Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47°S), Chile
Tectonic control on rock uplift, exhumation, and topography above an oceanic ridge collision: Southern Patagonian Andes (47°S), Chile
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DOI：
10.1002/2016tc004120
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发表时间：
2016-06-01
期刊：
影响因子：
4.2
通讯作者：
Strecker, Manfred R.
中科院分区：
文献类型：
--
作者：
Georgieva, Viktoria;Melnick, Daniel;Strecker, Manfred R.
会聚边缘的测深异常俯冲可以深刻影响俯冲动力学、岩浆作用以及上方板块的结构和地貌演化。北巴塔哥尼亚冰原 (NPI) 位于智利三重交汇点以东，南纬 47 度附近，智利海隆扩张中心与南美洲碰撞于此。该地区的特点是山顶海拔和地形的突然增加，这在地球动力学与冰川侵蚀对地形的影响的背景下一直存在争议。在这里，我们提供了地貌、热年代学和结构数据，这些数据记录了沿着 NPI 两侧迄今未被识别的断层的新构造活动。新的磷灰石 (U-Th)/He 基岩冷却年龄表明自 2-3 Ma 以来就有断层。我们推断，由于智利隆起三个连续段的紧密碰撞，斜向板块辐合的增强分区导致了一条类似于 140 公里长的弧前条子（NPI 块体）向北平移。在该模型中，NPI 地块北前缘的 Exploradores 逆冲断层的上盘发生了较大的隆起，而 Cachet 和 Liquine-Ofqui 右旋断层分别沿 NPI 地块的东侧和西侧解耦。局部伸展可能发生在其南部后缘，沿着正断层，与边缘平行伸展、构造沉降和沿安第斯山脊线的较低海拔有关。我们的新构造模型为智利三重交界处内陆的突变地形变化提供了新颖的解释，并强调了当地构造运动对冰川景观折返和地形模式的基本影响。
The subduction of bathymetric anomalies at convergent margins can profoundly affect subduction dynamics, magmatism, and the structural and geomorphic evolution of the overriding plate. The Northern Patagonian Icefield (NPI) is located east of the Chile Triple Junction at similar to 47 degrees S, where the Chile Rise spreading center collides with South America. This region is characterized by an abrupt increase in summit elevations and relief that has been controversially debated in the context of geodynamic versus glacial erosion effects on topography. Here we present geomorphic, thermochronological, and structural data that document neotectonic activity along hitherto unrecognized faults along the flanks of the NPI. New apatite (U-Th)/He bedrock cooling ages suggest faulting since 2-3 Ma. We infer the northward translation of an similar to 140 km long fore-arc sliver-the NPI block-results from enhanced partitioning of oblique plate convergence due to the closely spaced collision of three successive segments of the Chile Rise. In this model, greater uplift occurs in the hanging wall of the Exploradores thrust at the northern leading edge of the NPI block, whereas the Cachet and Liquine-Ofqui dextral faults decouple the NPI block along its eastern and western flanks, respectively. Localized extension possibly occurs at its southern trailing edge along normal faults associated with margin-parallel extension, tectonic subsidence, and lower elevations along the Andean crest line. Our neotectonic model provides a novel explanation for the abrupt topographic variations inland of the Chile Triple Junction and emphasizes the fundamental effects of local tectonics on exhumation and topographic patterns in this glaciated landscape.