冲绳海槽末次冰期以来黑潮流游移在沉积硅藻中的记录

文中描述冲绳海槽中段2个柱样沉积物中优势硅藻种相对含量,热带远洋种相对含量和硅藻组合的分布特征;讨论地层的划分和对比、冲绳海槽末次冰期鼎盛期的古黑潮流、全新世黑潮流游移等科学问题。结果表明,冲绳海槽末次冰期鼎盛期的古黑潮流在现今1000m等深线之间流过,当时的黑潮流宽度应小于50km;16ka—11kaB．P．随着海面上升,黑潮流越过西侧1000m等深线,向东海陆架偏移;全新世黑潮流分别在大约7ka—8kaB．P．1ka—4kaB．P．出现过两次黑潮流宽度变窄、强度变弱的游移。     

冲绳海槽北部全新世沟鞭藻孢囊组合及其古环境意义

通过B-3GC柱状样84个样品的分析,获得了冲绳海槽北部全新世高分辨率沟鞭藻孢囊记录。B-3GC柱状样中沟鞭藻孢囊化石丰富,包含14属28种孢囊。其中的Spiniferitesspp.和Operculodiniumcentrocarpum是沟鞭藻孢囊组合的优势组分,此外最常见的种类是Protoperidinium孢囊。通过与浮游有孔虫氧同位素指标对比,可以确定全新世Spiniferitesspp.和Operculodiniumcentrocarpum的含量变化主要与表层海水温度变化相关,Spiniferitesspp.是较暖水的标志,Operculodiniumcentrocarpum则指示了偏凉的海水。根据这一指标推测冲绳海槽北部早全新世的表层海水温度偏低,约6500aB.P.后由于黑潮及其分支(主要是对马暖流)的影响增强,导致海水温度升高。但在3700—2300aB.P.期间因黑潮及其分支强度有所减弱而引起该区域表层海水温度降低。孢囊组合中异养型沟鞭藻Protope-ridinium孢囊含量随时间逐渐降低,这一趋势可以作为海平面上升引起冲绳海槽北部陆源物质输入减少的有力证据。黑潮及其分支影响的加强造成约6000—3700aB.P.和约2300aB.P.以后两个时期冲绳海槽北部表层海水相对贫营养低生产力。     

南海北部191PC柱样沉积物中浮游有孔虫特征及其古环境意义

通过对在南海北部陆坡采取的191PC柱状样进行氧碳同位素测试、碳酸钙含量分析以及浮游有孔虫丰度和组合分析,初步划分了191PC柱状样的地层,并据此讨论了末次冰期以来浮游有孔虫丰度和组合的变化,并利用两种浮游有孔虫古生态转换函数再造了末次冰期以来的表层海水古温度和上层水体结构的变化,且由此反映出南海北部末次冰期以来季风演化的趋势。研究表明,该柱状样底部达到氧同位素III期;末次盛冰期到冰后期,南海北部冬季表层海水温度上升5.7—5.8℃,夏季温度上升1.4℃,温跃层总体呈变深的趋势,冬季混合层深度变浅,而夏季混合层深度变深,同时,表层海水垂直温差的变化也可能反映了由末次冰期到冰后期,南海北部具有冬季风减弱而夏季风加强的趋势。     

南海西沙海槽111PC孔的硅藻与古环境记录

对南海西沙海槽111PC孔沉积物中的硅藻化石研究表明,硅藻以热带、亚热带浮游性种类和近岸性种类为主,可划分出6个硅藻组合带,大体对应于浮游有孔虫氧同位素6个期次。结合有地层对比意义的属种及组合,建立了里斯冰期以来本孔的硅藻生物地层框架。硅藻丰度、属种组合变化指示海区气候经历了冰期-间冰期气候旋回及不稳定性波动。晚玉木冰期硅藻丰度高,冰后期、中玉木冰期次之,里斯冰期至早玉木冰期丰度较低,这与南海西南部不同,与南海东北相似但也不尽相同。里斯冰期至里斯玉木间冰期转换阶段,硅藻属种对气候变暖的反应较快。硅藻属种特征显示中玉木冰期气候为弱暖期,且有早晚两个暖湿阶段。硅藻属种的不连续分布也表明沉积环境在部分时段极不稳定。     

末次冰消期以来南海北部表层海水盐度变化

对南海北部MD05-2904孔上部0-398cm段共152个样品的硅藻鉴定结果进行主成分分析.根据主成分分析结果,探讨了末次冰消期以来南海北部表层海水盐度(SSS)变化历史,并分析其变化的主要原因.末次冰消期以来南海北部表层海水盐度呈阶段性变化,与季风降水强度变化趋势基本一致,表明季风降水强度变化可能是南海北部表层海水盐度变化的主要影响因素;珠江冲淡水是南海北部表层海水盐度变化另一个比较重要的影响因素,但其影响程度在全新世中晚期有所减弱.末次冰消期南海北部表层海水盐度变化硅藻记录还明显反映了新仙女木(Younger Dryas)这一短期气候事件,事件发生期间南海北部表层海水盐度明显上升,主要与当时季风降水明显减少有关.MD05-2904孔硅藻盐度记录基本可以与17940孔有孔虫盐度记录相对比,但也存在一定差异,尤其在全新世中晚期,主要与两者代表不同盐度含义有关,后者代表由局地淡水收支变化引起的盐度变化,而前者代表所有影响因素综合作用下的盐度变化.     

南海北部MD12-3429站位海水古生产力和溶解氧含量特征*

南海北部陆坡较高的沉积速率,为研究亚轨道尺度的气候变化提供了绝佳的材料。本次研究对南海北部MD12-3429站位(20°08.52′N,115°49.84′E,水深903m)0—35.21m沉积物中的底栖有孔虫属种进行统计,运用沉积物粗组分、底栖有孔虫丰度、特定环境下的底栖有孔虫属种含量(Cibicidoides wuellerstorfi,Uvigernia,Bulimina,Chilostomella oolina和Globobulimina pacifica)及底栖有孔虫堆积速率(BFAR)等指标综合研究MIS7期(约24.3万年)以来的南海北部初级生产力和中层水海水溶解氧含量的变化,并对其影响因素进行探讨分析。结果表明,该站位自MIS7期以来表层海水的营养总体呈现间冰期高、冰期低的特点,而底层水的溶解氧含量在间冰期低、冰期高,这可能受到东亚季风冬季风带来营养元素的影响。该站位水深903m,处于南海中层过渡带,本次研究的结果反映了南海北部中层水MIS7期以来营养与溶解氧含量特征。     

南海南部表层海水古温度估算与次表层海水特征变化

南海南部～2 MaBP以来的表层海水古温度估算表明,表层海水温度变化在更新世冰期旋回中波动比南海北部为小、保持比较温暖,但在长时间尺度上转换函数古水温仍然存在一定的变化趋势。转换函数古温度计算的低温时期并不与冰期相对应,表明南海南部具有独特的表层海洋演化特征,可能与次表层水体性质、上部水体结构等密切相关。过去2 MaBP以来的浮游有孔虫组合演化表明,南海南部海水温跃层呈现由氧同位素MIS79期向～53期相对变浅,自MIS 53期向布容／松山(B／M)古地磁界线附近变深,然后,自布容／松山界线以来又相对变浅的演化过程。     

19万年以来南海北部MD12-3429站浮游有孔虫记录的表层海水环境演化

南海北部陆坡具有较高的沉积速率,为古海洋和古气候演化提供了绝佳的研究材料。本研究对南海北部陆坡中部MD12-3429站(20°08.52’N, 115°49.84’E,水深903 m)的高分辨率沉积样品中的浮游有孔虫群进行研究,重建了海洋氧同位素期(MIS)6期以来上部水体结构和表层古生产力变化。并与陆坡底部MD12-3432站(19°16.88’N,116°14.52’E,水深2 125 m)对比,旨在进一步探讨南海北部陆坡上部水体环境的时空演化。结果表明：受到冰期冬季风增强和表层环流变化的共同影响,海表温度具有显著的冰期/间冰期旋回,冬季海表温度波动可达7–8°C;MIS2–4期和MIS 6期时, MD12-3429站的温跃层明显比MD12-3432站的深,可能与海平面下降后、河流输入在近岸地区形成的淡水盖层和强冬季风通过埃克曼输送形成的向岸流有关;浮游有孔虫Globigerinoidesbulloides+Neogloboquadrinadutertrei含量和非共生种/共生种比值显示南海北部陆坡初级生产力在MIS 6期晚期和MIS 2期显著增高,这可能是当时较低的海平面和较强的...     

黔西高原MIS3-MIS2期炭屑记录与火灾模式研究

火灾与气候、植被存在复杂的关系,搞清东亚季风区的火灾模式及其发生机制,对预测未来气候变化及火灾防治具有重要意义。通过对黔西高原MIS3—MIS2期间的古湖相沉积物进行炭屑分析并结合AMS~(14)C测年数据研究发现:MIS3晚期以来研究区的火灾主要发生于36.3—35 cal ka BP、26.2—17.6 cal ka BP期间,中粒炭屑和大炭屑分别在35、26.2、23.6 cal ka BP记录到3次地方火。研究区炭屑记录对冷干事件响应敏感,炭屑峰值区对应Heinrich事件(H事件)、末次冰盛期(LGM)等干旱事件,低值区对应DO事件,呈现千年旋回的特征。比对东亚地区的炭屑记录发现,在大范围的东亚季风区MIS2期比MIS3末期在火的强度和频率上都要高,与欧洲模式显著不同。火的发生机制可能受气候因素的控制,同时受植被类型的影响。     

东海表层沉积中的翼足类及其地质意义

对东海84个表层沉积中翼足类进行了定量分析,共获得7属15种,其中Limacinainflata在陆架外缘和上陆坡为优势种,Limacinatrochi formis,Creseisacicula和Creseis virgule在中外陆架最为丰富。根据翼足类的深度分布确定东海现代文石补偿深度在约600m水深处。以冲绳海槽北部柱状样B3GC为例,说明翼足类是研究地质时期古海洋学变化的重要证据。     

Paleoenvironmental change in the middle Okinawa Trough since the last deglaciation: Evidence from the sedimentation rate and planktonic foraminiferal record

Well-dated, high-resolution records of planktonic foraminifera and oxygen isotopes from two sediment cores, A7 and E017, in the middle Okinawa Trough reveal strong and rapid millennial-scale climate changes since ∼ 18 to 17 thousand years before present (kyr B.P.). Sedimentation rate shows a sudden drop at ∼ 11.2 cal. kyr B.P. due to a rapid rise of sea level after the Younger Dryas (YD) and consequently submergence of the large continental shelf on the East China Sea (ECS) and the retreat of the estuary providing sediment to the basin. During the last deglaciation, the relative abundance of warm and cold species of planktonic foraminifera fluctuates strongly, consistent with the timing of sea surface temperature (SST) variations determined from Mg/Ca measurements of planktonic foraminifera from one of the two cores. These fluctuations are coeval with climate variation recorded in the Greenland ice cores and North Atlantic sediments, namely Heinrich event 1 (H1), Bølling–Allerød (B/A) and YD events. At about 9.4 kyr B.P., a sudden change in the relative abundance of shallow to deep planktonic species probably indicates a sudden strengthening of the Kuroshio Current in the Okinawa Trough, which was synchronous with a rapid sea-level rise at 9.5–9.2 kyr B.P. in the ECS, Yellow Sea (YS) and South China Sea (SCS). The abundance of planktonic foraminiferal species, together with Mg/Ca based SST, exhibits millennial-scale oscillations during the Holocene, with 7 cold events (at about 1.7, 2.3–4.6, 6.2, 7.3, 8.2, 9.6, 10.6 cal. kyr BP) superimposed on a Holocene warming trend. This Holocene trend, together with centennial-scale SST variations superimposed on the last deglacial trend, suggests that both high and low latitude influences affected the climatology of the Okinawa Trough.     

Pulleniatina Minimum Events in the Andaman Sea (NE Indian Ocean): Implications for winter monsoon and thermocline changes

The late Quaternary record of Pulleniatina obliquiloculata was investigated from two well dated sediment cores from the Andaman Sea (NE Indian Ocean) to examine its paleoceanographic significance and the presence of the Pulleniatina Minimum Events (PME) in the western North Pacific. As in the Pacific, our study shows that PMEs exist in the Indian Ocean albeit with a lower intensity. The Holocene PME occurs between 4.5 and 3.0 cal ka BP with a considerable reduction in P. obliquiloculata abundance, and which matches well with the Pacific records influenced by the Kuroshio Current. Additionally, two significant minimum events of P. obliquiloculata are also seen during the Younger Dryas (YD) and late Last Glacial Maximum (LGM, 20–18 cal ka BP). Overall, the PMEs of the Andaman Sea are not current driven events like in the western Pacific margin either by the weakening of the Kuroshio Current or reduced winter SSTs. The PMEs of the Andaman Sea are characterised by lower abundances of thermocline species indicating the increased depth of the thermocline (DOT) and reduced winter SSTs mainly during the minimum events of the YD and late LGM. The high SSTs during the Holocene PME make this event a mystery. However, the presence of PMEs in the Andaman Sea suggests that these events are not confined to areas influenced by the Kuroshio Current but may be responding to a broad scale oceanographic–climatic process or mechanism which needs to be explored with a detailed study.     

Vegetation Evolution in the Northern South China Sea Region Since 40 ka BP?aAn Attempt To Reconstruct Palaeovegetation Based on Biomization (in English)

egetation evolution in the northern South China Sea region since 40 500 a BP is reconstructed using biomization procedure based on pollen data from deep sea core 17940. The result shows that, it is feasible to reconstruct palaeovegetation using biomization procedure, when pollen, particularly Pinus pollen, transported by wind over long distance is excluded. Results from factor analysis suggest that humidity and temperature are the two main factors determining vegetation evolution on land around the northern South China Sea. From 40 500 a BP to 11 100 a BP, broad-leaved evergreen forest (WAMF), and montane conifers(MGRF) occurred on hills and low mountains; while steppe (STEP) predominated on the exposed shelf. The main feature of the vegetation evolution is the frequent alternation between MGRF (or WAMF) and STEP, implying abrupt changes in millennium scale between humid/cold and dry/temperate climate. All abrupt climate events could be broadly correlated with Henrich events and Dansggard-Oscherge events. One of the events around 12 700 a BP, sees the occurrence of MGRF, suggesting that climate turned humid and cold rapidly. This may be correlated with the Younger Dryas event; Broad-leaved evergreen (WAMF) predominates since 11 000 a BP. During the early Holocene and late Holocene tropical rainforest (TRFO) or tropical seasonal forest (TSFO ) occurred several times.     

High-resolution sea surface temperature records derived from foraminiferal Mg/Ca ratios during the last 260 ka in the northern South China Sea

High-resolution sea surface temperatures (SST) derived from Mg/Ca ratios of Globeriginoides sacculifer at ODP Site 1144 were reported to reveal the SST changes during the last 260 ka in the northern South China Sea (SCS). The results indicate an average Holocene SST of about 26.7 °C, about 3.6 °C increase from LGM to the Holocene, and higher temperature during MIS 5.5 than the Holocene. These agree well with other foraminifer Mg/Ca and U^k₃₇ SST records in this region. The Mg/Ca records suggest warmer SSTs during MIS 3 in the northern SCS, compared with those in the eastern Pacific. Strong East Asian summer monsoon during MIS 3 indicated by paleoclimate records from nearby continents may account for it. Step-wise increases during terminations are shown in our SST record, and the beginning of deglacial warming occurs at about 19 ka, which precedes the change of oxygen isotopes, suggesting a tropical driven forcing for the SST change in the northern SCS. This is further supported by a robust semi-precessional cycle centering at  9.1 ka in the spectra of the SST record, which is absent in that of the oxygen isotopes. However, tropical driven forcing seems not to be indicated in another Mg/Ca SST record in the northern SCS [Oppo, D.W. and Sun, Y.B., 2005. Amplitude and timing of sea-surface temperature change in the northern South China Sea: Dynamic link to the East Asian monsoon. Geology, 33 (10): 785–788.]. The discrepancy may be caused by different post-deposition dissolutions of foraminifer tests at these two sites. Details about the modification of foraminifer Mg/Ca ratios after burial, however, are not well known in this region, and further studies are needed.     

四万年来南海北部周边地区植被演替序列—孢粉生物群区化方法恢复古植被的尝试

就南海北部海域17940孔的孢粉资料,利用孢粉生物群区化方法和因子分析方法,对南海北部周边地区4万年以来的植被演替序列进行研究。结果表明：对于深海沉积物,在排除远距离搬运的花粉尤其是松属（Pinus L.)花粉的噪音后,可以利用孢粉生物群区化方法恢复周边大陆古植被演替序列。因子分析表明,湿度和温度的变化是影响南海北部周边大陆植被演化的主要因子。在40500－11100aBP南海北部沿海大陆地区的古植被,主要为常绿阔叶林（WAMF）,山地针叶林（MRGF）分布于低山、丘陵、而广泛出露的大陆架上则发育了以蒿属(Artemisia L.)为主的草原（STEP）景观：末次冰期时环境变化的突出特征山地针叶林（MRGF）、常绿阔叶林（WAMF）与草原（STEP）之间的频繁交替,反映了气候冷湿和温干的千年级尺度的迅速变化,可以与Heinrich事件以及Dansggard-Oscherge事件进行对比。其中在7.0m处（12700aBP)所恢复的山地针叶林（MRGF）景观反映了一次气候变冷变湿的事件,可能与新仙女木事件相对应。全新世早期和末期较多出现热带雨林（TRFO0以及热带季雨林（TSFO）景观,而全新世中期以常绿阔叶林（WAMF）为主,缺乏热带雨林（TRFO）以及热带季雨林（TSFO）景观,可能表明在全新世中期尽管温度升高,但湿度有可能降低。     

南海永暑礁微型软体动物对晚全新世快速气候变化的响应

近2000年来的地球环境变化日益受到人们的关注,许多替代指标被用来指示快速的气候变化。本文试图通过南海永暑礁泻湖微型软体动物丰度和分异度的研究及其与北半球温度异常的对比,来阐述微型软体动物对快速气候变化的响应。研究表明,软体动物丰度变化的三个高值和三个低值较好地对应于北半球温度异常,显示了微型软体动物丰度对快速气候变化的灵敏反应。尤其重要的是“小冰期”和“中世纪暖期”被证明在南海也发生过。这表明快速的气候变化事件也会影响到热带海区。研究还证实另一次温暖的气候事件发生在大约 850A.D.—680A.D.之间。文中对软体动物分异度与气候变化的关系也作了探讨,并表明软体动物丰度和分异度是指示气候变化的有用指标。     

Vegetation and Climate Change during the Last Deglaciation in the Great Khingan Mountain,Northeastern China

The Great Khingan Mountain range, Northeast China, is located on the northern limit of modern East Asian Summer Monsoon (EASM) and thus highly sensitive to the extension of the EASM from glacial to interglacial modes. Here, we present a high-resolution pollen record covering the last glacial maximum and the early Holocene from a closed crater Lake Moon to reconstruct vegetation history during the glacial-interglacial transition and thus register the evolution of the EASM during the last deglaciation. The vegetation history has gone through distinct changes from subalpine meadow in the last glacial maximum to dry steppe dominated by Artemisia from 20.3 to 17.4 ka BP, subalpine meadow dominated by Cyperaceae and Artemisia between 17.4 and 14.4 ka BP, and forest steppe dominated by Betula and Artemisia after 14.4 ka BP. The pollen-based temperature index demonstrates a gradual warming trend started at around 20.3 ka BP with interruptions of several brief events. Two cold conditions occurred around at 17.2–16.6 ka BP and 12.8–11.8 ka BP, temporally correlating to the Henrich 1 and the Younger Dryas events respectively, 1and abrupt warming events occurred around at 14.4 ka BP and 11.8 ka BP, probably relevant to the beginning of the Bølling-Allerød stages and the Holocene. The pollen-based moisture proxy shows distinct drought condition during the last glacial maximum (20.3–18.0 ka BP) and the Younger Dryas. The climate history based on pollen record of Lake Moon suggests that the regional temperature variability was coherent with the classical climate in the North Atlantic, implying the dominance of the high latitude processes on the EASM evolution from the Last Glacial Maximum (LGM) to early Holocene. The local humidity variability was influenced by the EASM limitedly before the Bølling-Allerød warming, which is mainly controlled by the summer rainfall due to the EASM front covering the Northeast China after that.     

The vegetation and climate at the last glaciation on the emerged continental shelf of the South China Sea

Studies on the dispersal mechanism and source areas of pollen from hemipelagic sediments recovered from the continental slopes of the South China Sea (SCS) reveal that vegetation existed on the exposed shelves at the Last Glacial Maximum (LGM) and the latter part of the Marine Isotope Stage 3. At the low sea level stand, Artemisia-dominated grassland covered the northern continental shelf and tropical lowland rainforest and mangroves grew on the southern shelf ‘Sunda Land’. Consequently, the climate in the northern SCS must have been much colder and drier during the last glacial period compared to the present. Sunda Land experienced only a marginally lower temperature but was not drier than today. The enhanced contrast between the northern and southern parts of the SCS in vegetation and climate during the LGM may be ascribed, at least partly, to the strengthening of Winter Monsoon during the last glacial period.     

南沙海区晚第四纪浮游有孔虫演化及其古海洋学意义

通过对南沙海区17957和17958两柱状样中浮游有孔虫的研究,首次揭示了南海晚第四纪以来较长时间尺度上（0－800ka BP)存在δ18O 11期（约400ka BP)开始的粉红色Globigerinoides ruber大量出现和Globigerina rubescens较高相对丰度,δ18O 5e期（约120ka BP)的粉红色Gl9obigerinoides ruber 绝灭,Globoquadrina Conglomersata大量出现,Globorotalia truncatulinoides 左旋型分子绝对优势开始,和δ18O 4／5期界线附近（约80ka BP)的Globo quadrina conglomerata绝灭等三次浮游有孔虫演化事件,南沙与南海北部及西北太平洋等海区的浮游有孔虫演化事件对比 表明,南沙海区在400ka BP开始海水温跃层相对较深,至δ^18O 5e期时,受西北太平洋中层水加强的影响,南沙海水温跃层变浅,在δ^18O 5e至4／5期界线这段时期内与西北太平洋水体交换比较自由。