Magnetic properties of deep-sea sediments off southwest Greenland: Evidence for major differences between the last two deglaciations
Magnetic properties of deep-sea sediments off southwest Greenland: Evidence for major differences between the last two deglaciations
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格陵兰岛西南部深海沉积物的磁性：最近两次冰消期之间主要差异的证据
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发表时间：
1995
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通讯作者：
C. Hillaire‐Marcel
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作者：
J. Stoner;J. Channell;C. Hillaire‐Marcel
高分辨率岩石磁数据、原子质谱 14 C 日期、δ 18 O 以及来自位于格陵兰岛西南部的活塞核心 (HU90-013-013) 的粒度分析提供了最后两次冰消期的记录。在终止 I 期间，具有高体积磁化率 (k) 和低迟滞磁化率与体积磁化率之比 (k ARM / k ) 的明确区间晚于新仙女木期和标志着 2/1 阶段边界的 δ 18 O 变化，并与格陵兰冰盖从海岸线退缩到大陆内部的沉积学和地貌证据相关。在终止 II 期间，非常相似的磁信号与标记 6/5 冰期-间冰期过渡阶段的 δ 18 O 位移相一致，并在整个 5e 亚阶段持续存在。我们认为，在终端一和终端二期间，这种磁信号标志着来自格陵兰岛的大陆融水携带的碎屑。如果是这样，则终端 II 的磁同位素和氧同位素记录的同步变化表明格陵兰岛的冰川消退非常早且迅速，与终端 I 观察到的相对较晚的冰川消退形成鲜明对比。k 和 k ARM / k 的明显波动发生在终端 I（发生在距今 16 900 年）和终端 II δ 18 O 变化开始点以下。这些波动被解释为由于冰川消融开始时冰从大陆架上脱落而导致碎屑突然涌入盆地所致。
High-resolution rock magnetic data, atomic mass spectroscopy 14 C dates, δ 18 O, and grain-size analyses from a piston core (HU90-013-013) located off southwest Greenland provide a record of the last two deglaciations. During Termination I, a welldefined interval having high volumetric magnetic susceptibility (k) and a low ratio of anhysteretic susceptibility to volumetric magnetic susceptibility ( k ARM / k ) postdates the Younger Dryas and the δ 18 O change marking the stage 2/1 boundary and correlates with sedimentological and geomorphological evidence for Greenland ice-sheet retreat from the coastline to the continental interior. During Termination II, a very similar magnetic signal coincides with the δ 18 O shift marking the stage 6/5 glacial-interglacial transition and continues throughout substage 5e. We suggest that this magnetic signal, during both Termination I and Termination II, marks continental meltwater–carried detritus from Greenland. If so, the synchronous changes in magnetic and oxygen isotopic records at Termination II indicate very early and rapid deglaciation of Greenland, in contrast to the relatively late deglaciation observed for Termination I. Distinct fluctuations in k and k ARM / k occur below the onset of the δ 18 O change at Termination I (where they occur at ∼16 900 yr B.P.) and at Termination II. These fluctuations are interpreted as due to sudden influxes of detritus into the basin caused by unpinning of ice from the continental shelf at the inception of deglaciation.