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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >Using in situ cosmogenic ~(10)Be to identify the source of sediment leaving Greenland
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Using in situ cosmogenic ~(10)Be to identify the source of sediment leaving Greenland

机译：利用原位宇宙成因〜（10）Be识别离开格陵兰的沉积物来源

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摘要

We use the concentration of in situ ~(10)Be in quartz isolated from fluvial and morainal sand to trace sediment sources and to determine the relative contribution of glacerized and deglaciated terrain to Greenland's sediment budget. We sampled along the western, eastern, and southern margins of the Greenland Ice Sheet, and collected sediment sourced from glacerized (n = 19) and non-glacerized terrain (n = 10), from channels where sediment from glacerized and non-glacerized terrain is mixed (n = 28), from Holocene glacial-fluvial terraces (n = 4), and from one sand dune. In situ ~(10)Be concentrations in sediment range from 1600 to 34 000 atoms g-1. The concentration of in situ ~(10)Be in sediment sourced from non-glacerized terrain is significantly higher than in sediment sourced from glacerized areas, in mixed channel sediment, and in terrace sediment that was deposited during the Holocene. To constrain the timing of landscape exposure for the deglaciated portion of the Narsarsuaq field area in southern Greenland, we measured in situ ~(10)Be concentration in bedrock (n = 5) and boulder (n = 6) samples. Paired bedrock and boulder ages are indistinguishable at 1σ uncertainty and indicate rapid exposure of the upland slopes at ~10.5 ka. The isotope concentration in sediment sourced from non-glacerized terrain is higher than in sediment sourced from glacerized terrain because the non-glacerized landscape has been exposed to cosmic radiation since early Holocene deglaciation. Sediment from glacerized areas contains a low, but measurable concentration of ~(10)Be that probably accumulated at depth during a prolonged period of exposure, probably before the establishment of the Greenland Ice Sheet. The concentration of ~(10)Be in mixed fluvial sediment and in terrace sediment is low, and similar to the concentration in sediment from glacerized areas, which indicates that the Greenland Ice Sheet is the dominant source of sediment moving through the landscape outside the glacial margin in the areas we sampled.
机译：我们使用从河流和砂砾砂中分离出的石英中的原位〜（10）Be浓度来追踪沉积物来源，并确定冰川和冰川消融地形对格陵兰岛沉积物预算的相对贡献。我们沿格陵兰冰原的西部，东部和南部边缘采样，并收集了来自冰川化（n = 19）和非冰川化地形（n = 10）的沉积物，这些沉积物来自冰川化和非冰川化地形的沉积物。来自全新世冰河-河流阶地（n = 4）和一个沙丘的混合（n = 28）。沉积物中原位〜（10）Be的浓度范围为1600至34000个原子g-1。来自非冰川地区的沉积物中原位〜（10）Be的浓度显着高于冰川时期地区，混合河道沉积物和全新世沉积的阶地沉积物中的沉积物。为了限制格陵兰岛南部Narsarsuaq田间冰川区域的景观暴露时间，我们在基岩（n = 5）和巨石（n = 6）样品中现场测量了〜（10）Be浓度。成对的基岩年龄和巨石年龄在1σ不确定度下是无法区分的，并表明在〜10.5 ka处高地斜坡迅速暴露。来自非冰川化地形的沉积物中的同位素浓度高于来自冰川化地形的沉积物中的同位素浓度，因为自全新世早期冰消融化以来，非冰川化景观已暴露于宇宙辐射之下。冰川地区的泥沙含量很低，但可测量的浓度为〜（10）Be，可能是在长时间暴露期间（可能是在格陵兰冰盖建立之前）在深处积累的。河流相混合沉积物和梯田沉积物中〜（10）Be的浓度较低，与冰川地区的沉积物中的浓度相似，这表明格陵兰冰原是沉积物在冰川外景观中移动的主要来源。我们采样区域的边距。

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