共查询到20条相似文献，搜索用时 312 毫秒
1.
内蒙古黄旗海不同粒级湖泊沉积物Rb、Sr组成与环境变化 总被引：13，自引：0，他引：13
内蒙古黄旗海湖泊沉积物剖面层次结构清晰完整,通过对该剖面全样、77 μm~20 μm和小于20 μm三个不同粒级Rb、Sr含量和磁化率的系统测定,结果表明,湖泊沉积物中小于20 μm粒级成分的Rb、Sr含量和Rb/Sr值变化阶段明显,Rb/Sr值与磁化率分布曲线十分吻合,因此,小于20 μm粒级成分的Rb/Sr值与磁化率包含更加真实的古气候环境信息。Rb/Sr值反映了风化的强度,因而可以作为指示夏季风环流强度的代用指标。黄旗海湖泊沉积物的地球化学Rb、Sr元素含量和Rb/Sr值以及磁化率值波动特征具有深刻的环境演变背景,由此揭示的环境特征在一定程度上反映了全新世气候千百年尺度的波动变化,与全球气候波动有关。 相似文献
2.
Jade Petersen Bruno Wilhelm Marie Revel Yann Rolland Christian Crouzet Fabien Arnaud Elodie Brisset Eric Chaumillon Olivier Magand 《Journal of Paleolimnology》2014,51(3):343-355
We studied sediment cores from Lake Vens (2,327 m asl), in the Tinée Valley of the SW Alps, to test the paleoseismic archive potential of the lake sediments in this particularly earthquake-sensitive area. The historical earthquake catalogue shows that moderate to strong earthquakes, with intensities of IX–X, have impacted the Southern Alps during the last millennium. Sedimentological (X-ray images, grain size distribution) and geochemical (major elements and organic matter) analyses show that Lake Vens sediments consist of a terrigenous, silty material (minerals and organic matter) sourced from the watershed and diatom frustules. A combination of X-ray images, grain-size distribution, major elements and magnetic properties shows the presence of six homogenite-type deposits interbedded in the sedimentary background. These sedimentological features are ascribed to sediment reworking and grain sorting caused by earthquake-generated seiches. The presence of microfaults that cross-cut the sediment supports the hypothesis of seismic deposits in this system. A preliminary sediment chronology is provided by 210Pb measurement and AMS 14C ages. According to the chronology, the most recent homogenite events are attributable to damaging historic earthquakes in AD 1887 (Ligure) and 1564 (Roquebillière). Hence, the Lake Vens sediment recorded large-magnitude earthquakes in the region and permits a preliminary estimate of recurrence time for such events of ~400 years. 相似文献
3.
毛乌素沙地北缘泊江海子剖面粒度特征及环境意义 总被引：12，自引：8，他引：4
通过毛乌素沙地现代风成沙的粒度与泊江海子剖面沉积物粒度特征对比分析,确定了剖面中4个层位（290—210 cm、190—160 cm 、153.5—123.5 cm、50—40 cm）基本属于风成砂沉积,并且这些风成砂中间夹杂着三次湖相沉积,结合14C年代测定,我们认为此区域在4 000—5 000 a BP存在以下沉积（气候）旋回:至(4 958±84)a BP,沉积风成砂,反映该时期风沙活动强烈,气候干燥,冬季风强盛;(4 958±84)a BP前后,沉积物为灰绿色湖相层,表明这一时期存在短暂的湖面扩展,沙漠退缩;(4 958±84)—(4 793±74)a BP,沉积风成砂,反映了湖泊的退缩和沙漠的扩展;(4 793±74)—(4 536±70)a BP,湖相沉积物,反映了流域降水量的增多;(4 536±70)—(4 085±67)a BP沉积风成砂后,(4 085±67)a BP前后又出现了短暂的湖相沉积,之后又是风成砂沙沉积。 相似文献
4.
对居延海G36钻孔进行了系统磁性特征分析,并结合总有机碳含量和粒度等环境代用指标,在精确测年的基础上,探讨了居延海地区全新世时期以来的环境变化。结果显示,居延海岩芯磁性矿物主要存在于粗颗粒的沉积物中,载磁矿物为颗粒较粗的多畴磁铁矿;磁化率变化机制比较复杂,与干湿环境变化没有简单正（反）关系。根据G36沉积物环境代用指标的变化,大致可以将其分为4个干湿交替时期:6 700~4 600 a BP干旱时期,4 600~3 100 a BP湿润时期,3 100~2 500 a BP干旱时期以及1 800 a BP以来湖泊干涸。在这4个时期中,磁学参数记录了两次显著湿润事件和两次显著干旱事件。 相似文献
5.
安徽巢湖全新世湖泊沉积物磁化率与粒度组合的变化特征及其环境意义 总被引：27，自引：4，他引：23
通过对获取的巢湖湖泊沉积岩芯的磁化率与粒度组合特征的分析,结合孢粉及相邻其它区域的环境考古资料,得出该岩芯柱样所反映的环境变化信息。结果表明:(1)巢湖湖泊沉积物磁化率曲线在117 cm以下总体上比较平稳而略有下降,117 cm以上人类活动所导致的侵蚀作用加剧使得磁化率值异常升高;(2)本岩芯柱样117 cm以下样品的磁化率强度与粘土的百分比含量呈正相关,而与粉砂组分的百分比含量成负相关;(3)根据磁化率与粒度组合变化特征,结合孢粉分析及全新世以来区域气候变化背景,9 870 Cal a B.P.以来的巢湖流域古气候环境演变可以划分6个不同的时期:9 870~7 000 Cal a B.P.,气候呈温和略干的特点;7 000~4 750 Cal a B.P.,气候温暖湿润;4 750~2 170 Cal a B.P.,流域气候温和干燥,巢湖湖盆局部地区可能出露水面以上;2 170~1 040 Cal a B.P.,气候总体上温和湿润,但是冷暖波动明显;1 040~2 00 Cal a B.P.流域处在温凉稍湿的时期,人类活动逐渐加强;200 Cal a B.P.至今,流域总体上处于相对温暖湿润阶段。 相似文献
6.
鄱阳湖湖滨及湖口－彭泽段长江南岸有成群沙垄、沙山分布。2005年调查发现,可分为4个风成沙山期及7类沉积物。4个风成沙山期分别为95kaB. P.的老红沙山期、46kaB. P.的红沙山期、27kaB. P.~15kaB. P.左右的黄沙山期、250年来的近代沙山期。此外还有温暖时期沟谷里水动力作用下的次生堆积,湖滩上的风蚀残余沙以及黄沙山表面现代松散沙。比较不同时期风沙沉积的粒度组成,4个时期的风力大小基本呈现黄沙山期>近代沙山期>红沙山期>老红沙山期的状态,以上特点与末次间冰期以来多个亚冰期全球气候寒冷程度的变化具有可比性。 相似文献
7.
8.
Glacial Deposition Along an Ice-Contact Slope: An Example from the Southern Lake District, Chile 总被引：1，自引：0，他引：1
Susan E. Turbek & Thomas V. Lowell 《Geografiska Annaler: Series A, Physical Geography》1999,81(2):325-346
Glacially derived sediments and structures vary systematically with topographic position along ice-contact slopes near the margin of former temperate piedmont glaciers in the southern Lake District, Chile. Features along lower positions of the slopes include glaciolacustrine sediments and large-scalethrusting. Middle slope features include low-angle subglacial thrusting of thin slices of lacustrine sediment. Upper slope features include high-angle thrusting, and lodgement and flow till. Locally, the same ordering of these features occurs in vertical sequence.
A common theme that unifies the processes represented by these features is the distribution of hydrostatic pressure. Thicker ice (producing higher glacier overburden pressures) and aquicludes of fine-grained sediments toward the center of the basin result in high hydrostatic pressures, whereas thin ice and porous out-wash reduce these pressures at the top of the ice-contact slopes.However, such a distribution cannot completely explain the observed vertical sequences; hence, local variations in hydrostatic pressure because of lithologic contrasts probably play a role. Nowhere along the ice-contact slope are pervasively deformed glacial sediments observed; therefore they cannot be invoked to explain the low glacier profiles of these piedmont glacier lobes. 相似文献
A common theme that unifies the processes represented by these features is the distribution of hydrostatic pressure. Thicker ice (producing higher glacier overburden pressures) and aquicludes of fine-grained sediments toward the center of the basin result in high hydrostatic pressures, whereas thin ice and porous out-wash reduce these pressures at the top of the ice-contact slopes.However, such a distribution cannot completely explain the observed vertical sequences; hence, local variations in hydrostatic pressure because of lithologic contrasts probably play a role. Nowhere along the ice-contact slope are pervasively deformed glacial sediments observed; therefore they cannot be invoked to explain the low glacier profiles of these piedmont glacier lobes. 相似文献
9.
CHEN Lei SHEN Hongyuan JIA Yulian WU Jinglu LI Xusheng WEI Ling WANG Pengling 《地理学报》2008,18(3):373-384
Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986, the paper investigates the record of palaeolake stand state, sedimentary environmental evolution, and winter monsoon change. First, these samples are separated into three different grain size fractions, i.e., total sediments, 77–20 μm and <20 μm. Second, the chemical elements—Rb and Sr—of the grain size separation were tested and analyzed systematically in this paper. Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument, respectively. The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company. The results showed the elements and the ratios varied regularly with the grain size. But the ratio of Rb/Sr in the sediments <20 μm correlates positively with the magnetic susceptibility of these samples. Therefore, the ratio of Rb/Sr in the fraction <20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites. It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoen-vironment. 相似文献
10.
艾比湖干涸湖底不同地表类型风蚀强度及粉尘输移通量的风洞试验研究 总被引：2，自引：2，他引：0
以新疆准格尔盆地西部艾比湖干涸湖底及相关邻近地区7种不同形态的原状土为研究对象,通过风洞模拟试验,揭示干涸湖底不同地表类型的风蚀强度和沙/盐尘低空输送通量。结果表明：粉状盐漠和含盐量较低的淤泥-粘土混合物临界启动风速最低,硬质盐壳的临界启动风速最大;大于16 m·s-1的大风是造成艾比湖干涸湖底风蚀的主要动力,7种地表类型中湖相沉积物、风积物、粉状盐漠的风蚀率最大,是风蚀尘暴的主要尘源;风蚀过程中颗粒的初始运动主要集中在0~10 cm高度范围内,以近地面跃移为主,风积物、湖相沉积物和粉状盐漠的输移通量最大。 相似文献
11.
藏南沉错湖泊三角洲的沉积相及沉积环境 总被引：3，自引：0，他引：3
在西藏自治区沉错湖泊三角洲平原和湖内钻孔取芯 ,利用14 C和ESR测年方法建立了钻孔剖面的年代标尺。在岩芯描述、沉积物粒度分析和CaCO3含量分析基础上 ,对沉错湖泊三角洲的沉积环境和沉积相进行了解释分析。 36 7m长的岩芯大致记录了 5 5万年以来的沉积历史。全孔平均沉积速率约为 0 6 6 7mm/a。 16 92 0aBP以来三角洲的沉积速率较大 ,平均为 1 2 7mm/a。由于沉积物物质来源的多源性导致CaCO3在剖面上的无规律性变化。但是 ,沉积物粒度和沉积序列变化指示全套沉积由底部的冲积扇相向上过渡为水下扇亚相和三角洲沉积相。在大约 175 0 0aBP～ 14 0 0 0aBP时期 ,沉错存在高湖面阶段。沉积序列中记录了末次冰期最盛期 (LastGlacialMaximum )和新仙女木事件 (YoungerDryas)。沉积特征和沉积环境的变化主要受湖面涨缩变化所控制。而湖面升降变化的驱动因素主要为气候 ,尤其夏季风的强弱和冷事件 相似文献
12.
Zhengcai Zhang Zhibao Dong Jiyan Li 《Geografiska Annaler: Series A, Physical Geography》2015,97(4):681-693
Grain‐size characteristics of dune networks in the Tengger Desert of northwestern China were investigated. Grain‐size parameters (mean, standard deviation, skew, and kurtosis) were determined on dune surfaces at windward toe, stoss, crest and leeward toe locations. Multiple discriminant analyses were applied to distinguish deposition environments. Results indicated that the aeolian sediment is mainly composed of very fine and fine sand in the dune networks of the Tengger Desert. Sorting improves as grain size becomes finer. However, the relationships between mean grain size, skew, and kurtosis vary in space. There is a negative relationship between skew and sorting; similarly, the relationships between sorting and skew, and skew and kurtosis change in space. The sediment deposition environment includes aeolian sediment and lacustrine sediment. The lacustrine sediment provides the source material for dune windward toe and stoss formation and development, but the aeolian sediment provides the source material for dune crest and leeward toe formation and development. According to the log‐probability of grain size distributions, aeolian sediments in dune networks are composed of two distinct saltation populations. 相似文献
13.
青海苏干湖表层沉积物粒度分布模式 与大气粉尘记录 总被引：11，自引：0，他引：11
位于干旱区柴达木盆地具有年纹层的苏干湖是以地下水补给为主的内陆封闭湖泊, 其表层沉积物粒度具有多组分峰态分布特征, Weibull 函数的拟合结果发现, 其粒度分布全部具 有4 个基本组分: 超细粒组分, 众数粒径在1 μm 上下; 细粒组分, 众数粒径在5~10 μm; 粗粒组分, 众数粒径在50~100 μm; 砂组分, 众数粒径在500 $m 左右。粒度主峰出现在细 粒组分或者粗粒组分。直接来自大气粉尘的冬季湖泊冰面样品及当地尘暴样品的Weibull 函数粒度拟合也显现出了相似的分布模式, 冰面样品的粒度主峰位于众数粒径在15~20 μmm 的 细粒组分, 砂组分(众数粒径452.9μm) 的出现指示出砂粒在冬半年沿冰面而进入湖泊中心。 尘暴降尘样品在尘暴季节(5 月份) 和非尘暴季节(11 月份) 的粒度分布普遍具有3 个组分, 缺少砂组分, 强沙尘暴事件样品则由4 个组分组成, 粒度主峰均位于众数粒径在100~200 μm 的粗粒组分。结果显示, 苏干湖湖泊沉积能够较好记录当地大气粉尘, 砂组分与湖泊周边干旱地表经历的近地面强沙尘活动有关, 粗粒组分记录了区域性的尘暴事件, 细粒组分主要反映 流域径流状况, 超细粒组分代表干旱区的大气背景粉尘和气溶胶。研究表明, 苏干湖内陆湖 泊沉积客观记录了区域大气粉尘和尘暴事件, 具有重建干旱区大气粉尘变化历史的潜在优势。 相似文献
14.
鄱阳湖湖滨地区广泛分布着晚第四纪风沙沉积序列。在星子县沙岭沙山进行野外调查后选择蓼花剖面开展工作,测试了地质时代和粒度,对粒度结果使用端元分析模型进行研究,探讨该区域末次冰期中晚期的气候变化规律。结果显示：该剖面由湖相-古土壤-沙丘砂等沉积相叠覆堆积组成,形成于末次冰期中晚期（48.8—17.1 ka）。端元分析模型将粒度数据分解出3个不同的粒度端元,不同端元组分在垂向上呈峰谷交替的旋回变化,EM1代表粉砂端元组分,峰值对应湖相和古土壤发育时期;EM2和EM3代表中砂—粗砂端元组分,峰值对应沙丘砂发育期,这些峰谷交替变化的规律指示了末次冰期的季风演变以及气候波动变化,万年尺度上表现为LH10 (48.8—39.9 ka)和LH3～LH5 (28.1—17.1 ka)的冬季风强盛期,分别对应深海氧同位素的MIS3b和MIS2阶段。LH6～LH9 (39.9—28.1 ka)为温暖的夏季风时期,对应深海氧同位素的MIS3a阶段。这些变化与YZ洞石笋氧同位素以及格陵兰冰心有良好的对应,与全球气候变化基本一致。 相似文献
15.
Min Kyung Lee Yong Il Lee Hyoun Soo Lim Jae Il Lee Jeong Heon Choi Ho Il Yoon 《Journal of Paleolimnology》2011,45(2):127-135
Both radiocarbon and optically stimulated luminescence (OSL) dating methods were applied to test their suitability for establishing
a chronology of arid-zone lacustrine sediments using a 5.88-m-long core drilled from Lake Ulaan, southern Mongolia. Although
the radiocarbon and OSL ages agree in some samples, the radiocarbon ages are older than the corresponding OSL ages at the
550-cm depth horizon (late Pleistocene) and in the 100–300-cm interval (early to late Holocene). In the early to late Holocene,
radiocarbon ages are consistently older than OSL ages by 4,100–5,800 years, and in the late Pleistocene by 2,700–3,000 years.
Grain-size analysis of early to late Holocene sediments and one late Pleistocene sediment sample (550-cm depth) indicates
that eolian processes were the dominant sediment-transport mechanism. Also, two late Pleistocene sediments samples (from 400-
to 500-cm depths) are interpreted to have been deposited by both eolian and glaciofluvial processes. Accordingly, the radiocarbon
ages that were older than the corresponding OSL ages during the Holocene seem to have been a consequence of the influx of
14C-deficient carbon delivered from adjacent soils and Paleozoic carbonate rocks by the westerly winds, a process that is also
active today. In addition to the input of old reworked carbon by eolian processes, the late Pleistocene sediments were also
influenced by old carbon delivered by deglacial meltwater. The results of this study suggest that when eolian sediment transport
is suspected, especially in lakes of arid environments, the OSL dating method is superior to the radiocarbon dating method,
as it eliminates a common ‘old-carbon’ error problem. 相似文献
16.
内蒙古黄旗海不同粒级湖泊沉积物Rb、Sr组成与环境变化 总被引：2，自引：0，他引：2
Based on the geochemical elements Rb and Sr in sediments with three different grain size fractions from profile H3 on the northern lacustrine bottomland 13 m above the Huangqihai Lake surface in 1986,the paper investigates the record of palaeolake stand state, sedimentary environmental evolution,and winter monsoon change.First,these samples are separated into three different grain size fractions,i.e.,total sediments,77-20μm and〈20μm. Second,the chemical elements-Rb and Sr-of the grain size separation were tested and analyzed systematically in this paper.Then the elements compositions of these samples are measured using VP-320 mode fluorescence spectrum instrument,respectively.The magnetic susceptibility of these samples is measured using Kappabridge KLY-3 mode instrument made in Czech AGICO Company.The results showed the elements and the ratios varied regularly with the grain size.But the ratio of Rb/Sr in the sediments〈20μm correlates positively with the magnetic susceptibility of these samples.Therefore,the ratio of Rb/Sr in the fraction〈20 μm from the lake sediments reflected the strengthening of the weathering in the deposition sites.It is a good indicator of the summer monsoon-induced weathering and pedogenesis fluctuations and can be used to reconstruct the conditions of the paleoclimate and paleoenvironment. 相似文献
17.
东昆仑库木库里沙漠表层沉积物粒度特征、物源与沉积环境 总被引：1，自引：0，他引：1
对青藏高原北部世界海拔最高的库木库里沙漠周围冲积扇碎屑及沙漠表层沉积物粒度特征及元素组成研究结果显示：（1）库木库里沙漠表层沉积物以细砂为主,其次为极细砂,粉砂和中砂含量较少,有少量的黏粒,不含粗砂的组分,且粒度组成差异不大。（2）沉积物MZ范围2.70~2.90 φ,σ1范围0.80~1.10 φ,SK1范围0.26~0.44,KG范围2.27~3.62。（3）粒度主要呈近似对称的单峰分布,但细颗粒一侧有较细长的尾部。（4）沙漠表层沉积物元素组成与周围山麓冲洪积碎屑沉积物较为相似,尤其是沙漠西部的阿尔喀山北麓区域。（5）沉积物源判别表明,沙漠表层沉积物来源主要为阿尔喀山北麓及祁漫塔格山南麓碎屑沉积物,其形成环境主要为河流相沉积环境及浅湖相沉积环境。 相似文献
18.
连环湖马圈泡沉积物重金属污染及潜在生态风险 总被引：3，自引：0，他引：3
通过对连环湖马圈泡柱状沉积物重金属（Cr、Cu、Mn、Ni、Pb、Zn、Cd）等地球化学指标的分析, 对马圈泡沉积物污染历史进行了讨论。根据元素的变化趋势,结合颗粒组成指标,采用相关分析,富集状况及潜在生态风险评价,并辅以210Pb、137Cs测年数据,研究了自1937年以来该湖区沉积物重金属元素污染特征、来源、污染历史及污染程度。结果表明,1987年以前各元素含量变化趋势平稳,1987年至今,7种重金属元素含量均明显增加。重金属元素的来源包括自然来源和人为输入。从单向污染系数来看Cu、Ni、Cr、Pb、Zn属于中等污染强度,Mn、Cd达到了强污染程度;从综合污染系数来看,表层重金属元素主要为中等程度的污染。沉积物重金属污染历史与该区经济发展阶段相吻合可为其湖区生态环境的整治与改善提供基础性的数据资料。 相似文献
19.
20.
Hendrik Vogel Bernd Wagner Peter Rosén 《Geografiska Annaler: Series A, Physical Geography》2013,95(2):159-170
Here we present datasets from a hydroacoustic survey in July 2011 at Lake Torneträsk, northern Sweden. Our hydroacoustic data exhibit lake floor morphologies formed by glacial erosion and accumulation processes, insights into lacustrine sediment accumulation since the beginning of deglaciation, and information on seismic activity along the Pärvie Fault. Features of glacial scouring with a high‐energy relief, steep slopes, and relative reliefs of more than 50 m are observed in the large W‐basin. The remainder of the lacustrine subsurface appears to host a broad variety of well preserved formations from glacial accumulation related to the last retreat of the Fennoscandian ice sheet. Deposition of glaciolacustrine and lacustrine sediments is focused in areas situated in proximity to major inlets. Sediment accumulation in distal areas of the lake seldom exceeds 2 m or is not observable. We assume that lack of sediment deposition in the lake is a result of different factors, including low rates of erosion in the catchment, a previously high lake level leading to deposition of sediments in higher elevated paleodeltas, tributaries carrying low suspension loads as a result of sedimentation in upstream lakes, and an overall low productivity in the lake. A clear off‐shore trace of the Pärvie Fault could not be detected from our hydroacoustic data. However, an absence of sediment disturbance in close proximity to the presumed fault trace implies minimal seismic activity since deposition of the glaciolacustrine and lacustrine sediments. 相似文献