Dynamic processes controlling foreland development – the role of mechanical (de)coupling of orogenic wedges and forelands
Dynamic processes controlling foreland development – the role of mechanical (de)coupling of orogenic wedges and forelands
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DOI：
10.5194/smsps-1-17-2002
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发表时间：
2001-11
期刊：
影响因子：
--
通讯作者：
P. A. Ziegler;G. Bertotti;S. Cloetingh
中科院分区：
文献类型：
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作者：
P. A. Ziegler;G. Bertotti;S. Cloetingh
根据控制造山楔演化的俯冲系统的极性，我们区分前楔（弧前，前陆）和后楔（弧后，腹地）前陆。在安第斯型造山带的楔后域和喜马拉雅型造山带的楔前域和楔后域中，可以发育挠曲性前陆盆地和板内挤压构造。楔后前陆盆地的沉降完全受造山楔作用于前陆岩石圈的地形载荷的控制，而俯冲岩石圈板片的附加载荷则对楔前陆盆地的沉降有贡献。挠曲性前隆只有在造山楔和前陆岩石圈在岩石圈水平上机械解耦的情况下才发育。在造山楔与其前陆在地壳和/或mantlelithosphere水平之间的机械耦合条件下，挤压应力被传递到后者，诱导重新激活预先存在的地壳不连续性和广泛的地壳和岩石圈规模的折叠距离可达1700公里的碰撞前线。这种应力可能会加重潜在的预先存在的弯曲前凸或阻碍其发展。取决于地壳及其沉积盖层的厚度和流变结构，厚皮和/或薄皮逆冲断层可以传播到远至前陆，破坏先前存在的弯曲前陆盆地或阻碍其发展。与碰撞有关的挤压应力可以在俯冲带的形成过程中传递到前楔前陆，在俯冲带中有更多的浮力地壳到达俯冲带而导致俯冲受阻的时期，在造山楔与被动边缘的初始碰撞过程中，以及在碰撞后造山楔的过度增厚和抬升以及地幔后止点的发展过程中。前陆板内压扭构造的发育表明与碰撞有关的压应力的积累，因此强烈对应于：P. A。齐格勒（传真+41-061-421.55.35）前陆与相关造山楔在地壳和/或地幔岩石圈水平上的机械耦合。同造山期板内挤压构造的缺失表明造山楔与其前陆在力学上是分离的。造山楔与其前陆之间的力学耦合程度在时间和空间上都是变化的。造山楔与前陆的耦合与不耦合可能取决于它们共同边界带的几何形状和摩擦剪切强度。前陆的俯冲阻力，以及俯冲沉积物中高流体压力的积累，可能起着重要的作用。前楔状大陆地壳和地幔岩石圈可以俯冲到100- 150公里的深度，在那里它不再能支撑附着的大洋板片的重量而破裂。板片拆离作用导致造山带的抬升、地幔逆止作用的发展以及与碰撞有关的主要应力向前陆的传递。前陆的构造-地层记录监测与碰撞有关的应力场的演变、造山带与其前陆之间的机械耦合程度，从而有助于确定影响板块边缘的造山活动的年代。这些概念的基础上讨论了在欧洲，北非，阿拉伯和北美的古生代和年轻的造山带的选择前陆的演化。
Depending on the polarity of the subduction system controlling the evolution of an orogenic wedge, we distinguish between pro-wedge (fore-arc, foreland) and retrowedge (retro-arc, hinterland) forelands. Flexural foreland basins and/or intraplate compressional structures can develop in retro-wedge domains of Andean-type and in proand retro-wedge domains of Himalayan-type orogens. Whereas the subsidence of retro-wedge foreland basins is exclusively controlled by the topographic load exerted by the orogenic wedge on the foreland lithosphere, the additional load of the subducted lithospheric slab contributes towards the subsidence of pro-wedge foreland basins. Flexural forebulges develop only if the orogenic wedge and the foreland lithosphere are mechanically decoupled at lithospheric levels. Under conditions of mechanical coupling between an orogenic wedge and its foreland at crustal and/or mantlelithospheric levels, compressional stresses are transmitted into the latter, inducing reactivation of pre-existing crustal discontinuities and broad crustal and lithosphere scale folding at distances up to 1700 km from the collision front. Such stresses can accentuate potential pre-existing flexural forebulges or impede their development. Depending on the thickness and rheological structure of the crust and its sedimentary cover, thickand/or thin-skinned thrusts can propagate far into forelands, either disrupting pre-existing flexural foreland basins or impeding their development. Collision-related compressional stresses can be transmitted into pro-wedge forelands during 1) initiation of subduction zones, 2) periods of subduction impediment caused by the arrival of more buoyant crust at a subduction zone, 3) initial collision of an orogenic wedge with a passive margin, and 4) post-collisional over-thickening and uplift of an orogenic wedge and the development of a mantle-back-stop. Development of intraplate compressional/transpressional structures in forelands is indicative for the build-up of collision-related compressional stresses, and thus for strong Correspondence to: P. A. Ziegler (fax +41-061-421.55.35) mechanical coupling of a foreland with the associated orogenic wedge, either at crustal and/or mantle-lithospheric levels. The absence of syn-orogenic intraplate compressional structures suggests that the respective orogenic wedge and its foreland(s) were mechanically decoupled. The level of mechanical coupling between an orogenic wedge and its foreland is temporally and spatially variable. Mechanical coupling and uncoupling of orogenic wedges and their forelands probably depends on the geometry and frictional shear strength of their common boundary zone. Subduction resistance of the foreland, as well as the buildup of high fluid pressures in subducted sediments, presumably play an important role. Pro-wedge continental crust and mantle-lithosphere can be subducted to depths of 100– 150 km at which it can no longer support the weight of the attached oceanic slab and fails. Slab-detachment results in uplift of the orogen, mantle back-stop development and the transmission of major collision-related stresses into the forelands. The tectono-stratigraphic record of forelands monitors the evolution of collision-related stress fields, the level of mechanical coupling between an orogen and its foreland(s), and thus contributes to dating orogenic activity affecting a plate margin. These concepts are discussed on the base of the evolution of selected forelands of Palaeozoic and younger orogens in Europe, North Africa, Arabia and North America.