The record of Miocene climatic events in AND-2A drill core (Antarctica): Insights from provenance analyses of basement clasts
The record of Miocene climatic events in AND-2A drill core (Antarctica): Insights from provenance analyses of basement clasts
复制标题
AND-2A 钻芯（南极洲）中新世气候事件的记录：基底碎屑来源分析的见解
DOI：
10.1016/j.gloplacha.2010.10.002
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发表时间：
2011
影响因子：
3.9
通讯作者：
F. Talarico
中科院分区：
文献类型：
--
作者：
S. Sandroni;F. Talarico
本文介绍了罗斯海西南段（南麦克默多湾）AND-2A岩心首次恢复的早中新世晚期至晚中新世沉积冰川剖面中砾石大小碎屑的详细定量物源调查结果。这段时间是至关重要的，因为它包括了全球气候演变中的两个主要新生代事件：中新世中期气候最佳期和中新世中期气候过渡期。基底碎屑的岩石学和矿物化学数据可以区分出两种不同的诊断碎屑组合，这清楚地表明维多利亚地南部的两个特定区域是最有可能的来源：Mulock-Skelton冰川和Koettlitz-Blue冰川地区。碎屑源区的分布模式表明，碎屑源区在整个岩心层段中波动较大，这种变化可以解释为早中新世晚期至晚中新世麦克默多湾古地理演化的直接结果。与沉积学研究一致，砾石碎屑分布模式清楚地证明，南极冰盖在约17.35±0.14Ma（可能与气候最佳的开始有关）经历了剧烈的收缩，而在<ca。从与末次盛冰期相当的冰川情景（第1阶段）到非常动态的冰川环境（第2阶段）的100ka时间窗。阶段2条件持续到中中新世早期（至约14.2Ma），当时假设南极冰盖发生了一次大规模扩张，可能与中中新世气候转变的开始同时发生。因此，砾石碎屑物源和分布研究表明，这一时期古环境驱动因素的变化能够对南极冰盖产生深刻的影响，并表明该方法是重建古冰川流动方向和古地理情景的有力工具。
This paper includes the results of a detailed quantitative provenance investigation on gravel-size clasts occurring within the late Early to Late Miocene sedimentary glacimarine section recovered for the first time by the AND-2A core in the SW sector of the Ross Sea (southern McMurdo Sound, Antarctica). This period of time is of crucial interest, as it includes two of the major Cenozoic events in the global climatic evolution: the mid-Miocene climatic optimum and the middle Miocene climate transition. Petrographical and mineral chemistry data on basement clasts allow to individuate two different diagnostic clast assemblages, which clearly suggest two specific sectors of southern Victoria Land as the most likely sources: the Mulock–Skelton glacier and the Koettlitz–Blue glacier regions. Distribution patterns reveal high fluctuations of the detritus source areas throughout the investigated core interval, variations which can be interpreted as the direct result of an evolving McMurdo Sound paleogeography during the late Early to Late Miocene. Consistently with sedimentological studies, gravel-fraction clast distribution patterns clearly testify that the Antarctic ice sheet experienced a dramatic contraction at ca. 17.35±0.14Ma (likely correlated to the onset of the climatic optimum), and in a<ca. 100ka time window passing from a glacial scenario comparable to the last glacial maximum (Phase 1) to a very dynamic glacial environment (Phase 2). Phase 2 conditions persisted through the early Middle Miocene (to ca. 14.2Ma), when a major expansion of the Antarctic ice sheet is hypothesized, likely contemporaneously to the onset of the middle Miocene climate transition. Therefore, provenance and distribution studies of gravel-fraction clasts show that the variations of paleoenvironmental drivers characterising this period were able to exert deep transformation of the Antarctic ice sheet and reveal the methodology to be a powerful tool for the reconstruction of paleo-glacial-flow direction and paleogeographic scenarios.