DO4事件的精确定年及亚旋回特征: 来自福建龙岩仙云洞石笋的证据^*          下载免费PDF全文

车印平  肖海燕  姜修洋  蔡炳贵 《古地理学报》2020,22(2):377-384

DO4事件(Dansgaard-Oeschger event 4,简称DO4事件)是发生在MIS3阶段后期的1次明显升温事件。根据福建仙云洞石笋(编号XYⅢ-28)300~500 mm层段6个高精度²³⁰Th年龄和188个氧同位素数据,获得了29.13~27.94 kyrB.P.时期平均分辨率达7 yr的东亚夏季风强度的演变过程数据。该石笋 δ¹⁸O 记录的DO4事件起止时间为28.83±0.06~28.46±0.06 kyr B.P.,持续时间为0.37±0.06 kyr。相对基于GICC05年层计数时标NGRIP冰芯 δ¹⁸O 记录在DO4开始阶段的突变特征,仙云洞石笋记录的DO4事件开始阶段 δ¹⁸O 值在145±60 yr内偏负0.4‰,表现为相对缓慢的变化特征,这说明仙云洞所处的中国东南沿海地区有可能受到热带低纬海气耦合的影响。此外,仙云洞石笋 δ¹⁸O 记录揭示了在DO4事件内部及附近存在一系列的百年至十年际尺度夏季风增强事件,与格陵兰冰芯 δ¹⁸O 记录、阿拉伯海海盆反照率记录的DO4事件亚旋回结构在定年误差范围内相对应,表明东亚夏季风强度与北高纬温度变化和ITCZ(赤道辐合带)位置移动在百年至十年际尺度上存在紧密的联系。  相似文献   

中晚全新世湘西莲花洞石笋旋回沉积速率变化及其古气候意义     

张会领  余克服  赵建新  俸月星  林玉石  周玮  刘国辉 《中国岩溶》2017,36(4):580-590

石笋旋回沉积速率是按照石笋沉积旋回测年得到的沉积速率，是石笋沉积过程的重要参数和反演古气候变化的有效代用指标。旋回沉积速率的波动可能反应了地表温度和降雨量的变化，与夏季风强度存在关联。文章以湖南湘西莲花洞LH2石笋为材料，利用42个230Th年龄获得的石笋旋回沉积速率序列重建了8.6 ka BP以来湖南湘西地区温度和降雨雨量的变化历史: 8.6-4.2 ka BP期间，气候以高温多雨为特征，夏季风强，石笋生长率高，但气候并不稳定，存在一系列千年-百年尺度的波动；4.2-0.05 ka BP期间，气候整体偏冷干，旋回沉积速率偏低。总体上，在轨道尺度上，LH2石笋的旋回沉积速率与该石笋的δ18O值之间存在负相关关系。旋回沉积速率的重复性检验证明了旋回沉积速率古气候记录的有效性。石笋旋回沉积速率变化主要受北半球夏季太阳辐射量的控制和ITCZ的直接影响，在百年尺度上，旋回沉积速率的波动可能与中晚全新世的弱季风事件存在关联。   相似文献   

The δO and δC records in an aragonite stalagmite from Furong Cave, Chongqing, China: A-2000-year record of monsoonal climate     

Hong-Chun Li  Zhong-Hong Lee  Nai-Jung Wan  Chuan-Chou Shen  Ting-Yong Li  Dao-Xian Yuan  Yong-Heng Chen 《Journal of Asian Earth Sciences》2011,40(6):1151

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武都万象洞方解石现代沉积体系δ~(18)O值月变化特征   总被引：1，自引：0，他引：1  

白晓  桑文翠  李丰山  张德忠 《地球化学》2015,44(3):245-253

万象洞所在地大气降水同位素值年内波动较大,变化起止时间存在显著的年际差异。观测期内,武都降水同位素δD-δ18O组合特征与周边城市降水同位素多年平均值重建的区域降水雨水线基本重合,洞穴所在地区降水同位素具有很好的区域代表性。洞穴滴水同位素值年内变化幅度较小,基本反映了当地大气降水同位素值的月加权平均水平。洞穴次生碳酸盐与洞穴滴水之间符合同位素平衡分馏基本规律。季节尺度上,不同监测点滴水及次生碳酸盐δ18O值因受地下水混合作用强弱差异及洞穴温度的小幅变化等影响而略有差异;年际变化上,夏季风爆发前后降雨量的权重及爆发时间的早晚对洞穴滴水-碳酸盐体系同位素水平存在一定的影响。万象洞洞穴滴水、石笋氧同位素信号在年代际尺度上可以很好地指示区域内大气降水的同位素变化特征。  相似文献   

Formal subdivision of the Holocene Series/Epoch: a Discussion Paper by a Working Group of INTIMATE (Integration of ice‐core,marine and terrestrial records) and the Subcommission on Quaternary Stratigraphy (International Commission on Stratigraphy)     

M. J. C. Walker  M. Berkelhammer  S. Björck  L. C. Cwynar  D. A. Fisher  A. J. Long  J. J. Lowe  R. M. Newnham  S. O. Rasmussen  H. Weiss 《第四纪科学杂志》2012,27(7):649-659

This discussion paper, by a Working Group of INTIMATE (Integration of ice‐core, marine and terrestrial records) and the Subcommision on Quaternary Stratigraphy (SQS) of the International Commission on Stratigraphy (ICS), considers the prospects for a formal subdivision of the Holocene Series/Epoch. Although previous attempts to subdivide the Holocene have proved inconclusive, recent developments in Quaternary stratigraphy, notably the definition of the Pleistocene–Holocene boundary and the emergence of formal subdivisions of the Pleistocene Series/Epoch, mean that it may be timely to revisit this matter. The Quaternary literature reveals a widespread but variable informal usage of a tripartite division of the Holocene (‘early’, ‘middle’ or ‘mid’, and ‘late’), and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology. We propose an Early–Middle Holocene Boundary at 8200 a BP and a Middle–Late Holocene Boundary at 4200 a BP, each of which is linked to a Global Stratotype Section and Point (GSSP). Should the proposal find a broad measure of support from the Quaternary community, a submission will be made to the International Union of Geological Sciences (IUGS), via the SQS and the ICS, for formal ratification of this subdivision of the Holocene Series/Epoch. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Temporal and spatial variations in the discharge and dissolved organic carbon of drip waters in Beijing Shihua Cave,China   总被引：1，自引：0，他引：1  

Fengmei Ban  Genxing Pan  Jian Zhu  Binggui Cai  Ming Tan 《水文研究》2008,22(18):3749-3758

To detect the causal relationship between cave drip waters and stalagmite laminae, which have been used as a climate change proxy, three drip sites in Beijing Shihua Cave were monitored for discharge and dissolved organic carbon (DOC). Drip discharges and DOC were determined at 0 to 14‐day intervals over the period 2004–2006. Drip discharges show two types of response to surface precipitation variations: (1) a rapid response; and (2) a time‐lagged response. Intra‐annual variability in drip discharge is significantly higher than inter‐annual variability. The content of DOC in all drip waters varies inter‐ and intra‐annually and has good correlation with drip water discharge at the rapid response sites. High DOC was observed in July and August in the three years observed. The flushing of soil organic matter is dependent upon the intensity of rain events. The DOC content of drip water increases sharply above a threshold rainfall intensity (>50 mm d^?1) and shows several pulses corresponding with intense rain events (>25 mm d^?1). The DOC content was lower and less variable during the dry period than during the rainy period. The shape of DOC peak also varies from year to year as it is influenced by the intensity and frequency of rainfall. The different drip sites show marked differences in DOC response, which are dominated by hydrological behaviour linked to the recharge of the soil and karst micro‐fissure/porosity network. The results explain why not all stalagmite laminae are consistent with climate changes and suggest that the structure of the rainy season events could be preserved in speleothems. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Very high-frequency and seasonal cave atmosphere P_CO2 variability: Implications for stalagmite growth and oxygen isotope-based paleoclimate records     

James U.L. Baldini  Frank McDermott  Dirk L. Hoffmann  David A. Richards  Nicholas Clipson 《Earth and Planetary Science Letters》2008,272(1-2):118-129

Cave air P_CO2 at two Irish sites varied dramatically on daily to seasonal timescales, potentially affecting the timing of calcite deposition and consequently climate proxy records derived from stalagmites collected at the same sites. Temperature-dependent biochemical processes in the soil control CO₂ production, resulting in high summer P_CO2 values and low winter values at both sites. Large Large-amplitude, high-frequency variations superimposed on this seasonal cycle reflect cave air circulation. Here we model stalagmite growth rates, which are controlled partly by CO₂ degassing rates from drip water, by considering both the seasonal and high-frequency cave air P_CO2 variations. Modeled hourly growth rates for stalagmite CC-Bil from Crag Cave in SW Ireland reach maxima in late December (0.063 μm h^− 1) and minima in late June/early July (0.033 μm h^− 1). For well-mixed ‘diffuse flow’ cave drips such as those that feed CC-Bil, high summer cave air P_CO2 depresses summer calcite deposition, while low winter P_CO2 promotes degassing and enhances deposition rates. In stalagmites fed by well-mixed drips lacking seasonal variations in δ¹⁸O, integrated annual stalagmite calcite δ¹⁸O is unaffected; however, seasonality in cave air P_CO2 may influence non-conservative geochemical climate proxies (e.g., δ¹³C, Sr/Ca). Stalagmites fed by ‘seasonal’ drips whose hydrochemical properties vary in response to seasonality may have higher growth rates in summer because soil air P_CO2 may increase relative to cave air P_CO2 due to higher soil temperatures. This in turn may bias stalagmite calcite δ¹⁸O records towards isotopically heavier summer drip water δ¹⁸O values, resulting in elevated calcite δ¹⁸O values compared to the ‘equilibrium’ values predicted by calcite–water isotope fractionation equations. Interpretations of stalagmite-based paleoclimate proxies should therefore consider the consequences of cave air P_CO2 variability and the resulting intra-annual variability in calcite deposition rates.  相似文献   

云南寻甸地区全新世中期气候变化模式研究   总被引：1，自引：1，他引：0  

张会领  覃嘉铭  林玉石  蒲晓强  刘长华 《热带地理》2009,29(6)

通过对云南寻甸白石岩仙人洞1号石笋(XR1)进行TIMS-U系测年和氧碳同位素分析,揭示了该区全新世中期氧碳同位素气候演化的模式。依据石笋不同时段有机碳含量的变化,重建了基于石笋有机碳指标的气候变化模式。通过对比,发现这两种指标所记录的寻甸地区古气候变化过程几乎完全一致。云南寻甸地区全新世中期的气候演化可分为3个气候期:1)8 000—5 600 aBP为温暖湿润期,气温较高,降水丰沛,石笋的氧碳同位素偏负,有机碳含量偏高;2)5600—4500 aBP为气候突变期,气候由温湿变为冷干,石笋氧碳同位素持续偏正,有机碳含量持续降低;3)4500—2100 aBP为冷干气候期,该期气候稳定,氧同位素和有机碳含量变化不大,均维持在较低水平。  相似文献   

石笋氧同位素和微量元素记录的陕南地区4200～2000a B.P.高分辨率季风降雨变化   总被引：2，自引：0，他引：2  

谭亮成  蔡演军  安芷生  程海  易亮  艾思本 《第四纪研究》2014,34(6)

基于陕南祥龙洞石笋XL2的19个230Th年龄、218个氧同位素分析以及896个Sr/Ca分析数据,高分辨率重建了4200～1972a B.P.期间陕南地区季风降雨变化.重建结果显示陕南地区这一时期季风降雨有显著的127～105a和57a周期,可能分别受控于太阳活动、PDO和/或AMO的变化.重建时段有3次百年尺度的干旱事件,分别发生于2200～2100a B.P.,2900～2700a B.P.和3600～3400a B.P.,其中2900～2700a B.P.干旱事件对应于北大西洋地区2.8ka冷事件.对比研究显示,尽管祥龙洞石笋和董哥洞石笋δ18O记录整体一致,但除了2900～ 2700aB.P.干旱事件之外,其他两次干旱事件在董哥洞石笋记录中并不明显.而尽管总体上祥龙洞和和尚洞石笋δ18O记录的差异要大,但XL2的3次干旱事件在和尚洞记录都有明显体现.有精确年代控制的祥龙洞、董哥洞及和尚洞石笋氧同位素记录的差异,揭示晚全新世我国季风降雨在十一百年尺度存在区域差异.  相似文献   

东亚季风“2.8ka”事件高分辨率的石笋记录     

李伟  陈仕涛  吴帅男  张芳芳  汪永进 《第四纪研究》2014,34(6)

据湖北省神农架永兴洞一支石笋的8个230Th年龄、648个δ18O数据,建立了晚全新世4.40～ 1.75ka B.P.时段平均分辨率为4a的东亚夏季风演化序列,其中在2.92～ 2.74ka B.P.期间,δ18O发生显著正偏,幅度达2.5‰,指示一个显著的弱季风事件(这里称之“2.8ka”事件).该事件以夏季风缓慢减弱开始,迅速增强结束,事件内部有两个次一级的振荡旋回(两峰三谷结构),在内部细节与转型特征上类似湖北和尚洞石笋δ18O记录的“8.2ka”事件,暗示发生在全新世这两个冷事件的驱动机制基本一致.这两个弱季风事件都发生在太阳活动明显减弱时期,并分别与北大西洋Bond 2和Bond 5冰漂碎屑事件同步,表明百年尺度的东亚季风环流的演化由太阳活动和北高纬气候共同驱动.  相似文献