity vectors across the north–south-trending Kazerun and Karebas faults involves extension of up to 4 mm a–1 along the strike of the Zagros belt.
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| 3. |
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| 4. |
- Nilforoushan, Faramarz, et al.
(författare)
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Displacement fields and finite strains in a sandbox model simulating a fold-thrust-belt
- 2007
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 169:3, s. 1341-1355
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Tidskriftsartikel (refereegranskat)abstract
- A sandbox model consisting of two adjacent mechanically different decollements (frictional and viscous) loosely simulated the southeastern part of the Zagros fold-thrust-belt. Digital images of the model surface are used to coordinate passive markers on the surface and quantify displacement fields and estimate 2-D finite strains. These analyses show that, mapped in a fixed coordinate system, the deformation front propagates at different rates above the two decollements. Strain analysis of the model surface at different stages of deformation also shows that cumulative strain is more heterogeneous above the viscous decollement where strain domains are separated by fault zones. Maps of displacement fields, finite strain ellipses and dilatation also differ in character above the two decollements. Displacements above a viscous decollement decrease gradually towards the foreland, whereas they decrease sharply in front of the frontal thrust above the frictional decollement. Our analyses also show that the estimated finite strain depends not only on the density of the marker points chosen for the analysis, but also their initial distribution relative to the structures. This comparison shows that marker density limits measuring the actual strains in a heterogeneously deforming fold-thrust-belt and marker density and distribution have a strong impact on the strain analysed in nature. The similarity of our model with nature is examined with recent GPS study in the Zagros fold-thrust-belt (SW Iran) and shows, similar to the model results, that a weak salt decollement causes divergent movement in the sedimentary cover in SE Zagros.
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| 5. |
- Nilforoushan, Faramarz, et al.
(författare)
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Effect of basal friction on surface and volumetric strain in models of convergent settings measured by laser scanner
- 2008
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Ingår i: Journal of Structural Geology. - : Elsevier BV. - 0191-8141 .- 1873-1201. ; 30:3, s. 366-379
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Tidskriftsartikel (refereegranskat)abstract
- This paper uses measurements by a high-accuracy laser scanner to investigate the role of basal friction on surface and volumetric strains in sandbox models simulating fold-thrust belts and accretionary wedges. We monitor progressive deformation, wedge growth, and strain distribution in three models with similar initial boundary conditions but with different basal frictions. Our analyses show that, in addition to influencing the kinematics and geometry of model wedges, basal friction also governs both the surface and volumetric strains of the wedge. After 16.3% bulk shortening, the volume decreased 5 +/- 0.5%, 9.5 +/- 0.5% and 12.5 +/- 0.5% in the models shortened above low, intermediate and high friction decollements, respectively. Applied to nature, our model results suggest that more compaction and penetrative strain is expected in convergent settings with a high-friction decollement than those shortened above a low-friction decollement or a weak basal bed (like the salt formation under parts of the Zagros fold-thrust belt). This volume decrease probably reduces the porosity in the deformed lithologies.
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| 6. |
- Nilforoushan, Faramarz, et al.
(författare)
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GPS network monitors the Arabia-Eurasia collision deformation in Iran
- 2003
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Ingår i: Journal of Geodesy. - : Springer Science and Business Media LLC. - 0949-7714 .- 1432-1394. ; 77, s. 411-422
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Tidskriftsartikel (refereegranskat)abstract
- The rate of crustal deformation in Iran due to the Arabia–Eurasia collision is estimated. The results are based on new global positioning system (GPS) data. In order to address the problem of the distribution of the deformation in Iran, Iranian and French research organizations have carried out the first large-scale GPS survey of Iran. A GPS network of 28 sites (25 in Iran, two in Oman and one in Uzbekistan) has been installed and surveyed twice, in September 1999 and October 2001. Each site has been surveyed for a minimum observation of 4 days. GPS data processing has been done using the GAMIT-GLOBK software package. The solution displays horizontal repeatabilities of about 1.2 mm in 1999 and 2001. The resulting velocities allow us to constrain the kinematics of the Iranian tectonic blocks. These velocities are given in ITRF2000 and also relative to Eurasia. This last kinematic model demonstrates that (1) the north–south shortening from Arabia to Eurasia is 2–2.5 cm/year, less than previously estimated, and (2) the transition from subduction (Makran) to collision (Zagros) is very sharp and governs the different styles of deformation observed in Iran. In the eastern part of Iran, most of the shortening is accommodated in the Gulf of Oman, while in the western part the shortening is more distributed from south to north. The large faults surrounding the Lut block accommodate most of the subduction–collision transition.
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| 7. |
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| 8. |
- Walpersdorf, A, et al.
(författare)
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Difference in the GPS deformation pattern of North and Central Zagros (Iran)
- 2006
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Ingår i: Geophysical Journal International. - 0956-540X .- 1365-246X. ; 167:3, s. 1077-1088
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Tidskriftsartikel (refereegranskat)abstract
- Measurements on either side of the Kazerun fault system in the Zagros Mountain Belt, Iran, show that the accommodation of the convergence of the Arabian and Eurasian Plates differs across the region. In northwest Zagros, the deformation is partitioned as 3–6 mm yr−1 of shortening perpendicular to the axis of the mountain belt, and 4–6 mm yr−1 of dextral strike-slip motion on northwest–southeast trending faults. No individual strike-slip fault seems to slip at a rate higher than ∼2 mm yr−1. In southeast Zagros, the deformation is pure shortening of 8 ± 2 mm yr−1 occurring perpendicular to the simple folded belt and restricted to the Persian Gulf shore. The fact that most of the deformation is located in front of the simple folded belt, close to the Persian Gulf, while seismicity is more widely spread across the mountain belt, confirms the decoupling of the surface sedimentary layers from the seismogenic basement. A comparison with the folding and topography corroborates a southwestward propagation of the surface deformation. The difference in deformation between the two regions suggests that right-lateral shear cumulates on the north–south trending Kazerun strike-slip fault system to 6 ± 2 mm yr−1.
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