Exhumation along the Fairweather fault, southeastern Alaska, based on low‐temperature thermochronometry
Exhumation along the Fairweather fault, southeastern Alaska, based on low‐temperature thermochronometry
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基于低温测时法的沿阿拉斯加东南部费尔韦瑟断层的折返
DOI：
10.1029/2007tc002240
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发表时间：
2009
期刊：
影响因子：
4.2
通讯作者：
Aaron Berger
中科院分区：
文献类型：
--
作者：
R. McAleer;J. Spotila;E. Enkelmann;Aaron Berger
阿拉斯加南部的构造结标志着>1000公里长的太平洋-北美转换边缘和楚加奇-圣。伊莱亚斯带，俯冲和俯冲加积驱动快速会聚变形和岩石隆升。新的低温热年代测定法显示，强烈的造山变形并不局限于构造结的一侧，而是沿着右向费尔韦瑟断层向南沿着近300公里。磷灰石和锆石（U-Th）/He年龄为0.9和2.0 Ma，表明在费尔韦瑟断层附近（<10 km）的最大折返速率接近2 mm/a，沿整个板块边缘的平均折返速率沿着为>0.5 mm/a。我们估计，长期的岩石隆起可容纳该地区的断层-正常收敛量为1.3 mm/a。这表明费尔韦瑟断层是轻微的逆冲和高度分割，类似于中央圣安德烈亚斯断层。这种会聚仅占太平洋板块运动和大陆边缘之间的近距离的1/5，然而，这意味着沿着近海过渡断层沿着1-2 cm/a的逆冲-左旋运动弥补了不足。此外，热年代测定法显示，基岩冷却的显着增加与重冰川作用的开始相一致，类似于在太平洋西北部其他地区观察到的情况。然而，构造活跃的费尔韦瑟走廊的特点是自上新世气候变化以来的加速幅度和折返深度。
The southern Alaskan syntaxis marks the spectacular junction between the >1000‐km‐long Pacific–North America transform margin and the Chugach–St. Elias belt, where subduction and terrane accretion drive rapid convergent deformation and rock uplift. New low‐temperature thermochronometry reveals that intense orogenic deformation is not restricted to one side of the syntaxis but extends nearly 300 km south along the dextral Fairweather fault. Apatite and zircon (U‐Th)/He ages as young as 0.9 and 2.0 Ma suggest maximum exhumation rates of nearly 2 mm/a in close proximity (<10 km) to the Fairweather fault and average exhumation rates of >0.5 mm/a along the entire plate margin. We estimate that long‐term rock uplift accommodates ∼3 mm/a of fault‐normal convergence in this area. This suggests that the Fairweather fault is slightly transpressive and highly partitioned, analogous to the central San Andreas fault. This convergence only accounts for ∼1/5 of the obliquity between Pacific plate motion and the continental margin, however, implying the deficit is taken up by 1–2 cm/a thrust‐sinistral motion along the offshore Transition fault. Additionally, thermochronometry shows a marked increase in bedrock cooling coincident with onset of heavy glaciation, similar to what has been observed in other parts of the Pacific Northwest. The tectonically active Fairweather corridor is distinguished, however, by the magnitude of the acceleration and the depth of exhumation since Pliocene climate change.