Environmental anomalies in the northeastern East China Sea during the last 3 000 years:implications for El Nio activity in the Holocene

To reconstruct the productivity changes for the last 10 500 a in the northeastern East China Sea (ECS),biogenic compounds (such as carbonate,organic carbon and opal),marine micropaleontological fossils (planktonic foraminifera,benthic foraminifera,radiolarian and silicoflagellate) and the compositional characters of benthic foraminifera fauna analyses were carried out on a sediment core DOC082 obtained from the western slope of Okinawa Trough (29°13.93'N,128°08.53'E;1 128 m water depth).The long-term changes of biogenic and micropaleontological proxies display some similarities through the last 10 500 a,which show three different phases:lower values are recorded during the early and middle Holocene (before about 4 000 a BP),followed by an abrupt and remarkable increase at about 4 000 a BP,the late Holocene (after about 3 000 a BP) is characterized by continuously high values.The multi-proxy data of paleoproductivity and percents of benthic foraminifera genera (Uvigerina and Bulimina) show that during the early and middle Holocene (10 500-4 000 a BP) productivity was relatively low with a sudden and distinct increase at about 4 000 a BP,and the late Holocene (3 400-0 a BP) is marked by significantly higher productivity.Also,the radiolarian-based sea surface temperature (SST) records reveal a distinct decline in SST in the late Holocene after 3 200 a BP,very different from the early and middle Holocene.For the last 3 000 a,the enhanced biological productivity and distinctly lower SST indicate a major change of oceanographic conditions in the northeastern ECS.These marine environmental anomalies are consistent with other paleoclimatic records for the late Holocene in the Chinese continent and its surrounding regions.After analyzing the mechanisms of modern productivity and SST changes in the northeastern ECS,and based on the climatic anomalies in the Chinese continent and variations in the Kuroshio Current during modern El Nio periods,we suggest that the anomalous environmental conditions in the northeastern ECS may imply intensified El Nio activity during the late Holocene.     

Sedimentary response to volcanic activity in the Okinawa Trough since the last deglaciation

To investigate the relationship between volcanic activity and sediment record on regional and temporal scales, 158 surface sediment samples were collected from the East China Sea Shelf to the northern Okinawa Trough (OT), and two cores recovered in the northern and southern OT, respectively. Mineralogy, grain-size, and geochemical analyses of those samples show that: 1) volcanic glass, volcanic-type pyroxene, hypersthenes, and magnetite increase in sediment influenced by volcanic activity; 2) sediment grain sizes (and also silt content) increase in ash layers; and 3) the contents of Na₂O and Zr are higher, while terrigenous elements, e.g., TFe₂O₃ and K₂O, and biogenous compositions, e.g., CaO and Sr, are relatively lower in ash layers than those of non-ash layers. The distribution of volcanic ash has three distinguishing characteristics: 1) volcanic ash is more abundant in the northern and central OT than the southern OT; 2) volcanic ash increases from continental shelf to the trough; 3) the sediment during the last 12 000 a suggests stronger volcanic events than during 15 000–12 000 a. The eruptive locations, frequency, and volume of calderas are among the most important factors controlling the distributions of volcanic ash. In addition, the main Kuroshio warm current that extends northward probably impeded the diffusion of volcanic ash to the west and south in the OT. However, a southward current probably carried some volcanic ash toward southern OT.     

Environmental anomalies in the northeastern East China Sea during the last 3 000 years: implications for El Niño activity in the Holocene

To reconstruct the productivity changes for the last 10 500 a in the northeastern East China Sea (ECS), biogenic compounds (such as carbonate, organic carbon and opal), marine micropaleontological fossils (planktonic foraminifera, benthic foraminifera, radiolarian and silicoflagellate) and the compositional characters of benthic foraminifera fauna analyses were carried out on a sediment core DOC082 obtained from the western slope of Okinawa Trough (29°13.93′N, 128°08.53′E; 1 128 m water depth). The long-term changes of biogenic and micropaleontological proxies display some similarities through the last 10 500 a, which show three different phases: lower values are recorded during the early and middle Holocene (before about 4 000 a BP), followed by an abrupt and remarkable increase at about 4 000 a BP, the late Holocene (after about 3 000 a BP) is characterized by continuously high values. The multi-proxy data of paleoproductivity and percents of benthic foraminifera genera (Uvigerina and Bulimina) show that during the early and middle Holocene (10 500–4 000 a BP) productivity was relatively low with a sudden and distinct increase at about 4 000 a BP, and the late Holocene (3 400–0 a BP) is marked by significantly higher productivity. Also, the radiolarian-based sea surface temperature (SST) records reveal a distinct decline in SST in the late Holocene after 3 200 a BP, very different from the early and middle Holocene. For the last 3 000 a, the enhanced biological productivity and distinctly lower SST indicate a major change of oceanographic conditions in the northeastern ECS. These marine environmental anomalies are consistent with other paleoclimatic records for the late Holocene in the Chinese continent and its surrounding regions. After analyzing the mechanisms of modern productivity and SST changes in the northeastern ECS, and based on the climatic anomalies in the Chinese continent and variations in the Kuroshio Current during modern El Niño periods, we suggest that the anomalous environmental conditions in the northeastern ECS may imply intensified El Niño activity during the late Holocene.     

东海内陆架EC2005孔沉积物粒度分形特征

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西太平洋暖池核心区Ontong Java 海台古菌多样性研究

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末次冰消期以来东海内陆架沉积速率及其气候环境响应

对位于东海内陆架浙-闽沿岸泥质带的EC2005孔岩性、粒度以及AMS14C年代进行了分析,着重探讨了研究区自末次冰消期以来的沉积速率变化,划分出4个大的沉积阶段和4次快速沉积事件.千年时间尺度上大的沉积阶段主要受控于物源供应、海平面变化以及可容空间的大小.百年时间尺度上揭示的4次快速沉积事件主要受控于东亚冬季风的增强或...     

中更新世以来西菲律宾海上层水体结构演化特征——来自钙质超微化石Florisphaera profunda的证据

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末次冰消期以来东海内陆架沉积物磁化率的环境意义

对末次冰消期以来东海内陆架沉积物磁化率的影响因素及其蕴含的古环境信息进行了探讨.对位于浙闽沿岸泥质沉积中心附近的EC2005孔沉积物磁化率、岩性、粒度、常量元素、矿物以及AMS<'14>C测年数据进行了综合分析,得出以下主要结论:EC2005孔沉积物磁化率的变化受多种因素的制约,不同层位的主要控制因素不同,60.20～...     

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豫西银家沟杂岩体年代学、地球化学和岩石成因

银家沟杂岩体位于河南省灵宝市,主要岩石类型为二长花岗斑岩、钾长花岗斑岩和石英闪长斑岩,并有少量呈脉状产出的花岗闪长斑岩及闪长玢岩.该杂岩体是银家沟硫铁多金属矿床的成矿母岩.杂岩体的元素地球化学和锆石SHRIMP U-Pb年代学研究结果表明,银家沟杂岩体二长花岗斑岩、钾长花岗斑岩和花岗闪长斑岩的侵位年龄分别为147.5±2.1Ma、147.8±1.6Ma和142.0±2.0Ma,为晚侏罗世-早白垩世的产物.二长花岗斑岩和钾长花岗斑岩具有高的SiO2(65.17％ ～73.94％)和Al2O3含量(13.53％ ～ 15.96％)、非常高的K2O含量(5.03％ ～9.89％,多数大于6.0％),但具有低的Na2O(0.24％～1.86％,多数小于1.0％)、Fe2O3(0.82％～3.71％)、FeO(0.02％ ～ 1.62％)、MgO(0.23％～1.47％,多数小于1.0％)和CaO含量(0.08％～ 1.98％,多数小于0.4％),铝指数(ASI)为1.18～2.04,全部大于1.1,应为热液蚀变引起.杂岩体的稀土元素总量介于71.38×10-6～276.4×10-6,具有中等-微弱的Eu负异常(δEu介于0.57 ～0.88),稀土元素分馏强烈,其(La/Yb)N介于6.93 ～ 30.1之间,为轻稀土富集型.岩石具有低Sr(104×10-6～461×10-6,多数＜300×10-6)和Yb含量(0.90×10-6～2.10×10-6,绝大多数＜1.9×10-6).在原始地幔标准化的微量元素蜘蛛网图中,银家沟杂岩体富集Rb、Ba、Th、U、K、La、Ce、Nd、Hf、Zr等,强烈亏损Sr、P、Ti等,具有中等Nb、Ta亏损.主量、稀土和微量元素特征表明,岩石具后碰撞花岗岩类的地球化学特征,属后碰撞花岗岩.杂岩体的锶初始比值(Isr)为0.7069～0.7091,多数＜0.7085,εNd(t)值为-14.99～-10.57,亏损地幔单阶段Nd模式年龄为1.41～1.76Ga,两阶段Nd模式年龄为1.51～1.81Ga;钾长石206Pb/204Pb、207 Pb/204Pb和208Pb/204Pb比值变化范围分别为17.376 ～17.628、15.455～ 15.502和37.867～38.090,Nd、Sr和Pb同位素组成指示银家沟杂岩体最可能源自宽坪群、二郎坪群和太华群的混合物.银家沟杂岩体形成于晚侏罗世-早白垩世期间的EW向构造体制向NNE向构造体制转换环境,构造体制转换使东秦岭地区处于减压环境,下地壳大规模部分熔融,导致银家沟杂岩体形成.