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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 >Architecture, kinematics, and exhumation of a convergent orogenic wedge: A thermochronological investigation of tectonic-climatic interactions within the central St. Elias orogen, Alaska
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Architecture, kinematics, and exhumation of a convergent orogenic wedge: A thermochronological investigation of tectonic-climatic interactions within the central St. Elias orogen, Alaska

机译：会聚的造山楔的构造，运动学和掘出：阿拉斯加中部圣伊莱亚斯造山带中部构造-气候相互作用的热年代学调查

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The kinematics and architecture of orogenic systems along the leading edges of accreting terranes may be heavily influenced by climate, but little research has been devoted to the long-term effects of glacial erosion on orogenesis. Here we use low-temperature apatite and zircon (U-Th)/He and fission-track thermochronometry. along with subsidiary structural relationships and seismicity, to develop a new architectural model of the St. Elias orogen in southern Alaska, which is one of the best examples of a glaciated orogenic wedge worldwide. These data illustrate that the orogen consists of a deformational backstop on the leeward flank and a rapidly deforming and eroding, thin-skinned fold and thrust belt on the windward flank. A structure beneath the Bagley ice field separates these distinct deformational domains, which we propose is a backthrust that makes the orogen doubly-vergent. Thermochronometry within the orogenic wedge suggests that denudation and deformation are strongly influenced by glacial erosion. Long-term exhumation, at rates of up to 4 mm/yr, is concentrated within a narrow zone along the windward flank, where glacier equilibrium lines intersect the orogenic wedge. The onset of enhanced glaciation also coincided with a marked acceleration in exhumation across the orogenic wedge, accelerated backthrust motion, and a major shift in deformation away from the North American-Yakutat terrane suture (Chugach St. Elias fault). We propose that accelerated glacial erosion forced the redistribution of strain along the backthrust and an en echelon array of forethrusts that lie beneath the zone of heaviest glaciation, which in turn are systematically truncated by the backthrust. This focusing of deformation matches predictions from analytical models of orogenic wedges and implies a high degree of coupling between climate and tectonics in this glacially-dominated orogen.
机译：沿吸积地带前沿的造山系统的运动学和构造可能受到气候的严重影响，但很少有研究致力于冰川侵蚀对造山的长期影响。在这里，我们使用低温磷灰石和锆石（U-Th）/ He和裂变径迹热计时。连同辅助的结构关系和地震活动性一起，开发了阿拉斯加南部圣埃利亚斯造山带的新建筑模型，这是全球冰川造山楔的最好例子之一。这些数据表明，造山带由下风向侧面的形变逆止带和上风向侧面的快速变形和侵蚀，薄皮褶皱和逆冲带组成。巴格利冰场下方的结构将这些不同的变形区域分开，我们提出的是使造山带成倍增加的逆冲作用。造山楔内的温度测年表明，剥蚀和变形受到冰川侵蚀的强烈影响。长期掘尸以每年4毫米的速率集中在沿迎风翼的狭窄区域内，冰川平衡线与造山楔相交。冰川作用增强的开始还与穿过造山楔的掘出明显加速，逆冲运动加快以及变形远离北美-雅库塔特地层缝合线（Chugach St. Elias断层）发生了重大变化有关。我们认为，加速的冰川侵蚀迫使应力沿着后推力重新分布，并且在最重的冰川作用带下方的一排梯队阵列的前推力又被后推力系统地截断了。这种对变形的关注与造山楔分析模型的预测相符，并暗示了在这个以冰川为主的造山带中气候与构造之间的高度耦合。

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