Abstract The geological record of the eastern Sierras Pampeanas province, in the modern Andean broken foreland of Argentina can be divided into four main events: (1) Proterozoic to early Paleozoic collisional tectonics, (2) middle-late Paleozoic anorogenic magmatism, relief generation and glacial paleovalley formation followed by (3) a classical foreland filling in the Permian and two proximal alluvial sedimentation associated with (3) Cretaceous rifting and (4) Neogene intermontane foreland accumulation. The region lacks Silurian, Triassic and Jurassic records, commonly associated with unknown deformation and/or no-sedimentation stages (bypass zone?). In this work, we analyzed the Mesozoic (Triassic-Jurassic) Pampean unconformity, using low-temperature thermochronological modelling. After a rapid Carboniferous cooling track, a Triassic reheating followed by a slow Jurassic to Cretaceous cooling. Considering that (1) no Triassic basins have been described to date in the eastern Sierras Pampeanas (i.e., reheating cannot be related to burial), (2) coeval surface heat flows are anomalously high in western Sierras Pampeanas, in the Ischigualasto basin, and (3) our petrogenetic modelling on Triassic basalts evidence mantle potential temperatures of ~1350–1400 °C (i.e., the heat source cannot be related with an anomalously high basal heat flows and/or mantle plumes); we interpreted the formation of the Mesozoic unconformity as a result of ridge collision and slab window formation, followed by slab rollback. Both processes might have affected not only the surface heat flow but also triggered a lithospheric thickness reduction, which drove isostatic rebound. In this context, the Jurassic history of the unconformity could be associated with cooling by erosion and exhumation until the Cretaceous, when the region was under extension. Our model agrees with other observations like the formation of back-arc hydrocarbon-productive Triassic-Jurassic depocenters to the west (Cuyo and Ischigualasto basins) and the magmatic evolution, from 28° to 34° SL, described along the Chilean margin.

中文翻译：

---

冈瓦纳大陆西部前陆的三叠纪-侏罗纪热演化和折返：阿根廷潘佩纳山脉的热年代学和玄武岩热气压测量

摘要 阿根廷现代安第斯破碎前陆山脉潘佩纳斯山脉东部的地质记录可分为四个主要事件：(1) 元古代至早古生代碰撞构造，(2) 中晚古生代非造山岩浆作用、地貌生成和冰川古谷形成，然后是 (3) 二叠纪的经典前陆充填和与 (3) 白垩纪裂谷和 (4) 新近纪山间前陆堆积相关的两个近端冲积沉积。该地区缺乏志留纪、三叠纪和侏罗纪记录，通常与未知的变形和/或无沉积阶段（旁路带？）有关。在这项工作中，我们使用低温热年代学模型分析了中生代（三叠纪-侏罗纪）潘潘不整合面。经过石炭纪的快速冷却轨迹，a 三叠纪再加热，随后侏罗纪至白垩纪缓慢冷却。考虑到 (1) 迄今为止，在潘佩纳山脉东部尚未描述三叠纪盆地（即，再加热与埋藏无关），(2) 在伊斯基瓜拉斯托盆地的潘佩纳山脉西部，同时期地表热流异常高，以及(3) 我们对三叠纪玄武岩的成岩模型表明地幔潜在温度约为 1350–1400 °C（即热源不能与异常高的基底热流和/或地幔柱有关）；我们将中生代不整合的形成解释为脊碰撞和板片窗口的形成，然后是板片回滚。这两个过程可能不仅影响了地表热流，还引发了岩石圈厚度减少，从而推动了等静压回弹。在这种情况下，不整合面的侏罗纪历史可能与侵蚀和剥脱导致的冷却有关，直到白垩纪，当该地区处于扩张状态时。我们的模型与其他观察结果一致，例如西部（Cuyo 和 Ischigualasto 盆地）弧后产烃三叠纪-侏罗纪沉积中心的形成以及沿智利边缘描述的从 28° 到 34° SL 的岩浆演化。