Formation and evolution of an extensive blue ice moraine in central Transantarctic Mountains, Antarctica
Formation and evolution of an extensive blue ice moraine in central Transantarctic Mountains, Antarctica
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南极洲中部横贯南极山脉广泛的蓝色冰碛的形成和演化
DOI：
10.1017/jog.2019.83
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发表时间：
2020
影响因子：
3.4
通讯作者：
Kaplan, Michael R.
中科院分区：
文献类型：
--
作者：
Kassab, Christine M.;Licht, Kathy J.;Petersson, Rickard;Lindbäck, Katrin;Graly, Joseph A.;Kaplan, Michael R.
阿切纳尔莫雷纳山是一个陆地沉积物档案，保存了多个冰川周期的冰盖动态和气候记录。类似的记录也存在于欧洲大陆其他地方的蓝色冰雹中，但人们对这些冰雹是如何形成的了解有限。基于探地雷达(GPR)数据与冰层速度和地表暴露年龄的集成，我们提出了一个模型来解释广泛的、连贯的蓝色冰凌序列的形成。在阿切纳尔山与冰雹脊垂直和平行的探地雷达断面(100和25兆赫)揭示了一个内部结构，其内部结构由相对干净的冰和陡峭的碎屑带交替形成，延伸到深度，并在可见的情况下延伸到基岩下表面。沉积物沿着这些碎片带从深处带到地表，并从冰中升华出来，随着时间的推移而积累(>；300ka)。倾斜反射层的内部模式，加上不断增加的表面暴露年龄，表明沉积物依次暴露在冰川和碎屑横向堆积形成冰雹的地方。冰雹的地下结构各不相同，并可与基本夹带条件的变化联系在一起。我们推测，较高浓度的碎片可能是在较冷的冰川时期被带进冰层中的，或者是被带到了更靠近冰川序列的地方。
Mount Achernar moraine is a terrestrial sediment archive that preserves a record of ice-sheet dynamics and climate over multiple glacial cycles. Similar records exist in other blue ice moraines elsewhere on the continent, but an understanding of how these moraines form is limited. We propose a model to explain the formation of extensive, coherent blue ice moraine sequences based on the integration of ground-penetrating radar (GPR) data with ice velocity and surface exposure ages. GPR transects (100 and 25 MHz) both perpendicular and parallel to moraine ridges at Mount Achernar reveal an internal structure defined by alternating relatively clean ice and steeply dipping debris bands extending to depth, and where visible, to the underlying bedrock surface. Sediment is carried to the surface from depth along these debris bands, and sublimates out of the ice, accumulating over time (>300 ka). The internal pattern of dipping reflectors, combined with increasing surface exposure ages, suggest sequential exposure of the sediment where ice and debris accretes laterally to form the moraine. Subsurface structure varies across the moraine and can be linked to changes in basal entrainment conditions. We speculate that higher concentrations of debris may have been entrained in the ice during colder glacial periods or entrained more proximal to the moraine sequence.
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