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1.
青藏高原中部发育一系列独立的内流断陷湖盆，其中位于南亚季风区边缘的错鄂湖盆发育了巨厚的湖泊沉积，是研究高原内部地质环境变迁与构造-气候旋回的理想场所。本文对青藏高原中部错鄂孔197m沉积岩心Sr、Rb、Zr含量及其比值以及沉积物有机质δ^13C、TOC含量进行了分析，同时结合岩性、粒度、粘土矿物组成，初步建立了青藏高原中部2．8Ma来岩石化学风化的相对强度和古环境演化过程。研究表明，2．8Ma来青藏高原中部经历了三次剧烈的环境演化过程：在约197～170m(2．8～2．5Ma)之间，低Sr含量，高Rb／Sr和Zr／Rb值记录了较弱的化学风化过程，δ^13C、TOC含量反映气候前期暖干，后期偏凉湿，揭示冷湿气候的云杉林突然增加，沉积岩性明显变粗，反映了一次强烈的构造隆升运动；在约170～38．5m(约2．5～0．8Ma)之间，高Sr含量，低Rb／Sr和Zr／Rb值记录流域经历较强的化学风化过程，δ^13C、TOC含量反映高原中部总体处于温湿或凉湿的环境下，沉积岩性较细，高原总体处于相对剥蚀夷平阶段；在38．5～0m(约0．8～0Ma)段，Sr含量处于相对低值，Rb／Sr值相对较高，化学风化相对较弱，δ^13C、TOC含量表明高原中部处于较寒冷的环境之中，沉积岩性的再次明显变粗表明高原中部又经历了一次强烈的构造运动，并使高原中部整体隆升到4000m以上，奠定了现代高原面的基本格局。 相似文献
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青藏高原中部发育有一系列独立的内流断陷湖盆,其中位于南亚季风区边缘的错鄂湖盆发育了巨厚的湖泊沉积,是研究高原内部地质环境变迁与构造-气候旋回的理想场所。本文对青藏高原中部错鄂孔197m沉积岩心Sr、Rb、Zr含量及其比值以及沉积物有机质δ^13C、TOC含量进行了分析,同时结合岩性、粒度、粘土矿物组成,初步建立了青藏高原中部2．8Ma来岩石化学风化的相对强度和古环境演化过程。结果表明,2．8Ma来青藏高原中部经历了三次剧烈的环境演化过程：在约2．8～2．5Ma期间,低Sr含量,高Rb／Sr和Zr／Rb值记录了较弱的化学风化过程, 相似文献
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湖泊沉积物记录的藏中地区2.8Ma以来的环境演变历史 总被引：4，自引：0，他引：4
对青藏高原中部错鄂钻孔岩芯湖泊沉积物δ13C、总有机碳(TOC)、总氮(TN)、C/N和Rb/Sr比值等进行了分析,并结合岩性、孢粉组合特征等,建立了2.8Ma以来藏中地区的环境演化序列、区域构造活动和湖盆演化过程.研究显示,大约在2.8Ma,错鄂构造成盆,2.6Ma的构造运动之后,湖泊扩张,夏季风降水增加,湖泊沉积物以青灰色泥为主,藏中地区总体上处于温湿或凉湿的环境下;约0.78Ma后,沉积岩性明显变粗,湖盆快速充填,反映了强烈的构造隆升运动,并使高原中部整体隆升到4000m以上,δ13C和TOC反映藏中地区环境具明显的高寒特点;高原剧烈隆升时期,化学风化较弱,而在高原相对稳定的剥蚀夷平阶段,化学风化较强,说明藏中地区的化学风化在受气候强烈影响的同时,又受高原阶段性的构造隆升所控制. 相似文献
4.
Late Cenozoic Chemical Weathering and Environmental Changes Recorded in the Co Ngoin Sediments,Central Qinghai-Tibet Plateau 总被引：1，自引：2，他引：1
CHEN Shiyue JIN Zhangdong WANG Sumin SHEN Ji Nanjing Institute of Geography Limnology Chinese Academy of Sciences Nanjing Jiangsu School of Environment Planning Liaocheng University Liaocheng Shandong Institute of Earth Environment Chinese Academy of Sciences Xi’an Shaanxi 《《地质学报》英文版》2005,79(3):384-391
A series of faulted inland basins were developed in the central Qinghai-Tibet Plateau, among which the Co Ngoin Basin containing thick lacustrine sediments is located in the peripheral area of the Indian monsoon. In this paper, we present the weathering history and paleoclimatic changes in the last 2.8 Ma based on studies of high-resolution temporal distributions of Sr, Rb and Zr concentrations, Rb/Sr and Zr/Rb ratios and δ ^13C and TOC for the Co Ngoin sediments, in combination with the sediment properties, grain size distribution and clay mineralogy. The sedimentary records indicate three environmental stages in the last 2.8Ma. At the core depth of 197-170m (about 2.8-2.5Ma), low-intensity chemical weathering in the Co Ngoin catchment was experienced under warm-dry to cool-wet climate conditions with relatively low Sr concentration and high Rb/Sr and Zr/Rb ratios. The sudden occurrence of both subalpine coniferous forest and coarses and and gravel sediments in the Co Ngoin core reflects a strong tectonic uplift. The high Sr concentrations and low Rb/Sr and Zr/Rb ratios reflect a relatively strong chemical weathering between 2.5Ma and 0.8Ma (at the core depth of 170-38.5m) under a temperate/cool and wet climate, characterized by mud and silt with fine sand, probably indicating a stable process of denudation and planation of the plateau. Above the depth of 38.5m (about 0.8-0Ma), the coarsening of sediments indicates a strong tectonic uplift and a relatively low intensity of chemical weathering as supported by the record of sediments having relatively low Sr concentrations and high Rb/Sr and Zr/Rb ratios. Since then, the plateau has taken the shape of the modern topographic pattern above 4000m a.s.l. 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
7.
粒度分组:提取古环境变化信息的一种有效方法 总被引：3，自引：0，他引：3
对南京老虎山黄土-古土壤剖面全样和三个粒级组分(《2 μm、2～45μm和》45 μm)的Rb/Sr比值进行了系统研究.结果表明,Rb/Sr比值是衡量黄土和古土壤化学风化强度的良好地球化学指标;粒度分组是利用Rb/Sr比值研究古环境变化的有效方法.通过粒度分组,可以排除不同粒度组分之间由于Rb/Sr初始比值不同造成的互相干扰.《2 μm粒级的(Rb/Sr)-Sr反相关图的R2值最大(达0.97),说明该粒级指示化学风化作用的灵敏度最高,研究Rb/Sr比值这一地球化学指标最理想. 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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青藏高原2.8Ma来的环境演化及其对构造事件响应 总被引：2，自引：2，他引：0
本文根据青藏高原中部错鄂湖深钻研究的最新成果,结合东部若尔盖盆地湖泊沉积物记录,探讨了青藏高原2.8Ma以来的环境演化过程和高原构造隆升运动对环境演化的影响。初步研究显示:大约2.8MaBP错鄂湖构造成盆;2.6MaBP左右孢粉组合、粒度特征、岩性变化等均记录了一次强烈的构造隆升运动;2.6Ma~0.8Ma时段,高原可能处于一种整体隆升过程中的相对夷平阶段;若尔盖古湖揭示了0.9MaBP来的3次构造隆升运动,反映了高原环境演变的三个阶段;和黄土底界相当的错鄂湖沉积记录显示并未干旱的特征;黄土旺盛堆积时期(L15、L9、L6)高原湖泊记录的气候特征为偏湿气候。 相似文献
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陕西岐山黄土剖面Rb、Sr组成与高分辨率气候变化 总被引：29，自引：0，他引：29
陕西岐山五里铺全新世黄土剖面层次结构清晰完整。通过对该剖面Rb,Sr含量和磁化率系统测定表明，黄土中Rb,Sr含量和Rb/Sr值明显不同于古土壤，它们作为气候替代指标比磁化率更灵敏，分辨率更高。Rb,Sr高含量及低Rb/Sr值指示冬季风占优势的干旱期，相对低的Rb,Sr含量及高的Rb/Sr值指示夏季风占优势的湿润时期。揭示在大约6000－5000aBP曾出现一次以干旱为特征的明显气候恶化期，使全新世“大暖期”分裂形成两个主要的土壤期。黄土高原南部自全新世以来，经历了黄土沉积→土壤发育→黄土覆盖→土壤再度发育→黄土堆积及现代表土的发展演化阶段。 相似文献
11.
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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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
15.
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
16.
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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江汉盆地是长江出三峡后第一个大型卸载区,近2.77 Ma以来堆积了近300m的碎屑沉积物,主要由河流相和湖沼相组成,形成了多个沉积旋回。选择江汉盆地中心位置的ZL钻孔,利用ICP-MS方法展开微量元素组成分析,细粒组分中微量元素含量与各粒组含量相关性并不明显,主要是5~7粒级组分表现出微弱的相关性.可见,粒度并非ZL钻孔微量元素丰度的主控因素。钻孔岩心中大部分亲石元素、亲硫元素相对上部陆壳均出现明显富集,亲铁元素总体低于上部陆壳,可能与江汉盆地总体上更多地接受了来自上游而非扬子古陆本地深源物质风化碎屑沉积有关。Sr、V/Ni和Sr/Ba值的变化则表明江汉盆地在2.6~2.43 Ma B.P.时可能有咸化湖的发育,而在2.1 Ma B.P.左右存在过一段大湖发育期。 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