Slate Range Thermochronology - 2013-07-31

New mapping combined with fault-slip and thermochronological data show middle Miocene to recent extension and exhumation of the Slate Range, eastern California, is produced by the active Searles Valley fault system and the Slate Range detachment, an older middle Miocene low-angle normal fault. Offset middle Miocene rocks record a combined ~9 km of west-directed extension over the last ~14 Ma for the fault zones. (U-Th)/He apatite cooling ages of samples from the central and southern Slate Range indicate that footwall cooling began around 14 Ma; we interpret this as the age of initiation of motion on the Slate Range detachment. This timing is consistent with inferences made using stratigraphic and structural criteria. Data from the northern Slate range show rapid fault slip began along the Searles Valley fault at ~4 Ma; data from the central and southern Slate Range can be interpreted to present cooling at 5 to 6 Ma. This timing correlates to the results of nearby studies, suggesting a strain transition in the surrounding area between ~6-3 Ma. Data collected are most consistent with a westward migration in the locus of transtensional deformation, and show that the initiation of that deformation commonly lags the timing predicted by plate reconstructions by a few million years.

新的制图技术与滑移和热年代学数据相结合，揭示了加利福尼亚东部板岩山脉从中新世中期至近代的伸展和抬升现象，此现象由活跃的塞勒斯谷断层系统及板岩山脉断离带，即一个更古老的中新世低角度正断层所引起。中间中新世岩石的位移记录了在过去的约140万年中，断层带向西方向累计约9公里的伸展。来自中央和南部板岩山脉的(U-Th)/He磷灰石冷却年龄表明，脚墙冷却始于约140万年前；我们将此解释为板岩山脉断离带运动开始的年龄。这一时间与利用地层学和结构学标准得出的推断相一致。北部板岩山脉的数据显示，在约400万年前沿塞勒斯谷断层开始发生快速的断层滑移；中央和南部板岩山脉的数据可解释为在500万至600万年前发生冷却。这一时间与附近研究的成果相吻合，表明在约600万至300万年前该区域发生了应变转换。收集到的数据与横跨伸展变形中心的向西迁移最为一致，并显示出该变形的起始时间通常滞后于板块重建预测的时间数百万年。