The Andes are thought to be formed through discrete contractional stages separated by periods of little to no orogenic construction. This paper analyzes the intervals between the main contractional phases that built the Southern Central Andes between 35° and 37°S in order to determine whether they were characterized by neutral, contractional or extensional conditions. During an interruption in orogenesis between the Late Cretaceous and the Miocene shortening phases, two extensional stages are recorded through the opening of a series of intra- and retro-arc basins. U-Pb dating of detrital zircons in a sample collected from the Los Ángeles unit, a syn-extensional volcano-sedimentary succession located at ∼35°40'S along the Chile and Argentina international border, provided a maximum depositional age of 67.1 +2.4/−0.9 Ma. This age, in association with evidence of regional crustal thinning, suggests a previously unrecognized extensional phase during latest Cretaceous times. Limited shortening succeeded this extensional event and was followed by a second extensional episode during late Oligocene and earliest Miocene times. While the first extensional event was restricted to the core of the Late Cretaceous orogen, the second episode affected a wide area ranging between the present forearc and retroarc areas. A structural section across the Malargüe fold-thrust belt at ∼36°S indicates inversion of normal faults where extension was focused and new thrust generation in areas not affected by extensional deformation. Our data reveal that the growth of the Southern Central Andes is the product of a complex alternation of contractional and extensional phases, with inherited structures playing a role in their tectonic evolution. A comparison with other Cordilleran orogenic systems such as the Puna-Altiplano plateau, the northern Peruvian Andes and the North American Sevier-Laramide orogenic belt, suggests that extensional deformation in the Southern Central Andes responds better to changes in plate kinematics, rather than to localized events within a continuous contractional setting.

中文翻译：

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中南部安第斯山脉的交替收缩和伸展（35°–37°S）

安第斯山脉被认为是通过离散的收缩阶段形成的，这些阶段被很少或没有造山运动的时期分开。本文分析了在 35°和 37°S 之间建造中南部安第斯山脉的主要收缩阶段之间的间隔，以确定它们是否具有中性、收缩或伸展条件的特征。在晚白垩世和中新世缩短阶段之间的造山作用中断期间，通过一系列弧内和弧后盆地的开口记录了两个伸展阶段。从洛杉矶单元收集的样品中碎屑锆石的 U-Pb 年代测定提供了最大沉积年龄为 67.1 +2.4/− 的同延火山沉积序列，位于~35°40'S 沿智利和阿根廷国际边界0.9 毫安。这个年纪，与区域地壳变薄的证据相关，表明在白垩纪晚期有一个以前未被认识的伸展阶段。有限的缩短接替了这一伸展事件，随后在渐新世晚期和中新世最早时期发生了第二次伸展事件。虽然第一次伸展事件仅限于晚白垩世造山带的核心，但第二次事件影响了当前弧前区和弧后区之间的广泛区域。Malargüe 褶皱冲断带在～36°S 的构造剖面表明正断层反转，其中伸展集中，并且在不受伸展变形影响的区域产生了新的逆冲断层。我们的数据显示，中南部安第斯山脉的增长是收缩和伸展阶段复杂交替的产物，继承结构在其构造演化中发挥作用。与其他科迪勒拉造山系统，如普纳-高原高原、秘鲁北部安第斯山脉和北美塞维尔-拉拉米特造山带的比较表明，中南部安第斯山脉的伸展变形对板块运动学的变化反应更好，而不是对局部的连续收缩环境中的事件。