Late Quaternary slip rate on the Kern Canyon fault at Soda Spring, Tulare County, California
Late Quaternary slip rate on the Kern Canyon fault at Soda Spring, Tulare County, California
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加利福尼亚州图莱里县苏打泉克恩峡谷断层的晚第四纪滑移率
作者：
C. Amos;K. Kelson;D. Rood;D. Simpson;R. S. Rose
克恩峡谷断层代表了加州中东部内华达山脉南部的一个主要构造和地理边界。以往对Kern峡谷断裂的研究强调了其作为晚白垩世和新近纪剪切带在内华达山脉南部构造发育中的重要性。然而，对晚第四纪活动性历史的研究，由于克恩峡谷断层的偏远性质，以及在克恩河北部流域内由集中的河流和冰川侵蚀驱动的深顺行发掘，一直受到混淆。最近获得的沿Kern峡谷断层约140公里长的机载激光雷达（光探测和测距）地形提供了活动地表轨迹的全面视图。Kern峡谷北部断层的高分辨率激光雷达衍生数字高程模型（dem）能够识别Soda Spring（36.345°N, 118.408°W）附近以前未被识别的晚第四纪冰碛。发育在苏打泉冰碛上的以北向为主的断崖，表现出向西向上的位移，缺乏明显的走滑分离作用，与整个克恩峡谷断层的详细测绘和挖沟一致。由激光雷达dem得出的陡崖-正常地形剖面表明，梯奥加终末冰碛峰的正常位移至少为2.8 +0.6/ -0.5 m。泰奥加冰碛巨石的宇宙成因10Be暴露测年得到了一个以18.1±0.5 ka （n = 6）为中心的紧密年龄群，表明这一时期的最小正常意义上的断层滑动率为~ 0.1-0.2 mm/yr。综上所述，这些结果提供了Kern峡谷断层晚第四纪活动的第一个清晰文件，并强调了它在容纳内华达山脉南部内部变形中的作用。
The Kern Canyon fault represents a major tectonic and physiographic boundary in the southern Sierra Nevada of east-central California. Previous investigations of the Kern Canyon fault underscore its importance as a Late Cretaceous and Neogene shear zone in the tectonic development of the southern Sierra Nevada. Study of the late Quaternary history of activity, however, has been confounded by the remote nature of the Kern Canyon fault and deep along-strike exhumation within the northern Kern River drainage, driven by focused fluvial and glacial erosion. Recent acquisition of airborne lidar (light detection and ranging) topography along the ∼140 km length of the Kern Canyon fault provides a comprehensive view of the active surface trace. High-resolution, lidar-derived digital elevation models (DEMs) for the northern Kern Canyon fault enable identification of previously unrecognized offsets of late Quaternary moraines near Soda Spring (36.345°N, 118.408°W). Predominately north-striking fault scarps developed on the Soda Spring moraines display west-side-up displacement and lack a significant sense of strike-slip separation, consistent with detailed mapping and trenching along the entire Kern Canyon fault. Scarp-normal topographic profiling derived from the lidar DEMs suggests normal displacement of at least 2.8 +0.6/–0.5 m of the Tioga terminal moraine crest. Cosmogenic 10Be exposure dating of Tioga moraine boulders yields a tight age cluster centered around 18.1 ± 0.5 ka ( n = 6), indicating a minimum normal-sense fault slip rate of ∼0.1–0.2 mm/yr over this period. Taken together, these results provide the first clear documentation of late Quaternary activity on the Kern Canyon fault and highlight its role in accommodating internal deformation of the southern Sierra Nevada.