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全新世岱海流域化学风化及其对气候事件的响应 总被引：12，自引：0，他引：12
通过对岱海 12.08 m沉积岩芯 210Pb和 AMS- 14C精确定年及地球化学、物理指标的综合分析,重建了包括 8.2 ka冷期、中世纪暖期 (MWP)和小冰期 (LIA)等典型气候事件在内的全新世以来所经历的化学风化及其环境演化过程.全新世早-中期 (9.0～ 3.5 ka),岱海流域处于温暖湿润气候环境,主要环境特征表现为流域化学风化显著增强、生物生产力逐步提高、湖泊水位大幅度抬升.在 7.90～ 8.25 ka期间存在一次冷气候事件,其发生时间与来自湖沼、海洋、生物组合和极地冰芯等在内的全球环境记录基本一致,具体表现为流域化学风化减弱、湖泊生产力降低以及湖泊水位下降. 2.5 ka以来,岱海沉积物中环境指标的显著变化,表明进入气候波动更频繁的新冰期.岱海沉积物中的指标变化也展示了本世纪以来的气候增暖过程,但其化学风化强度还没有达到 MWP的程度. 相似文献
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乌梁素海和岱海沉积磷形态分布的差异性研究 总被引：3，自引：0，他引：3
湖泊沉积物中磷的含量及形态分布等地球化学信息可以用来反演湖泊流域的古环境及污染历史。本文以乌梁素海和岱海两个不同类型的湖泊为研究对象,对两个湖泊沉积柱芯中磷形态分布的差异性进行了研究。结果表明,乌梁素海和岱海沉积柱芯中沉积磷的主导形态均为ACa P、De P和 Or P,但乌梁素海表层沉积物和沉积柱芯中Al P和 ACa P的含量水平明显高于岱海,而Ex P、De P和 Or P的含量水平明显低于岱海。两个湖泊沉积磷形态分布的差异性能较好地揭示出湖泊流域的地理环境、化学风化程度以及湖泊富营养化类型的差异性,沉积柱芯中ACa P含量及其分布特征能很好的指示湖泊自身发展过程中的富营养化水平,而De P含量及其分布特征则能较好的揭示出整个湖泊流域的古环境古气候信息。 相似文献
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岱海盆地位于鄂尔多斯周缘断裂系的东北角,总体走向NEE,南北两侧均由断裂控制.岱海盆地南缘分布两条平行于边界断裂的地貌陡坎,延伸方向65°,总长约20km,形似断层陡坎.本文用开挖探槽、分析地层沉积过程的方法,查明了这两条地貌陡坎均为全新世形成的湖岸阶地的前缘陡坎,不是断裂活动错断地表的结果.结合全新世的气候资料,分析了湖岸阶地的形成时间和过程.一级陡坎形成于2115±80aB.P.之后,记录了最后一次高湖面的位置;二级陡坎形成于10000aB.P.至6165土105aB.P.之后,即全新世暖期开始之后的第一次湖侵至岱海第二次大的湖侵期.二级陡坎地层沉积记录了两次大的湖进湖退过程,第一次湖进时间为10000aB.P.,湖退时间9450±1260aB.P.;第二次湖进时间6700aB.P.,湖退时间6165± 105aB.P.,其间有一次级湖退过程,时间为7620±930aB.P..两级阶地前缘陡坎的形成时间与孢粉等记录的中国北方全新世温度变化相对应. 相似文献
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岱海位于半干旱区东部边缘及东亚夏季风的尾闾区，生态环境体系脆弱，气候和环境变化敏感，是研究环境变化的理想地区。65个湖泊表层及入湖河流冲积物样品的孢粉分析揭示了岱海表层孢粉沉积特征及孢粉来源。岱海表层孢粉主要来源于区域性植被的孢粉，其总体特征反映了区域植被的组成，但不同部位孢粉组合的差异反映了湖滨当地植被的变化。受沉积环境的影响，岱海湖区孢粉浓度总体上要低于入湖河流孢粉浓度，湖区中部孢粉浓度最高。岱海孢粉以河流携带的为主，同时受风力传播的影响。蒿、藜科、桦、虎榛子等花粉和蕨类孢子以河流搬运的为主，松、禾本科及莎草科花粉可能还受风力传播的影响。一些仅在个别样品中出现且百分比很低的花粉类型如豆科、十字花科等还有可能是昆虫、鸟类或人类活动携带而来。 相似文献
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岱海沉积物元素地球化学特征反映的末次冰期以来季风/干旱过渡区的水热条件变迁 总被引：3，自引：2，他引：1
对季风/干旱过渡区封闭湖泊岱海两支沉积物岩芯进行了元素地球化学特征分析.结果揭示,沉积物中易(溶)迁移元素和难(溶)迁移的相对含量及其与铝元素的比值可以很好地表征流域化学风化强度的变化.进而指示盆地的水热状态.过去大约16.2kaB.P.以来,易迁移元素含量以及与铝元素比值较高的几个阶段,如大约14.5～11.7kaB.P.,10.3～9.0kaB.P.,6. 7～3.5kaB.P.,3.2～2.6kaB.P.和1.7～1.2kaB.P.代表了岱海盆地化学风化较强、水热条件较好的时期,其中以大约6.7～3.5kaB.P.期间的水热条件最为优越,可以认为是流域气候的适宜期.而沉积物中难(溶)迁移元素在大约14.5kaB.P.前,11.7～10.3ka B.P.,3.5～3.2kaB.P.和2.6～1.7kaB.P.期间以及1.2kaB.P.以来的相对高含量则代表了流域相对较弱的化学风化强度和较为低下的水热状态.大约9.0～6.7kaB.P.期间,沉积物较高的CaO/MgO比值与降低的易迁移元素含量指示了流域较高温度条件以及由此导致的高蒸发率.综合岱海沉积物已有的有机质、碳酸盐、花粉组合、湖面变化等方面的数据,认为岱海盆地末次冰期以来,水热同期的模式涵盖了岱海除大约9.0～6.7kaB.P.外的各个阶段.而大约9.0～6.7kaB.P.期间,季风有效降水与温度变化的不一致现象可能更多地反映了岱海自身的自然环境特点对区域大尺度气候变化的反馈. 相似文献
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岱海蒙人原稱之為岱哈淖爾(Daikha Nor),漢人則又稱之為岱海或日太海。按岱海乃為一內陸鹹湖位於綏東高原之西南部,四圍皆山形如盆地,拔海三千九百十呎,東與豐鎮及北與卓資山各距有一百華里(約五十餘公里)。岱海盆地自東北至西南長有 相似文献
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岱海两支岩芯独立的高分辨率代用指标序列揭示了季风/干旱过渡区全新世适宜期的气候环境特征。研究表明,在约7.9~3.5kaB.P.期间,岱海流域出现植被繁盛、生产力相对增强和降水丰富的状况,显示气候条件相当适宜;而在约10.0~7.6kaB.P. 期间,流域气候以相对干燥为特征。这与早先认为的岱海流域全新世初期为适宜期,且降水丰富的结果明显不同。比较岱海与鄂尔多斯-内蒙古高原中部其他湖沼记录,季风/干旱过渡区的气候适宜期基本集中在约8~3kaB.P.的全新世中期,尽管各记录在适宜期的起止时间、表现特征上存在一些差异。这些差异的产生,一方面可能体现了不同的局地地形、植被、水文条件等对区域水热条件的不同反馈,另一方面则可能暗示不同的沉积序列、测年材料之间难以进行精细的对比。沉积序列的连续性、稳定性及高分辨率、测年材料的适用性是进行全新世气候、环境特征研究的前提。 相似文献
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青藏高原北部可可西里库赛湖沉积物及风成物的粒度特征 总被引：4，自引：1，他引：3
对青藏高原北部可可西里地区库赛湖钻孔沉积物、冰面风成物和流域风成物粒度特征进行了研究,结果表明:库赛湖冰面风成物的粒度特征同流域风成物的粒度特征具有明显的区别,而钻孔沉积物的粒度分布特征却和流域风成物的粒度分布特征相似.对库赛湖钻孔沉积物端元组分的分析表明,库赛湖沉积物的来源主要有径流搬运、风力和冰川搬运组分构成,所占的平均比例分别为55.5%,35.9%和8.5%.库赛湖沉积物风成物端元组分的粒度分布特征,得到了冰面风成物粒度特征的验证.尽管没有获得径流搬运组分的样品,但钻孔沉积物的粒度分布特征同流域风成物的粒度分布特征具有的相似性,可能说明,由于库赛湖地区降水较少,湖区径流不发育,流域的风化作用很弱,流域风成物通过流水汇人径流,成为径流搬运的主要物质来源. 相似文献
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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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岱海14 C测年的现代碳库效应研究* 总被引：2，自引：0，他引：2
碳库效应的复杂性是影响建立湖泊沉积物高精度年代序列的一大障碍。本项研究通过我国内蒙古半干旱区封闭湖泊表层沉积物、湖水、现生沉水植物狐尾藻、现生鲤鱼鱼骨和湖岸表层土壤等一系列样品的14 C年代测定,表明现代岱海确实存在碳库效应。碳库效应年龄因湖水盐度在湖区的不均而有所变化,岱海西部湖区弓坝河径流补给量大,湖水盐度较东部稍低,碳库效应年龄也略小于东部湖区。表层沉积物中有机质包含浮游生物和沉水植物的混合信息,因而其碳库效应年龄较沉水植物年龄轻,岱海湖心表层沉积物碳库效应年龄在2000a左右。这一碳库效应年龄较通过沉积钻孔14 C年龄线性回归获得的年龄偏大,可能的原因是在时间序列上碳库效应并非恒定。 相似文献
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Grain-size distributions of fluvial, eolian and marine sediments were explicated decades ago. For lake sediments, however, there is still great uncertainty in explaining the genesis of grain-size components due to the inherent complexity of their polymodal distributions. In this study, the grain-size components of the surface sediments of Daihai Lake, Inner Mongolia, were partitioned using a lognormal distribution function and the relationship between the identity of each component and the specific sedimentary environment was investigated. The data indicate that the modern clastic sediments of Daihai Lake contain five distinct unimodal grain-size distributions representing five grain-size components. Each of the components retains its identity including modal size, manner of transportation and environment of deposition although the relative percentage varies with the hydraulic condition throughout the lake. These components are specified from fine to coarse modes as long-term suspension clay, offshore-suspension fine silt and medium-to-coarse silt, and nearshore-suspension fine sand and saltation medium sand. The percentage of the components interpreted as an indication of nearshore environments displays a negative correlation with water depth across the modern lakebed, suggesting a model for linking the nearshore components in sediment cores to the lake level status in the geological past. The model was applied to a sediment core from the lake where high percentages of the nearshore components in the core sediments were correlated with low regional precipitations reconstructed on the pollen profile of the same core. The coincidences between two independent proxies do not only demonstrate the validity of lognormal distribution function in partitioning polymodal sediments but also reveals the potential of the grain-size component–lake level status model for lake’s paleohydrological reconstruction. 相似文献
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内蒙古河套盆地为受断裂控制形成的新生代断陷盆地,盆地中积水成湖,称河套古湖。晚更新世时期,河套古湖为继承性闭塞型断陷湖。上更新统主要为湖泊沉积体系,地层划分建组为上部东河村组、中部万水泉组、下部达拉特组。达拉特组在湖盆连续沉降条件及半深湖深湖中硫酸盐型、碳酸盐型湖水交替环境下沉积形成。万水泉组在湖盆沉降速率与沉积速率大体平衡条件及浅湖半深湖中半咸水湖环境下沉积形成。东河村组在湖盆沉降速率小于沉积速率条件下以及半咸水湖、局部时期为碳酸盐湖环境下的滨浅湖中沉积形成。晚更新世末期,河套古湖处于大湖水期,晋陕内蒙古交界处河流袭夺、河套盆地北侧山前断裂强烈活动和超强地震导致河套古湖湖水快速外泄,银川盆地、河套盆地、晋陕峡谷贯通而形成今日黄河河道。 相似文献
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Effect of groundwater on the ecological water environment of typical inland lakes in the Inner Mongolian Plateau 
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下载免费PDF全文 To explore the causes of the ecological environment deterioration of lakes in the Inner Mongolia Plateau, this study took a typical inland lake Daihai as an example, and investigated the groundwater recharge in the process of lake shrinkage and eutrophication. Using the radon isotope (222Rn) as the main means of investigation, the 222Rn mass balance equation was established to evaluate the groundwater recharge in Daihai. The spatial variability of 222Rn activity in lake water and groundwater, the contribution of groundwater recharge to lake water balance and its effect on nitrogen and phosphorus pollution in lake water were discussed. The analysis showed that, mainly controlled by the fault structure, the activity of 222Rn in groundwater north and south of Daihai is higher than that in the east and west, and the difference in lithology and hydraulic gradient may also be the influencing factors of this phenomenon. The 222Rn activity of the middle and southeast of the underlying lake is greater, indicating that the 222Rn flux of groundwater inflow is higher, and the runoff intensity is greater, which is the main groundwater recharge area for the lake. The estimated groundwater recharge in 2021 was 3 017×104 m3, which was 57% of the total recharge to the lake, or 1.6 times and 8.1 times that of precipitation and surface runoff. The TN and TP contents in Daihai have been rising continuously, and the average TN and TP concentrations in the lake water in 2021 were 4.21 mg·L?1 and 0.12 mg·L?1, respectively. The TN and TP contents entering the lake with groundwater recharge were 6.8 times and 8.7 times above those of runoff, accounting for 87% and 90% of the total input, respectively. The calculation results showed that groundwater is not only the main source of recharge for Daihai, but also the main source of exogenous nutrients. In recent years, the pressurized exploitation of groundwater in the basin is beneficial in increasing the groundwater recharge to the lake, reducing the water balance difference of the lake, and slowing down the shrinking degree of the lake surface. However, under the action of high evaporation, nitrogen and phosphorus brought by groundwater recharge would become more concentrated in the lake, leading to a continuous increase in the content of nutrients and degree of eutrophication. Therefore, the impact of changes in regional groundwater quantity and quality on Daihai is an important issue that needs further assessment. 相似文献
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Daihai Lake, a modern lacustrine rift basin, located in Inner Mongolia, North China, serves as an important modern analog for understanding deltaic depositional processes in an active rift setting. Two of the deltas (Yuanzigou delta and Bulianghe delta) on the margins of Daihai Lake were surveyed to compare and contrast stacking patterns using aerial photographs, field trenching and sediment sampling. Shallow cores and trench data collected from the margins of Daihai Lake indicate that a variety of depositional processes have been active since Daihai Lake formed. Two 3-D sedimentation models which employ chronostratigraphic correlation technique were generated. The chronostratigraphic sedimentation models predict and represent the architectures and sand-body continuity of sediments. Stratigraphical coincidence of the broad sheeted drifts and channel erosion suggests a coupling between downslope and alongslope processes. Distributary mouth bars are prevalent in the front of deltas on steeper slopes due to the dominance of down-slope flows. On the contrary, the along-slope currents favor the development of distal bar deposits with sheeted sandbodies on gentle depositional slopes. This study provides an insight into the architecture of complex sedimentary facies associated with highlighting key differences between downslope flows and alongslope currents. The distribution of sand within these deltas is of particular interests, with applications in understanding the architecture of hydrocarbon reservoirs formed in lacustrine rift basin. 相似文献
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近800a来内蒙古岱海湖水的盐度定量及其气候意义 总被引：6，自引：0，他引：6
在干旱半干旱地区 ,封闭湖泊的湖水盐度对气候变化反应敏感。首先通过现生介形类 (Lim nocytherecf.inopinata)壳体与湖水Sr/Ca比值的测定确定了Sr/Ca的分配系数 ;然后测试现代岱海湖水盐度与湖水Sr/Ca比值 ,建立湖水盐度与湖水Sr/Ca比值的函数关系 ;最后利用湖泊沉积剖面中介形类壳体的Sr/Ca比值定量恢复了岱海湖水近 80 0a来的盐度。通过分析岱海湖水盐度变化过程 ,揭示了研究区小冰期前期降水增加的冷湿气候 ,这明显不同于东部其它地区的冷干气候 ;研究区在小冰期中后期以偏干旱气候为主 ,这与东部其它地区干冷气候相一致 ;推测了 2 1世纪初 10～ 2 0a ,岱海地区降水将有所增加 ,干旱趋于缓和。 相似文献