西北冰洋楚科奇海台08 P23孔氧同位素3期以来的古海洋与古气候记录

摘要

Multi-proxy investigations have been performed on core 08P23,which was collected from the Chukchi Plateau, western Arctic Ocean,during the third Chinese National Arctic Research Expedition.The core was dated to Marine Isotope Stage(MIS)3 by a combination of AMS 14 C dating and regional core correlation.A total of 5 prominent ice-rafted detritus(IRD)events were recognized in MIS 2 and MIS 3 .The IRD events in MIS 3 originated from the vast carbonate rock outcrops of the Canadian Arctic Archipelago and the clastic quartz in MIS 2 may have had a Eura-sian origin.Most -δ18 O and -δ13 C values of Neogloboquadrina pachyderma(sinistral)(Nps)in core 08P23 are lighter than the average values of the surface sediments.The light Nps-δ18 O and -δ13 C values in the two brown layers in MIS 1 and MIS 3 resulted from meltwater events,and those in the gray layers in MIS 3 were caused by enhanced sea ice formation.The Nps-δ18 O values vary inversely with those of Nps-δ13 C in MIS 2,indicating that the study area was covered by thick sea ice or an ice sheet with cold temperatures and little meltwater,which prevented bioproductivity and sea-atmosphere exchange,as well as water mass ventilation.The covarying light values of Nps-δ18 O and -δ13 C in MIS 1 and MIS 3 resulted from meltwater and/or brine rejection.%通过中国第三次北极科学考察在北冰洋楚科奇海台采集的08P23孔样品的多项指标分析以及与其他孔的沉积记录综合对比，将08P23孔沉积物初步分为氧同位素3期（MIS 3）-MIS 1的沉积序列。MIS 3以来，楚科奇海台08P23孔可以识别出5个显著的冰筏碎屑（Ice-Rafted Detritus，IRD）事件，分别出现在MIS 2和MIS 3。其中，MIS 3的IRD事件中碎屑碳酸盐岩主要来自于加拿大北极群岛分布广泛的古生代碳酸盐岩露头，MIS 2的IRD事件中碎屑石英可能来源于欧亚大陆边缘。该孔大部分层位浮游有孔虫左旋厚壁新方球虫Neogloboquadrina pachyderma （sinistral）（Nps）的δ18 O和δ13 C都轻于表层沉积物中的平均值。MIS 3中两个褐色层中偏轻的Nps-δ18 O和Nps-δ13 C值是由冰融水造成；MIS 1和MIS 3灰色层中偏轻的Nps的δ18 O和δ13 C值指示海冰形成速率的提高，导致轻同位素卤水的生产和下沉。MIS 2的Nps的δ18 O和δ13 C值变化趋势相反，是因为温度急剧降低导致Nps-δ18 O变重，海水冻结成冰，海气交换明显降低使得Nps-δ13 C偏轻。MIS 1和MIS 3的Nps的δ18 O和δ13 C受到融冰水或轻同位素卤水影响导致同时偏轻。