Extensional fault-bend folds, also called rollovers, are one of the most common structures in extensional settings. Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitat...Extensional fault-bend folds, also called rollovers, are one of the most common structures in extensional settings. Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative modeling of geometric relations between normal faults and the strata in their hanging walls. However, the oblique simple shear has a rather serious issue derived from the shear direction, particularly above convex bends. We use geometric and experimental methods to study the deformation of extensional fault-bend folds on convex bends. The results indicate that whether the fault bends are concave or convex, the shear direction of the hanging wall dips toward the main fault. On this basis, we improve the previous geometric model by changing the shear direction above the convex bends. To illustrate basin history, our model highlights the importance of the outer limit of folding instead of the growth axial. Moreover, we propose a new expression for the expansion index that is applicable to the condition of no deposition on the footwall. This model is validated by modeling a natural structure of the East China Sea Basin.展开更多
This paper presents two conceptual models of displacement transfer, reverse sym- metry model and infinitely equal division model, based on the fault-bend folding theory. If the fault shape is held constant in the tren...This paper presents two conceptual models of displacement transfer, reverse sym- metry model and infinitely equal division model, based on the fault-bend folding theory. If the fault shape is held constant in the trend, then the distribution of slip magnitude, geometry of imbricate structures and its axial surface map all display reverse symmetry on the process of displacement transfer, as called reverse symmetry model in this paper. However, if the ramp height of thrust fault decreases gradually along its strike, the displacement is postulated to be equally and infinitely divided to every thrust that is formed subsequently, this kinematic process is described using infinitely equal division model. In both models, displacement transfer is characterized by the regular changes of imbricate thrusting in the trend. Geometric analysis indicates that the displacement transfer grads can be estimated using the tangent of deflective angle of hinterland structures. Displacement transfer is often responsible for the distortion and branching of the surface anticlines, especially in the region where the multi-level detachment structures is developed. We also present some examples from the frontal structures of the Southern Tianshan fold-and-thrust belt, Xinjiang, China. Displacement transfer between deep imbricate thrusts in the middle segment of Qiulitag anticline zone causes the Kuqatawu and Southern Qiulitag deep an- ticlines left-lateral echelon. The region, where these two deep anticlines overlap, is characterized by duplex structures, and extends about 18 km. The shallow anticline is migrated southward displaying obvious “S” form in this area.展开更多
文摘Extensional fault-bend folds, also called rollovers, are one of the most common structures in extensional settings. Numerous studies have shown that oblique simple shear is the most appropriate mechanism for quantitative modeling of geometric relations between normal faults and the strata in their hanging walls. However, the oblique simple shear has a rather serious issue derived from the shear direction, particularly above convex bends. We use geometric and experimental methods to study the deformation of extensional fault-bend folds on convex bends. The results indicate that whether the fault bends are concave or convex, the shear direction of the hanging wall dips toward the main fault. On this basis, we improve the previous geometric model by changing the shear direction above the convex bends. To illustrate basin history, our model highlights the importance of the outer limit of folding instead of the growth axial. Moreover, we propose a new expression for the expansion index that is applicable to the condition of no deposition on the footwall. This model is validated by modeling a natural structure of the East China Sea Basin.
基金the National Natural Science Foundation of China(Grant No.49972077).
文摘This paper presents two conceptual models of displacement transfer, reverse sym- metry model and infinitely equal division model, based on the fault-bend folding theory. If the fault shape is held constant in the trend, then the distribution of slip magnitude, geometry of imbricate structures and its axial surface map all display reverse symmetry on the process of displacement transfer, as called reverse symmetry model in this paper. However, if the ramp height of thrust fault decreases gradually along its strike, the displacement is postulated to be equally and infinitely divided to every thrust that is formed subsequently, this kinematic process is described using infinitely equal division model. In both models, displacement transfer is characterized by the regular changes of imbricate thrusting in the trend. Geometric analysis indicates that the displacement transfer grads can be estimated using the tangent of deflective angle of hinterland structures. Displacement transfer is often responsible for the distortion and branching of the surface anticlines, especially in the region where the multi-level detachment structures is developed. We also present some examples from the frontal structures of the Southern Tianshan fold-and-thrust belt, Xinjiang, China. Displacement transfer between deep imbricate thrusts in the middle segment of Qiulitag anticline zone causes the Kuqatawu and Southern Qiulitag deep an- ticlines left-lateral echelon. The region, where these two deep anticlines overlap, is characterized by duplex structures, and extends about 18 km. The shallow anticline is migrated southward displaying obvious “S” form in this area.
