Abstract One of the most conspicuous features of the Andean chain is the change in its trajectory from NW-SE to N-S at 18°S known as the Bolivian Orocline. Although the Central Andes rotation pattern (CARP) agrees roughly with the geometry of the orocline, large variations and greater than expected rotation magnitudes cannot be explained by a progressive oroclinal bending history alone. In this work, 621 oriented samples from Mesozoic and Cenozoic rocks in three different areas in the Precordillera of northern Chile, north of Calama, were analyzed. The samples were subjected to different demagnetization processes to isolate the characteristic magnetic remanence and calculate the tectonic rotations. By sampling pretectonic, syntectonic and post-tectonic units, the rotation history of different structural blocks was determined and related to specific deformational events. The results obtained from Lower Cretaceous units intruded or overlain by Upper Cretaceous units not rotated or recording smaller rotations indicate the existence of 20° clockwise and 20° counterclockwise rotated sites related to the Late Cretaceous Peruvian orogenic event. Data obtained from Upper Cretaceous-lowermost Paleocene rocks show areas slightly clockwise rotated (10–15°) and not rotated during the early Paleocene “K-T" deformation event. Remanence data from Upper Cretaceous-Eocene units across the area indicate as much as 20° clockwise rotation in the hanging wall of the Eocene Chintoraste-Quetena-Rabonas-Jaspe Reverse Fault System, whereas the footwall was unaffected. This Eocene rotation occurred during the early stages of the Eocene-Oligocene Incaic orogenic phase, prior to emplacement of the 40–37 Ma Fortuna Granodiorite Complex. Current models propose that rotations in CARP were entirely Cenozoic and largely accomplished in a single Paleogene event. Our data indicate that each of the Peruvian, K-T and Incaic deformation events contributed to CARP, with each event generating a non-uniform pattern of rotations which was superimposed on prior rotations in a non-uniform manner.

中文翻译：

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来自智利北部 Precordillera 的古地磁数据：与多相变形历史相关的多相旋转历史

摘要 安第斯链最显着的特征之一是其轨迹在 18°S 处从 NW-SE 到 NS 的变化，称为玻利维亚 Orocline。尽管中央安第斯山脉旋转模式 (CARP) 与斜斜的几何形状大致一致，但仅靠渐进的斜斜历史不能解释大的变化和大于预期的旋转幅度。在这项工作中，分析了来自智利北部 Precordillera 和 Calama 北部三个不同地区的中生代和新生代岩石的 621 个定向样品。对样品进行不同的退磁过程以分离特征剩磁并计算构造旋转。通过对前构造、同构造和后构造单元进行采样，确定了不同结构块的旋转历史并与特定的变形事件相关。从上白垩统未旋转或记录较小旋转的单元侵入或覆盖的下白垩统单元获得的结果表明，存在与晚白垩世秘鲁造山事件相关的顺时针 20°和逆时针旋转 20°的地点。从上白垩世-最低古新世岩石获得的数据显示，在早古新世“KT”变形事件期间，区域略微顺时针旋转（10-15°）并且没有旋转。来自该地区上白垩世-始新世单元的剩磁数据显示高达 20°始新世 Chintoraste-Quetena-Rabonas-Jaspe 逆断层系统的上盘顺时针旋转，而下盘不受影响。这种始新世旋转发生在始新世-渐新世印加造山阶段的早期阶段，在 40-37 Ma 的福尔图纳花岗闪长岩复合体就位之前。目前的模型表明，CARP 的旋转完全是新生代的，并且主要是在单个古近纪事件中完成的。我们的数据表明，秘鲁、KT 和印加语变形事件中的每一个都对 CARP 做出了贡献，每个事件都产生了不均匀的旋转模式，并以非均匀的方式叠加在先前的旋转上。