Folding and boudinage of oblique single layers under non-plane conditions

非平面条件下倾斜单层的折叠和布丁

• 批准号: 492904003
• 负责人: Professor Dr. Gernold Zulauf
• 金额: --
• 依托单位: Ústav geologie a paleontologie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/492904003?language=en
• 关键词: Folding; boudinage; oblique; single; layers

Folds and boudins provide information on kinematics, strain, rheology and deformation history of rocks. That’s why the conditions during which both structures develop should be well known. As most of the theory and modelling of folds and boudins are based on coaxial plane-strain, current reviews of folding and boudinage in journals and textbooks are largely restricted to two dimensions. This is unfortunate as new 3D survey techniques allow detailed geometrical recording of 3D folds and boudins resulting in an increasing number of such structures described from natural tectonites. 3D folds and boudins may also develop if the initial orientation of the competent layering is oblique with respect to the principal strain axes. While orthogonal single layers result in symmetric, cylindrical structures, oblique single layers will be converted into asymmetric folds and boudins and even into periclinal folds, although the bulk strain is plane. The situation is still more complex if the layering is initially oblique on the one hand, and bulk strain is not plane, on the other hand. In such cases of 3D strain fields, the directions of maximum shortening rate in the competent layer varies continuously with time and the base strain rate on which a buckling or necking instability would be superimposed is therefore also changing. Consequently, folds and boudins are tending to be non-cylindrical and asymmetric, and both structures may develop simultaneously or even in sequence. As numerical and physical experiments focusing on coaxial deformation of oblique single layers under non-plane conditions are lacking, our understanding of the evolution of related 3D structures is restricted. For this reason we will carry out scaled experiments using non-linear viscous rock analogues to show the impact of viscosity ratio between layer and matrix and of the initial layer inclination on the deformation geometry under bulk flattening and bulk constrictional conditions. The main aim of the present proposal is to show how, under bulk constriction and bulk flattening, dome-and-basin folding on the one hand, and tablet boudinage on the other hand, will change into coeval folding and boudinage when the initial attitude of the layer varies with respect to the principal strain axes. Apart from uninterrupted studies, which imply a final strain of 60%, we will carry out incremental studies to show how fast and in which way the individual structures are growing with time. As folding and boudinage of oblique single layers is common in various geological settings where rocks are imposed by flattening or constrictional strain (e.g. gneiss domes, salt domes), the present project will be of interest for a large number of structural geologists, who can use the new results to constrain the conditions of folding and boudinage in natural non-plane environments.

褶皱和石香肠提供了岩石的运动学、应变、流变学和变形历史的信息。这就是为什么这两种结构发展的条件应该是众所周知的。由于大多数褶皱和石香肠的理论和建模都是基于共轴平面应变，目前在期刊和教科书中对褶皱和石香肠的评论主要限于二维。这是不幸的，因为新的3D测量技术允许详细的几何记录的3D褶皱和石香肠，导致越来越多的这样的结构描述的天然构造岩。三维褶皱和石香肠也可能发展，如果初始方向的主管分层是倾斜的相对于主应变轴。虽然正交单层导致对称的圆柱形结构，但倾斜单层将转化为不对称褶皱和石香肠，甚至转化为斜周褶皱，尽管体应变是平面的。如果一方面分层最初是倾斜的，另一方面体应变不是平面的，情况就更加复杂。在这种情况下的三维应变场，在主管层的最大缩短率的方向随时间连续变化，并在其上的屈曲或颈缩不稳定的基础应变率，因此也在变化。因此，褶皱和石香肠往往是非圆柱形和不对称的，这两种结构可能同时或甚至顺序发展。由于缺乏非平面条件下斜单层共轴变形的数值和物理实验，限制了我们对相关三维结构演化的理解。出于这个原因，我们将进行缩放实验，使用非线性粘性岩石类似物显示层和基质之间的粘度比和初始层倾斜的变形几何形状的影响下，批量压扁和批量压缩条件。本建议的主要目的是显示，在体积收缩和体积变平，圆顶和盆地褶皱的一方面，和另一方面，平板石香肠，将变成同时代的褶皱和石香肠时，层的初始姿态相对于主应变轴变化。除了不间断的研究，这意味着最终应变为60%，我们将进行增量研究，以显示单个结构随着时间的推移增长的速度和方式。由于褶皱和石香肠的倾斜单层是常见的各种地质环境中的岩石是由压扁或收缩应变（如片麻岩圆顶，盐丘），本项目将感兴趣的大量的结构地质学家，谁可以使用新的结果来约束条件的褶皱和石香肠在自然非平面环境。