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首页> 外文期刊>Quaternary geochronology >Further constraint of the in situ cosmogenic Be-10 production rate in pyroxene and a viability test for late Quaternary exposure dating
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Further constraint of the in situ cosmogenic Be-10 production rate in pyroxene and a viability test for late Quaternary exposure dating

机译：进一步约束原位宇宙中的粉红素中的产率和后期季曝光约会的活力测试

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摘要

Beryllium-10 (Be-10) in quartz represents the most common in situ cosmogenic nuclide used for quantifying Earthsurface processes, primarily due to the prevalence of quartz in the Earth's crust. However many landscapes lack quartz-bearing rocks, thus other nuclide-mineral pairs are required for geochronometric and geomorphic applications. Here we describe the successful isolation and measurement of in situ Be-10 concentrations in pyroxene from two mafic sample sets: (i) andesite boulders of the Murimotu Formation debris avalanche on Mt. Ruapehu, New Zealand, and (ii) dolerite cobbles deposited in a similar to 100 m vertical transect at Mt. Gran by Mackay Glacier, Antarctica. Precise radiocarbon age constraint of the New Zealand site provides further geological constraint of the reference (at sea level and high latitude) Be-10 production rate in pyroxene, which we find to be indistinguishable from a previous estimate. Combining our results with previous data yields a reference production rate of 3.2 +/- 0.8 at. g(-1) yr(-1) (n= 5; 'Lm' scaling). Application of this rate to the glacial cobbles at Mackay Glacier yields a relatively coherent chronology of ice surface lowering between similar to 14 and 6 ka, which is broadly consistent with a well-constrained quartz-based Be-10 chronology from nearby nunataks. Improving the viability of in situ Be-10 for geological applications in mafic domains requires increased analytical precision beyond current levels. This improvement may be best achieved by further modification of the quartz-based methodologies for Be-10 purification, in order to better handle the high cationic contaminant loads of ferromagnesian minerals. In addition, further Be-10 measurements from suitable mafic sedimentary deposits with independent age control (e.g. existing cosmogenic He-3 calibration sites) will help to refine estimates of the reference production rate.
机译：石英中的Beryllium-10（BE-10）代表最常见的原位富含核素，用于量化地面过程，主要是由于地壳中石英的普遍性。然而，许多景观缺乏石英岩石，因此地球组织和地貌应用需要其他核素 - 矿物对。在这里，我们描述了来自两种MAFIC样品集的原位BE-10浓度原位的分离和测量：（i）MT.MT.Ruapehu，新西兰和（ii）Dolerite Cobbles的Murimotu Creadlation葡萄干葡萄干博尔南那的博尔德斯。 A类似于Mt的100米垂直横断。Gran by Mackay Glacier，南极洲。新西兰网站的精确射线碳增长率为参考（海平面和高纬度）提供了进一步的地质限制（在海平面和高纬度）的辉石中的产量，我们发现与之前的估计无法区分。将我们的结果与以前的数据相结合，产生了3.2 +/- 0.8的参考生产率。 g（-1）Yr（-1）（n = 5;'lm'缩放）。在Mackay冰川的冰川鹅卵石中将这种速率的应用产生了与14和6ka相似的冰表面的相对相干的年代学，这与来自附近的纳坦塔克斯的良好约束的石英的BE-10年学相对一致。提高原位BE-10用于MAFIC域中的地质应用需要增加超出电流水平的分析精度。通过进一步修改基于石英的方法的BE-10纯化的进一步修改，可以最好地实现这种改进，以便更好地处理铁麦芽玉米矿物的高阳离子污染物荷载。此外，来自合适的MAFIC沉积沉积物的进一步是-10测量，具有独立年龄控制（例如，现有的宇宙原期HE-3校准点）将有助于改进参考生产率的估计。

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