共查询到17条相似文献，搜索用时 209 毫秒
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流域生物、化学风化对小冰期气候变化的响应 总被引：2，自引：3，他引：2
岱海近500年沉积物的孢粉，介形类和地球化学记录表现了流域生物，化学风化对全球性小冰期气候波动明显而快速的响应，孢粉量的下降，化学风化强度的减弱（高Rb/Sr比值）以及意外湖花介（Limnocythere inopinata)的繁盛反映了小冰期最盛期岱海地区以干旱为特征的气候环境及其造成的高矿化度湖水，其中，介形类丰度及种类对环境变化的反应最迅速，植被生长的调节则要缓慢一些，内陆湖泊流域植被的衰弱与干旱环境下化学风化强度的减弱以及风尘作用的加强是相辅相成的。 相似文献
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早全新世降温事件的湖泊沉积证据 总被引：12，自引：1，他引：12
我国华北干旱－半干旱区封闭湖泊流域化学风化历史记录了全新世以来次级的气候环境波动过程。高精度的沉积物地球化学、物理及生物参数变化表明，在全新世早－中期过渡阶段存在一次强降温气候事件，具体表现为流域化学风化减弱（高Rb/Sr比）、湖泊产生力减弱（低有机碳）以及湖泊水位下降。虽然该事件的寒冷程度比Younger Dryas弱，但是其与来自湖沼（包括北极、非洲、北美、西欧、青藏高原、祁连山等）、海洋（比北大西洋、地中海、加勒比海等）、欧－美大陆生物组合、极地冰芯等在内的环境记录的冷事件发生时间基本一致，集中发生于8.0-8.5ka B.P.之间。 相似文献
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湖泊沉积物不同粒级组分的元素含量特征及其环境指示意义①——以内蒙古黄旗海为例 总被引：1，自引：0，他引：1
黄旗海湖泊柱状沉积物的全样、77~20 μm、<20 μm粒级的钛(Ti)、锰(Mn)、锶(Sr)、銣(Rb)、钡(Ba)、锆(Zr)等元素含量分析表明,元素在湖泊沉积物各粒级组分的丰度存在较大差异:Ti、Zr倾向于在粗颗粒中富集,Mn、Sr、Rb倾向于在细颗粒中富集,Ba的富集粒级不明显。Ti、Zr与Mn、Rb的颗粒粒级富集倾向可能是其硅酸盐矿物颗粒碎化过程的结果,而Sr则与湖泊自生碳酸盐有关。元素比值Zrc/（Rbc+Bac）、Zrc/Rbc与Ti、Zr的粒度效应Tic/Tif、Zrc/Zrf指示了沉积物重、轻矿物的相对比率,是流域侵蚀强度与湖泊涨缩的信息指示;Ba、Rb与Sr在细粒级的含量之比Baf/Srf、Rbf/Srf指示了硅酸盐与碳酸盐矿物的相对含量,是流域风化、侵蚀搬运强度与湖泊过程（包括物理/化学/生物）等混合信息指示,没有明确的环境指向性。 相似文献
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对大别山北麓0.78 Ma以来的黄土-古土壤样品的磁化率及Rb和Sr的地球化学特征研究表明,相对高的w(Rb)和w(Rb)/w(Sr)值及低w(Sr)值指示夏季风占优势的湿润时期,对应古土壤层;相对低的w(Rb)和w(Rb)/w(Sr)值及高w(Sr)值指示冬季风占优势的干旱期,磁化率相对较低,对应黄土层。剖面的w(Rb)/w(Sr)值自下至上降低反映大别山北麓地区的风化作用逐渐减弱,也揭示自0.78 Ma以来气候具有由湿向干的趋势;磁化率与w(Rb)/w(Sr)值的对比分析表明,它们的变化曲线存在显著不同,原因可能是由于磁化率在古土壤中的增强机制比较复杂所致,w(Rb)/w(Sr)值作为气候替代指标比磁化率更灵敏。与洛川剖面相比,大别山黄土-古土壤的w(Rb)较高而w(Sr)较低及Rb、Sr较强的分异能力特征反映了大别山气候整体较为温湿,沉积物遭受的风化程度更强。 相似文献
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通过对秭归盆地峡口剖面千佛崖组细碎屑岩样品的元素地球化学分析,恢复了区域内中侏罗世早期古气候的演化历程。结果显示:样品的化学风化指数(CIA)校正值的变化可分为2个阶段,在千佛崖组底部和中上部其平均值分别为82和64,微量元素风化指标Rb/Sr和古气候指标Sr/Cu(2.3,7.9)和C值(1.13,0.52)也有相同的反映,这指示了沉积物源区发生过由古气候转变导致的化学风化强度的减弱。利用P元素含量与Fe/Mn的变化特征,重建了区域古温度和古湿度的演化趋势。多元地球化学指标综合指示了研究区在中侏罗世早期为温暖、潮湿气候类型,而在中侏罗世中晚期区域内的干热化事件,使得气候转变为温暖、干旱的半潮湿气候类型,随着干热化趋势的不断加剧,最终气候过渡为干旱、炎热的半干旱气候类型,这与前人基于古植物研究得出的古气候变化过程相吻合,为盆地内中侏罗世早期古气候演化的进一步研究提供了地球化学方面的证据和参考。 相似文献
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Rb/Sr ratio, CaCO3 content, organic carbon (Corg) concentration, magnetic suscep-tibility and clay mineralogy of 4.0 m sediments samples recovered from Daihai Lake, northern China, are presented in the paper. Weathering and paleoclimatic change history during the last 2300 years is reconstructed in terms of the variations of Rb/Sr ratios in the sediment sequence, including the Little Ice Age and Medieval Warm Period. Our results suggest that the evolution processes of weathering and paleoclimate can be rebuilt in terms of the variations of Rb/Sr ratios in the lake sediment sequence, in combination with magnetic susceptibility, Corg, CaCO3 contents and clay mineralogy. 相似文献
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The Rb/Sr ratios of lake sediments have been suggested as indicators of weathering intensity by increasing work. However,
the geochemistry of Rb/Sr ratios of lake sediments is variable between different lakes. In this study, we investigated the
spatial and temporal patterns of Rb/Sr ratios, as well as those of other major elements in surface sediments of Lake Qinghai.
We find that the spatial pattern of Rb/Sr ratios of the bulk sediments correlates well with that of the mass accumulation
rate, and those of the terrigenous fractions, e.g., SiO2, Ti, and Fe. The temporal variations of Rb/Sr ratios also synchronize with those of SiO2, Ti, and Fe of each individual core. These suggest that Rb/Sr ratios of the surface sediments are closely related to terrigenous
input from the catchment. Two out of eight cores show similar trends between Rb/Sr ratios and precipitation indices on decadal
scales; however, the other cores do not show such relationship. The result of this study suggests that physical weathering
and chemical weathering in Lake Qinghai catchment have opposite influence on Rb/Sr ratios of the bulk sediments, and they
compete in dominating the Rb/Sr ratios of lake sediments on different spatial and temporal scales. Therefore, it is necessary
to study the geochemistry of Rb/Sr ratio of lake sediments (especially that on short term timescales) particularly before
it is used as an indicator of weathering intensity of the catchment. 相似文献
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青藏高原中部2.8Ma以来的化学风化与环境演化的湖泊沉积记录 总被引：2，自引：0，他引：2
对采自青藏高原中部错鄂湖泊钻孔近200m以上深处、形成于2.8Ma以来的沉积岩岩芯中Sr,Rb,Zr含量变化及Rb/Sr,Zr/Rb比进行了研究,并结合其岩性、粒度、粘土矿物组成,分析了该地区2.8Ma来化学风化的相对强度和古环境演化过程。研究表明,2.8Ma来青藏高原中部的环境经历了3个演化阶段：在深约197－170m(2.8-2.5Ma)岩性段,低Sr含量,高Rb/Sr和Zr/Rb比揭示的是较弱的化学风化过程,反映了与当时强烈的高原隆升运动有关;在约170－38.5m（约2.5-0.8Ma)段,高Sr含量,低Rb/Sr和Zr/Rb比记录的是该流域较强的化学风化阶段,与高原在稳定期中部总体处于温湿或凉湿的环境下的结论吻合;在38.5-0m（约0.8-0Ma)段,总体Sr含量处于相对低值,Rb/Sr比相对较高,化学风化相对较弱,表明高原中部处于较寒冷的环境之中,高原整体已隆升到4000m以上。 相似文献
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柴达木察尔汗贝壳堤剖面Sr同位素及其环境意义 总被引：6，自引：0，他引：6
根据对柴达木盆地察尔汗古湖贝壳堤剖面酸不溶组分和酸溶组分的提取及其87Sr/86Sr的测定,结合沉积物中Rb/Sr的变化,指出Sr同位素组成特征可有效指示源区化学风化和沉积区古环境变化;依据酸溶组分中盐度指标Sr/Ca, Sr/Ba值与Sr同位素组成曲线的对比分析,揭示酸溶组分Sr同位素可以较好的指示水体形成时的盐度。通过分析贝壳堤剖面化学风化和部分盐度变化过程,探讨了研究区晚更新世39.6~ 17.1 ka BP(未经校正的AMS 14C测年结果,全文同)湖泊高湖面的演化历史。 相似文献
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Roles of sorting and chemical weathering in the geochemistry and magnetic susceptibility of Xiashu loess, East China 总被引：1，自引：0，他引：1
Fuchun Li Zhangdong Jin Changren Xie Jiayi Feng Libo Wang Yongzhao Yang 《Journal of Asian Earth Sciences》2007,29(5-6):813-822
Uncertainties in paleoenvironmental interpretations for traditional chemical analysis of bulk samples result from different grain-size sub-populations of sediments containing variable distributions of elements and minerals. Therefore, it is important to understand the elemental and mineral distribution in different grain sizes in determining the quantitative relationship between chemical weathering and climatic change. We sieved a series of Xiashu loess samples into three sub-populations of different grain sizes (<2, 2–45 and >45 μm, respectively), and then analyzed each population for rubidium (Rb), strontium (Sr), rare earth elements and magnetic susceptibility. In comparison with elemental concentrations of bulk samples, clay mineralogy and illitic crystallinity, our results show that distinct elemental distributions and magnetic susceptibilities for different grain-size sub-populations are controlled by sorting and/or chemical weathering, although we also suggest that the Xiashu loess may have the same provenance as the Central Chinese Loess. Maximum concentrations of Rb and fine-grained magnetic minerals in the less than 2 μm sub-population, coupled with our finding of maximum Sr in the larger than 45 μm fraction, indicate that Sr was lost during chemical weathering. Grain-size sub-population analysis is, therefore, an effective method for extracting paleoenvironmental information, because individual sub-populations show minimal variations in initial Rb/Sr ratios compared to bulk analysis of all sizes together. Furthermore, a negative correlation between Rb/Sr ratios and Sr concentrations for the <2 μm fraction (R2 = 0.97) may indicate that clay is a sensitive indicator of intensity of chemical weathering and is an ideal sub-population for determining Rb/Sr ratios, but not for magnetic susceptibility. 相似文献
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本文系统地测试了陕西洛川黄土-古土壤剖面中的Rb,Sr含量和磁化率。通过对比该剖面2．50MaB．P．以来Rb／Sr曲线和磁化率曲线,发现两者的形状和变化的相位十分相似,然而两者的相对振幅却有明显的差别。Rb／Sr曲线记录了0．80MaB．P．左右一次重要的气候转型界面,揭示了黄士和古土壤内部次一级的气候波动旋回,反映了早更新世黄土高原较温暖潮湿的特点以及更新世以来气候由湿向干的变化趋势。研究表明,Rb／Sr值可以作为衡量东亚夏季风环流强度变化的较为敏感的替代性指标。 相似文献
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1IntroductionGlobal change studies on the decennial and cen-tennial timescales,which can help put together the in-formation from long timescale study and meteorologicalstudy,is crucial for predicting future global changes(Hegerl,1998;Wang Pinxian and Jian Zhimin,1999;Wang Sumin et al.,1998).Lacustrine sedi-ments characterized by their continuity,major sedi-mentation rate,and high resolution can provide usefulinformation for reconstructing the past global changes(Steven,1996;Wang Sumin and … 相似文献