Constraints on the Emplacement Age of the Heart Mountain Slide, Northwestern Wyoming
Constraints on the Emplacement Age of the Heart Mountain Slide, Northwestern Wyoming
复制标题
怀俄明州西北部心脏山滑坡就位年龄的限制
DOI：
10.1086/678279
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
A. Wulff
中科院分区：
文献类型：
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作者：
D. Malone;J. Craddock;M. H. Anders;A. Wulff
心脏山滑坡是迄今为止地球上已知的最大的陆地滑坡存款。该滑坡覆盖面积至少为3400平方公里，上板块岩石包括2-4公里的古生代碳酸盐岩和始新世火山岩，突出于始新世景观的45公里之外。精确的滑动年龄和持续时间是定位模型的关键，也是滑动对区域始新世河流系统的影响。为了解决时间问题，我们从基底流体化层2公里的幻灯片的分离故障（银门，MT）和40公里的下坡，接近幻灯片的脚趾（白色山，怀俄明州）的锆石采样。在这个基底层中，我们已经确定了与部分凝固岩浆一致的矿物含量和特征。我们解释这些观察结果是一致的滑动灾难性地肢解一个活跃的岩浆体，与基底断层层混合。结果表明，近端和远端锆石U/Pb结晶年龄非常相似：银门（n = 48）为48.78 ± 0.51 Ma，白色山（n = 22）为48.88 ± 0.22 Ma。这些锆石年龄从基底层紧密括号中使用各种放射性年龄始新世Absaroka火山单位参与的运动阶段的幻灯片和那些沉积后的侵位，包括碎屑U/Pb锆石年龄从解剖克兰德尔砾岩河流系统。我们对这些数据的解释是，该滑坡发生于48.87 ± 0.20 Ma。
The Heart Mountain slide is the largest terrestrial landslide deposit as yet recognized on Earth. The slide covers an area of at least 3400 km2, and the upper-plate rocks include 2–4 km of Paleozoic carbonate and Eocene volcanic rocks thrust out over 45 km of Eocene landscape. The precise age and duration of sliding is critical to emplacement models as well the slide’s effect on regional Eocene river systems. To address the timing issues, we sampled zircons from the basal fluidized layer 2 km from the slide’s breakaway fault (Silver Gate, MT) and 40-km downslope, nearer the slide’s toe (White Mountain, WY). Within this basal layer, we have identified mineral content and features consistent with a partially solidified magma. We interpret these observations to be consistent with the slide catastrophically dismembering an active magma body that mixed with the basal fault layer. The results yield remarkably similar U/Pb zircon crystallization ages at the proximal and distal locations: 48.78 ± 0.51 Ma at Silver Gate (n = 48) and 48.88 ± 0.22 Ma at White Mountain (n = 22). These zircon ages from the basal layer are tightly bracketed using various radiometric ages of Eocene Absaroka volcanic units involved in the movement phase of the slide and those deposited after emplacement, including detrital U/Pb zircon ages from the dissected Crandall Conglomerate river system. Our interpretation of the data is that the slide was catastrophically emplaced at 48.87 ± 0.20 Ma.