Late Holocene sediment deposits in Pine Island Bay, West Antarctica, are hypothesized to be linked to intensive meltwater drainage during the retreat of the paleo-Pine Island Ice Stream after the Last Glacial Maximum. The uppermost sediment units show an abrupt transition from ice-proximal debris to a draped silt during the late Holocene, which is interpreted to coincide with rapid deglaciation. The small scale and fine sorting of the upper unit could be attributed to origins in subglacial meltwater; however the thickness and deposition rate for this unit imply punctuated- rather than continuous-deposition. This, combined with the deposit's location seaward of large, bedrock basins, has led to the interpretation of this unit as the result of subglacial lake outbursts in these basins. However, the fine-scale sorting of the silt unit is problematic for this energetic interpretation, which should mobilize and deposit a wider range of sediment sizes. To resolve this discrepancy, we present an alternative mechanism in which the silt was sorted by a distributed subglacial water system, stored in bedrock basins far inland of the grounding line, and subsequently eroded at higher flow speeds during retreat. We demonstrate that this mechanism is physically plausible given the subglacial conditions during the late Holocene. We hypothesize that similar silt units observed elsewhere in Antarctica downstream of bedrock basins could be the result of the same mechanism.

中文翻译：

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松岛湾撤退期间淤泥分选和沉积的冰下水文排水假设

据推测，西南极洲松岛湾的晚全新世沉积物与末次盛冰期后古松岛冰流撤退期间的密集融水排放有关。在全新世晚期，最上面的沉积物单元显示出从近冰碎片到覆盖淤泥的突然转变，这被解释为与快速冰川消融相吻合。上部单元的小规模和精细分选可归因于冰下融水的起源；然而，该单元的厚度和沉积速率意味着间断而非连续沉积。再加上该矿床位于大型基岩盆地向海的位置，导致将该单元解释为这些盆地中冰下湖爆发的结果。然而，淤泥单元的精细分类对于这种充满活力的解释是有问题的，它应该调动和沉积更广泛的沉积物尺寸。为了解决这种差异，我们提出了一种替代机制，其中淤泥由分布式冰下水系统分类，储存在接地线内陆的基岩盆地中，随后在撤退过程中以更高的流速侵蚀。我们证明，考虑到全新世晚期的冰下条件，这种机制在物理上是合理的。我们假设在南极洲其他地方在基岩盆地下游观察到的类似淤泥单元可能是相同机制的结果。我们提出了另一种机制，其中淤泥通过分布的冰下水系统进行分类，储存在接地线内陆的基岩盆地中，随后在撤退过程中以更高的流速侵蚀。我们证明，考虑到全新世晚期的冰下条件，这种机制在物理上是合理的。我们假设在南极洲其他地方在基岩盆地下游观察到的类似淤泥单元可能是相同机制的结果。我们提出了另一种机制，其中淤泥通过分布的冰下水系统进行分类，储存在接地线内陆的基岩盆地中，随后在撤退过程中以更高的流速侵蚀。我们证明，考虑到全新世晚期的冰下条件，这种机制在物理上是合理的。我们假设在南极洲其他地方在基岩盆地下游观察到的类似淤泥单元可能是相同机制的结果。