Forebergs are landforms characterized by low, elongated ridges or hills rising above the surrounding alluvial fans or floodplains, and are typically formed by folding associated with thrust faulting. Forebergs in the Gobi-Altay range, south-central Mongolia, have developed in the forelands of mountains transpressionally uplifted in restraining bends along the E–W-trending sinistral strike-slip Bogd fault. Along the easternmost part of the Bogd fault, six forebergs have formed in the foreland of the Artz Bogd restraining-bend. We surveyed one of these forebergs to ascertain the fault geometry associated with its formation and understand how it has developed over time. This foreberg is ~6 km long and ~1 km wide and rises about 40 m above the low-lying floodplain. We also constrained its evolution using cosmogenic ¹⁰Be denudation rates measured from individual catchments along the foreberg, and morphometric analyses using a high-resolution DEM generated from images captured by an unmanned aerial vehicle. We suggest that the foreberg evolved via fault-propagation folding, developing an asymmetric across-foreberg topographic profile. This asymmetry results in differences in ¹⁰Be catchment-wide denudation rates and geomorphic metrics between its northern and southern slopes, causing migration of the drainage divide of the growing foreberg to adjust to the tectonic regime. By analyzing the along-foreberg variation in denudation rates and geomorphic metrics, we infer that the foreberg formed via lateral growth and linking of four discrete segments. Our study illuminates the formation of a unique landform and sheds light on how a structure enlarges both vertically and laterally during the early stage of thrust-related fold developments.

前兆是地势特征，其特征是低矮，细长的山脊或丘陵上升到周围的冲积扇或洪泛区之上，通常由与冲断层相关的褶皱形成。蒙古中南部的戈壁-阿勒泰山脉的前山在沿E-W向左旋走滑博格德断层的约束弯曲中被压抑隆起的山地前陆中发展。沿着博格德断层的最东端，在阿尔茨·博格德限制弯曲的前部形成了六个前堡。我们调查了其中一个前兆，以确定与断层形成有关的断层几何形状，并了解其随着时间的推移如何发展。该前堡长约6公里，宽约1公里，位于低洼洪泛区上方约40 m。我们还使用宇宙起源¹⁰限制了它的进化从沿前堡的各个集水区测得的剥蚀率，以及使用从无人机拍摄的图像生成的高分辨率DEM进行形态分析。我们建议前缘通过断层传播折叠演化，发展出不对称的跨前山地形轮廓。这种不对称导致差异为¹⁰流域北部和南部斜坡之间的集水区剥蚀率和地貌度量，导致生长的前山的排水沟迁移，以适应构造条件。通过分析剥蚀率和地貌度量的沿前山沿变化，我们推断前山是通过横向生长和四个离散部分的链接而形成的。我们的研究阐明了独特地形的形成，并揭示了在与冲断有关的褶皱发展的早期阶段，结构在垂直和横向上如何扩大。