The Experts below are selected from a list of 3954 Experts worldwide ranked by ideXlab platform
M. Jiang - One of the best experts on this subject based on the ideXlab platform.
-
carbonate sedimentation in a starved Pull Apart Basin middle to late devonian southern guilin south china
Basin Research, 2001Co-Authors: Daizhao Chen, Maurice E. Tucker, J. Zhu, M. JiangAbstract:Geological mapping and sedimentological investigations in the Guilin region, South China, have revealed a spindle- to rhomb-shaped Basin filled with Devonian shallow- to deepwater carbonates. This Yangshuo Basin is interpreted as a Pull-Apart Basin created through secondary, synthetic strike-slip faulting induced by major NNE-SSW-trending, sinistral strikeslip fault zones. These fault zones were initially reactivated along intracontinental basement faults in the course of northward migration of the South China continent. The nearly N-S trending margins of the Yangshuo Basin, approximately coinciding with the strike of regional fault zones, were related to the master strike-slip faults; the NW-SE-trending margins were related to parallel, oblique-slip extensional faults. Nine depositional sequences recognized in Givetian through Frasnian strata can be grouped into three sequence sets (Sequences 1-2, 3-5 and 6-9), reflecting three major phases of Basin evolution. During Basin nucleation, most Basin margins were dominated by stromatoporoid biostromes and bioherms, upon a low-gradient shelf. Only at the steep, fault-controlled, eastern margin were thick stromatoporoid reefs developed. The subsequent progressive offset and Pull-Apart of the master strike-slip faults during the late Givetian intensified the differential subsidence and produced a spindle-shaped Basin. The accelerated subsidence of the Basin centre led to sediment starvation, reduced current circulation and increased environmental stress, leading to the extensive development of microbial buildups on platform margins and laminites in the Basin centre. Stromatoporoid reefs only survived along the windward, eastern margin for a short time. The architectures of the Basin margins varied from aggradation (or slightly backstepping) in windward positions (eastern and northern margins) to moderate progradation in leeward positions. A relay ramp was present in the north-west corner between the northern oblique fault zone and the proximal part of the western master fault. In the latest Givetian (corresponding to the top of Sequence 5), a sudden subsidence of the Basin induced by further offset of the strike-slip faults was accompanied by the rapid uplift of surrounding carbonate platforms, causing considerable platform-margin collapse, slope erosion, Basin deepening and the demise of the microbialites. Afterwards, stromatoporoid reefs were only locally restored on topographic highs along the windward margin. However, a subsequent, more intense Basin subsidence in the early Frasnian (top of Sequence 6), which was accompanied by further sharp uplift of platforms, caused more profound slope erosion and platform backstepping. Poor circulation and oxygen-depleted waters in the now much deeper Basin centre led to the deposition of chert, with silica supplied by hydrothermal fluids through deep-seated faults. Two `subdeeps\\\' were diagonally arranged in the distal parts of the master faults, and the relay ramp was destroyed. At this time, all Basin margins except the western one evolved into erosional types with gullies through which granular platform sediments were transported by gravity flows to the Basin. This situation persisted into the latest Frasnian. This case history shows that the carbonate platform architecture and evolution in a Pull-Apart Basin were not only strongly controlled by the tectonic activity, but also influenced by the oceanographic setting (i.e. windward vs. leeward) and environmental factors.
-
Carbonate sedimentation in a starved Pull‐Apart Basin, Middle to Late Devonian, southern Guilin, South China
Basin Research, 2001Co-Authors: Daizhao Chen, Maurice E. Tucker, J. Zhu, M. JiangAbstract:Geological mapping and sedimentological investigations in the Guilin region, South China, have revealed a spindle- to rhomb-shaped Basin filled with Devonian shallow- to deepwater carbonates. This Yangshuo Basin is interpreted as a Pull-Apart Basin created through secondary, synthetic strike-slip faulting induced by major NNE-SSW-trending, sinistral strikeslip fault zones. These fault zones were initially reactivated along intracontinental basement faults in the course of northward migration of the South China continent. The nearly N-S trending margins of the Yangshuo Basin, approximately coinciding with the strike of regional fault zones, were related to the master strike-slip faults; the NW-SE-trending margins were related to parallel, oblique-slip extensional faults. Nine depositional sequences recognized in Givetian through Frasnian strata can be grouped into three sequence sets (Sequences 1-2, 3-5 and 6-9), reflecting three major phases of Basin evolution. During Basin nucleation, most Basin margins were dominated by stromatoporoid biostromes and bioherms, upon a low-gradient shelf. Only at the steep, fault-controlled, eastern margin were thick stromatoporoid reefs developed. The subsequent progressive offset and Pull-Apart of the master strike-slip faults during the late Givetian intensified the differential subsidence and produced a spindle-shaped Basin. The accelerated subsidence of the Basin centre led to sediment starvation, reduced current circulation and increased environmental stress, leading to the extensive development of microbial buildups on platform margins and laminites in the Basin centre. Stromatoporoid reefs only survived along the windward, eastern margin for a short time. The architectures of the Basin margins varied from aggradation (or slightly backstepping) in windward positions (eastern and northern margins) to moderate progradation in leeward positions. A relay ramp was present in the north-west corner between the northern oblique fault zone and the proximal part of the western master fault. In the latest Givetian (corresponding to the top of Sequence 5), a sudden subsidence of the Basin induced by further offset of the strike-slip faults was accompanied by the rapid uplift of surrounding carbonate platforms, causing considerable platform-margin collapse, slope erosion, Basin deepening and the demise of the microbialites. Afterwards, stromatoporoid reefs were only locally restored on topographic highs along the windward margin. However, a subsequent, more intense Basin subsidence in the early Frasnian (top of Sequence 6), which was accompanied by further sharp uplift of platforms, caused more profound slope erosion and platform backstepping. Poor circulation and oxygen-depleted waters in the now much deeper Basin centre led to the deposition of chert, with silica supplied by hydrothermal fluids through deep-seated faults. Two `subdeeps\\\' were diagonally arranged in the distal parts of the master faults, and the relay ramp was destroyed. At this time, all Basin margins except the western one evolved into erosional types with gullies through which granular platform sediments were transported by gravity flows to the Basin. This situation persisted into the latest Frasnian. This case history shows that the carbonate platform architecture and evolution in a Pull-Apart Basin were not only strongly controlled by the tectonic activity, but also influenced by the oceanographic setting (i.e. windward vs. leeward) and environmental factors.
Hamid Javanbakht Jabarabadi - One of the best experts on this subject based on the ideXlab platform.
-
The Dinevar transtensional Pull-Apart Basin, NW Zagros Mountains, Iran: a geological study and comparison to 2D finite element elastic models
International Journal of Earth Sciences, 2019Co-Authors: Seyed Tohid Nabavi, Seyed Ahmad Alavi, Hamid Javanbakht JabarabadiAbstract:The Dinevar transtensional Pull-Apart Basin is a NW–SE trending Basin located in the northwest part of the Zagros Mountains, Sanandaj–Sirjan tectonic zone, Iran. This Basin was formed by oblique extension in a strike-slip fault system, which was controlled by the pre-existing Sahneh and the Mianrahan faults. In addition to a field study, we constructed a 2D finite element elastic model based on the major fault segments. According to the field study, various geological structures are formed around the pre-existing fault segments, including pencil structures with 13
-
the dinevar transtensional Pull Apart Basin nw zagros mountains iran a geological study and comparison to 2d finite element elastic models
International Journal of Earth Sciences, 2019Co-Authors: Seyed Tohid Nabavi, Seyed Ahmad Alavi, Hamid Javanbakht JabarabadiAbstract:The Dinevar transtensional Pull-Apart Basin is a NW–SE trending Basin located in the northwest part of the Zagros Mountains, Sanandaj–Sirjan tectonic zone, Iran. This Basin was formed by oblique extension in a strike-slip fault system, which was controlled by the pre-existing Sahneh and the Mianrahan faults. In addition to a field study, we constructed a 2D finite element elastic model based on the major fault segments. According to the field study, various geological structures are formed around the pre-existing fault segments, including pencil structures with 13 < aspect ratio < 19, tight to open asymmetric folds, oblique–normal faults, synthetic and antithetic faults, normal and reverse fault drags, and negative and hybrid-type flower structure. FE-model results show that around the fault step is a zone of displacement gradient that indicates extension (transtension) within the overlapping zone. Consequently, subsidence is predicted over the releasing fault step. The modelled stress distributions within the fault step and around the fault segment tips are asymmetric. Elastic modelling shows that the mean normal stress within the step is tensional, which would impede plastic yield, while the region outside the step is characterised by compressive mean normal stress. The mean normal stress pattern is characterised by a regional minimum, localised inside the extensional step (transtension zone), and two local maximum and minimum couples, formed at the advancing and retreating sides, respectively, in the fault segment tips. The results show that two main subsidence regions (depocentres or sub-Basins) form along and in the proximity of the fault segment tips. The imposed relative motion is entirely accommodated by creep on the faults, which causes plastic strain to accumulate outside the faults, mostly localised within the fault step. This localised strain between fault segments could initiate connecting faults or reactivate earlier faults, generally at high angles relative to the master fault segments as suggested by the stress and strain patterns. The rotation and magnitude variation in the stress and strain trajectories reflects heterogeneous deformation. In general, the Dinevar transtensional Pull-Apart Basin is characterised by an elongate rhomboidal- to trapezoidal-shaped geometry. The modelled stress distribution and strain localisations within the Basin are in general agreement with the locations of fault segments within the Dinevar transtensional Pull-Apart Basin.
Daizhao Chen - One of the best experts on this subject based on the ideXlab platform.
-
carbonate sedimentation in a starved Pull Apart Basin middle to late devonian southern guilin south china
Basin Research, 2001Co-Authors: Daizhao Chen, Maurice E. Tucker, J. Zhu, M. JiangAbstract:Geological mapping and sedimentological investigations in the Guilin region, South China, have revealed a spindle- to rhomb-shaped Basin filled with Devonian shallow- to deepwater carbonates. This Yangshuo Basin is interpreted as a Pull-Apart Basin created through secondary, synthetic strike-slip faulting induced by major NNE-SSW-trending, sinistral strikeslip fault zones. These fault zones were initially reactivated along intracontinental basement faults in the course of northward migration of the South China continent. The nearly N-S trending margins of the Yangshuo Basin, approximately coinciding with the strike of regional fault zones, were related to the master strike-slip faults; the NW-SE-trending margins were related to parallel, oblique-slip extensional faults. Nine depositional sequences recognized in Givetian through Frasnian strata can be grouped into three sequence sets (Sequences 1-2, 3-5 and 6-9), reflecting three major phases of Basin evolution. During Basin nucleation, most Basin margins were dominated by stromatoporoid biostromes and bioherms, upon a low-gradient shelf. Only at the steep, fault-controlled, eastern margin were thick stromatoporoid reefs developed. The subsequent progressive offset and Pull-Apart of the master strike-slip faults during the late Givetian intensified the differential subsidence and produced a spindle-shaped Basin. The accelerated subsidence of the Basin centre led to sediment starvation, reduced current circulation and increased environmental stress, leading to the extensive development of microbial buildups on platform margins and laminites in the Basin centre. Stromatoporoid reefs only survived along the windward, eastern margin for a short time. The architectures of the Basin margins varied from aggradation (or slightly backstepping) in windward positions (eastern and northern margins) to moderate progradation in leeward positions. A relay ramp was present in the north-west corner between the northern oblique fault zone and the proximal part of the western master fault. In the latest Givetian (corresponding to the top of Sequence 5), a sudden subsidence of the Basin induced by further offset of the strike-slip faults was accompanied by the rapid uplift of surrounding carbonate platforms, causing considerable platform-margin collapse, slope erosion, Basin deepening and the demise of the microbialites. Afterwards, stromatoporoid reefs were only locally restored on topographic highs along the windward margin. However, a subsequent, more intense Basin subsidence in the early Frasnian (top of Sequence 6), which was accompanied by further sharp uplift of platforms, caused more profound slope erosion and platform backstepping. Poor circulation and oxygen-depleted waters in the now much deeper Basin centre led to the deposition of chert, with silica supplied by hydrothermal fluids through deep-seated faults. Two `subdeeps\\\' were diagonally arranged in the distal parts of the master faults, and the relay ramp was destroyed. At this time, all Basin margins except the western one evolved into erosional types with gullies through which granular platform sediments were transported by gravity flows to the Basin. This situation persisted into the latest Frasnian. This case history shows that the carbonate platform architecture and evolution in a Pull-Apart Basin were not only strongly controlled by the tectonic activity, but also influenced by the oceanographic setting (i.e. windward vs. leeward) and environmental factors.
-
Carbonate sedimentation in a starved Pull‐Apart Basin, Middle to Late Devonian, southern Guilin, South China
Basin Research, 2001Co-Authors: Daizhao Chen, Maurice E. Tucker, J. Zhu, M. JiangAbstract:Geological mapping and sedimentological investigations in the Guilin region, South China, have revealed a spindle- to rhomb-shaped Basin filled with Devonian shallow- to deepwater carbonates. This Yangshuo Basin is interpreted as a Pull-Apart Basin created through secondary, synthetic strike-slip faulting induced by major NNE-SSW-trending, sinistral strikeslip fault zones. These fault zones were initially reactivated along intracontinental basement faults in the course of northward migration of the South China continent. The nearly N-S trending margins of the Yangshuo Basin, approximately coinciding with the strike of regional fault zones, were related to the master strike-slip faults; the NW-SE-trending margins were related to parallel, oblique-slip extensional faults. Nine depositional sequences recognized in Givetian through Frasnian strata can be grouped into three sequence sets (Sequences 1-2, 3-5 and 6-9), reflecting three major phases of Basin evolution. During Basin nucleation, most Basin margins were dominated by stromatoporoid biostromes and bioherms, upon a low-gradient shelf. Only at the steep, fault-controlled, eastern margin were thick stromatoporoid reefs developed. The subsequent progressive offset and Pull-Apart of the master strike-slip faults during the late Givetian intensified the differential subsidence and produced a spindle-shaped Basin. The accelerated subsidence of the Basin centre led to sediment starvation, reduced current circulation and increased environmental stress, leading to the extensive development of microbial buildups on platform margins and laminites in the Basin centre. Stromatoporoid reefs only survived along the windward, eastern margin for a short time. The architectures of the Basin margins varied from aggradation (or slightly backstepping) in windward positions (eastern and northern margins) to moderate progradation in leeward positions. A relay ramp was present in the north-west corner between the northern oblique fault zone and the proximal part of the western master fault. In the latest Givetian (corresponding to the top of Sequence 5), a sudden subsidence of the Basin induced by further offset of the strike-slip faults was accompanied by the rapid uplift of surrounding carbonate platforms, causing considerable platform-margin collapse, slope erosion, Basin deepening and the demise of the microbialites. Afterwards, stromatoporoid reefs were only locally restored on topographic highs along the windward margin. However, a subsequent, more intense Basin subsidence in the early Frasnian (top of Sequence 6), which was accompanied by further sharp uplift of platforms, caused more profound slope erosion and platform backstepping. Poor circulation and oxygen-depleted waters in the now much deeper Basin centre led to the deposition of chert, with silica supplied by hydrothermal fluids through deep-seated faults. Two `subdeeps\\\' were diagonally arranged in the distal parts of the master faults, and the relay ramp was destroyed. At this time, all Basin margins except the western one evolved into erosional types with gullies through which granular platform sediments were transported by gravity flows to the Basin. This situation persisted into the latest Frasnian. This case history shows that the carbonate platform architecture and evolution in a Pull-Apart Basin were not only strongly controlled by the tectonic activity, but also influenced by the oceanographic setting (i.e. windward vs. leeward) and environmental factors.
Seyed Tohid Nabavi - One of the best experts on this subject based on the ideXlab platform.
-
The Dinevar transtensional Pull-Apart Basin, NW Zagros Mountains, Iran: a geological study and comparison to 2D finite element elastic models
International Journal of Earth Sciences, 2019Co-Authors: Seyed Tohid Nabavi, Seyed Ahmad Alavi, Hamid Javanbakht JabarabadiAbstract:The Dinevar transtensional Pull-Apart Basin is a NW–SE trending Basin located in the northwest part of the Zagros Mountains, Sanandaj–Sirjan tectonic zone, Iran. This Basin was formed by oblique extension in a strike-slip fault system, which was controlled by the pre-existing Sahneh and the Mianrahan faults. In addition to a field study, we constructed a 2D finite element elastic model based on the major fault segments. According to the field study, various geological structures are formed around the pre-existing fault segments, including pencil structures with 13
-
the dinevar transtensional Pull Apart Basin nw zagros mountains iran a geological study and comparison to 2d finite element elastic models
International Journal of Earth Sciences, 2019Co-Authors: Seyed Tohid Nabavi, Seyed Ahmad Alavi, Hamid Javanbakht JabarabadiAbstract:The Dinevar transtensional Pull-Apart Basin is a NW–SE trending Basin located in the northwest part of the Zagros Mountains, Sanandaj–Sirjan tectonic zone, Iran. This Basin was formed by oblique extension in a strike-slip fault system, which was controlled by the pre-existing Sahneh and the Mianrahan faults. In addition to a field study, we constructed a 2D finite element elastic model based on the major fault segments. According to the field study, various geological structures are formed around the pre-existing fault segments, including pencil structures with 13 < aspect ratio < 19, tight to open asymmetric folds, oblique–normal faults, synthetic and antithetic faults, normal and reverse fault drags, and negative and hybrid-type flower structure. FE-model results show that around the fault step is a zone of displacement gradient that indicates extension (transtension) within the overlapping zone. Consequently, subsidence is predicted over the releasing fault step. The modelled stress distributions within the fault step and around the fault segment tips are asymmetric. Elastic modelling shows that the mean normal stress within the step is tensional, which would impede plastic yield, while the region outside the step is characterised by compressive mean normal stress. The mean normal stress pattern is characterised by a regional minimum, localised inside the extensional step (transtension zone), and two local maximum and minimum couples, formed at the advancing and retreating sides, respectively, in the fault segment tips. The results show that two main subsidence regions (depocentres or sub-Basins) form along and in the proximity of the fault segment tips. The imposed relative motion is entirely accommodated by creep on the faults, which causes plastic strain to accumulate outside the faults, mostly localised within the fault step. This localised strain between fault segments could initiate connecting faults or reactivate earlier faults, generally at high angles relative to the master fault segments as suggested by the stress and strain patterns. The rotation and magnitude variation in the stress and strain trajectories reflects heterogeneous deformation. In general, the Dinevar transtensional Pull-Apart Basin is characterised by an elongate rhomboidal- to trapezoidal-shaped geometry. The modelled stress distribution and strain localisations within the Basin are in general agreement with the locations of fault segments within the Dinevar transtensional Pull-Apart Basin.
J. Zhu - One of the best experts on this subject based on the ideXlab platform.
-
carbonate sedimentation in a starved Pull Apart Basin middle to late devonian southern guilin south china
Basin Research, 2001Co-Authors: Daizhao Chen, Maurice E. Tucker, J. Zhu, M. JiangAbstract:Geological mapping and sedimentological investigations in the Guilin region, South China, have revealed a spindle- to rhomb-shaped Basin filled with Devonian shallow- to deepwater carbonates. This Yangshuo Basin is interpreted as a Pull-Apart Basin created through secondary, synthetic strike-slip faulting induced by major NNE-SSW-trending, sinistral strikeslip fault zones. These fault zones were initially reactivated along intracontinental basement faults in the course of northward migration of the South China continent. The nearly N-S trending margins of the Yangshuo Basin, approximately coinciding with the strike of regional fault zones, were related to the master strike-slip faults; the NW-SE-trending margins were related to parallel, oblique-slip extensional faults. Nine depositional sequences recognized in Givetian through Frasnian strata can be grouped into three sequence sets (Sequences 1-2, 3-5 and 6-9), reflecting three major phases of Basin evolution. During Basin nucleation, most Basin margins were dominated by stromatoporoid biostromes and bioherms, upon a low-gradient shelf. Only at the steep, fault-controlled, eastern margin were thick stromatoporoid reefs developed. The subsequent progressive offset and Pull-Apart of the master strike-slip faults during the late Givetian intensified the differential subsidence and produced a spindle-shaped Basin. The accelerated subsidence of the Basin centre led to sediment starvation, reduced current circulation and increased environmental stress, leading to the extensive development of microbial buildups on platform margins and laminites in the Basin centre. Stromatoporoid reefs only survived along the windward, eastern margin for a short time. The architectures of the Basin margins varied from aggradation (or slightly backstepping) in windward positions (eastern and northern margins) to moderate progradation in leeward positions. A relay ramp was present in the north-west corner between the northern oblique fault zone and the proximal part of the western master fault. In the latest Givetian (corresponding to the top of Sequence 5), a sudden subsidence of the Basin induced by further offset of the strike-slip faults was accompanied by the rapid uplift of surrounding carbonate platforms, causing considerable platform-margin collapse, slope erosion, Basin deepening and the demise of the microbialites. Afterwards, stromatoporoid reefs were only locally restored on topographic highs along the windward margin. However, a subsequent, more intense Basin subsidence in the early Frasnian (top of Sequence 6), which was accompanied by further sharp uplift of platforms, caused more profound slope erosion and platform backstepping. Poor circulation and oxygen-depleted waters in the now much deeper Basin centre led to the deposition of chert, with silica supplied by hydrothermal fluids through deep-seated faults. Two `subdeeps\\\' were diagonally arranged in the distal parts of the master faults, and the relay ramp was destroyed. At this time, all Basin margins except the western one evolved into erosional types with gullies through which granular platform sediments were transported by gravity flows to the Basin. This situation persisted into the latest Frasnian. This case history shows that the carbonate platform architecture and evolution in a Pull-Apart Basin were not only strongly controlled by the tectonic activity, but also influenced by the oceanographic setting (i.e. windward vs. leeward) and environmental factors.
-
Carbonate sedimentation in a starved Pull‐Apart Basin, Middle to Late Devonian, southern Guilin, South China
Basin Research, 2001Co-Authors: Daizhao Chen, Maurice E. Tucker, J. Zhu, M. JiangAbstract:Geological mapping and sedimentological investigations in the Guilin region, South China, have revealed a spindle- to rhomb-shaped Basin filled with Devonian shallow- to deepwater carbonates. This Yangshuo Basin is interpreted as a Pull-Apart Basin created through secondary, synthetic strike-slip faulting induced by major NNE-SSW-trending, sinistral strikeslip fault zones. These fault zones were initially reactivated along intracontinental basement faults in the course of northward migration of the South China continent. The nearly N-S trending margins of the Yangshuo Basin, approximately coinciding with the strike of regional fault zones, were related to the master strike-slip faults; the NW-SE-trending margins were related to parallel, oblique-slip extensional faults. Nine depositional sequences recognized in Givetian through Frasnian strata can be grouped into three sequence sets (Sequences 1-2, 3-5 and 6-9), reflecting three major phases of Basin evolution. During Basin nucleation, most Basin margins were dominated by stromatoporoid biostromes and bioherms, upon a low-gradient shelf. Only at the steep, fault-controlled, eastern margin were thick stromatoporoid reefs developed. The subsequent progressive offset and Pull-Apart of the master strike-slip faults during the late Givetian intensified the differential subsidence and produced a spindle-shaped Basin. The accelerated subsidence of the Basin centre led to sediment starvation, reduced current circulation and increased environmental stress, leading to the extensive development of microbial buildups on platform margins and laminites in the Basin centre. Stromatoporoid reefs only survived along the windward, eastern margin for a short time. The architectures of the Basin margins varied from aggradation (or slightly backstepping) in windward positions (eastern and northern margins) to moderate progradation in leeward positions. A relay ramp was present in the north-west corner between the northern oblique fault zone and the proximal part of the western master fault. In the latest Givetian (corresponding to the top of Sequence 5), a sudden subsidence of the Basin induced by further offset of the strike-slip faults was accompanied by the rapid uplift of surrounding carbonate platforms, causing considerable platform-margin collapse, slope erosion, Basin deepening and the demise of the microbialites. Afterwards, stromatoporoid reefs were only locally restored on topographic highs along the windward margin. However, a subsequent, more intense Basin subsidence in the early Frasnian (top of Sequence 6), which was accompanied by further sharp uplift of platforms, caused more profound slope erosion and platform backstepping. Poor circulation and oxygen-depleted waters in the now much deeper Basin centre led to the deposition of chert, with silica supplied by hydrothermal fluids through deep-seated faults. Two `subdeeps\\\' were diagonally arranged in the distal parts of the master faults, and the relay ramp was destroyed. At this time, all Basin margins except the western one evolved into erosional types with gullies through which granular platform sediments were transported by gravity flows to the Basin. This situation persisted into the latest Frasnian. This case history shows that the carbonate platform architecture and evolution in a Pull-Apart Basin were not only strongly controlled by the tectonic activity, but also influenced by the oceanographic setting (i.e. windward vs. leeward) and environmental factors.
