Western Ross Sea sedimentary environment reconstruction since the Last Glacial Maximum based on organic carbon and biomarker analyses
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摘要: 本文研究采自位于南极罗斯海西部的ANT32-RB16C柱状沉积物,根据粒度、有机碳和生物标志化合物数据探讨末次冰盛期(24.8 ~20 ka BP)以来该地区有机质来源及沉积环境特征。该柱状样记录了冰架下沉积、冰架前沉积、开阔海域沉积的沉积环境。指示有机质来源的生物标志化合物指标表明该柱状样中所含有机质主要为浮游植物、细菌等海源输入,同时伴有少量陆源物质混合输入。末次冰盛期,由于冰架的影响有机质含量较低,环流影响使得有机质受低等浮游藻类生物等海源影响较大。末次冰消期(20~11.7 ka BP),罗斯冰架消退,冰川溶解释放的有机质在此沉积,使得陆源有机质输入增多,有机质含量升高。进入全新世,有机质含量较末次冰盛期和末次冰消期明显升高,海源输入比例增大,同时细菌等原核生物增多,导致短链正构烷烃降解程度较大。研究区的氧化还原环境主要受冰架与海冰限制作用的影响,与有机质含量和高氧的南极底层水关系不大。总体来说,从末次冰盛期到末次冰消期,研究区沉积环境受罗斯冰架进退影响,全新世以来受气候变化影响。Abstract: Analyses of grain size, organic carbon and biomarker have been carried out for the core ANT32-RB16C, in order to identify the source of organic matter and reconstruct the sedimentary environment since the Last Glacial Maximum in the western Ross Sea. From the bottom to the top within the core, sub-ice-shelf, pre-ice-shelf and open-marine sedimentary environments can be differentiated. The combined parameters of biomarker indicate that organic matter is mainly a mixed input of terrigenous and marine origin. During the Last Glacial Maximum (24.8–20 ka BP), under the influence of ice sheet and the current condition, the organic matter content was low and its source was associated mainly with a marine origin, with a relatively low plankton productivity. During the Last Deglaciation (20–11.7 ka BP), the organic matter released by the dissolution of the glaciers in the retreat process of the Ross Ice Shelf, caused the increase of terrestrial organic matter. During the Holocene, the content of organic matter increased significantly, together with the proportion of marine origin input. The number of prokaryotes such as bacteria increased, resulting in a greater degree of degradation of short-chain n-alkanes. The redox condition in the study area is mainly affected by the ice shelf and sea ice limitation, and has little relationship with the organic matter content and the high-oxygen Antarctic Bottom Water. In general, from the Last Glacial Maximum to the Last Deglaciation, the study area sedimentary environment was affected by the Ross Ice Shelf, and by the climate since the Holocene.
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Key words:
- organic matter /
- biomarker /
- sedimentary environment /
- Last Glacial Maximum /
- Ross Sea
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图 1 南极罗斯海ANT32-RB16C、其他岩芯和WDC冰芯[18]位置及区域环流
1. ANT32-JB06岩芯[8];2.ANT32-JB04岩芯[19];3.GC1606岩芯[20];AASW.南极表层水;AABW.南极底层水;CDW.绕极深层水;MCDW.变性绕极深 层水;DSW.高密度陆架重水;ISW.冰架水
Fig. 1 Locations of Core ANT32-RB16C, other cores and WDC ice core[18] and circulation patterns of the Ross Sea
1. Core ANT32-JB06[8]; 2. Core ANT32-JB04[19]; 3. Core GC1606[20]; AASW. Antarctic Surface Water; AABW. Antarctic Bottom Water; CDW. Circumpolar Deep Water; MCDW. Modified Circumpolar Deep Water; DSW. Dense Shelf Water; ISW. Ice Shelf Water
图 4 ANT32-RB16C沉积柱状样岩性、粒度组分、TOC变化和WDC δ18O记录[18]
ACR.南极冷反转事件;Ⅰ.末次冰消期沉积记录振荡时期(粒度组分出现明显变化,而有机碳及生物标志物指标均无明显变化);Ⅱ.晚全新世沉 积记录振荡时期(有机碳及生物标志物指标均出现明显变化,而粒度组分无明显变化)
Fig. 4 Grain size variation of Core ANT32-RB16C and WDC δ18O record[18]
ACR. Antarctica Cold Reversal; Ⅰ. oscillation period of sedimentary records in the Last Deglaciation; Ⅱ. oscillation period of sedimentary records in Late Holocene
图 5 ANT32-RB16C柱状沉积物正构烷烃及姥鲛烷(Pr)、植烷(Ph)指标
ACR.南极冷反转事件;Ⅰ.末次冰消期沉积记录振荡时期;Ⅱ.晚全新世沉积记录振荡时期
Fig. 5 The n-alkanes, pristine and phytane parameters of Core ANT32-RB16C
ACR. Antarctica Cold Reversal; Ⅰ. oscillation period of sedimentary records in Last Deglaciation; Ⅱ. oscillation period of sedimentary records in Late Holocene
图 6 ANT32-RB16C柱状沉积物三环萜烷相对组成及其他萜烷指标
ACR.南极冷反转事件;Ⅰ.末次冰消期沉积记录振荡时期;Ⅱ.晚全新世沉积记录振荡时期
Fig. 6 The tricyclic terpane constitute and other terpane parameters of Core ANT32-RB16C
ACR. Antarctica Cold Reversal; Ⅰ. oscillation period of sedimentary records in Last Deglaciation; Ⅱ. oscillation period of sedimentary records in Late Holocene
表 1 ANT32-RB16C沉积柱状样AMS14C测年数据及日历年龄
Tab. 1 AMS14C data and calendar age of Core ANT32-RB16C
层位/cm 测试材料 测量值/a BP (碳库年龄+
老碳年龄)/a日历年龄
/a BP0~2 有机碳 6 000±30 5 008 4~6 有机碳 5 150±30 5 008 521 6~8 有机碳 5 440±30 5 008 778 42~44 有机碳 9 620±40 5 008 44~46 有机碳 8 960±30 5 008 4 627 72~74 有机碳 16 400±50 5 008 13 988 74~76 有机碳 17 520±50 5 008 15 143 136~138 有机碳 25 610±100 5 008 138~140 有机碳 24 910±90 5 008 20 385 154~156 有机碳 26 390±110 5 008 204~206 有机碳 25 040±100 5 008 23 755 206~208 有机碳 27 410±130 5 008 230~232 有机碳 25 420±100 5 008 24 762 注:日历年龄由Bacon 2.3.3程序拟合后的年龄减去碳库年龄与老碳年龄之和5 008 a所得。 -
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