Abstract We use two-dimensional numerical simulations to investigate the interaction of folding (buckling) and thrusting (localized shearing) during the structural evolution of fold-and-thrust belts (FTB). We model layer-parallel shortening of mechanically strong layers resting above a weaker layer, referred to as detachment. We consider a viscoplastic rheology with linear viscosity and frictional-plastic Drucker-Prager yield criterion. The detachment thickness is larger in one model half and only this geometrical thickness perturbation triggers folding and thrusting in the simulations. We conduct a systematic analysis to quantify the impact of model parameters, such as magnitude of the thickness perturbation or detachment rheology (frictional or viscous), on the FTB evolution. The magnitude of the perturbation determines whether, or not, folding is favoured over thrusting and, hence, controls the progressive interaction of folding and thrusting during FTB evolution. The asymmetry of modelled anticlines is proportional to the relative height of the initial perturbation. We also adapt the model configuration to specific mechanical stratigraphies of two regions in natural FTB, namely the Haute-Chaine of the Jura Mountains (Switzerland) and the Foothills of Alberta (Canada). The modelled fold and thrust geometries agree with different types of observed anticlinal structures, such as symmetric detachments folds and asymmetric thrust-folds. Our results suggest that an initial stage of low-amplitude buckling likely occurred prior to the main folding and thrusting phase. We argue that folding and thrusting are equally important and interacting processes during the structural evolution of many natural FTB.

中文翻译：

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褶皱和冲刺带演化过程中褶皱和冲刺的相互作用：从数值模拟和应用到瑞士侏罗山和加拿大山麓的见解

摘要 我们使用二维数值模拟来研究折叠推力带 (FTB) 结构演化过程中折叠（屈曲）和推力（局部剪切）的相互作用。我们模拟位于较弱层上方的机械强层的层平行缩短，称为分离。我们考虑具有线性粘度和摩擦塑性 Drucker-Prager 屈服准则的粘塑性流变学。一个模型一半的脱离厚度更大，只有这种几何厚度扰动会触发模拟中的折叠和推力。我们进行了系统分析，以量化模型参数对 FTB 演化的影响，例如厚度扰动或脱离流变学（摩擦或粘性）的大小。扰动的大小决定了 折叠优于推力，因此在 FTB 进化过程中控制折叠和推力的渐进相互作用。模拟背斜的不对称性与初始扰动的相对高度成正比。我们还使模型配置适应自然 FTB 中两个区域的特定机械地层，即侏罗山脉的上链（瑞士）和阿尔伯塔山麓（加拿大）。模拟的褶皱和逆冲几何形状与观察到的不同类型的背斜结构一致，例如对称分离褶皱和不对称逆冲褶皱。我们的结果表明，低幅度屈曲的初始阶段可能发生在主要折叠和推力阶段之前。