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Using spatial patterns of fluvial incision to constrain continental-scale uplift in the Andes
Global and Planetary Change ( IF 3.9 ) Pub Date : 2020-03-01 , DOI: 10.1016/j.gloplacha.2020.103119
L.A. Evenstar , A.E. Mather , A.J. Hartley

Abstract Geomorphic archives, particularly longitudinal river profiles, are increasingly used as a proxy to reconstruct uplift rates in mountainous regions. Within the Atacama Desert, Northern Chile, slow, long-term erosion creates exceptional preservation of fluvial and alluvial surfaces. This enables river incision patterns to be used on a continental-scale (>250 km) along the western margin of the Andes (18°00'S to 20°15′S) and over a time frame from Miocene to Present day. The data show marked compartmentalisation of fluvial system behaviour with changes in incision rates from south to north creating 3 distinctly different regions. Within these different sectors, incision rates are broadly consistent between rivers suggesting a regional rather than a river specific control on rates. In Sector 1 (18°05′S to 19°20'S) the fluvial systems are exorheic with a terminal base level (the lowest base level to which the river system can erode) in the Pacific Ocean and span the Coastal Cordillera, Longitudinal Valley, Precordillera and western edge of the Western Cordillera. This constrains the total uplift over these regions to a minimum of 1200 m in 11 Myr with incision rates of ~200–120 m/Myr consistent with rapid but sustained uplift of the Andes in the Late Miocene. In Sector 2 (19°20'S to 19°50'S), to the immediate south, the rivers are shorter and terminate in the Longitudinal Valley, spanning only the Longitudinal Valley, Precordillera and the western edge of the Western Cordillera with lower incision rates of 100–50 m/Myr. Comparison of incision rates between Sector 1 and 2 can constrain the uplift of the Coastal Cordillera to 60 m/Myr which is in keeping with previous studies from the region. In southernmost Sector 3 (19°50'S to 20°10'S), the fluvial systems terminate in the Longitudinal Valley and span only the Longitudinal Valley and eastern part of the Precordillera with low incision rates of 50 to 25 m/Myr. Differences between Sectors 2 and 3 are attributable to drainage loss by tectonic beheading of catchments through uplift of the Cordillera de Domeyko fault system, placing a minimum constrain on uplift in this region of 50 to 25 m/Myr. This study demonstrates the applicability of large-scale fluvial archives to access not just the timing of uplift on a continental scale, but also the relative uplift of individual tectonic provinces.

中文翻译:

使用河流切口的空间模式来限制安第斯山脉的大陆尺度隆升

摘要 地貌档案,尤其是纵向河流剖面,越来越多地被用作重建山区抬升率的代理。在智利北部的阿塔卡马沙漠,缓慢、长期的侵蚀为河流和冲积表面创造了特殊的保护。这使得河流切口模式能够在沿安第斯山脉西缘(18°00'S 至 20°15'S)以及从中新世至今的时间范围内在大陆尺度(>250 公里)上使用。数据显示了河流系统行为的显着划分,从南到北的切割率发生了变化,形成了 3 个截然不同的区域。在这些不同的部门中,河流之间的切割速率大体上是一致的,这表明对速率的控制是区域性的,而不是特定于河流的。在扇区 1(18°05'S 到 19°20' S) 河流系统是外流的,在太平洋有一个终端基准面(河流系统可以侵蚀到的最低基准面),跨越沿海科迪勒拉山脉、纵向谷、前科迪勒拉山脉和西科迪勒拉山脉的西部边缘。这将这些地区的总抬升限制在 11 Myr 中至少为 1200 m,切割速率约为 200-120 m/Myr,与晚中新世安第斯山脉的快速但持续抬升一致。在第 2 区(19°20'S 至 19°50'S),紧邻南部,河流较短并终止于纵向谷,仅跨越纵向谷、前科迪勒拉和西科迪勒拉的西部边缘,切割率较低,为 100 –50 m/Myr. 比较第 1 区和第 2 区的切入率可以将沿海山脉的抬升限制在 60 m/Myr,这与该地区先前的研究一致。在最南端的第 3 区(19°50'S 至 20°10'S),河流系统终止于纵向谷,仅跨越纵向谷和 Precordillera 东部,切割速率低,为 50 至 25 m/Myr。第 2 区和第 3 区之间的差异可归因于通过 Cordillera de Domeyko 断层系统的隆起对集水区进行构造截断造成的排水损失,在该区域对隆起的最小限制为 50 至 25 m/Myr。这项研究证明了大规模河流档案不仅可以访问大陆尺度上的隆起时间,还可以访问各个构造省的相对隆起时间。
更新日期:2020-03-01
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