Bailey Ian, Hemming Sidney, Reilly Brendan T, Rollinson Gavyn, Williams Trevor, Weber Michael E, Raymo Maureen E, Peck Victoria L, Ronge Thomas A, Brachfeld Stefanie, O'Connell Suzanne, Tauxe Lisa, Warnock Jonathan P, Armbrecht Linda, Cardillo Fabricio G, Du Zhiheng, Fauth Gerson, Garcia Marga, Glueder Anna, Guitard Michelle, Gutjahr Marcus, Hernández-Almeida Iván, Hoem Frida S, Hwang Ji-Hwan, Iizuka Mutsumi, Kato Yuji, Kenlee Bridget, Martos Yasmina M, Pérez Lara F, Seki Osamu, Tripathi Shubham, Zheng Xufeng
Camborne School of Mines University of Exeter Penryn Campus Cornwall UK.
Lamont-Doherty Earth Observatory Columbia University Palisades NY USA.
Paleoceanogr Paleoclimatol. 2022 Jul;37(7):e2022PA004433. doi: 10.1029/2022PA004433. Epub 2022 Jul 12.
Ice loss in the Southern Hemisphere has been greatest over the past 30 years in West Antarctica. The high sensitivity of this region to climate change has motivated geologists to examine marine sedimentary records for evidence of past episodes of West Antarctic Ice Sheet (WAIS) instability. Sediments accumulating in the Scotia Sea are useful to examine for this purpose because they receive iceberg-rafted debris (IBRD) sourced from the Pacific- and Atlantic-facing sectors of West Antarctica. Here we report on the sedimentology and provenance of the oldest of three cm-scale coarse-grained layers recovered from this sea at International Ocean Discovery Program Site U1538. These layers are preserved in opal-rich sediments deposited ∼1.2 Ma during a relatively warm regional climate. Our microCT-based analysis of the layer's in-situ fabric confirms its ice-rafted origin. We further infer that it is the product of an intense but short-lived episode of IBRD deposition. Based on the petrography of its sand fraction and the Phanerozoic Ar/Ar ages of hornblende and mica it contains, we conclude that the IBRD it contains was likely sourced from the Weddell Sea and/or Amundsen Sea embayment(s) of West Antarctica. We attribute the high concentrations of IBRD in these layers to "dirty" icebergs calved from the WAIS following its retreat inland from its modern grounding line. These layers also sit at the top of a ∼366-m thick Pliocene and early Pleistocene sequence that is much more dropstone-rich than its overlying sediments. We speculate this fact may reflect that WAIS mass-balance was highly dynamic during the ∼41-kyr (inter)glacial world.
在过去30年里，西南极洲是南半球冰盖流失最为严重的地区。该地区对气候变化的高度敏感性促使地质学家研究海洋沉积记录，以寻找西南极冰盖（WAIS）过去不稳定事件的证据。斯科舍海堆积的沉积物有助于实现这一目的，因为它们接收来自西南极洲面向太平洋和大西洋区域的冰山漂流物（IBRD）。在此，我们报告了在国际大洋发现计划U1538站点从该海域回收的三个厘米级粗粒层中最古老一层的沉积学特征和物源情况。这些层保存在富含蛋白石的沉积物中，这些沉积物是在相对温暖的区域气候期间于约120万年前沉积的。我们基于显微CT对该层原地结构的分析证实了其冰山漂流成因。我们进一步推断，它是一次强烈但短暂的IBRD沉积事件的产物。根据其砂质部分的岩石学特征以及其中所含角闪石和云母的显生宙氩-氩年龄，我们得出结论，其中所含的IBRD可能源自西南极洲的威德尔海和/或阿蒙森海湾区。我们将这些层中高浓度的IBRD归因于WAIS从现代接地线向内陆退缩后崩解的“脏”冰山。这些层还位于一个约366米厚的上新世和早更新世序列的顶部，该序列比其上覆沉积物富含更多的坠石。我们推测这一事实可能反映出在约41 kyr（间）冰期世界期间，WAIS的质量平衡具有高度动态性。
