Spatial extent of rapid denudation in the glaciated St. Elias syntaxis region, SE Alaska
Spatial extent of rapid denudation in the glaciated St. Elias syntaxis region, SE Alaska
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DOI：
10.1002/jgrf.20136
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发表时间：
2013-09
期刊：
影响因子：
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通讯作者：
D. Grabowski;E. Enkelmann;T. Ehlers
中科院分区：
文献类型：
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作者：
D. Grabowski;E. Enkelmann;T. Ehlers
雅库塔特地体与北美板块的持续碰撞形成了阿拉斯加东南部的圣埃利亚斯山脉。先前发表的碎屑锆石裂变径迹测年的沙子大小的材料检测到非常快速的岩石剥蚀在圣埃利亚斯山脉的结区域，但快速折返的大小和空间范围是难以捉摸的，由于冰川覆盖，抑制直接基岩研究。提出了两种可能的机制来解释苏厄德-马拉斯皮纳冰川下发生的快速剥蚀，这两种机制在快速挖出的岩石的空间范围上有所不同。本研究评估了圣埃利亚斯结区快速剥蚀的空间范围。我们研究了马拉皮纳冰川的鹅卵石大小的物质。岩石学分类被用作一种物源工具，并结合锆石和钛铁矿（U-Th）/He分析，以揭示冰川碎屑的冷却速率。总共有1998个鹅卵石被分类在该领域。对91个薄片进行了岩相学表征，并测量了59个鹅卵石的（U-Th）/He年龄。14个卵石显示3-2 Ma的年轻冷却年龄，来自未变形和变形的岩浆岩和变质岩的各种岩性。老年人口在12、27和36 Ma达到峰值。冷却年龄和映射已知程度的不同岩性表明，一个更大的，然后以前假设的面积的圣埃利亚斯结地区经历了快速折返。快速的岩石折返延伸到接触断层之外，包括苏厄德-马拉斯皮纳冰川集水区的大部分。
The ongoing collision of the Yakutat Terrane with the North American Plate formed the St. Elias Range in southeastern Alaska. Previously published detrital zircon fission track dating of sand‐size material detected very rapid rock denudation within the syntaxis region of the St. Elias Range, but the size and spatial extent of the rapid exhumation are elusive due to the glacial cover that inhibits direct bedrock studies. Two possible mechanisms were suggested to explain the rapid denudation occurring underneath the Seward‐Malaspina Glacier, which differ in their spatial extent of rapidly exhumed rocks. This study evaluates the spatial extent of rapid denudation at the St. Elias syntaxis region. We investigate the cobble‐sized material of the Malaspina Glacier. Petrological classifications are used as a provenance tool and combined with zircon and titanite (U‐Th)/He analysis to reveal cooling rates of the glacial detritus. In total, 1998 cobbles are classified in the field. Petrographic characterization is conducted on 91 thin sections and the (U‐Th)/He ages of 59 cobbles are measured. Fourteen cobbles reveal young cooling ages of 3–2 Ma originating from various lithologies of undeformed and deformed magmatic and metamorphic rocks. Older age populations peak at 12, 27, and 36 Ma. The cooling ages and the mapped known extent of the different lithologies suggest that a larger then previously assumed area of the St. Elias syntaxis region experienced rapid exhumation. Rapid rock exhumation extends beyond the Contact Fault and comprises most of the Seward‐Malaspina Glacier catchment.