Abstract Along convergent plate boundaries, the negative buoyancy of the lithosphere pulls the slab into subduction. Bending and offscraping of the downgoing plate are processes occurring at subduction zones and acting against plate motions. These localised dissipative processes cause extensional deformation in the bulge-foredeep region and thrusting and folding in the thrust wedge respectively. Within this framework, widespread early subduction-related extensional structures affecting pre-orogenic rocks of the downgoing plate of fossil subduction systems, are commonly interpreted as induced by extension occurring in the forebulge-foredeep zone. Slab pull is to date, rarely considered as a potential causative process when interpreting basin-scale pre-shortening extensional structures. The problem of distinguishing slab-pull and foreland flexuring induced extensional structures relates to the fact that for most belts, slab pull and forebulge-foredeep flexuring are expected to produce extension roughly in the same direction (i.e. parallel to the foredeep-belt system) and, when syn-kinematic strata are not available, discriminating between these two processes is arduous. In this work we present a field investigation of basin-scale extensional faults from the downgoing plate of the Oman Mts. fossil subduction system. Syn-kinematic strata indicate that normal fault development largely predated extension in the bulge-foredeep region. Herein, we argue that such faulting occurred during the transition from induced to self-sustained subduction, when the negative buoyancy of the slab started to exceed the resisting forces and the downgoing plate began to be pulled towards the trench.

中文翻译：

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阿曼山脉从诱导俯冲到自持俯冲过渡的地质记录

摘要 沿着会聚板块边界，岩石圈的负浮力将板块拉入俯冲。下沉板块的弯曲和剥落是发生在俯冲带并对抗板块运动的过程。这些局部耗散过程分别导致凸出前深区域的拉伸变形和推力楔中的推力和折叠。在这个框架内，影响化石俯冲系统下行板块的前造山岩的广泛的早期俯冲相关伸展结构，通常被解释为由发生在前隆起-前深区的伸展引起。迄今为止，在解释盆地尺度预缩短伸展结构时，板坯拉力很少被视为潜在的成因过程。区分板坯拉力和前缘弯曲引起的伸展结构的问题与以下事实有关：对于大多数带，板坯拉力和前缘-前缘弯曲预计会在大致相同的方向（即平行于前缘-带系统）产生伸展，并且，当同运动地层不可用时，区分这两个过程是困难的。在这项工作中，我们对阿曼山脉下行板块的盆地尺度伸展断层进行了实地调查。化石俯冲系统。同运动地层表明，正断层的发育在很大程度上早于凸起前深区域的伸展。在这里，我们认为这种断层发生在从诱导俯冲到自持俯冲的转变过程中，