The upper plate of the Arabia-Eurasia collision zone experienced orogen-perpendicular to orogen-parallel extension from 25–22 to 10–9 Ma. Although such an extension occurred during widespread collisional deformation, it is not clear if it is a local feature or if represents a major phase of upper plate extension. In this study we combine anisotropy of magnetic susceptibility (AMS) with fault kinematic analysis and sedimentologic data from 16.2- to 7.6-My-old deposits of the Upper Red Formation of the intermontane Tarom Basin (NW Iran). These strata present syndepositional, normal faults and offer the possibility to gain new insights into the spatial extent of such a Miocene extension. AMS data from the central and northern sectors of the basin document a tectonic fabric with a magnetic lineation parallel to the strike of the orogen, suggesting a compressional tectonic overprint. Conversely, the southern margin of the basin presents a purely sedimentary magnetic fabric despite a ~NE–SW orogen-perpendicular extension. This suggests that basin formation was not driven by extensional tectonics. Rather, the normal faults are gravity instabilities induced as also documented by coeval landslide deposits. This allows concluding that the orogen-perpendicular extension observed in few sectors of the collision zone is not regionally pervasive and hence it is not controlled by large-scale processes. Combined, our results indicate that if orogen-parallel extension associated with tectonic denudation and metamorphic core complex development occurred in certain sectors of the collision zone (Takab complex), it must have ended before 19–16 Ma, when widespread upper plate contractional deformation started.

阿拉伯-欧亚大陆碰撞带的上板块经历了从 25-22 Ma 到 10-9 Ma 的造山带垂直于造山带的平行伸展。尽管这种伸展发生在广泛的碰撞变形期间，但尚不清楚它是局部特征还是代表上板块伸展的主要阶段。在这项研究中，我们将磁化率 (AMS) 的各向异性与断层运动学分析和沉积学数据相结合，这些数据来自山间 Tarom 盆地（伊朗西北部）上部红色地层的 16.2 至 7.6 米古沉积物。这些地层呈现同沉积的正断层，并提供了对这种中新世延伸的空间范围获得新见解的可能性。盆地中部和北部的 AMS 数据记录了一个构造结构，其磁力线平行于造山带的走向，暗示一个压缩构造叠印。相反，盆地南缘尽管有~NE-SW 造山带垂直延伸，但呈现出纯粹的沉积磁性结构。这表明盆地的形成不是由伸展构造驱动的。相反，正断层是重力不稳定性引起的，正如同时期的滑坡沉积物所记录的那样。这使得可以得出结论，在碰撞区的少数扇区中观察到的造山带垂直延伸不是区域性的，因此它不受大规模过程的控制。综合起来，我们的结果表明，如果与构造剥蚀和变质核复合体发育相关的造山带平行伸展发生在碰撞带的某些部分（Takab 复合体），它必定在 19-16 Ma 之前结束，