Paleoglaciology of the central East Antarctic Ice Sheet as revealed by blue-ice sediment
Paleoglaciology of the central East Antarctic Ice Sheet as revealed by blue-ice sediment
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蓝冰沉积物揭示了南极东部冰盖中部的古冰川学
DOI：
10.1016/j.quascirev.2022.107718
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发表时间：
2023
影响因子：
4
通讯作者：
Schwartz, R.
中科院分区：
文献类型：
--
作者：
Kaplan, M.R.;Licht, K.J.;Lamp, J.L.;Winckler, G.;Schaefer, J.M.;Graly, J.A.;Kassab, C.M.;Schwartz, R.
我们给出了∼100个宇宙成因的表面暴露年龄，包括75个新的分析，在山上的一个蓝色冰雹复合体。位于横贯北极山脉中部的洛冰川冰川负责人阿切纳尔说。10Be-3He-26Al年龄和以前公布的硼浓度记录了南极东部冰盖(EAIS)自沉积物开始积累以来的过去行为，大约0.5-1 Ma。对10Be的样本进行了分析，这些样本来自Law Glacier Surface Record<；100年的暴露记录，表明它们在第一次暴露时可能具有可以忽略不计的遗传。在整个MIS6和MIS5期间，劳冰川表面经历了相对较小的表面高程波动，可能是在以前的时期，因为地貌特征完整，冰川上的暴露年龄一致，范围从∼210到∼86ka；MIS5在两个不同地区的平均年龄分别为106m±9.1ka[n=14a]和106m±5.1ka[n=0.51ka]。尽管我们推测，自0.5-1 Ma以来，Law冰川总体上一直相对接近目前的形态，但对阿切纳尔蓝冰冰川结构的干扰有时似乎很明显，特别是在最后两个冰川周期之前。观测到的最大扰动发生在附近的刘易斯悬崖冰舌膨胀接近或早于500-400ka时。与∼20ka蓝色冰脊相关的最小冰层厚度增加了30m，侧向冰脊指示∼冰川表面在∼9.2ka±10.5ka处升高了40-50m。我们的发现支持，随着时间的推移，侧向吸积形成了山体。阿切纳尔蓝冰冰原序列，并暗示，其他类似的南极沉积。我们将蓝色冰雹解释为有时代表相对恒定的出口冰川条件，并同意先前的研究，即它们反映了接近平衡的形式。蓝冰沉积物是南极洲未得到充分利用和可确定年代的古冰川和古气候档案，包括以前的冰面动力学，并可能在MIS5及之前的时期作为旧冰的储存库。
We present ∼100 cosmogenic surface exposure ages, including 75 new analyses, for a blue-ice moraine complex at Mt. Achernar, head of Law Glacier, in the central Transantarctic Mountains. The10Be–3He–26Al ages along with previously-published boron concentrations chronicle past behavior of the East Antarctic Ice Sheet (EAIS) along the edge of the polar plateau since the sediments started to accumulate, around 0.5–1 Ma. Samples analyzed for10Be from the Law Glacier surface record <100 years of exposure, indicating they likely have negligible inheritance when first exposed. The Law Glacier surface experienced relatively minor fluctuations in surface elevation throughout MIS 6 and 5, and likely during prior periods, as geomorphic features are intact and exposure ages are coherent on the moraine, ranging from ∼210 to ∼86 ka; respective means for MIS 5 till in two different areas are 106 ± 9.1 ka [n = 4 ages] and 106 ± 5.1 ka [n = 6]. Although we infer the Law Glacier has been relatively close to its current configuration generally since 0.5–1 Ma, disturbances to Achernar blue-ice moraine architecture seem apparent at times especially prior to the last two glacial cycles. The largest observed disturbance occurred when the nearby Lewis Cliffs Ice Tongue expanded either close to, or earlier than, 500-400 ka. A minimum ice thickness increase of 30 m is associated with the ∼20 ka blue-ice ridges, and a lateral moraine indicates the Law Glacier surface was ∼40–50 m higher at ∼9.2 ± 0.5 ka. Our findings support that lateral accretion over time formed the Mt. Achernar blue-ice moraine sequence, and by implication, other analogue Antarctic deposits. We interpret blue-ice moraines as representing, at times, relatively constant outlet glacier conditions and concur with prior studies that they reflect near-equilibrium forms. Blue-ice sediments are an underutilized and dateable paleoglaciologic and paleoclimate archive in Antarctica, including for former ice surface dynamics and possibly as a repository of old ice during periods such as MIS 5 and prior.
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