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1.
白令海特征区域的表层沉积硅藻分布及其古海洋学意义 总被引：1，自引：1，他引：0
对白令海表层沉积物样品进行硅藻分析,共鉴定硅藻30属56种(含变种),并确定17种硅藻新记录,其中包括Kisseieviella carina等3种化石种。白令海表层沉积物中的硅藻优势种为Neodenticula seminae,Fragilariopsis cylindrus和Fragilariopsis oceanica,在白令海北部陆坡深水区附近以Neodenticula seminae为主,而在白令海北部陆架以Fragilariopsis cylindrus和Fragilariopsis oceanica为主。对硅藻结果进行聚类分析,可以划分出3个硅藻组合,硅藻组合Ⅰ代表海冰种硅藻组合,组合Ⅱ代表受阿拉斯加流影响的大洋浮游硅藻组合,组合Ⅲ代表上述两个硅藻组合之间的过渡组合。Fossula arctica是17种硅藻新记录之一,首次记录于白令海表层沉积物中,其百分含量分布趋势与Fragilariopsis cylindrus和Fragilariopsis oceanica的相近,在白令海北部陆架为11.7%~17.1%,而在陆坡深水区附近明显减少,是继Fragilariopsis cylindrus和Fragilariopsis oceanica之后白令海又一海冰指示种,并有望成为一种有效的海冰变化替代物运用于晚第四纪以来白令海海冰进退历史研究。 相似文献
2.
冲绳海槽DGKS9603孔细粒沉积物元素组合特征及其意义 总被引：8，自引：3，他引：8
通过对冲绳海槽DGKS9603孔柱样高密度取样,提取样品中小于2μm的黏土粒级组分,利用ICP-AES进行常、微量元素含量分析后,再经多种方法处理数据,发现该孔沉积物物源时段分明:距今45～43ka以生物源作用为主,距今43～41ka以火山作用为主,距今41.0～11.2ka以陆源作用为主,距今11.2～0.0ka以生物源作用为主.元素和氧化物含量的垂向变化主要受古气候、古环境变化的影响.DGKS9603孔沉积物元素地球化学特征清晰地记录了E3,YD,H1,LGM,H2,H3,H5七次变冷事件,并表明该孔很可能受到了A,B,C三次火山事件的影响. 相似文献
3.
通过对南黄海中部B10岩心的碳酸钙、常量元素和微量元素分析发现,岩心的地球化学特征基本反映了该海区晚第四纪气候变化、海面波动以及沉积物供应的变化.在玉木亚间冰期(末次冰期亚间冰期)高海面时期,黄河可能直接注入南黄海,在南黄海中部发育水下三角洲沉积.晚玉木冰期(末次冰期盛冰期),南黄海出露成陆,局部发育陆相泥炭层.冰后期(全新世)海侵到达现今80 m等深线附近的时间大约在距今13 ka。在距今11.0～10.3 ka出现新仙女木事件.全新世中晚期海面进一步上升,沉积物粒度较细,化学风化作用加强.岩心50～0 cm段沉积物中的碳酸钙、氧化钙、锶、氧化镁含量及Sr/Ba比值低,而铜等微量元素含量增加,这可能与公元1855年黄河北迁后进入南黄海中部的黄河物质减少有关. 相似文献
4.
腾格里沙漠南缘土门剖面41LD-52L层段由3层黄土状亚砂土、5层砂黄土、2层湖湘和2层古土壤组成,其年代为14 930~11 640aBP,相当于末次冰消期。分析结果表明,整个末次冰消期层段以粉砂含量占绝对优势,分布范围/平均值21.69%~79.47%/50.33%;砂含量次之,为3.97%~75.37%/38.17%;黏土含量最少,为2.34%~34.02%/11.50%。各不同粒级沉积物、Mz、σ等在垂直方向上呈相反的镜像对称变化。该层段粒度（Mz）指示腾格里沙漠南缘末次冰消期经历了4个以东亚夏季风为主的暖湿气候（W1-W4）与4个冬季风为主的冷干气候（C1-C4）,其中W2、W3和W4暖事件与格陵兰GRIP冰心记录的晚阿勒罗德（late Allerd）、早阿勒罗德和波令（Blling）等暖事件对应;C1、C2和C3冷事件与新仙女木（Younger Dryas,YD）和阿勒罗德（Inter Allerd Cold Period,IACP）冷事件对应。同时,该指标指示的新仙女木冷期（12650~11640aBP）与波令-阿勒鲁德暖期（14930~12650aBP）,可分别与格陵兰GRIP冰心氧同位素记录的新仙女木冷期、波令-阿勒鲁德暖期（B/A转换）在气候性质和相位上具有较好的对应关系。它们之间的良好的对比关系表明,腾格里沙漠南缘气候波动的驱动机制可能与格陵兰冰心代表的北半球高纬度热盐环流驱动机制密切相关。 相似文献
5.
《海洋地质与第四纪地质》2016,(1)
腾格里沙漠南缘土门剖面41LD-52L层段由3层黄土状亚砂土、5层砂黄土、2层湖湘和2层古土壤组成,其年代为14 930~11 640aBP,相当于末次冰消期。分析结果表明,整个末次冰消期层段以粉砂含量占绝对优势,分布范围/平均值21.69%~79.47%/50.33%;砂含量次之,为3.97%~75.37%/38.17%;黏土含量最少,为2.34%~34.02%/11.50%。各不同粒级沉积物、Mz、σ等在垂直方向上呈相反的镜像对称变化。该层段粒度(Mz)指示腾格里沙漠南缘末次冰消期经历了4个以东亚夏季风为主的暖湿气候(W1-W4)与4个冬季风为主的冷干气候(C1-C4),其中W2、W3和W4暖事件与格陵兰GRIP冰心记录的晚阿勒罗德(late Allerd)、早阿勒罗德和波令(Blling)等暖事件对应;C1、C2和C3冷事件与新仙女木(Younger Dryas,YD)和阿勒罗德(Inter Allerd Cold Period,IACP)冷事件对应。同时,该指标指示的新仙女木冷期(12650~11640aBP)与波令-阿勒鲁德暖期(14930~12650aBP),可分别与格陵兰GRIP冰心氧同位素记录的新仙女木冷期、波令-阿勒鲁德暖期(B/A转换)在气候性质和相位上具有较好的对应关系。它们之间的良好的对比关系表明,腾格里沙漠南缘气候波动的驱动机制可能与格陵兰冰心代表的北半球高纬度热盐环流驱动机制密切相关。 相似文献
6.
末次冰期以来冲绳海槽北部古气候变化的孢粉记录 总被引：2，自引：0，他引：2
通过分析冲绳海槽北部CSH1柱状样的孢粉组合,重建了海槽区邻近岛屿末次冰期以来的植被和气候变化史.将所测岩心的孢粉记录从下到上分为三期:Ⅰ期为热带山地针叶林的繁盛期,松属及亚热带高山的常绿针叶林含量较高,气候干燥温暖;Ⅱ期为旱生草本植物繁盛期,蒿属大量出现,气候干冷;Ⅲ期为常绿阔叶、落叶阔叶林及蕨类植物繁盛期,常绿阔叶及落叶阔叶林成分增加,蕨类孢子达到极高值,草本植物含量剧减,气候温暖潮湿.将一些主要科属花粉的百分含量曲线与格陵兰冰心GISP2δ18O曲线进行了对比分析,发现各花粉百分含量曲线分别在距今4.1~4.6,11.7~13.0,15.4,23.2,29.4,47.4ka显示出了一系列明显的次级波动,这些次级波动与格陵兰冰心δ18O曲线所记录的4ka左右的降温事件、新仙女木(Younger Dryas)事件和Heinrich事件H1,H2,H3和H5在时代上相吻合.尽管格陵兰及北大西洋地区的气候变化影响冲绳海槽地区的途径和载体尚不清楚,但北半球高纬度的气候变化所引发的东亚季风强度在数百年或千年尺度的波动可能是其主要的机制. 相似文献
7.
对南海北部陆坡Site4B站位末次冰盛期晚期至全新世(30~120cm)长链脂肪醇分布及碳同位素组成进行讨论,结果表明,长链脂肪醇碳优势指数(CPI,10.49~24.56)、平均碳链长(ACL,28.91~29.99)以及平均碳同位素组成(–28.85±0.97‰~–32.92±1.38‰)均反映了陆源C3植物来源,代表了沉积物中陆源输入。Site4B站位末次冰盛期末至晚更新世末(65~102cm,19.343~11.636ka BP)普遍较低的陆源输入均响应了大规模的冰融水事件19ka-MWP、MWP-1A、MWP-1B(melt water pulse,MWP)和暖气候事件(B/A事件),不具冰期/间冰期旋回变化特征。在末次冰盛期晚期(102~120cm)和全新世(30~60cm,10.490~约7.104 ka BP)陆源输入的旋回变化均反映了加强/减弱的冬季风/夏季风旋回变化,其中在末次冰盛期晚期记录一次冬季风最强事件,在早全新世至9.940ka BP记录一次夏季风最强事件。通过Site4B站位末次冰盛期末至晚更新世末(19.343~约11.636 ka BP)千年尺度陆源输入分布特征和全球冰期/间冰期旋回气候变化的对比,发现不具明确的区域对比性,可能受到低纬地区局地环境的作用所致。 相似文献
8.
南海北部ZHS-176孔古海洋学记录:氧同位素和有机碳 总被引：1，自引：0，他引：1
对南海北部陆坡ZHS-176孔进行浮游有孔虫氧同位素和有机碳的研究,重建了末次冰期以来的古气候演化历史。ZHS-176孔浮游有孔虫氧同位素分析揭示了末次冰期期间的气候波动,如末次盛冰期、Heinrich事件1、Blling-Allerd暖期与新仙女木事件在南海北部陆坡均有响应。同时,在全新世阶段存在3个强降水期和3个弱降水期。ZHS-176孔有机碳以生物成因为主,随着夏季风的增强,陆源物质含量增加,但在3kaBP以后由于华南地区夏季风减弱而导致陆源输入减少。 相似文献
9.
新仙女木（Younger Dryas）事件是末次冰消期持续升温过程中的一次突然降温的典型非轨道事件,对于研究古气候、古环境的快速突变事件和短周期现象,合理评估现今气候一环境条件并做出气候变化的预测有着重要的意义。它是一个全球性的事件,中国东部陆架海也普遍发现了“新仙女木”事件的沉积记录。由于中国东部陆架位于欧亚大陆和太平洋之间,受季风的强烈影响,因此有着独特的响应。在“新仙女木”事件发生时,海平面在-50m水深位置稍微下降或振荡徘徊,在-50m线上则以湖泊沼泽、埋藏河床、风沙沉积记录为主,-50m以下则以海洋沉积记录为主,这条线的附近则存在沼泽泥炭和古潮流沙脊。 相似文献
10.
博斯腾湖末次冰消期新仙女木事件的碳酸盐同位素记录 总被引：1，自引：0，他引：1
钟巍 《海洋地质与第四纪地质》1998,18(3):87-94
新仙女木事件是发生于末次冰消期中的一次十分强烈的气候突然变冷事件,共突然性及全球性特征引起人们高度重视。根据新疆南疆博斯腾湖湖相沉积碳酸盐稳定同位素组成,同时结合孢粉及ＣａＣＯ３含量分析,揭示了新仙女木事件的存在。 相似文献
11.
N. O. Chistyakova E. V. Ivanova B. Risebrobakken E. A. Ovsepyan Ya. S. Ovsepyan 《Oceanology》2010,50(4):573-581
Environmental changes in the surface and bottom water layers of the Ingøydjupet Basin and the history of the Atlantic Water inflow to the southwestern Barents Sea during the last 16 ka are reconstructed based on planktic and benthic foraminiferal assemblages. The multiproxy study of sediment cores PSh-5159R and PSh-5159N, including AMS 14C dating, provides a time resolution of about 200 years for the deglaciation, 100 years for the Holocene, and 25–50 years for the last 400 years. Stable polar conditions with the sea ice at the surface were typical for the Early Deglaciation period. Unstable bottom settings and the onset of ice rafting marked the Oldest Dryas. The cold Atlantic Water inflow increased notably during the Bölling-Alleröd interstadial nearby the site location and then decreased during the Younger Dryas. The initial Holocene was characterized by abrupt warming in bottom and surface water layers, especially ～9.7–7.6 ka BP. Stable conditions prevailed during the Middle Holocene. Remarkable changes in the sea-surface temperature and bottom environments occurred during the last 2.5 cal. ka BP. 相似文献
12.
Sea surface temperature variations in the southwestern South China Sea over the past 160 ka 总被引：1，自引：0，他引：1
Sea surface temperatures (SSTs) in the southwestern South China Sea have been reconstructed for the past 160 ka using the Uk37 paleothermometer from the core MD01-2392. The temperature differences between glacial times (MISs 6 and 2) and interglacial times (MISs 5.5 and 1) are 2.2~2.5 ℃. Younger Dryas event during the last deglaciation was documented in both the planktonic foraminiferal δ18O and SST records. After MIS 5.5, SSTs displayed a progressive cooling from 28.6 to 24.5 ℃, culminating at the LGM. During this gradual cooling period, warm events such as MISs 5.3, 5.1 and 3 were also clearly documented. By comparison of SST between the study core and Core 17954, a pattern of low or no meridional SST gradients during the interglacial periods and high meridional SST gradients during the glacial periods was exhibited. This pattern indicates the much stronger East Asian winter monsoon at the glacial than at the interglacial periods. Spectral analysis gives two prominent cycles: 41 and 23 ka, with the former more pronounced, suggesting that SSTs in the southern SCS varied in concert with high-latitude processes through the connection of East Asian winter monsoon. 相似文献
13.
E. V. Ivanova I. O. Murdmaa E. M. Emelyanov E. A. Seitkalieva E. P. Radionova G. N. Alekhina S. M. Sloistov 《Oceanology》2016,56(1):118-130
This paper presents reconstructions of ice sheet boundaries, lacustrine and marine paleobasins, as well as the connections of the Barents and Baltic seas with the North Atlantic from the Last Glacial Maximum to the Holocene. The reconstructions are based on original and published data obtained from the northern and western parts of the Barents Sea and Baltic depressions with account for the available regional schematic maps of deglaciation. The early deglaciation of the Scandinavian–Barents ice sheet culminated with the Bølling-Allerød interstadial (14.5–12.9 cal ka BP), which was characterized by a more vigorous Atlantic meridional overturning circulation (AMOC) and a corresponding increase in surface Atlantic water inflow into the Barents Sea through deep troughs. The Baltic Ice Lake (BIL) remained a dammed-up isolated basin during deglaciation from 16.0 to 11.7 cal ka BP. In the Younger Dryas (YD), the lake drained into the North Sea and was replaced by a brackish Yoldia Sea (YS) at the beginning of the Holocene (Preboreal, 11.7–10.7 cal ka BP), due to a limited connection between two basins through the Närke Strait. In the Barents Sea, the next increase in the Atlantic water influx into the deep basins corresponded to terminal YD and Preboreal events with a culmination in the Early Holocene. The Yoldia Sea became a lake again during the next stage, the Ancylus (~10.7–8.8 cal ka BP). Atlantic water inflow both into the Barents and Baltic seas varied during the Holocene, with a maximum contribution in the Early Holocene, when the Littorina Sea (LS, 8–4 cal ka BP) connection with the North Sea via the Danish Straits was formed to replace the Ancylus Lake. The recent, post-Littorina stage (PS, the last 4 cal ka) of the Baltic Sea evolution began in the Late Holocene. 相似文献
14.
J. T. Andrews R. K. Matthews L. E. Osterman G. H. Miller C. Hillaire-Marcel K. M. Williams 《Geo-Marine Letters》1987,7(1):23-30
Stable isotope measurements on molluses from raised marine deposits, and on foraminifera in a piston core, define a series of light isotope events. A major event is14C dated at ca. 10.3 ka and is correlated with a marked isotopic excursion in HU77-021-156. This event is followed by a dramatic rise in diatom and, slightly later, in benthic foraminiferal abundances. Molluses record another light event around 8 ka. Major fluctuations in both 18O and 13C around 10.3 ka suggests that the Hudson Strait ice stream may have responded to the Younger Dryas climatic oscillation. 相似文献
15.
西格陵兰位于北极—北大西洋地区,其海洋环境演变受西格陵兰洋流中冷、暖水团的显著影响。本文运用主成分分析方法对西格陵兰Disko湾DA06-139G孔沉积物中主要硅藻属种进行研究,试图揭示5000a BP以来西格陵兰洋流中冷、暖水团强度变化对研究区海洋环境的影响。5000—3800a BP期间,东格陵兰寒流携带的极地冷水团强度较弱,而北大西洋暖水团势力较强,Disko湾地区海洋环境较为温暖。3800—2000a BP期间,西格陵兰洋流中极地冷水团势力呈现阶段性增强,此时Disko湾地区气候缓慢转冷,海冰覆盖面积逐渐增加。2000a BP以后,特别是650a BP之后,样品在主成分轴一上的得分显著增高,表明Disko湾气候明显变冷,来自东格陵兰寒流的极地冷水团强度显著增强。Disko湾中晚全新世以来的硅藻记录及样品在主成分轴一上的得分所指示的极地冷水团的强度变化与格陵兰冰芯温度及海冰变化等具有较好的一致性,说明研究区海流特征与大气温度、海冰等环境要素密切相关。 相似文献
16.
The 4.2 ka event that occurred during the period from 4 500–3 900 a BP was characterized by cold and dry climates and resulted in the collapse of civilizations around the world. The cause of this climatic event, however, has been under debate. We collected four corals(Porites lutea) from Yongxing Island, Xisha Islands, South China Sea, dated them with the U-series method, and measured the annual coral growth rates using X-ray technology. The dating results showed that the coral growth ages were from 4 500–3 900 a BP, which coincide well with the period of the4.2 ka event. We then reconstructed annual sea surface temperature anomaly(SSTA) variations based on the coral growth rates. The growth rate-based SSTA results showed that the interdecadal SSTA from 4 500–3 900 a BP was lower than that during modern times(1961–2008 AD). A spectral analysis showed that the SSTA variations from4 500–3 900 a BP were under the influence of El Ni?o-Southern Oscillation(ENSO) activities. From 4 500–4 100 a BP, the climate exhibited La Ni?a-like conditions with weak ENSO intensity and relatively stable and lower SSTA amplitudes. From 4 100–3 900 a BP, the climate underwent a complicated period of ENSO variability and showed alternating El Ni?o-or La Ni?a-like conditions at interdecadal time scales and large SSTA amplitudes. We speculate that during the early and middle stages of the 4.2 ka event, the cold climate caused by weak ENSO activities largely weakened social productivity. Then, during the end stages of the 4.2 ka event, the repeated fluctuations in the ENSO intensity caused frequent extreme weather events, resulting in the collapse of civilizations worldwide. Thus, the new evidence obtained from our coral records suggests that the 4.2 ka event as well as the related collapse of civilizations were very likely driven by ENSO variability. 相似文献