Oblique-slip along transform fault boundaries is often partitioned between a strike-slip system and thrust faults that accommodate contraction. However, topography along the Yakutat-North American transform (Fairweather fault), is asymmetric with low-terrain above active thrusts on the western, Yakutat side of the transform and high topography on the continental side with peaks >4500 m (Mount Fairweather: 4671 m) to the west of the Border Ranges fault, limited recorded earthquakes >M4, and no apparent reverse faults to generate the highest terrain. In this study we compile, for the first time, published U-Pb zircon, Ar/Ar and K-Ar (hornblende, muscovite, and biotite) and U-Th/He and fission-track (zircon and apatite) bedrock ages (109) from 75 samples to investigate the exhumation history of the Fairweather Range region, complemented by a published detrital sample (ZFT and AFT) and 13 new Ar/Ar (hornblende, biotite, and K-feldspar) ages on 9 bedrock samples from both sides of the Fairweather fault. Additionally, we examined published seismicity and geodetic data of the Fairweather region and assessed if plate paleo-vectors correlate with the cooling history of the Fairweather Range. Cooling age, seismic, and block-motion patterns indicate the Fairweather Range has been vertically extruded between the Fairweather and the Border Ranges faults as a coherent block since ca. 25 Ma. The pre-6 Ma Pacific plate motion (N30°W) aligns with the N33°W strike of the Fairweather Fault whereas a hypothetical pre-6 Ma Yakutat microplate paleo-vector of (N39°W) does not: indicating a post-6 Ma timing for Yakutat microplate counter-clockwise rotation (9°). We infer that rotation and impingement of the Yakutat microplate along the Fairweather fault at ca. 3 Ma led to the development of the Fairweather restraining bend and increased cooling rates. The resultant thickened Fairweather welt and the ∼30 km thick southeast end of the Yakutat microplate compounded double-indenter tectonics into Alaska's southeast convergent corner

中文翻译：

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费尔韦瑟变换渐新世边界以呈现造山作用：费尔韦瑟范围垂直挤压和雅库塔特微板块的旋转。 3马


沿转换断层边界的斜滑通常分为走滑系统和适应收缩的逆冲断层。然而，沿雅库塔特-北美转换（费尔韦瑟断层）的地形是不对称的，转换的西侧雅库塔特一侧的活动逆冲断层上方地势较低，而大陆一侧的地势较高，山峰 > 4500 米（费尔韦瑟山：4671 m) 在边界山脉断层以西，记录的>M4地震有限，并且没有明显的逆断层产生最高地形。在这项研究中，我们首次汇编了已发表的 U-Pb 锆石、Ar/Ar 和 K-Ar（角闪石、白云母和黑云母）以及 U-Th/He 和裂变径迹（锆石和磷灰石）基岩年龄（ 109）从 75 个样本中调查了 Fairweather Range 地区的折返历史，并辅以已发表的碎屑样本（ZFT 和 AFT）以及来自这两个地区的 9 个基岩样本的 13 个新的 Ar/Ar（角闪石、黑云母和钾长石）年龄。费尔韦瑟断层两侧。此外，我们还检查了费尔韦瑟地区已发表的地震活动和大地测量数据，并评估了板块古矢量是否与费尔韦瑟山脉的冷却历史相关。冷却年龄、地震和块体运动模式表明，自大约 1970 年以来，费尔韦瑟山脉一直在费尔韦瑟断层和边界山脉断层之间垂直挤压，成为一个连贯的块体。 25 马。 6 Ma 之前的太平洋板块运动 (N30°W) 与 Fairweather 断层的 N33°W 走向一致，而假设的 6 Ma 之前的 Yakutat 微板块古矢量 (N39°W) 则不然：表明 6 Ma 后的板块运动Ma 计时 Yakutat 微孔板逆时针旋转 (9°)。我们推断雅库塔特微板块沿费尔韦瑟断层的旋转和撞击大约在 3 Ma 导致了 Fairweather 约束弯曲的发展并提高了冷却速率。 由此产生的加厚的 Fairweather 沿带和约 30 公里厚的 Yakutat 微板块东南端将双压头构造复合到阿拉斯加的东南汇聚角