Folding and boudinage of an oblique single layer

褶皱和结合部提供了岩石应变、流变和变形历史的信息。这就是为什么这两种结构形成的条件应该众所周知的原因。几乎所有的褶皱和束缚的理论和建模都是基于垂直于主应变轴的一层（或多层）的同轴变形。在这种条件下，褶皱和束缚体同时生长或作为单个结构单独发育。然而，如果分层是斜向所有三个远场主应变率，情况就完全不同了，而且更加复杂。在这种情况下，主管层中最大缩短率的方向随时间连续变化，因此会叠加屈曲或颈缩失稳的基应变率也在变化。因此，褶皱和结合可以按顺序发育。由于缺乏这两种结构顺序生长的实验证据，我们将使用非线性粘性岩石模拟物进行比例实验，以显示层倾角对变形几何形状的影响。主要目的是约束在体同轴平面应变下适合褶皱和束缚（或夹胀结构）顺序发展的条件（粘度比、层倾角、有限应变）。它将进一步展示当层的姿态改变时，折叠将如何改变为装订（反之亦然）。由于斜向主管层的褶皱和褶皱在各种环境（如造山带、盐丘）中都很常见，因此本项目将引起大量构造地质学家的兴趣，他们可以利用新的结果来约束自然环境中的褶皱和褶皱条件。

Folds and boudins provide information on strain, rheology and deformation history of rocks. That is why the conditions during which both structures develop should be well known. Nearly all the theory and modelling of folds and boudins are based on coaxial deformation of a layer (or layers) oriented perpendicular to the principal strain axes. Under such conditions folds and boudins grow simultaneously or develop separately as single structures. The situation, however, is entirely different and more complex if the layering is oblique to all three far-field principal strain rates. In such cases 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 may develop in sequence. As experimental evidence for sequential growth of both structures is lacking, we will carry out scaled experiments using non-linear viscous rock analogues to show the impact of layer inclination on the deformation geometry. The main aim is to constrain the conditions (viscosity ratio, layer inclination, finite strain) which are suitable for the sequential development of folds and boudins (or pinch-and-swell structures) under bulk coaxial plane strain. It will further be shown how folding will change to boudinage (and vice versa) when the attitude of the layer is changing. As folding and boudinage of an oblique competent layer is common in various settings (e.g. orogens, 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 environments.