Mechanics of Contrasting Structural Styles in Fold/Thrust Belts

各前陆褶皱和冲断带的变形样式有明显差异。尽管存在这些差异，但在冲断带和褶皱带的总体拓扑结构上却有显著的相似之处，即冲断带和褶皱带均表现出：(1)主要构造向克拉通方向递减的系统间距，(2)共同的区域滑脱和(3)多个较小的内部滑脱水平。样式（褶皱与断裂）的根本差异可能与地层的强度、堆积顺序和流变学有关。通过对非线性黏性流体层状层序的流动不稳定性分析，确定褶皱主导和断裂主导的褶皱/冲断带一级构造的起始和局部化。该理论将预测主要构造的间距，无论是褶皱还是逆冲，在层状层序中，为宾夕法尼亚高原省和爱达荷-怀俄明-犹他逆冲带的地层层序提供一系列地质上合理的代表。对这些构造的有限演化进行非线性流变学的进一步分析将集中在从褶皱到断裂的过渡上，这可能是在爱达荷-怀俄明-犹他冲断带观测到的变形的原因。因此，本研究将试图统一前陆褶皱与冲断带的形成机制。

There are apparent differences in the style of deformation between various foreland fold and thrust belts. Despite these differences, the overall topology of foreland belts is remark- ably similar in that both thrust belts and fold belts show, (1) a cratonward decreasing systematic spacing of major structures, (2) a shared regional decollement and (3) multiple lesser internal decollements levels. The fundamental differences in style (folding vs. faulting) can be related to the strength, stacking order and rheology of the stratigraphy. By applying an analysis of the flow instability of a layered sequence for a non- linear viscous fluid, the initiation and localization of first order structures in both fold-dominated and fault-dominated fold/ thrust belts will be determined. This theory will predict the spacing of major structures, whether folds or thrusts, within a layered sequence for a range of geologically plausible represen- tations of the stratigraphic sequences of the Plateau Province of Pennsylvania and the Idaho-Wyoming-Utah thrust belt. Further analysis of the finite evolution of these structures for a non- linear rheology will focus on the transition from folding to faulting that may be responsible for the observed deformation in the Idaho-Wyoming-Utah thrust belt. Thus, this study will attempt to unify the mechanisms for the origin of foreland fold and thrust belts.