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.

中文翻译：

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南极洲中部跨南极山脉大面积蓝色冰碛的形成与演化

Mount Achernar 冰碛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。类似的记录存在于大陆其他地方的其他蓝色冰碛中，但对这些冰碛如何形成的了解有限。我们提出了一个模型来解释广泛、连贯的蓝色冰碛序列的形成，该模型基于探地雷达 (GPR) 数据与冰速和地表暴露年龄的整合。GPR 横断面（100 和 25 MHz）与 Mount Achernar 的冰碛脊垂直和平行，揭示了一个内部结构，由交替的相对干净的冰和陡峭倾斜的碎片带延伸到深度，并且在可见的地方延伸到下面的基岩表面。沉积物沿着这些碎屑带从深处被带到地表，并从冰中升华，随着时间的推移积累（>300 ka）。倾斜反射器的内部模式，加上表面暴露年龄的增加，表明沉积物的顺序暴露，冰和碎片横向积聚形成冰碛。整个冰碛的地下结构各不相同，并且可能与基础夹带条件的变化有关。我们推测，在较冷的冰川时期，冰中可能夹带了较高浓度的碎片，或者夹带更接近冰碛序列。整个冰碛的地下结构各不相同，并且可能与基础夹带条件的变化有关。我们推测，在较冷的冰川时期，冰中可能夹带了较高浓度的碎片，或者夹带更接近冰碛序列。整个冰碛的地下结构各不相同，并且可能与基础夹带条件的变化有关。我们推测，在较冷的冰川时期，冰中可能夹带了较高浓度的碎片，或者夹带更接近冰碛序列。