Classifying curved orogens based on timing relationships between structural development and vertical-axis rotations
Classifying curved orogens based on timing relationships between structural development and vertical-axis rotations
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DOI：
10.1130/0-8137-2383-3(2004)383
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
A. Weil;A. Sussman
中科院分区：
文献类型：
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作者：
A. Weil;A. Sussman
地质学家早就认识到弯曲造山带的重要性并探索其意义。在过去的几十年里，已经提出了几个分类方案，弯曲造山带，主要是基于位移和应变轨迹之间的关系，和几何形状。然而，确定弧形造山带的应变轨迹路径和完整的位移场是困难的。通常只测量总应变场的一个分量是可能的，但实际上不可能测量整个位移场。此外，这些分类方案中的许多已经改变或修改了一些关键术语的原始定义，最值得注意的是单词orocline，其在文献中传播了混乱（例如，阿拉斯加和玻利维亚的造山带）。为了避免与分类弯曲带相关的一些模糊性和混乱，我们提出了一个新的分类方案，基于构造趋势或纹理（主要逆冲断层和褶皱的方向）和次级强加曲率（初始逆冲断层和褶皱之后获得的旋转）之间的角度关系。这样，弯曲带的分类可以艾德为三大类：（1）造山带，（2）前进弧，（3）原始弧。造山带是那些最初是线性的，在随后的变形事件中弯曲的造山带。渐进弧与带的生长同时发展其弧形性质。原生弧是那些在初始变形过程中继承曲率而在随后的变形过程中没有明显收紧的造山系统。确定一个弯曲造山带是通过原生、次生还是渐进机制形成的，一个标准是构造趋势的偏离与带内发生的垂直轴旋转之间的时间和空间关系。目前，确定这种关系，从而确定弯曲造山带的运动学分类（原生、前进或次生）的最有用的地质技术是古地磁学和详细构造分析的结合。在确定了给定弯曲带的适当运动学分类之后，重点应放在用获得曲率的机制（例如，压头、弯曲、扳手等）。通过这种方式，变形的运动学与过程的力学分离，其通常可以由一个以上的运动学模型描述。
Geologists have long recognized the importance and sought the meaning of curved orogenic belts. Over the last few decades, several classifi cation schemes have been proposed for curved orogens that have been largely based on the relationship between, and geometry of, displacement and strain trajectories. However, determination of strain trajectory paths and the complete displacement fi eld of an arcuate orogen is diffi cult at best. It is often possible to measure only one component of the total strain fi eld, but virtually impossible to measure the complete displacement fi eld. In addition, many of these classifi cation schemes have changed or modifi ed original defi nitions for some key terms, most notably the word orocline, which has propagated confusion in the literature (e.g., the Alaskan and Bolivian oroclines). To avoid some of the ambiguity and confusion associated with classifying curved belts, we propose a new classifi cation scheme based on the angular relationship between structural trend or grain (orientation of major thrusts and folds) and secondary imposed curvature (rotations acquired subsequent to initial thrusting and folding). In this manner, classifi cation of curved belts can be simplifi ed into three broad categories: (1) oroclines, (2) progressive arcs, and (3) primary arcs. Oroclines are those orogens that were originally linear and were curved during a subsequent deformation event. Progressive arcs develop their arcuate nature contemporaneously with growth of the belt. Primary arcs are those orogenic systems that inherit curvature during initial deformation and experience no appreciable tightening during subsequent deformation. The one criterion for ascertaining whether a curved orogen developed through a primary, secondary, or progressive mechanism is the temporal and spatial relationship between the deviation in structural trend and the vertical-axis rotation that took place within the belt. At present, the most useful geologic technique for determining such a relationship, and hence the kinematic classifi cation (primary, progressive, or secondary), of a curved orogen is the combination of paleomagnetism and detailed structural analysis. Following identifi cation of the appropriate kinematic classifi cation for a given curved belt, emphasis should be placed on qualifying that classifi cation with the mechanism by which curvature was attained (e.g., indenter, buckling, wrenching, etc.). In this way, the kinematics of deformation is separated from the mechanics of the process, which can often be described by more than one kinematic model.