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首页> 外文期刊>Quaternary geochronology >Using correlated tephras to refine radiocarbon-based age models, upper and lower Whitshed Lakes, south-central Alaska
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Using correlated tephras to refine radiocarbon-based age models, upper and lower Whitshed Lakes, south-central Alaska

机译：使用相关的Tephras来改进基于RadioCarbon的年龄模型，占地面积和低级Whitshed Lakes，阿拉斯加南部

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摘要

Tephra deposits correlated between nearby lakes provide the opportunity to improve age estimates of the sediment sequences, even if the ages of the tephras are previously unknown. We explore this potential using cryptotephras and visible tephra deposits in sediment cores from Upper and Lower Whitshed Lakes near Cordova, Alaska. Each tephra was described in terms of visual stratigraphy and shard morphology, and the major-oxide glass geochemistry was analyzed. Independent age models were developed for the cores using radiocarbon ages and profiles of short-lived radioisotopes for the near-surface sediments. Four tephras were correlated between the two lakes based on the magnitude and spacing of magnetic susceptibility peaks and glass major-oxide geochemistry. These correlations confirm agreement of the age models because the independently modeled confidence intervals overlap for each correlated tephra. The stratigraphic correlations were subsequently used to improve the age models by extracting the subset of possible age-model iterations that produce similar ages for each of the four correlated tephras at the two lakes. The iterations that agree within 25 years for each correlated tephra were used to create tephra-matched age models for both lakes, which narrowed the width of the 95% confidence intervals of the age models by 3% overall and reduced the uncertainty in age estimates of the correlated tephras by 34% on average. This synchronization technique may be useful in other studies that have multiple independently dated records with confident stratigraphic correlations.
机译：附近湖泊之间的Tephra沉积物提供了改善沉积物序列的年龄估计的机会，即使Tephras的年龄以前未知。我们探讨了使用CryptotePtoToTephras和可见的Tephra沉积物，从阿拉斯加的Cordova附近的上下Whitshed Lakes沉积物核心。在视觉地层和碎片形态方面描述了每个Tephars，并且分析了主要氧化物玻璃地球化学。使用无线电金时代的核心开发了独立年龄模型，以及用于近表面沉积物的短寿命放射性同位素的曲线。基于磁性敏感性峰和玻璃主要氧化物地球化学的幅度和间距，两个湖泊之间存在四个Tephras。这些相关性证实了年龄模型的协议，因为每个相关的Tephra的独立建模的置信区间重叠。随后使用地层相关性通过提取可能的年龄模型迭代的子集来改善年龄模型，该模型迭代的子集产生类似于两个湖泊的四个相关的Tephras中的每个相关的Tephras。在25年内同意每种相关的Tephra的迭代用于为两个湖泊创造Tephra匹配的年龄模型，这使得年龄模型的95％置信区间的宽度整体缩小了3％，并降低了年龄估计的不确定性与平均相关的Tephras将34％达到34％。该同步技术在其他研究中可以是有用的，其具有具有自信地层相关性的多个独立日期的记录。

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