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1.
据年层计数和TIMSU系测年结果,建立了南京汤山葫芦洞YT石笋年际精度时间标尺(18000～14000aB.P.)。除石笋顶部5mm层段外,高分辨率的δ18O、灰度和年层厚度3种指标在百年尺度上具有相当一致的对应关系,表明这3种指标对气候因素变化响应比较敏感。综合石笋δ18O和本区古植被资料,估计末次盛冰期和波令暖期年均温分别达7℃和15℃。石笋揭示的末次盛冰期气候可进一步划分为4个阶段:1)18150～16900aB.P.,年均温和洞穴湿度逐步下降;2)16900～16100aB.P.,年均温和洞穴湿度相对稳定,可进一步划分为3个暖峰和两个冷谷;3)16100～15600aB.P.,年均温快速下降,按氧同位素平衡方程计算,其冷谷可能接近于0℃,但洞穴湿度比前期下降幅度并不大;4)15600～14750aB.P.,年均温和洞穴湿度比较稳定。这种气候演化的阶段性和突变性与北大西洋地区气候记录可以对比,反映极地与东亚季风气候受共同的驱动机制支配。从石笋4种指标(δ18O、δ13C、灰度和年层厚度)的功率谱图中识别出不同尺度的太阳活动周期成分,其中80aGleissberg周期特别显著,表明末次盛冰期边界条件下太阳活动仍是短尺度气候变化的主要驱动力。 相似文献
2.
位于青藏高原与黄土高原过渡带的甘肃武都万象洞石笋WXSM51和WXSM52提供了MIS 5(118~79kaB.P.)高分辨率的δ18 O记录。研究表明, 万象洞石笋δ18 O值与夏季风强度呈负相关关系, 与我国西南部的贵州董歌洞石笋δ18 O记录有良好的对应关系, 并与高纬度的格陵兰NGRIP冰芯δ18 O记录和65°N太阳辐射强度有很好的一致性, 说明万象洞石笋δ18 O记录了118~79kaB.P.期间亚洲季风强度的变化, 同时也说明东亚季风强度的变化和全球气候变化同步, 而且主要受控于北半球太阳辐射强度的变化。同时它与地中海碳酸盐记录有很好的相似性, 和巴西石笋δ18 O记录在千年尺度上表现出相反的变化趋势, 说明东亚季风区、地中海地区以及巴西季风区之间存在密切的联系, 指示了南北半球气候在千年尺度上存在"跷跷板"(seesaw)现象。万象洞石笋δ18 O记录的MIS 5b与MIS 5a突发性转换, 与NGRIP冰芯δ18 O记录相似, 而与神农架记录存在差异, 说明万象洞地区对亚洲季风强度的响应更为敏感。 相似文献
3.
通过对贵州都匀七星洞4根石笋42件系统的TIMS230Th测年及694件稳定同位素分析,揭示的气候变化记录时限范围连续1～15万年,稳定同位素样品平均分辨率晚期达150～220a,早期达440～530a。研究表明,石笋δ18O曲线,相当于海洋记录的终止点Ⅰ及终止点Ⅱ具有特别明显的突变,其年龄分别为11.3kaB.P.及129.3kaB.P.,应为晚更新世顶、底界线的准确年代。晚更新世与深海氧同位素记录MIS2～MIS5e相对应的气候地层单元,其界限年代也分别得到了明确的界定。相当于格陵兰冰芯记录、北大西洋沉积记录的YD事件、Heinrich气候突变事件,几个石笋记录取得了一致的准确定位及定年。其中YD事件为12.76～11.52kaB.P.;Heinrich事件的H1～H6分别为17～15kaB.P.,24.6kaB.P.,30.5kaB.P.,39.3kaB.P.,47.8～46.8kaB.P.以及60.4kaB.P.。对其与北大西洋沉积及格陵兰冰芯记录所揭示的短尺度气候突变事件的可比性,表明东亚季风气候变化,与高纬度地区的气候变化呈遥相关响应,对研究东亚季风气候驱动机制及其与全球气候变化的响应关系和对晚更新世的地层学研究,均具有特别重要的意义。 相似文献
4.
天山南北麓巨厚的新生代地层记录着天山构造隆升与沉积环境演化的历史。在对新疆塔西河剖面进行磁性地层研究的基础上,通过沉积学分析,确定自8.1M a以来塔西河剖面存在4个沉积相组合,对应的沉积环境演化分为4个阶段:1)在8.105.75M aB.P.之前为浅湖沉积环境;2)在5.754.27M aB.P.为扇三角洲沉积环境;3)在4.273.44M aB.P.为滨浅湖沉积环境;4)在3.44M aB.P.之后为冲积扇沉积旋回期。塔西河剖面沉积环境演化、岩相与沉积速率的变化等共同揭示出天山自8.1M aB.P.以来先后经历了构造活动稳定期（>5.75M aB.P.）、过渡期（5.753.44M aB.P.）以及快速强烈间歇性隆升期（<3.44M aB.P.）等3个构造活动阶段,并且自3.44M aB.P.,构造活动有增强的趋势。 相似文献
5.
在第四纪的末次冰期、新冰期和小冰期期间,位于大峡谷入口处的则隆弄跃动冰川发生多次的快速前进,多次发生阻塞雅鲁藏布江事件,在大峡谷以上河段形成4期(Ⅳ~Ⅰ)的林芝古堰塞湖。14 C测年结果指示第2次、第3次和第4次堰塞湖分别发生在9760~11300aB.P.,1220±40~1660±40aB.P.和287±93~394±83aB.P.。估计Ⅳ~Ⅱ期堰塞湖库容量约2150km3,835km3和81km3。冰川阻塞湖坝的溃决释放突发性洪水,对下游的雅鲁藏布大峡谷河段及下游地区的环境产生巨大的影响。 相似文献
6.
内陆封闭湖泊自生碳酸盐氧同位素组成与大气降水同位素组成、空气相对湿度和地面气温这三个参数相关。我国季风带的青海湖与色林错的δ18O曲线非常相似,说明古气候变化受相同因素驱动。在10500～9500aB．P．的末次冰期向全新世的过渡期,这两个湖泊的δ18O值大幅度下降,这是夏季风雨水的低δ18O值的缘故。属于西风带的玛纳斯湖和季风带的青海湖的δ18O曲线基本上是对称的。大约9500～4000aB．P,图形由对称转变为相似,据此推论当时夏季风的影响范围可能达到新疆北部。 相似文献
7.
测定了新疆罗布泊地区湖相沉积物CK-2钻孔样品的总有机碳含量（TOC）及其同位素组成、碳酸盐含量和C/N比值等环境代用指标,以及石膏矿物的质谱-铀系年龄。测试结果表明,20～9kaB.P.期间沉积物δ13Corg.在-23.4‰～-16.1‰之间波动且阶段性明显,与TOC呈现良好的相关关系,整体变化趋势同南极Dome C冰芯中记录的全球大气CO2浓度一致;C/N比值表明有机碳来源主要是陆生高等植物。因此大气CO2浓度变化是影响20～9kaB.P.期间罗布泊湖相沉积物δ13Corg.值变化的主导因素,周围山体上C3/C4植物相对生物量的变化则是另一重要因素。依据δ13Corg.的变化序列将此时间段湖区古环境的演化分成6个阶段:20.0～14.1kaB.P.期间受到末次盛冰期的影响,气温偏低,湖水丰沛;14.1～13.3kaB.P.是一个气候不稳定期,冷暖波动较频繁,但以暖为趋势;13.3～12.8kaB.P.期间经历了一段冷期,于12.8kaB.P.结束了末次冰期,随后气候开始转暖至11.8kaB.P.;其后气温再次变冷并维持到10kaB.P.;最后从10kaB.P.进入全新世暖期。δ13Corg.序列明显向偏负方向变化,表明该地区变暖的趋势相当明显。罗布泊地区日益干旱化是全球气候变化的结果,尤其是受到全球CO2浓度的不断升高所制约。 相似文献
8.
本文参考绝对年代测试结果、基于地球化学分析和区域地层对比等手段,对青藏高原东部边缘及华北地区近40多个第四纪泥石流沉积剖面进行了分析,初步认为我国第四纪泥石流沉积主要集中大约在1.8～1.6MaB.P.、0.7MaB.P.、0.5MaB.P.、0.14MaB.P.～80000aB.P.、40000～25000aB.P.、8000～5000aB.P.和200aB.P.以来共7个阶段。泥石流发育与区域乃至全球性气候波动呈现出大致同步的规律性;同时,不同地区泥石流发育历史存在明显的差异。云南小江流域的泥石流几乎贯穿整个第四纪时期,很少间断;甘肃白龙江流域第四纪期间泥石流活动受全球气候波动影响明显;太行山东麓及北京地区的泥石流活动主要集中在晚更新世以来。 相似文献
9.
选择位于西风环流显著影响区的巴里坤湖作为研究对象,采用14C测年建立了巴里坤湖沉积剖面约9400cal.aB.P.以来的时间序列。对该湖泊剖面沉积物的矿物X射线衍射、自生碳酸盐稳定同位素、碳酸盐含量和粒度指标的综合分析表明,9400cal.aB.P.以来,巴里坤湖地区的气候环境变化大致经历了冷干（9400～7400cal.aB.P.）-暖湿（7400～5900cal.aB.P.）-暖干（5900～3100cal.aB.P.）-凉湿（3100～1100cal.aB.P.）-冷干（1100～500cal.aB.P.）-暖干（500cal.aB.P.以来）的气候变化过程,该过程基本上同周边区域的气候环境变化记录相一致。在3800cal.aB.P.左右,北疆地区的几个典型湖泊沉积记录序列都指示该时期气候环境发生了较为明显的转折,可能暗示了这一时期亚洲中部干旱区（至少在北疆地区）大气环流状况发生了重大调整。 相似文献
10.
结合含水量、TOC含量和TOC/TN比值变化曲线,18·5kaB·P·以来的四海龙湾玛珥湖沉积物全岩有机碳同位素组成（δ13CTOC）记录可划分为3个阶段:1)末次冰期晚期（18·5～14·7kaB·P·）,δ13CTOC值偏正,变化范围为-29·50‰～-26·18‰,平均值约为-28·10‰;2)末次冰消期（14·7～11·7kaB·P·）,δ13CTOC值显著偏负,变化范围为-33·92‰～-28·40‰,平均值约为-31·75‰,在δ13CTOC值变化曲线上表现为一个低谷,但在类似YoungerDryas的冷干事件期间（12·7～11·7kaB·P·）,δ13CTOC值再次显著偏正,最高可达-28·4‰;3)全新世以来（11·7kaB·P.至今）,δ13CTOC值变化幅度不大（-30·85‰～-27·37‰）,基本上都在平均值-29·1‰左右。研究表明,大气CO2浓度变化是影响18·5kaB·P·以来四海龙湾玛珥湖δ13CTOC值变化的主导因素。 相似文献
11.
Julie Dabkowski Nicole Limondin‐Lozouet Pierre Antoine Julian Andrews Alina Marca‐Bell Vincent Robert 《第四纪科学杂志》2012,27(8):790-799
Marine Isotope Stage (MIS) 11 palaeoclimate has so far been documented in marine and ice sheet isotopic records. However, excepting some lacustrine pollen records, very little is known about palaeoclimatic conditions in continental areas. This study uses geochemical records in calcareous tufa deposits from rivers as a basis for reconstructing temperate palaeoclimatic conditions. Tufa deposits are now proven to record high‐quality palaeoclimatic information in recent to Holocene deposits. Work on older interglacial tufas is just starting and in this paper we present the first comprehensive results from a MIS 11 tufa. The tufa comes from the Seine Valley (La Celle, northern France). Geochemical data in the tufa calcite are interpreted to record primarily air temperature (δ18O) and humidity (δ13C and Mg/Ca and Sr/Ca). The combined data identify a warm and wet climatic optimum followed by two temperature decreases associated with oscillations in humidity. These marked climatic variations recorded through the La Celle profile are strongly coherent with the palaeoenvironmental reconstructions from malacological data. The abrupt climatic and environmental events recorded could be related to short‐term degradation of vegetation cover in Europe, which is itself controlled by global palaeoclimatic events. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
12.
13.
利用介形虫壳体δ18O,δ13C及其沉积物有机质δ13C同位素组成等环境代用指标,重建了西北干旱区艾比湖地区近1500年来气候环境演化特征。结果表明,气候不稳定性不但出现在时段约660～760A.D.及约1380～1500A.D.由暖干变冷湿的气候转换时期,也出现在时段约1050～1150A.D.及约1850～1940A.D.由冷湿变暖干的转换时期。尤其是由冷湿到暖干的气候转换时期,频繁而大幅度的气候变化影响湖泊水环境的稳定连续性,限制了介形虫等湖泊生物的生存,造成湖泊生态环境系统的破坏。而在百年尺度上艾比湖地区气候表现为暖干、冷湿的组合特征。约1850年开始,气候出现明显的干旱化趋势。 相似文献
14.
通过对ODP184航次1147/1148站位约4MaB.P.以来沉积物中来源于定鞭金藻的生物标志化合物的研究,对南海北部晚上新世以来的古海洋生产力、表层海水温度及CO2分压的变化情况进行了探讨.定鞭金藻生产力与硅藻生产力一样在0.9MaB.P.以前比较稳定地保持在较低水平,而0.9MaB.P.后定鞭金藻生产力较高,且呈现冰期低间冰期高的波动,硅藻生产力则呈现持续升高的趋势.由C37烯酮不饱和度指标获得的南海北部4MaB.P.以来表层海水的UK′37温度与浮游有孔虫壳体δ18O具有较好的相关性,且能显示出0.9MaB.P.来的19个氧同位素期,表明将U37K′37温标应用到晚第四纪以前基本上是可行的.由δ13C37:2计算的表层海水pCO2显示,晚上新世的pCO2要高于300μL/L,而第四纪的pCO2尽管存在波动,却基本上在300μL/L以下.计算出的晚第四纪的pCO2十分稳定,与同期的大气pCO2历史变化不一致.这可能与计算中简单地假定某些参数(如生长速率)为常数有关,这些参数在第四纪冰期间冰期旋回中可能有较大变化. 相似文献
15.
Late Pleistocene paleoclimatic variability on the northeastern Qinghai–Tibetan Plateau (NE QTP) was reconstructed using a chronology based on AMS 14C and 230Th dating results and a stable oxygen isotopic record. These are derived from lake carbonates in a 102-m-long Qarhan sediment core (ISL1A) collected from the eastern Qaidam Basin. Previous research indicates that the δ18O values of lacustrine carbonates are mainly controlled by the isotopic composition of lake water, which in turn is a function of regional P/E balance and the proportion of precipitation that is monsoon-derived on the NE QTP. Modern isotopic observations indicate that the δ18O values of lake carbonates in hyper-arid Qaidam Basin are more positive during the warm and wet period. Due to strong evaporation and continental effect in this basin, the positive δ18O values in the arid region indicate drier climatic conditions. Based on this interpretation and the δ18O record of fine-grained lake carbonates and dating results in ISL1A, the results imply that drier climatic conditions in the Qarhan region occurred in three intervals, around 90–80 ka, 52–38 ka and 10–9 ka, which could correspond to late MIS 5, middle MIS 3 and early Holocene, respectively. These three phases were almost coincided with low lake level periods of Gahai, Toson and Qinghai Lakes (to the east of Qarhan Lake) influenced by ASM on the orbital timescales. Meanwhile, there was an episode of relatively high δ18O value during late MIS 3, suggesting that relatively dry climatic condition in this period, rather than “a uniform Qarhan mega-paleolake” spanning the ∼44 to 22 ka period. These results insight into the understanding of “the Greatest Lake Period” on the QTP. 相似文献
16.
P. K. Gautam A. C. Narayana P. Kiran Kumar P. G. Bhavani M. G. Yadava A. J. T. Jull 《第四纪科学杂志》2021,36(1):138-151
The Indian monsoon carries large amounts of freshwater to the northern Indian Ocean and modulates the upper ocean structure in terms of upwelling and productivity. Freshwater-induced stratification in the upper ocean of the Bay of Bengal is linked to the changes in the Indian monsoon. In this study, we test the usefulness of δ18O and δ13C variability records for Globigerina bulloides and Orbulina universa to infer Indian monsoon variability from a sediment core retrieved from the southwestern Bay of Bengal encompassing the last 46 kyr record. Results show that the northeast monsoon was dominant during the Last Glacial Maximum. Remarkable signatures are observed in the δ18O and δ13C records during the Marine Isotope Stage (MIS) 3 to MIS-1. Our study suggests that Indian monsoon variability is controlled by a complex of factors such as solar insolation, North Atlantic climatic shifts, and coupled ocean–atmospheric variability during the last 46 kyr. 相似文献
17.
Miryam Bar-Matthews Avner Ayalon Alan Matthews 《Geochimica et cosmochimica acta》2003,67(17):3181-3199
The oxygen and carbon stable isotope compositions of cave speleothems provide a powerful method for understanding continental climate change. Here, we examine the question of the regionality of this isotopic record and its linkage with the marine isotopic record in the Eastern Mediterranean (EM) region. The study presents a new, accurately dated 250-kyr δ18O and δ13C record determined from speleothems of the Peqiin Cave, Northern Israel. Its comparison with the continuous 185-kyr isotopic record of the Soreq Cave speleothems from Central Israel reveals striking similarities. Thus, a strong regional climatic signal, brought about by variations in temperature and rainfall amount, is reflected in both cave records. Low δ18O minima in the Peqiin profile for the last 250- to 185-kyr period (interglacial marine isotopic stage 7) match the timing of sapropels 9 to 7 and are indicative of high rainfall in the EM region at these times. The combined Soreq and Peqiin δ18O record for the last 250 kyr excellently matches the published Globigerinoides ruber (G. ruber) marine δ18O record for the EM Sea, with the isotopic compositional difference ΔG.ruber-speleothems remaining relatively constant at −5.6 ± 0.7‰, thus establishing for the first time a robust, exploitable link between the land and the marine isotopic records. The correspondence of low δ18O speleothem values and high cave water stands with low G. ruber δ18O values during interglacial sapropel events indicates that these periods were characterized by enhanced rainfall in the EM land and sea regions. By use of sea surface temperatures derived from alkenone data as a proxy for land temperatures at the Soreq Cave, we calculate the paleorainfall δ18O values and its amounts. Maximum rainfall and lowest temperature conditions occurred at the beginning of the sapropel events and were followed by decrease in rainfall and increase in temperatures, leading to arid conditions. The record for the last 7000 yr shows a trend toward increasing aridity and agrees well with climatic and archeological data from North Africa and the Middle East. 相似文献
18.
多年平均表层水温超过28℃的"西太平洋暖池",是全球海平面高度的加热中心和大气三大环流的辐散中心。为评价西太平洋暖池中心区域海洋生物泵的演化特征、规律与机制,本文以位于热带西太平洋暖池核心区——Ontong Java海台的WP7柱状样为材料,通过提取浮游有孔虫δ13C组成、底栖有孔虫群落和钙质超微化石下透光带属种Florisphaera profunda相对百分含量变化等指标,反演该区250kaB.P.以来的古生产力的演化历史。研究结果表明,250kaB.P.以来西太平洋暖池中心区的古生产力演化与地球轨道变化控制的冰期-间冰期旋回以及岁差控制的太阳辐照率密切相关。在冰期-间冰期尺度上,西太平洋暖池中心区距今250ka以来的生产力变化间冰期明显低于冰期,而且在间冰期阶段生产力相对稳定,冰期波动幅度较大。在冰期或间冰期背景下显著的岁差周期是该区古生产力演化的又一重要特征。而且在岁差波段生物生产力的变化可能领先极地冰体积变化2～4ka左右。热带东西太平洋的古生产力演化在冰期-间冰期变化和岁差尺度上存在ENSO式的变动机制,而且二者互相调谐,产生了似30ka和19ka周期,并出现了"半30ka周期"和半岁差周期。此外,WP7孔Neogloboqudrina dutertrei的δ13C显示在MIS 1/2,MIS 3/4和MIS 5e/6的冰期向间冰期的过渡期的冰消期阶段存在变轻事件,可能与数千年尺度的大洋环流演化有关。 相似文献
19.
Eleonora Regattieri Giovanni Zanchetta Russell N. Drysdale Ilaria Isola John C. Hellstrom Adriano Roncioni 《Quaternary Research》2014
Relatively few radiometrically dated records are available for the central Mediterranean spanning the marine oxygen isotope stage 6–5 (MIS 6–5) transition and the first part of the Last Interglacial. Two flowstone cores from Tana che Urla Cave (TCU, central Italy), constrained by 19 U/Th ages, preserve an interval of continuous speleothem deposition between ca. 159 and 121 ka. A multiproxy record (δ18O, δ13C, growth rate and petrographic changes) obtained from this flowstone preserves significant regional-scale hydrological changes through the glacial/interglacial transition and multi-centennial variability (interpreted as alternations between wetter and drier periods) within both glacial and interglacial stages. The glacial stage shows a wetter period between ca. 154 and 152 ka, while the early to middle Last Interglacial period shows several drying events at ca. 129, 126 and 122 ka, which can be placed in the wider context of climatic instability emerging from North Atlantic marine and NW European terrestrial records. The TCU record also provides important insights into the evolution of local environmental conditions (i.e. soil development) in response to regional and global-scale climate events. 相似文献