收稿日期: 2011-12-28
修回日期: 2012-01-18
网络出版日期: 2012-02-10
基金资助
国家自然科学基金重点项目“重建西北冰洋晚第四纪的古海洋与古气候演变历史”(编号：41030859)；中国第三次北极科学考察以及国际极地年中国行动计划资助项目；中国地质调查局项目（编号：水[2011]01-14-04）资助.
Late Quaternary Terrigenous Sedimentation in the Western Arctic Ocean as Exemplified by a Sedimentary Record from the Alpha Ridge
Received date: 2011-12-28
Revised date: 2012-01-18
Online published: 2012-02-10
通过西北冰洋阿尔法脊B84A孔中—晚第四纪以来的沉积物颜色旋回，Mn、Ca元素相对含量、颜色反射率、有孔虫丰度、冰筏碎屑(IRD)含量、粒度组分及其敏感性分析的综合研究，建立了B84A孔的地层年代框架，其沉积物被划分为MIS 12～MIS 1的沉积序列。阿尔法脊B84A孔可以识别出12个IRD事件，它们大多出现在冰消期，并认为其源区为加拿大北极群岛地区。这些IRD事件反映了加拿大北极冰盖的崩塌和气候变化。阿尔法脊B84A孔沉积物的环境敏感组分分别为细组分(4~9 μm)和粗组分(19~53 μm)，两者的变化趋势相反，主要由海冰和洋流进行搬运，指示了洋流的强度变化。B84A孔的平均沉积速率约为0.4 cm/ka，与阿尔法脊周围地区沉积速率相近。相比于近岸的高沉积速率，其限制因素主要为大面积海冰覆盖造成的较低的生产力和由于长距离搬运造成的较低的陆源输入量。
刘伟男，王汝建，陈建芳，程振波，陈志华，孙烨忱 . 西北冰洋阿尔法脊晚第四纪的陆源沉积物记录及其古环境意义[J]. 地球科学进展, 2012 , 27(2) : 209 -216 . DOI: 10.11867/j.issn.1001-8166.2012.02.0209
Terrigenous components in sediment core B84A from the Alpha Ridge, western Arctic Ocean, have been investigated to reconstruct the Mid to Late Quaternary variations in sedimentation, source regions, and related climate changes. The core stratigraphy, evaluated by a combination of variations in Mn content, color cycles, foraminiferal abundance, and lithological correlation, extends back to estimated Marine Isotope Stage (MIS) 12. Twelve ice rafted detritus (IRD, >250 μm) events were identified and interpreted to mostly occur during the deglacial periods. The Canadian Arctic covered by ice sheets during glacial periods is suggested to be the major source region. The IRD events likely indicate the collapses of ice sheets, possibly in relation to abrupt climate changes. Grain size analysis of B84A indicates sedimentologically sensitive components in core B84A in the silt subfractions 4~9 μm and 19~53 μm, which are inferred to be mainly transported by currents and sea ice, respectively. Downcore variability of these two fractions may indicate changes in ice drift and current strength. In accordance with previous studies in the central Arctic Ocean, average sedimentation rate in core B84A is about 0.4 cm/ka. In comparison with relatively high sedimentation rates at the margins, sedimentation in the central Arctic Ocean is limited by sea ice cover and related low bioproductivity, as well as long distance from the source regions of terrigenous sediment.
Key words： IRD event; Terrigenous component; Sedimentation rate; Alpha Ridge; Late Quaternary
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