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Wei Wang - One of the best experts on this subject based on the ideXlab platform.
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effect of basement structure and salt tectonics on deformation styles along strike an example from the kuqa Fold thrust belt west china
Tectonophysics, 2018Co-Authors: Yuan Neng, Hongwei Yin, Huiwen Xie, Wei WangAbstract:Abstract The Kuqa Fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, Fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-Fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core Detachment Fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the Fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and Folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.
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calculating Detachment depth and dip angle in sedimentary wedges using the area depth graph
Journal of Structural Geology, 2018Co-Authors: Wei Wang, Hongwei Yin, Dong Jia, Peng ZhouAbstract:Abstract: We apply the area–depth–strain method (ADS) to predict the depth and the dip angle for an underlying bedding-parallel Detachment in sedimentary wedge structures with stratigraphic wedge strata using an area–depth graph. An area–depth relationship is proposed and simplified to a linear relationship with depth as a function of excess area. This proposed ADS method gives the depth and dip angle of the Detachment at any location in sedimentary wedges. The method does not yield the shortening magnitude from the area-depth graph because the area-depth relationship is different for this structural example from the established methods. We test the method by predicting the Detachment depth and dip angle of two natural wedge structures that are well constrained: the Niger Delta Fold-and-thrust belt, which has a single Detachment, and the Cascadia Detachment Fold, which has multiple Detachments. The predicted geometric values are generally consistent with the geometric characteristics of the two systems. The ADS method is a powerful method for constructing subsurface structural geometries using well constrained near-surface geometry for decollement sedimentary wedges, and is independent of bed-length, bed-thickness and regional horizon throws.
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Calculating Detachment depth and dip angle in sedimentary wedges using the area–depth graph
Journal of Structural Geology, 2018Co-Authors: Wei Wang, Hongwei Yin, Dong Jia, Peng ZhouAbstract:Abstract: We apply the area–depth–strain method (ADS) to predict the depth and the dip angle for an underlying bedding-parallel Detachment in sedimentary wedge structures with stratigraphic wedge strata using an area–depth graph. An area–depth relationship is proposed and simplified to a linear relationship with depth as a function of excess area. This proposed ADS method gives the depth and dip angle of the Detachment at any location in sedimentary wedges. The method does not yield the shortening magnitude from the area-depth graph because the area-depth relationship is different for this structural example from the established methods. We test the method by predicting the Detachment depth and dip angle of two natural wedge structures that are well constrained: the Niger Delta Fold-and-thrust belt, which has a single Detachment, and the Cascadia Detachment Fold, which has multiple Detachments. The predicted geometric values are generally consistent with the geometric characteristics of the two systems. The ADS method is a powerful method for constructing subsurface structural geometries using well constrained near-surface geometry for decollement sedimentary wedges, and is independent of bed-length, bed-thickness and regional horizon throws.
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Effect of basement structure and salt tectonics on deformation styles along strike: An example from the Kuqa Fold–thrust belt, West China
Tectonophysics, 2018Co-Authors: Yuan Neng, Hongwei Yin, Huiwen Xie, Wei WangAbstract:Abstract The Kuqa Fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, Fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-Fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core Detachment Fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the Fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and Folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.
John Suppe - One of the best experts on this subject based on the ideXlab platform.
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compressional salt tectonics and synkinematic strata of the western kuqa foreland basin southern tian shan china
Basin Research, 2012Co-Authors: Xin Wang, John SuppeAbstract:The synkinematic strata of the Kuqa foreland basin record a rich history of Cenozoic reactivation of the Palaeozoic Tian Shan mountain belt. Here, we present new constraints on the history of deformation in the southern Tian Shan, based on an analysis of interactions between tectonics and sedimentation in the western Kuqa basin. We constructed six balanced cross-sections of the basin, integrating surface geology, well data and a grid of seismic reflection profiles. These profiles show that the Qiulitage Fold belt on the southern edge of the Kuqa basin developed by thin-skinned compression salt tectonics. The structural styles have been influenced by two major factors: the nature of early-formed diapirs and the basinward depositional limit of the Kumugeliemu salt. Several early diapirs developed in the western Kuqa basin, soon after salt deposition, which acted to localize the subsequent shortening. Where diapirs had low relief and a thick overburden they tended to tighten into salt domes 3000–7000 m in height. Conversely, where the original diapirs had higher relief and a thinner overburden they tended to evolve into salt nappes, with the northern flanks of the diapirs thrusting over their southern flanks. Salt was expelled forward, up dip along the mother salt layer, tended to accumulate at the distal pinch-out of Kumugeliemu salt located at the Qiulitage Fold belt. Furthermore, the synkinematic strata (6–8 km thick) of the Kuqa basin indicate that during the Cenozoic reactivation of the Tian Shan, shortening of the western Kuqa basin was mainly in the hinterland until the early Miocene. Then, compression spread simultaneously southwards to the Dawanqi anticline, the Qiulitage Fold belt and the southernmost blind Detachment Fold at the end of Miocene. The western Kuqa basin has a shortening of ca. 23 km. We consider that ca. 9 km was consumed from the end of the Miocene (5.2/5.8 Ma) to the early Pleistocene (2.58 Ma) and another ca. 14 km have been absorbed since then. Thus, we obtain a ca. 3.4/2.8 mm year-1 average shortening from 5.2/5.8 to 2.58 Ma, followed by a 60–90% increase in average shortening rate to ca. 5.4 mm year-1 since 2.58 Ma. This suggests that the reactivation of the modern Tian Shan has been accelerating up to the present day.
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mechanisms of active Folding of the landscape southern tian shan china
Journal of Geophysical Research, 2007Co-Authors: Aurelia Hubertferrari, John Suppe, Ramon Gonzalezmieres, Xin WangAbstract:[1] We explore the kinematic mechanisms of active large-scale Folding, based on analysis of two adjacent major anticlines in Tian Shan (central Asia) that share an acceleration of shortening rate leading to topographic emergence and Folded geomorphic surfaces. Their Folding mechanisms are fundamentally different. Yakeng anticline is a gentle pure shear Detachment Fold with 1200 m of shortening and a well-constrained history of growth beginning at 5.5 Ma with an order-of-magnitude increase in shortening rate from 0.16 to ∼1.2–1.6 mm/yr at ∼0.16–0.21 Ma. The shape of the deformed topographic surface and of subsurface horizons deposited during deformation is a linearly proportional image at reduced amplitude of the deeper structure, which shows that instantaneous uplift rates have been pointwise linearly proportional to the current finite Fold amplitude. In contrast, Quilitak anticline is a complex fault bend Fold with uplift rates proportional to the sine of the fault dip, showing discontinuities in uplift rate across active axial surfaces. The 10- to 20-km-wide anticline is topographically emergent only in a central 5- to 7-km-wide mountainous uplift, the abrupt southern edge of which is marked by ∼600- to 700-m-high triangular facets that result from active Folding of a pediment across an active axial surface. The giant facets are shown to form by kink band migration and record postemergence deformation since an order-of-magnitude acceleration in shortening rate from ∼0.6 to ∼4–5 mm/yr, apparently contemporaneous with Yakeng. Sections logged across the active ∼115-m-wide hinge zone show that recent strata provide a bed-by-bed record of Fold scarp growth, which is quantitatively deciphered by fitting bed shapes to a finite width kink band migration model.
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Relief and shortening in Detachment Folds
Journal of Structural Geology, 2006Co-Authors: Ramon Gonzalez-mieres, John SuppeAbstract:We present new thickness-relief methods for determining shortening S(z), mean shortening SðzÞ and curvimetric shortening Sc(z) as a function of height in well-imaged structures. Thickness-relief measurements allow us to constrain the fractions of the deformation that are layer-parallel pure shear, simple shear, and flexural, and to measure the excess area Ae of Fold cores caused, for example, by flow of evaporites. The key measurements are made in the thickness domain, which allows for more certain determination of regional stratigraphic gradients, which is required for reliable separation of structural relief from primary stratigraphic thickness variations. We apply these methods to a diverse set of active Detachment Folds from the fronts of the Nankai trough Japan, Cascadia accretionary wedge Oregon, southern Tianshan China and Agbami anticline deep-water Niger delta. Three of these Folds can be approximated by pure-shear Detachment Fold models because more than 95% of the shortening is by layer-parallel heterogeneous pure shear plus horizontal compaction. For this reason curvimetric shortening is one to two orders of magnitude less than total shortening. In contrast, Agbami anticline shows layer-parallel stretching above the excess area of the Fold core. In all examples the layer-parallel simple-shear component is negligible or absent. 2006 Elsevier Ltd. All rights reserved.
Yuan Neng - One of the best experts on this subject based on the ideXlab platform.
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effect of basement structure and salt tectonics on deformation styles along strike an example from the kuqa Fold thrust belt west china
Tectonophysics, 2018Co-Authors: Yuan Neng, Hongwei Yin, Huiwen Xie, Wei WangAbstract:Abstract The Kuqa Fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, Fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-Fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core Detachment Fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the Fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and Folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.
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Effect of basement structure and salt tectonics on deformation styles along strike: An example from the Kuqa Fold–thrust belt, West China
Tectonophysics, 2018Co-Authors: Yuan Neng, Hongwei Yin, Huiwen Xie, Wei WangAbstract:Abstract The Kuqa Fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, Fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-Fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core Detachment Fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the Fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and Folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.
Xin Wang - One of the best experts on this subject based on the ideXlab platform.
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compressional salt tectonics and synkinematic strata of the western kuqa foreland basin southern tian shan china
Basin Research, 2012Co-Authors: Xin Wang, John SuppeAbstract:The synkinematic strata of the Kuqa foreland basin record a rich history of Cenozoic reactivation of the Palaeozoic Tian Shan mountain belt. Here, we present new constraints on the history of deformation in the southern Tian Shan, based on an analysis of interactions between tectonics and sedimentation in the western Kuqa basin. We constructed six balanced cross-sections of the basin, integrating surface geology, well data and a grid of seismic reflection profiles. These profiles show that the Qiulitage Fold belt on the southern edge of the Kuqa basin developed by thin-skinned compression salt tectonics. The structural styles have been influenced by two major factors: the nature of early-formed diapirs and the basinward depositional limit of the Kumugeliemu salt. Several early diapirs developed in the western Kuqa basin, soon after salt deposition, which acted to localize the subsequent shortening. Where diapirs had low relief and a thick overburden they tended to tighten into salt domes 3000–7000 m in height. Conversely, where the original diapirs had higher relief and a thinner overburden they tended to evolve into salt nappes, with the northern flanks of the diapirs thrusting over their southern flanks. Salt was expelled forward, up dip along the mother salt layer, tended to accumulate at the distal pinch-out of Kumugeliemu salt located at the Qiulitage Fold belt. Furthermore, the synkinematic strata (6–8 km thick) of the Kuqa basin indicate that during the Cenozoic reactivation of the Tian Shan, shortening of the western Kuqa basin was mainly in the hinterland until the early Miocene. Then, compression spread simultaneously southwards to the Dawanqi anticline, the Qiulitage Fold belt and the southernmost blind Detachment Fold at the end of Miocene. The western Kuqa basin has a shortening of ca. 23 km. We consider that ca. 9 km was consumed from the end of the Miocene (5.2/5.8 Ma) to the early Pleistocene (2.58 Ma) and another ca. 14 km have been absorbed since then. Thus, we obtain a ca. 3.4/2.8 mm year-1 average shortening from 5.2/5.8 to 2.58 Ma, followed by a 60–90% increase in average shortening rate to ca. 5.4 mm year-1 since 2.58 Ma. This suggests that the reactivation of the modern Tian Shan has been accelerating up to the present day.
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mechanisms of active Folding of the landscape southern tian shan china
Journal of Geophysical Research, 2007Co-Authors: Aurelia Hubertferrari, John Suppe, Ramon Gonzalezmieres, Xin WangAbstract:[1] We explore the kinematic mechanisms of active large-scale Folding, based on analysis of two adjacent major anticlines in Tian Shan (central Asia) that share an acceleration of shortening rate leading to topographic emergence and Folded geomorphic surfaces. Their Folding mechanisms are fundamentally different. Yakeng anticline is a gentle pure shear Detachment Fold with 1200 m of shortening and a well-constrained history of growth beginning at 5.5 Ma with an order-of-magnitude increase in shortening rate from 0.16 to ∼1.2–1.6 mm/yr at ∼0.16–0.21 Ma. The shape of the deformed topographic surface and of subsurface horizons deposited during deformation is a linearly proportional image at reduced amplitude of the deeper structure, which shows that instantaneous uplift rates have been pointwise linearly proportional to the current finite Fold amplitude. In contrast, Quilitak anticline is a complex fault bend Fold with uplift rates proportional to the sine of the fault dip, showing discontinuities in uplift rate across active axial surfaces. The 10- to 20-km-wide anticline is topographically emergent only in a central 5- to 7-km-wide mountainous uplift, the abrupt southern edge of which is marked by ∼600- to 700-m-high triangular facets that result from active Folding of a pediment across an active axial surface. The giant facets are shown to form by kink band migration and record postemergence deformation since an order-of-magnitude acceleration in shortening rate from ∼0.6 to ∼4–5 mm/yr, apparently contemporaneous with Yakeng. Sections logged across the active ∼115-m-wide hinge zone show that recent strata provide a bed-by-bed record of Fold scarp growth, which is quantitatively deciphered by fitting bed shapes to a finite width kink band migration model.
Hongwei Yin - One of the best experts on this subject based on the ideXlab platform.
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effect of basement structure and salt tectonics on deformation styles along strike an example from the kuqa Fold thrust belt west china
Tectonophysics, 2018Co-Authors: Yuan Neng, Hongwei Yin, Huiwen Xie, Wei WangAbstract:Abstract The Kuqa Fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, Fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-Fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core Detachment Fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the Fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and Folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.
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calculating Detachment depth and dip angle in sedimentary wedges using the area depth graph
Journal of Structural Geology, 2018Co-Authors: Wei Wang, Hongwei Yin, Dong Jia, Peng ZhouAbstract:Abstract: We apply the area–depth–strain method (ADS) to predict the depth and the dip angle for an underlying bedding-parallel Detachment in sedimentary wedge structures with stratigraphic wedge strata using an area–depth graph. An area–depth relationship is proposed and simplified to a linear relationship with depth as a function of excess area. This proposed ADS method gives the depth and dip angle of the Detachment at any location in sedimentary wedges. The method does not yield the shortening magnitude from the area-depth graph because the area-depth relationship is different for this structural example from the established methods. We test the method by predicting the Detachment depth and dip angle of two natural wedge structures that are well constrained: the Niger Delta Fold-and-thrust belt, which has a single Detachment, and the Cascadia Detachment Fold, which has multiple Detachments. The predicted geometric values are generally consistent with the geometric characteristics of the two systems. The ADS method is a powerful method for constructing subsurface structural geometries using well constrained near-surface geometry for decollement sedimentary wedges, and is independent of bed-length, bed-thickness and regional horizon throws.
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Calculating Detachment depth and dip angle in sedimentary wedges using the area–depth graph
Journal of Structural Geology, 2018Co-Authors: Wei Wang, Hongwei Yin, Dong Jia, Peng ZhouAbstract:Abstract: We apply the area–depth–strain method (ADS) to predict the depth and the dip angle for an underlying bedding-parallel Detachment in sedimentary wedge structures with stratigraphic wedge strata using an area–depth graph. An area–depth relationship is proposed and simplified to a linear relationship with depth as a function of excess area. This proposed ADS method gives the depth and dip angle of the Detachment at any location in sedimentary wedges. The method does not yield the shortening magnitude from the area-depth graph because the area-depth relationship is different for this structural example from the established methods. We test the method by predicting the Detachment depth and dip angle of two natural wedge structures that are well constrained: the Niger Delta Fold-and-thrust belt, which has a single Detachment, and the Cascadia Detachment Fold, which has multiple Detachments. The predicted geometric values are generally consistent with the geometric characteristics of the two systems. The ADS method is a powerful method for constructing subsurface structural geometries using well constrained near-surface geometry for decollement sedimentary wedges, and is independent of bed-length, bed-thickness and regional horizon throws.
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Effect of basement structure and salt tectonics on deformation styles along strike: An example from the Kuqa Fold–thrust belt, West China
Tectonophysics, 2018Co-Authors: Yuan Neng, Hongwei Yin, Huiwen Xie, Wei WangAbstract:Abstract The Kuqa Fold–thrust belt (KFTB) has a complex thrust-system geometry and comprises basement-involved thrusts, decollement thrusts, triangle zones, strike-slip faults, transpressional faults, and pop-up structures. These structures, combined with the effects of Paleogene salt tectonics and Paleozoic basement uplift form a complex structural zone trending E–W. Interpretation and comprehensive analysis of recent high-quality seismic data, field observations, boreholes, and gravity data covering the KFTB has been performed to understand the characteristics and mechanisms of the deformation styles along strike. Regional sections, Fold–thrust system maps of the surface and the sub-salt layer, salt and basement structure distribution maps have been created, and a comprehensive analysis of thrust systems performed. The results indicate that the thrust-Fold system in Paleogene salt range can be divided into five segments from east to west: the Kela-3, Keshen, Dabei, Bozi, and Awate segments. In the easternmost and westernmost parts of the Paleogene salt range, strike-slip faulting and basement-involved thrusting are the dominant deformation styles, as basement uplift and the limits of the Cenozoic evaporite deposit are the main controls on deformation. Salt-core Detachment Fold–thrust systems coincide with areas of salt tectonics, and pop-up, imbricate, and duplex structures are associated with the main thrust faults in the sub-salt layer. Distribution maps of thrust systems, basement structures, and salt tectonics show that Paleozoic basement uplift controlled the Paleozoic foreland basin morphology and the distribution of Cenozoic salt in the KFTB, and thus had a strong influence on the segmented structural deformation and evolution of the Fold–thrust belt. Three types of transfer zone are identified, based on the characteristics of the salt layer and basement uplift, and the effects of these zones on the fault systems are evaluated. Basement uplift and the boundary of the salt deposit generated strike-slip faults in the sub-salt layer and supra-salt layers at the basin boundary (Model A). When changes in the basement occurred within the salt basin, strike-slip faults controlled the deformation styles in the sub-salt layer and shear-zone dominated in the supra-salt layer (Model B). A homogeneous basement and discontinues salt layer formed different accommodation zones in the sub- and supra-salt layers (Model C). In the sub-salt layer the thrusts form imbricate structures on the basal decollement, whereas the supra-salt layer shows overlapping, discontinuous faults and Folds with kinds of salt tectonics, and has greater structural variation than the sub-salt layer.