Abstract The Iglesia basin hosts a key sedimentary archive of the evolution of the southern Central Andes. This basin is classically interpreted as recording the transition from an outer- to an inner-wedge-top (piggyback basin) depozone in the early Bermejo foreland basin system. In this study, we reevaluate the tectonic evolution of the Iglesia basin based on the interpretation of 2D seismic reflection data, structural geology, zircon U Pb geochronology, and provenance analysis. We report an extensional event that initiated the basin opening. Our results indicate normal faulting development and synextensional deposition from the latest Oligocene (?)-earliest Miocene to middle Miocene. Since the middle Miocene, extensional activity experienced a progressive decrease in changing to shortening and basin inversion between the middle-late Miocene. The latter stage coincided with the full development of Pampean flat-slab subduction indicating maximum plate coupling at that time. Our findings challenge the idea of uninterrupted Paleogene to Neogene flexural subsidence related to the Andean orogenic-load in the backarc area. Therefore, the results of this study have important consequences for the early evolution of the Bermejo foreland basin and ultimately, for the growth of the southern Central Andes.

中文翻译：

---

中安第斯山脉南部的伊格莱西亚盆地：前陆盆地楔顶沉积前弧后伸展的记录

摘要 伊格莱西亚盆地拥有中安第斯山脉南部演化的重要沉积档案。该盆地被经典地解释为记录了早期 Bermejo 前陆盆地系统中从外部到内部楔形顶部（背负式盆地）沉积带的转变。在这项研究中，我们根据二维地震反射数据的解释、构造地质学、锆石 U Pb 年代学和物源分析，重新评估了伊格莱西亚盆地的构造演化。我们报告了引发盆地开放的伸展事件。我们的结果表明从最新的渐新世 (?)-最早的中新世到中新世的正常断层发育和同伸沉积。中中新世以来，中新世中晚期伸展活动逐渐减少，向缩短和盆地反转转变。后一阶段恰逢潘佩斯平板俯冲全面发展，表明当时板块耦合最大。我们的研究结果挑战了与弧后地区安第斯造山带载荷相关的古近纪至新近纪连续弯曲沉降的观点。因此，这项研究的结果对 Bermejo 前陆盆地的早期演化以及最终对中安第斯山脉南部的生长具有重要影响。