The long-term burial of organic carbon in marginal seas plays a critical role in Earth’s carbon cycle and climate change. However, the mechanism of organic carbon (OC) burial in the Okinawa Trough (OT) during glacial-interglacial timescales remains unclear. In this study, we analyzed the foraminiferal carbon isotopes, total organic carbon (TOC), and δ13C-TOC over the past 200 ka in core Z1 collected in the central OT. We aimed to reveal the history of OC burial in the middle Okinawa Trough during the past 200 ka, and we combined our findings with relevant paleoenvironmental indices to reveal underlying mechanisms. We found reduced surface primary productivity during MIS 6, which may indicate changes in the pathways of the Kuroshio Current (KC). Furthermore, we observed decoupling between high TOC flux and low OC burial during glacial periods. We proposed that the dilution effect caused by the high sedimentation rate and poor OC preservation during the glacial period resulted in the low TOC content. Ventilation of the North Pacific Intermediate Water (NPIW) regulated the redox conditions of the intermediate water in the Okinawa Trough. Additionally, the intensified Kuroshio Current during interglacial phases led to water column stratification, creating reducing conditions in the bottom water and facilitating improved OC preservation. Subsequently, the enhanced water column oxygenation resulting from the oxygen carried by the intensified glacial NPIW weakened the burial of OC. This study sheds new light on our understanding of the carbon cycle in marginal seas on a glacial-interglacial timescale.

The Kyushu-Palau Ridge and adjacent basins are ideal locations for investigating the formation and evolution of marginal seas and initiation of plate subduction. In this study, the tectonic-sedimentary features and crustal structure of the Kyushu-Palau Ridge and adjacent basins were investigated using newly obtained deep seismic reflection and borehole data. The initial mechanism of subduction in the West Philippine Sea and its tectonic evolution are discussed. Two sets of sedimentary strata with different provenances occur in the eastern Philippine Basin. The thickness of the lower strata is variable, and most of the sediment was sourced from island arc volcanism on the Kyushu-Palau Ridge. These strata thicken towards the Kyushu-Palau Ridge, and volcaniclastic rock aprons are developed near the foot of the Kyushu-Palau Ridge. The upper strata have a relatively uniform thickness and comprise fine-grained, deep-water marine sediments. The crustal thickness of the West Philippine and Parece Vela Basins is 6-7 km, which is similar to the global average thickness of oceanic crust. The Moho beneath the West Philippine Basin has a broad and undulating form that mimics the thickness of the oceanic crust beneath the sediments. The depth to the Moho decreases towards the Central Basin Spreading Center. The Moho beneath the Parece Vela Basin is planar, which is in contrast to the undulating nature of the oceanic crust base in this area. The West Philippine Basin may have been located at the northern margin of Australia in the Southern Hemisphere during the Mesozoic. It developed gradually in a continental margin arc as a result of Palaeogene inter-arc and oceanic extension and contains fragments of continental crust. Seismic profiles and drillhole data in the West Philippine Basin reveal that compression occurred during the Eocene. Subduction along the paleo-Izu-Bonin-Mariana arc may have been caused by the far-field effects of the India-Asia collision. Subduction was accompanied by lateral propagation and a compressive stress field until the break-up of the island arc at ca. 30 Ma.

Hainan Island, the largest island in the northwestern South China Sea (SCS), is characterized by many tropical mountainous rivers that flow into the SCS. The geochemistry of these riverine sediments and the factors controlling the weathering intensity are still not well understood. In this study, sedimentary geochemistry has been investigated by using 45 riverine sediments collected from 18 major rivers on Hainan Island. The Hainan riverine sediments are only first-cycle rather than polycyclic sediments, and they faithfully reflect the present weathering intensity. The high and steady values of the Chemical Index of Alteration (CIA) indicate that the riverine sediments at different parts of the Hainan Island have overall undergone intensive chemical weathering. The low values of Weathering Index of Parker (WIP) and high α C a , α K , α S r , and α B a values of north Hainan indicate the highest weathering degree, which is mainly influenced by the flat topography. The values of α N a , α K , α S r , and α B a of southwest Hainan which are higher than those of east Hainan suggest that the leaching of elements such as Na, K, Sr, and Ba is more extreme (i.e., more intensive weathering). These are mainly caused by the different physical denudation due to different summer precipitation. Overall, the Hainan Island is featured by intensive chemical weathering and is classified as a typical transport-limited weathering regime. Therefore, the geochemistry of the riverine sediments of the Hainan Island is different from that of sediments in tectonically active regions (e.g., Taiwan Island).

基于AMS14C年龄和底栖有孔虫氧同位素建立的地层年代框架,重点探讨了冲绳海槽中北部CSHC-15孔MIS6期以来(约200 ka)底栖有孔虫δ13C特征及其古海洋指示意义.结果显示,冰期-间冰期表层初级生产力和有机质通量的变化是导致底栖有孔虫δ13C值在MIS4和MIS6期负偏而在MIS1、MIS3和MIS5期正偏的主要原因.MIS2期的底栖有孔虫δ13C正偏,指示了 NPIW侵入冲绳海槽,导致通风性加强,底层水呈弱氧化状态.甲烷渗漏引发的甲烷厌氧氧化作用(AOM)是导致CSHC-15孔底栖有孔虫在MIS4期碳同位素大幅负偏的原因.

深海多金属结核与富钴结壳富含Mn、Co、Ni、Cu及稀土等元素,极具资源潜力,因而广受关注.选择采集自九州-帕劳海脊南段水深约3000?m的6个多金属结核和2个富钴结壳样品进行地球化学特征研究.结果显示本区样品Mn/Fe比值为0.88～1.07,Co及稀土元素含量高,与库克群岛多金属结核元素特征相似,表现出典型的水成成因特征.与其他地区水成结核、结壳相比,样品具有较高的Ca含量,可能和其所在位置海脊部位水深较浅、位于碳酸盐补偿深度(CCD)以上有关.样品表现出Y负异常、Nd含量高等水成结核的特点,但微弱的Ce正异常特征与其他地区水成多金属结核/壳的强烈Ce正异常特征不同,这表明其生长于弱氧化环境.本区结核分布在CCD以上,最小溶氧层(OMZ)以下,是一种水成成因、贫氧生长的新型多金属结核,其物质来源、成矿模式将为揭示多金属结核的形成分布规律提供一条全新的认识途径.同时研究区结核、结壳Co及稀土元素含量较高,且分布位置较浅,易于开采,具有一定的资源潜力.

通过对东海外陆坡–冲绳海槽GSW1孔沉积物孔隙水δ13C、δ18O、δ11B、δ37Cl同位素和C1?、SO2-4、K+、Na+等离子指标的分析,探讨了沉积物早期成岩作用、流体来源、迁移和氧化环境的变化.研究发现,GSW1孔孔隙水溶解无机碳主要来自海水和有机质,SO2-4浓度随深度下降比较平缓,C1?浓度远低于海水,该孔表层沉积物中硫酸盐消耗主要由有机质硫酸盐还原作用(OSR)所控制,甲烷厌氧氧化作用(AOM)发生在4 m以下更深的层位.OSR产生的H2S向上扩散富集并被氧化,是导致GSW1孔110～360 cm处SO2-4浓度未明显下降的主要因素.孔隙水SO2-4浓度整体随着深度增加呈减小的趋势,表明GSW1孔沉积环境由氧化、次氧化环境逐渐转变为还原环境.δ11B、δ37C1值垂向变化波动较大,一方面受到早期成岩阶段有机质降解的影响,也可能与孔隙流体扩散以及沉积物/孔隙水相互作用有关.

The Kuroshio current transports large amounts of heat and water vapor into the South China Sea (SCS) through the Luzon Strait and plays a key role in modulating the surrounding hydroclimate. However, there is no detailed high-resolution history of the Kuroshio intrusion into the SCS preceding the Holocene. Here, clay mineral assemblages and Sr–Nd isotopic values (87Sr/86Sr and εNd) of core CS11 represent the relative abundance of Taiwan and Luzon fluvial sediment contributions in the SCS deep basin, which can be further used as proxies of relative variation of the Kuroshio intrusion into the SCS over the past 40 kyr. Combined with linear sedimentation rate (LSR) and results of previous studies, we demonstrate that variations of Kuroshio currents between the SCS and the open Pacific display opposing trends within each marine isotope stage, similar to the waxing and waning of its modern configuration. The El Niño–Southern Oscillation (ENSO) has acted as the key factor driving variations of the Kuroshio currents over the past 40 kyr. During late marine isotope stage (MIS) 3, the Kuroshio intrusion into the SCS gradually decreased due to decline in intensity of El Niño-like conditions, while an El Niño-like state favored the Kuroshio intrusion into the SCS during MIS 2, in particular during the Last Glacial Maximum (LGM) when Kuroshio transport in the open Pacific weakened. The Kuroshio intrusion into the SCS was largely sluggish in the early Holocene, when a La Niña-like condition prevailed, and then the Kuroshio intrusion was enhanced during the middle to late Holocene under the influence of increased El Niño frequency.

The North Pacific subtropical gyre (NPSTG) redistributes heat and moisture between low and high latitudes and plays a key role in modulating the global climate change and ecosystem. Recent evidence suggests intensification and poleward shift of the subtropical gyres over the last decades due to global warming, but insufficient observations have hampered insight into the integrated effects of ocean-atmosphere interactions at longer timescales. Here we present the first high-resolution (∼12 years) grain-size record from Core CF1 in the Okinawa Trough, western subtropical North Pacific, to reconstruct the evolution of the western boundary Kuroshio Current (KC) of NPSTG during the Late Holocene. Our results indicate the KC slow-down during 4.6–2.0 ka, followed by quick enhancement after 2.0 ka, with centennial-scale variabilities (500–700 years) superimposed on the long-term trend. Over millennial timescales, gradually increased pole-to-equator thermal gradient, due to orbital forcing mechanisms, resulted in long-term enhanced KC, whereas solar activity triggered phase changes in the tropical Pacific mean state and controlled KC anomalies on centennial timescales. We suggest that both forcing mechanisms resulted in ocean-atmosphere feedback provoking concurrent changes in mid-latitude westerly and subtropical easterly winds over the North Pacific, alternating their dominance as source regions causing the dynamic changes of KC at different timescales. Our findings offer insight into the role of external forcing mechanisms in the NPSTG changes before the Anthropocene, which have profound implications for the deeper understanding of changes in ocean gyres under global warming scenarios.

基于AMS14C测年、有机碳、氮含量及其同位素等指标分析,探讨了冲绳海槽中南部OKT-3孔末次冰消期以来沉积物有机质来源及其对古海洋环境演化的响应.结果显示,OKT-3孔沉积物中有机质主要由中国大陆和中国台湾等陆源有机质,以及海洋自生有机质组成.末次冰消期至全新世晚期(17.3～4 ka B.P.),中国大陆源有机质贡献逐渐下降,中国台湾源有机质贡献逐渐上升,表明海平面变化、黑潮变动是该阶段有机质来源的主要控制因素.4～1.5 ka期间,陆源有机质供给变化趋势与黑潮变动不一致,表明该时期陆源输入非黑潮单一控制,还可能受季风降雨等变化影响.值得注意的是,OKT-3孔海源有机质贡献在B-A和PB时期高、YD时期低,与北太平洋地区的生产力变化相似,反映了北太平洋中层水(NPIW)对海水表层生产力的控制作用,NPIW是连通冲绳海槽与北太平洋的重要纽带.

The South Yellow Sea (SYS) is strongly influenced by large amounts of sediment input from surrounding rivers, but the dispersal patterns of these sediments, especially how they accumulate in the central Yellow Sea mud (CYSM) region, have not been well illustrated. Here, we present a detailed temporal variation record of the clay mineral compositions from core YSC-10 of the northern SYS near the western margin of the CYSM, trying to investigate sediment provenance and to discuss transport processes occurring during the Holocene. The clay mineral assemblages of core YSC-10 mainly consist predominantly of illite (68 +/- 3%), followed by chlorite (15 +/- 2%) and kaolinite (10 +/- 2%), with scarce amounts of smectite (6 +/- 3%). Combined with published data, our results suggest that the fine sediments of core YSC-10 are most likely a mixing product of the Huanghe (Yellow River), Changjiang (Yangtze River) and Korean Peninsula small river sediments, with notable temporal changes. During 8.4-6.4 ka, the Huanghe sediments from the Bohai Sea flowed directly into the SYS and played major roles in the sedimentation therein. In addition, as the modern ocean circulation pattern was formed similar to 6 ka, the ocean front developed along the Shandong Peninsula coastal area of the SYS, which would have prevented the dispersal of the Huanghe sediments to the CYSM. The Changjiang sediments delivered by the diluted water replaced those from the Huanghe as the main source of the CYSM during the period of 6.4-4.2 ka. After 4.2 ka, the coastal shear front weakened and moved seawards due to the weakening and eastward shift of the Yellow Sea Warm Current (YSWC) in winter and the weakening and shrinking of the Yellow Sea Cold Water Mass (YSCWM) in summer. The Huanghe sediments seem to have increased and fluctuated frequently to core YSC-10 since then. Our study thus highlights that the coastal shear front may have played an important role in the source-to-sink processes of the SYS.

铁锰结壳富集Co、Cu、Mn、Ni、Ti、V、REE、Y和Zn等关键金属,研究其富集于结壳的规律以及相关地质环境制约因素对于未来开发利用这些海底金属资源十分重要.本文对九州-帕劳海脊南部13°20′N新发现的铁锰结壳样品进行了矿物学、元素地球化学和电子探针微区分析,发现其成分较为均一,未遭受明显的磷酸盐化作用,属于单层型水生成因结壳.Co、Ni等高含量关键金属主要富集在水羟锰矿内,其中主要以晶格态形式存在的Co所经历的表面氧化还原反应是其累积富集的关键;而Ni除了与Co一样通过置换Mn或占据晶格空位而呈现富集特征外,还大量以吸附态形式存在.Ti、V和REY等通过表面络合、晶格进入以及共沉淀作用富集在以六方纤铁矿为主的铁羟基氧化物组分内.Cu、Zn的晶格进入能力不足,加之海水Cu含量偏低,Zn的弱吸附作用共同导致它们以相对低含量形式分散分布.基于Co经验公式揭示结壳的形成起始于晚中新世,未出现明显生长间断,但持续生长时间不足导致结壳的关键金属累积富集程度低于全球主要结壳成矿区.不过,研究区理想的水深条件、较低的沉积速率、稳定的构造环境、合适的最小含氧带水深分布和远离非成矿物质的大规模稀释影响,都是本区结壳未来持续性增生和进一步富集关键金属的有利条件.

The Philippine Sea is a typical region of aeolian dust reposition and is located within the Western Pacific Warm Pool. Here, we use the paleomagnetic stratigraphy and the grain‐size distributions of Quaternary abyssal deposits in the Central Philippine Sea to investigate the factors controlling regional sedimentary and paleoenvironmental changes. Our principal results are as follows: (a) A reliable geochronologic framework for Quaternary sediments in the Central Philippine Sea is established. (b) An eastward expansion of the regional depocenter in the Middle Pleistocene is observed. (c) The mean grain size of the abyssal sediments is 7–8 µm, and there are only minor differences between the sites. Comparison of the geochronological framework with various paleoenvironmental events during the Mid‐Pleistocene Transition shows that sedimentary processes can be correlated to a major transition in global climate which affected regions from the Asian interior to the tropical Pacific, and that changes in aeolian sedimentation are likely the predominant factor responsible. A derived grain‐size proxy of the sedimentary dynamics and its comparison with various paleoenvironmental proxies show that the relative contributions are roughly estimated as 23%, 9%, and 68% for aeolian inputs, oceanic circulation, and the tropical Pacific zonal SST gradient, respectively, in the studied region. The relative importance of tropical processes in abyssal sedimentary dynamics highlights the possibility of the long‐term influence of (sub)mesoscale eddies in the upper ocean, via regional upwelling and unique submarine topography, on the deepest part (>5,000 m) of the Central Philippine Sea, from meteorological to geological timescales.

九州-帕劳海脊及两侧的盆地是研究边缘海形成演化和板块俯冲起始机制的理想区域.利用最新采集的深反射地震数据并结合钻孔数据,研究了九州-帕劳海脊及其东西两侧盆地的构造沉积特征及地壳结构,探讨了西菲律宾海的起源及沿古伊豆-博宁-马里亚纳弧的俯冲起始机制.地震剖面和钻孔岩心揭示西菲律宾海盆发育上、下两套不同来源的沉积物盖层,其中下部地层厚度差别大,多为火山物质,来源于九州-帕劳海脊的岛弧火山作用,表现为向海脊方向的持续增厚,靠近海脊的山脚下发育火山碎屑岩裙;上部地层厚度较为稳定,为一套大洋的深水细粒沉积物.西菲律宾海盆和帕里西维拉海盆的地壳厚度约为6～8?km,接近全球平均洋壳厚度;西菲律宾海盆的莫霍面呈宽缓的褶皱状,与沉积物之下的洋壳基底基本同步起伏.西菲律宾海盆在中生代可能位于南半球澳大利亚的北缘,是在陆缘弧(包含部分大陆碎片)的基础上,因古近纪弧间伸展和海底扩张而逐步发展起来的.西菲律宾海盆的地震剖面和钻井均揭示了始新世时期的构造挤压事件,沿古伊豆-博宁-马里亚纳弧的俯冲起始可能是印亚碰撞的远场效应引起的诱导俯冲,俯冲过程伴随着侧向传播和持续的挤压应力场,直到约30?Ma开始岛弧裂离.该研究对揭示东南亚板块构造演化过程和板块俯冲起始机制具有一定的理论意义.

菲律宾海是西太平洋典型的风尘汇集区,也是南极底层水影响的远端地区.由于水深较大等原因,这一热点地区沉积物的古环境研究尚未全面展开.本文对菲律宾海中部XT06孔沉积物开展了磁性地层和粒度测试工作,分析了XT06孔沉积记录的年代学特征和沉积过程,初步探讨了区域沉积演化的控制因素与古环境意义.结果表明:(1)通过系统交变退磁实验,XT06孔沉积物可以辨识出6个磁极性区间,分别对应于布容正极性时、加拉米洛亚极性时、奥杜维尔正极性时和松山负极性时.通过与国际标准磁极性序列对比,发现XT06孔的沉积速率由快转慢,指示了在1.0～1.5 Ma曾发生过一次明显的沉积转折,可能代表了区域深海沉积中心的迁移,与东亚-西太平洋构造活动等密切相关.(2)XT06沉积物属于典型的远洋悬浮体,反映了较弱的沉积动力环境.通过多种粒度分析方法的交叉对比和验证,发现XT06孔沉积物包含粗、细两个互为消长的动力学组分,指示了较为稳定的深海沉积环境.通过对比其他古环境指标,我们推测在构造时间尺度上,亚洲内陆干旱化导致的粉尘输入增加可能是控制XT06孔沉积物粒度逐步变细的主要因素;而在更高时间分辨率上XT06孔沉积物粒度粗细变化可能主要受深海环流强度的控制作用,体现了冰期南极深/底层水团影响减弱、而间冰期增强的区域特征.本文结果展现了菲律宾海中部沉积过程的一些关键特征,揭示了菲律宾海沉积记录在深入研究地球系统多圈层耦合过程中的巨大潜力.

Changes in marine export productivity may have played a prominent role in the atmospheric CO 2 rise and associated warming of the last deglaciation, via their impact on the air‐sea partitioning of CO 2 . To study the evolution of marine export production in the western subtropical Pacific Ocean during the last deglaciation and the mechanisms governing these changes, 230 Th‐normalization has been applied on a sediment core retrieved from the Okinawa Trough. The reconstructed export productivity record shows two prominent peaks, centered around 14 and 17 ka. Given that phytoplankton growth at our study site is limited by the availability of nutrients today, elevated macro‐nutrient supply must have been responsible for sustaining the two deglacial productivity peaks. Specifically, higher nutrient supply originating from the subpolar gyre via subsurface water advection, with enhanced vertical mixing in the subpolar gyre during early HS1 and enhanced wind‐driven upwelling during the B/A, would have fueled phytoplankton productivity and export. In contrast, reduced nutrient supply to the euphotic zone caused by gyre circulation changes would have lead to decreased export production during the Holocene. These observations lend support to a predominant control of nutrient availability on the evolution of the marine carbon cycle in the subtropical west Pacific Ocean across the last deglaciation.

通过对东海陆坡—冲绳海槽中北部两个水体剖面的碳、氯、硼同位素和离子浓度的分析,探讨了水体剖面的离子和同位素组成的控制因素、水体来源以及现代水体交换过程.结果表明,水体剖面中表层水、次表层水、中层水体的性质明显不同,ST2水体剖面K+、Ca2+、SO42?等离子浓度整体随深度增加而升高,δ13C、δ11B、δ37Cl垂向变化波动较大,ST19剖面离子浓度、同位素垂向变化趋势与ST2剖面相反.ST2、ST19水体剖面表层水(0～100?m)和次表层水(100～300?m)主要来源于黑潮表层水(Kuroshio?Surface?Water,KSW)和黑潮热带水(Kuroshio?Tropical?Water,KTW),同时受长江冲淡水(Changjiang?Diluted Water,CDW)/陆架水影响;中层水体(300～1000?m)组成与北太平洋中层水(North?Pacific?Intermediate?Water,NPIW)和南海中层水(South?China?Sea?Intermediate?Water,SCSIW)相似.两水体剖面水体组成存在较为明显的南北差异,可能与所处海区地理位置、CDW/陆架水传输路径、区域性地形导致局部上升流、水体剖面中NPIW与SCSIW占比不同有关.

基于东海陆坡区OT12-01孔长度为5.35 m沉积物AMS 14C测年、高分辨率粒度分析和XRF岩芯元素扫描数据,识别出了末次冰盛期(LGM)至全新世期间发生的多次滑塌事件.研究发现,OT12-01孔全新世晚期沉积层缺失,LGM至全新世期间呈现AMS 14C年龄模式频繁倒转、沉积物粒度、元素比值垂向上多处突变或"错动"等特征,保存了LGM至全新世非连续的沉积记录.OT12-01孔沉积物主要来源于低海平面时期的长江/黄河物质,OT12-01孔是由中国大陆陆源物质在东海陆架经水动力分选,细颗粒被搬运至东海陆坡后,发生多次滑塌形成.LGM时期物源供给是OT12-01孔形成滑塌沉积的重要因素,末次冰消期海平面快速上升可能是高频滑塌沉积的触发原因,而低海平面时期甲烷水合物溢出、频繁的地震和火山喷发可能是海底滑坡作用发生的诱因.

基于国际海洋古全球变化研究项目(IMAGES)在西菲律宾海本哈姆海台获取的高质量柱状沉积物岩芯MD06-3047(17°00.44′N、124°47.93′E),利用颗石藻下透光带属种Florisphaera profunda的相对丰度以及初级生产力转换函数,恢复了260ka以来西菲律宾海上部水体营养跃层以及初级生产力的变化历史.发现该区域26万年以来初级生产力冰期-间冰期变化特征较不明显,冰期生产力平均值略高于间冰期.通过与前人已发表的指示东亚冬季风强弱的伊利石/蒙脱石记录和热带太平洋纬向表层海水温度梯度记录的对比,提出MIS 8期以来,热带西菲律宾海古生产力变化的主要受控因素在MIS 5a左右发生明显转变.在MIS 8后期至MIS 5a之间,初级生产力受到长期类ENSO过程的影响较为显著,当热带东西太平洋海水表层温度梯度较小的时期,认为热带太平洋处于类El Ni(n)o状态,此时西菲律宾海营养跃层相对较浅,生产力较高,反之则相反.而在MIS 5末期至末次冰消期时段,生产力受东亚冬季风的影响相对于长期ENSO过程更强,可能掩盖了后者的古生产力信号.冰期东亚冬季风加强,一方面,可以引起上部水体混合加强,增加下部营养物质向上的输送,另一方面大量风尘物质的输入可以刺激颗石藻的生长;反之在冰消期,水体混合较弱,风尘输入显著减少,生产力也随之降低.

基于有孔虫AMS14 C年龄年代框架,通过冲绳海槽中南部的OKT12孔沉积物黏土矿物的分析,探讨了16 ka以来冲绳海槽细颗粒沉积物的物源变化及其对源区气候的响应.研究结果显示,10 ka时黏土矿物组成发生明显变化,伊利石、绿泥石含量增加,高岭石、蒙皂石含量减少,指示物源由之前的长江和东海陆架源转变为台湾源.受到海平面上升影响,长江河口和冲绳海槽距离增加,夏季风增强,黑潮增强,既搬运台湾来源物质,又阻碍长江物质跨陆架输运,在这些因素综合作用下,长江物质减少、台湾物质增加.高岭石/(伊利石+绿泥石)和绿泥石/(伊利石+蒙皂石)比值在4 ka以来增加指示全新世晚期台湾源区侵蚀强度发生变化.4 ka前后物源判别显示,OKT12孔沉积物来源由台湾东北部河流变为台湾东南部河流,反映了该时期季风降雨导致源区台湾不同区域的侵蚀差异,可能与ITCZ南移、ENSO活动增强有关.

Paleotemperature records were reconstructed for the past 13.3kyr using the alkenone unsaturation index (UK′37) and the tetraether index of 86 carbon atoms (TEX86) proxies measured in sediment core OKI-151, which was collected in the southern Okinawa Trough. The UK′37- and TEX86-derived temperatures for the top sample are close to the modern mean annual sea-surface temperature (SST). Changes in SSTs in the southern Okinawa Trough were primarily controlled by the western tropical Pacific Ocean, low-latitude winter insolation, and sea-level rise. Unlike previous studies, we found that the high-latitude North Atlantic played no significant role in the SST variations in this area. Moreover, SSTs in the southern Okinawa Trough decoupled from the East Asian summer monsoon system in the last 13.3kyr. The UK′37- and TEX86-based SSTs dropped significantly at 7.6–6.9kyr BP (centered on 7.3kyr BP). These findings suggest that the cold event at 7.3kyr BP was widely recorded in the Okinawa Trough. However, the TEX86-based SSTs dropped approximately 14°C during this period for an unknown reason.