We thank the reviewer for raising this point and would like to use this opportunity to explain a ... more We thank the reviewer for raising this point and would like to use this opportunity to explain a little bit better. As described, and published in Johannsen et al. (2005), this outcrop contains 8 sets if “deformation band bundles”. In the following we will use the nomenclature of that paper. The bundles of “thick deformation bands” consist of deformation bands (or most likely: disaggregation bands”, sensu Fossen et al. (2007 – J Geol Soc L, vol 164 pp 755-769) consisting dominantly of undeformed grains, and 7 sets of different orientated sets of “thin deformation bands” in which the grain size is significantly reduced by cataclasis. The use of “thin” and “thick” is therefor a representation of the relative grainsize (thickness of deformation bands being roughly 3 times the grain size). These deformation bands occur in bundles, of anywhere between 2 to “dozens” of sub-parallel striking, anatomizing deformation bands. Locally within these bundles, highly polished, striated planes are ...
In this study we aim to understand effects of internal layering on the structural evolution of th... more In this study we aim to understand effects of internal layering on the structural evolution of the Late Permian Zechstein onshore the northern Netherlands. We study the well-imaged reflections of the 30-150 m thick Zechstein 3 anhydrite-carbonate intra-salt stringer across 6500 km 2 of 3D seismic data. We show that the Z3 stringer can be used to provide an unprecedented, basin-scale view of the 3-D internal structure of the salt. The seismic interpretation is used to evaluate the regional variation in structural style defined by rupture and folding of the stringer, and to assess the relationship with the sub- and suprasalt sediments. Before its disruption the stringer was a continuous sheet with a complex pattern of thickness variation. This thickness variation played an important role in the initiation of down-building of Early Triassic post-salt sediments and associated passive deformation of the salt. The stringer’s further deformation was controlled by regional variation in salt...
Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on ... more Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on fault segment linkage and fracture connectivity is not well understood. We present an analogue modeling study using cohesive powder with pre-formed joint sets in the upper layer, varying the angle between joints and a rigid basement fault. We analyze interpreted map-view photographs at maximum displacement for damage zone width, number of connected joints, number of secondary fractures, degree of segmentation and area fraction of massively dilatant fractures. Particle imaging velocimetry helps provide insights on deformation history of the experiments and illustrate the localization pattern of fault segments. Results show that with increasing angle between joint-set and basement-fault strike the number of secondary fractures and the number of connected joints increases, while the area fraction of massively dilatant fractures shows only a minor increase. Models without pre-existing joints...
The grabens of Canyonlands National Park are a young and active system of sub-parallel, arcuate g... more The grabens of Canyonlands National Park are a young and active system of sub-parallel, arcuate grabens, whose evolution is the result of salt movement in the subsurface and a slight regional tilt of the faulted strata. We present results of ground-penetrating radar (GPR) surveys in combination with field observations and analysis of high-resolution airborne imagery. GPR data show intense faulting of the Quaternary sediments at the flat graben floors, implying a more complex fault structure than visible at the surface. Direct measurements of heave and throw at several locations to infer fault dips at depth, combined with observations of primary joint surfaces in the upper 100 m, suggest a highly dilatant fault geometry. Sinkholes observed in the field as well as in airborne imagery give insights in local dilatancy and show where water and sediments are transported underground. Based on correlations of paleosols observed in outcrops and GPR profiles, we argue that either the grabens ...
Salt structures are represented in two strikingly different ways. In studies using 3D seismic and... more Salt structures are represented in two strikingly different ways. In studies using 3D seismic and well data that focus on the sub-or suprasalt sediments the evaporites are shown as homogeneous bodies. On the other hand, studies of the internal structure of salt show the extremely complex internal geometry with much less attention to the structure of the surrounding sediments. Numerical models of salt tectonics also tend to assume relatively homogeneous rheological models, and consequently produce relatively simple internal structures. New developments in microstructure analysis, combined with 3D seismic study of complex internal structures in salt form the basis of integrating these two. A review and synthesis of the mechanical and transport properties and their extrapolation to relevant strain rates must be based on an understanding of the microscale deformation mechanisms in natural laboratories and measurement of salt flow in-situ. Dislocation creep and grain boundary dissolution...
In the literature salt structures are represented in two strikingly different ways. In studies fr... more In the literature salt structures are represented in two strikingly different ways. In studies from hydrocarbon exploration and production using 3D seismic and well data that focus on the sub-or suprasalt sediments, the evaporites are shown as homogeneous bodies. On the other hand, studies of the internal structure of salt show the extremely complex internal geometry with much less attention to the structure of the surrounding sediments. Most current numerical and analogue models of salt tectonics also tend to assume relatively homogeneous rheological models, and consequently produce relatively simple internal structures. New developments in microstructure analysis, combined with 3D seismic study and modelling of complex internal structures in salt form the basis of integrating these two. A review and synthesis of the mechanical and transport properties and their extrapolation to relevant strain rates must be based on an understanding of the microscale deformation mechanisms in natu...
Recently significant progress has been made towards a better understanding of structures and proc... more Recently significant progress has been made towards a better understanding of structures and processes, which determine permeability or sealing capacity of faults in layered sequences. Based on new results from laboratory (Adam et al. 2005, Holland et al. in prep., van Gent et al. subm.), field (Holland et al. 2006) and numerical studies (Abe & Mair 2005, Giese et al., in prep.) we are now able to use structural, mechanical and kinematic information to go beyond the traditional approaches using only lithological information. Studies have shown three major characteristics of layered systems which are responsible for the properties of developing faults: if material properties and stress conditions enable hybrid fractures, the mechanical contrast between the layers, and the occurrence of fault sealing processes. In sequences with low contrast between the layers the relation between layer properties and stress conditions will determine the characteristics of the resulting faults. If the...
The late Permian Zechstein evaporites in the northern Netherlands were exceptionally well imaged ... more The late Permian Zechstein evaporites in the northern Netherlands were exceptionally well imaged in [Formula: see text] of prestack depth migration 3D seismic data. Seismic reflections of a 30–150-m-thick Zechstein 3 anhydrite-carbonate stringer, which was encased in thick layers of rock salt, provided an unparalleled, basin-scale view of the 3D internal structure of a giant salt basin. Seismic data were used to map the regional variation of the intrasalt stringer to analyze its role in deformation styles and salt flow as well as its interaction with the sub- and suprasalt sediments. From our interpretation of the stringer, the salt layers, and the encasing sediments, three regional structural stringer styles can be defined and were analyzed in the context of regional salt kinematics. Our results revealed that the current stringer initially formed a continuous sheet of anhydrite and carbonate, embedded in salt of varying thickness. After the onset of syndepositional gravitational gl...
We thank the reviewer for raising this point and would like to use this opportunity to explain a ... more We thank the reviewer for raising this point and would like to use this opportunity to explain a little bit better. As described, and published in Johannsen et al. (2005), this outcrop contains 8 sets if “deformation band bundles”. In the following we will use the nomenclature of that paper. The bundles of “thick deformation bands” consist of deformation bands (or most likely: disaggregation bands”, sensu Fossen et al. (2007 – J Geol Soc L, vol 164 pp 755-769) consisting dominantly of undeformed grains, and 7 sets of different orientated sets of “thin deformation bands” in which the grain size is significantly reduced by cataclasis. The use of “thin” and “thick” is therefor a representation of the relative grainsize (thickness of deformation bands being roughly 3 times the grain size). These deformation bands occur in bundles, of anywhere between 2 to “dozens” of sub-parallel striking, anatomizing deformation bands. Locally within these bundles, highly polished, striated planes are ...
In this study we aim to understand effects of internal layering on the structural evolution of th... more In this study we aim to understand effects of internal layering on the structural evolution of the Late Permian Zechstein onshore the northern Netherlands. We study the well-imaged reflections of the 30-150 m thick Zechstein 3 anhydrite-carbonate intra-salt stringer across 6500 km 2 of 3D seismic data. We show that the Z3 stringer can be used to provide an unprecedented, basin-scale view of the 3-D internal structure of the salt. The seismic interpretation is used to evaluate the regional variation in structural style defined by rupture and folding of the stringer, and to assess the relationship with the sub- and suprasalt sediments. Before its disruption the stringer was a continuous sheet with a complex pattern of thickness variation. This thickness variation played an important role in the initiation of down-building of Early Triassic post-salt sediments and associated passive deformation of the salt. The stringer’s further deformation was controlled by regional variation in salt...
Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on ... more Dilatant faults often form in rocks containing pre-existing joints, but the effects of joints on fault segment linkage and fracture connectivity is not well understood. We present an analogue modeling study using cohesive powder with pre-formed joint sets in the upper layer, varying the angle between joints and a rigid basement fault. We analyze interpreted map-view photographs at maximum displacement for damage zone width, number of connected joints, number of secondary fractures, degree of segmentation and area fraction of massively dilatant fractures. Particle imaging velocimetry helps provide insights on deformation history of the experiments and illustrate the localization pattern of fault segments. Results show that with increasing angle between joint-set and basement-fault strike the number of secondary fractures and the number of connected joints increases, while the area fraction of massively dilatant fractures shows only a minor increase. Models without pre-existing joints...
The grabens of Canyonlands National Park are a young and active system of sub-parallel, arcuate g... more The grabens of Canyonlands National Park are a young and active system of sub-parallel, arcuate grabens, whose evolution is the result of salt movement in the subsurface and a slight regional tilt of the faulted strata. We present results of ground-penetrating radar (GPR) surveys in combination with field observations and analysis of high-resolution airborne imagery. GPR data show intense faulting of the Quaternary sediments at the flat graben floors, implying a more complex fault structure than visible at the surface. Direct measurements of heave and throw at several locations to infer fault dips at depth, combined with observations of primary joint surfaces in the upper 100 m, suggest a highly dilatant fault geometry. Sinkholes observed in the field as well as in airborne imagery give insights in local dilatancy and show where water and sediments are transported underground. Based on correlations of paleosols observed in outcrops and GPR profiles, we argue that either the grabens ...
Salt structures are represented in two strikingly different ways. In studies using 3D seismic and... more Salt structures are represented in two strikingly different ways. In studies using 3D seismic and well data that focus on the sub-or suprasalt sediments the evaporites are shown as homogeneous bodies. On the other hand, studies of the internal structure of salt show the extremely complex internal geometry with much less attention to the structure of the surrounding sediments. Numerical models of salt tectonics also tend to assume relatively homogeneous rheological models, and consequently produce relatively simple internal structures. New developments in microstructure analysis, combined with 3D seismic study of complex internal structures in salt form the basis of integrating these two. A review and synthesis of the mechanical and transport properties and their extrapolation to relevant strain rates must be based on an understanding of the microscale deformation mechanisms in natural laboratories and measurement of salt flow in-situ. Dislocation creep and grain boundary dissolution...
In the literature salt structures are represented in two strikingly different ways. In studies fr... more In the literature salt structures are represented in two strikingly different ways. In studies from hydrocarbon exploration and production using 3D seismic and well data that focus on the sub-or suprasalt sediments, the evaporites are shown as homogeneous bodies. On the other hand, studies of the internal structure of salt show the extremely complex internal geometry with much less attention to the structure of the surrounding sediments. Most current numerical and analogue models of salt tectonics also tend to assume relatively homogeneous rheological models, and consequently produce relatively simple internal structures. New developments in microstructure analysis, combined with 3D seismic study and modelling of complex internal structures in salt form the basis of integrating these two. A review and synthesis of the mechanical and transport properties and their extrapolation to relevant strain rates must be based on an understanding of the microscale deformation mechanisms in natu...
Recently significant progress has been made towards a better understanding of structures and proc... more Recently significant progress has been made towards a better understanding of structures and processes, which determine permeability or sealing capacity of faults in layered sequences. Based on new results from laboratory (Adam et al. 2005, Holland et al. in prep., van Gent et al. subm.), field (Holland et al. 2006) and numerical studies (Abe & Mair 2005, Giese et al., in prep.) we are now able to use structural, mechanical and kinematic information to go beyond the traditional approaches using only lithological information. Studies have shown three major characteristics of layered systems which are responsible for the properties of developing faults: if material properties and stress conditions enable hybrid fractures, the mechanical contrast between the layers, and the occurrence of fault sealing processes. In sequences with low contrast between the layers the relation between layer properties and stress conditions will determine the characteristics of the resulting faults. If the...
The late Permian Zechstein evaporites in the northern Netherlands were exceptionally well imaged ... more The late Permian Zechstein evaporites in the northern Netherlands were exceptionally well imaged in [Formula: see text] of prestack depth migration 3D seismic data. Seismic reflections of a 30–150-m-thick Zechstein 3 anhydrite-carbonate stringer, which was encased in thick layers of rock salt, provided an unparalleled, basin-scale view of the 3D internal structure of a giant salt basin. Seismic data were used to map the regional variation of the intrasalt stringer to analyze its role in deformation styles and salt flow as well as its interaction with the sub- and suprasalt sediments. From our interpretation of the stringer, the salt layers, and the encasing sediments, three regional structural stringer styles can be defined and were analyzed in the context of regional salt kinematics. Our results revealed that the current stringer initially formed a continuous sheet of anhydrite and carbonate, embedded in salt of varying thickness. After the onset of syndepositional gravitational gl...
Uploads
Papers by Heijn van Gent