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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Paleomagnetism in the Precordillera of northern Chile (22 °30'S): implications for the history of tectonic rotations in the Central Andes
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Paleomagnetism in the Precordillera of northern Chile (22 °30'S): implications for the history of tectonic rotations in the Central Andes

机译：智利北部前陆（22°30'S）的古磁性：对安第斯中部构造旋转历史的启示

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Widespread clockwise rotations in Mesozoic and Lower Tertiary rocks of northern Chile have been interpreted as the sum of two rotational events separated in time: an early rotation related to local deformation plus a late rotation related to wholesale rotation of northern Chile linked to Late Cenozoic oroclinal bending in the Central Andes. In this paper we report new paleomagnetic data from Cretaceous, upper Oligocene and Miocene sedimentary rocks in the Precordillera of northern Chile. The results suggest that all these rocks acquired their remanence at or close to the time of deposition. The lack of rotation in undeformed lower Miocene strata clearly indicates that clockwise rotations found in underlying, faulted and folded Cretaceous rocks were completed before the Late Cenozoic. Results from nearby localities in deformed upper Oligocene strata would argue for little (～5 °) rotation since the late Oligocene. Data from widely separated Miocene localities covering an area of about 5000 km~2 in the Calama basin strongly suggest that northern Chile did not undergo significant wholesale rotation during the Late Cenozoic. This, together with previous paleomagnetic evidence against Neogene rigid-body-like rotation of the southern Peruvian forearc, suggests that the curved shape of the Central Andean forearc was not significantly enhanced during the Late Cenozoic. By inference, all of the rotation in most Mesozoic and Lower Tertiary rocks of northern Chile was accomplished in the Cretaceous and/or Early Cenozoic, when the locus of deformation in the Central Andes was localized in the present forearc region.
机译：智利北部中生代和下第三纪岩石中广泛的顺时针旋转被解释为时间上分开的两个旋转事件的总和：与局部变形有关的早期旋转加上与智利北部与新生代晚斜向弯曲有关的整体旋转有关的后期旋转在安第斯山脉中部。在本文中，我们报告了智利北部前岩的白垩纪，上渐新世和中新世沉积岩的新古磁数据。结果表明，所有这些岩石在沉积时或接近沉积时都获得了剩磁。未变形的下中新世地层缺乏旋转，这清楚地表明，在下，新生代之前，在下伏，断裂和折叠的白垩纪岩石中发现的顺时针旋转已经完成。上渐新世变形地层附近地区的结果表明，自渐新世晚期以来几乎没有旋转（〜5°）。来自卡拉马盆地约5000 km〜2的中新世地区的广泛数据强烈表明，智利北部在新生代末期没有发生明显的整体旋转。这与先前针对秘鲁南部前臂的新近纪刚性体旋转的古地磁证据一起，表明安第斯中部前臂的弯曲形状在新生代晚期并未得到明显增强。据推论，智利北部大多数中生代和下第三纪岩石的所有旋转都是在白垩纪和/或早新生代完成的，当时安第斯山脉中部的变形轨迹位于目前的前臂地区。

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