Abstract Thick- and thin-skinned “hybrid” thrust belts are typically developed in areas where crustal shortening was preceded by extension and normal faulting. They have been recognized in many places within the Central Andean backarc regions of Peru, Argentina, and Bolivia. In contrast, these structures have not been broadly studied in forearc regions. To understand the geometry and kinematics of this style of tectonism in a forearc setting related to Andean-type subduction zones, we used field and industrial 2D seismic data to study the Potrerillos thrust and fold belt and the Salar de Pedernales Basin in northern Chile (26°S). Our results indicate that the structure in this region consists of a dominantly east-verging contracting system composed of large basement thrusts, Mesozoic inverted normal faults, and shallow thrust-related folds. Large basement thrust ramps and imbricated wedges represent the most prominent basement structures, which accommodated major crustal shortening. Reactivated and tectonically inverted Mesozoic extensional structures also constitute an important structural component, especially beneath the Salar de Pedernales Basin. These exhibit asymmetrical inverted anticlines with arrowhead shapes on the hanging walls of the inverted normal faults. The subsidiary shallow thrust-related folds commonly display fault bend and propagation folds that primarily accommodated the shortening of the Mesozoic and Cenozoic stratified deposits overlying the basement thrusts and cored anticlines. The age of the contraction in this region is poorly constrained; however, many of the oldest sequences accumulated in the top of the syn-rift sequences and related to synorogenic deposits, can be correlated with those identified in neighboring regions (e.g., Salar de Atacama, Salar de Punta Negra basins and Frontal Cordillera, among others), which have reported Upper Cretaceous ages. Based on this stratigraphic correlation we suggest that orogenesis may have begun in the Late Cretaceous with basin inversion, and then continued during the Cenozoic with basement thrusting.

中文翻译：

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弧内前缘混合冲断带的几何形状和发育：来自智利北部安第斯中部的 Potrerillos 带的见解

摘要 厚皮和薄皮“混合”逆冲带通常发育在地壳缩短之前有伸展和正断层作用的地区。它们在秘鲁、阿根廷和玻利维亚的中部安第斯弧后地区的许多地方都得到了认可。相比之下，这些结构尚未在弧前区域得到广泛研究。为了了解与安第斯型俯冲带相关的前弧环境中这种构造运动的几何学和运动学，我们使用现场和工业二维地震数据来研究智利北部的 Potrerillos 逆冲褶皱带和 Salar de Pedernales 盆地（26 °S)。我们的研究结果表明，该地区的构造主要由大型基底逆冲断层、中生代倒置正断层和浅层逆冲断层构成的东向收缩系统组成。大型基底逆冲斜坡和叠瓦状楔形代表了最突出的基底结构，它们适应了主要的地壳缩短。重新激活和构造倒置的中生代伸展构造也是重要的构造组成部分，尤其是在佩德纳莱斯盆地下方。这些在倒转正断层的上壁上表现出不对称的倒背斜，带有箭头形状。附属的浅层逆冲褶皱通常显示断层弯曲和扩展褶皱，主要适应覆盖基底逆冲断层和取芯背斜的中、新生代层状沉积物的缩短。该地区收缩的年龄限制很差；然而，在同裂谷层序顶部积累的许多最古老的层序与同生沉积物有关，可以与邻近地区（例如，阿塔卡马盐沼、蓬塔内格拉盐沼和额叶山脉等）确定的序列相关联，已经报道了上白垩纪时代。基于这种地层对比，我们认为造山作用可能始于晚白垩世盆地反转，然后在新生代基底逆冲期间继续。