Abstract Two tectonic shortening events created the first-order structural characteristics of the Puna plateau: one in the Paleozoic and a second during the Andean Orogeny in the Cenozoic. To constrain the structural characteristics and timing of Andean deformation in the Puna plateau, we focus on differentiating these two shortening events and provide cooling ages (apatite fission track and apatite (U–Th)/He) to determine the amount of Andean exhumation on the hanging-wall of major Cenozoic faults. Two contrasting expressions of shortening are documented. In Ordovician strata, strain requires four stages: folding, flattening through cleavage formation, low-angle faulting and local distributed shear. In the Mesozoic and Cenozoic strata, shortening is expressed as reverse faults, fault-propagation folds and dipping panels. Dissimilarities reflect different P-T conditions and amount of strain, as structures in the Ordovician rocks require higher temperatures and strain than Andean structures in the Mesozoic and Cenozoic strata. Furthermore, local Cretaceous AFT cooling ages in pervasively cleaved Ordovician rocks reveal these rocks did not reach temperatures compatible with cleavage formation during the Andean event. Lastly, our data show a middle Eocene to Oligocene exhumation history that supports an overall continuous development of the Andean thrust belt in the Puna plateau since the early Cenozoic.

中文翻译：

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阿根廷西北部安第斯中部普纳高原的变形历史

摘要 两次构造缩短事件创造了普纳高原的一级构造特征：一次是古生代，一次是新生代安第斯造山运动。为了限制普纳高原安第斯变形的结构特征和时间，我们专注于区分这两个缩短事件并提供冷却年龄（磷灰石裂变轨迹和磷灰石（U-Th）/He）来确定安第斯高原上的安第斯折返量新生代主要断层的挂壁。记录了两种截然不同的缩短表达方式。在奥陶系地层中，应变需要四个阶段：折叠、劈理形成变平、低角度断层和局部分布剪切。在中、新生代地层中，缩短表现为逆断层、断层传播褶皱和倾斜板。差异反映了不同的 PT 条件和应变量，因为奥陶系岩石中的结构比中生代和新生代地层中的安第斯构造需要更高的温度和应变。此外，普遍劈裂的奥陶纪岩石中的局部白垩纪 AFT 冷却年龄表明，这些岩石在安第斯事件期间没有达到与劈理形成相容的温度。最后，我们的数据显示了中始新世至渐新世的挖掘历史，支持自新生代早期以来普纳高原安第斯冲断带的整体持续发展。普遍劈裂的奥陶纪岩石中的局部白垩纪 AFT 冷却年龄表明，这些岩石在安第斯事件期间没有达到与劈理形成相容的温度。最后，我们的数据显示了中始新世至渐新世的挖掘历史，支持自新生代早期以来普纳高原安第斯冲断带的整体持续发展。普遍劈裂的奥陶纪岩石中的局部白垩纪 AFT 冷却年龄表明，这些岩石在安第斯事件期间没有达到与劈理形成相容的温度。最后，我们的数据显示了中始新世至渐新世的挖掘历史，支持自新生代早期以来普纳高原安第斯冲断带的整体持续发展。