黄河泛滥平原全新世沙尘暴活动的历史记录——以颖河上游一典型剖面为例   总被引：1，自引：0，他引：1  

李胜利  黄春长  庞奖励 《沉积学报》2008,26(1):144-150

研究了淮河支流颖河上游嵩山东麓一典型全新世黄土-古土壤剖面,获得了较高时间分辨率的磁化率、粒度成分和>0.063mm粒级百分比含量等环境代用指标系列。通过地层对比研究,确定了该剖面的基本年代框架。分析了颖河上游全新世黄土-土壤磁化率、粒度特征,论证了颖河上游全新世黄土-土壤物质粒度成分与黄河泛滥沉积沙尘暴活动关系,揭示了颖河上游全新世黄河泛滥平原沙尘暴活动特征。3100aBP以来气候趋于干旱,黄河下游泛滥频率增加,风沙活动范围显著扩大,沙尘暴活动强烈。  相似文献   

西藏高原沱沱河盆地渐新世-中新世湖相碳酸盐岩稀土元素地球化学特征与正铕异常成因初探   总被引：7，自引：0，他引：7  

伊海生  林金辉  赵西西  周恳恳  李军鹏  黄华谷 《沉积学报》2008,26(1):1-10

对采自沱沱河盆地通天河剖面渐新世雅西措群和中新世五道梁群地层中的湖相灰岩和白云岩样品进行了稀土元素和微量元素分析。研究结果表明,湖相碳酸盐岩稀土元素总量（∑REE）变化于36.23×10-6～189.64×10-6,28件样品平均值为78.58×10-6。稀土元素的页岩标准化配分形式具有中组稀土富集的特点,正铕异常极为明显,在渐新统与中新统界线处Eu/Eu*比达到最大值7.15,这也是首次在陆地湖泊沉积记录中观察到的正Eu异常。根据稀土元素的分布以及Eu与Ba含量的同步变化特点,提出该区湖相碳酸盐岩中Eu的异常富集可能与湖底喷流热水有关。   相似文献   

尼泊尔地区季节性水文负荷对地震活动性的调制作用     

王晨旭  熊永良  张鲁鹏  姜中山  张芮  乔家原 《大地测量与地球动力学》2020,40(6):596-600

利用尼泊尔地区GPS时间序列季节性信号,构建区域季节性三维位移场和应力应变场模型,再结合降水和地震目录等数据,研究该地区季节性水文负荷对地震活动性的调制作用。结果表明：1）季节性地表位移与降水存在较强的时空相关性;2）季风期的降水对断层的长期运动趋势产生扰动,使库仑应力得到一定程度的释放,进而对地震活动产生抑制作用,并影响地震发生时间。  相似文献   

江南断裂带（宣城段）断层泥中石英颗粒微形貌特征及年代学意义     

沈仕豪  赵田  张文媛  吴昊  汪雅菲 《大地测量与地球动力学》2020,40(10):1049-1054

在野外地质调查基础上,对江南断裂带宣城敬亭山剖面上采集的3件断层泥样品中的石英颗粒进行透射扫描电镜（SEM）微形貌观察与统计。结果显示,江南断裂带为活动断裂,在新近纪和第四纪时期具明显的活动性,活动始于中新世,晚更新世达到高峰,活动方式以蠕滑为主;至全新世,断裂以粘滑方式持续活动;沿断裂带的地震记录表明,至近现代断裂仍处于活动状态。这些结论对于正确评价江南断裂带在第四纪的活动规律及该区自然灾害预防等具有重要意义。  相似文献   

聊城-兰考断裂中段第四纪活动研究     

孙杰  王斐斐  马兴全  赵显刚  李涛  张扬  段永红 《大地测量与地球动力学》2020,40(12):1254-1258

为研究聊城-兰考断裂中段的第四纪活动特征,采用浅层地震勘探和钻孔联合剖面相结合的探测方法,跨断裂布设5条浅层地震勘探测线和1条钻孔联合地质剖面。钻孔联合地质剖面揭示聊城-兰考断裂中段上断点埋深为61.4~64.5 m,结合地层年代学结果判定,聊城-兰考断裂中段为晚更新世早期活动断裂。  相似文献   

Detailed seismicity mapping of the Altai-Sayan zone using large averaging areas     

A.A. Dergachev   《Russian Geology and Geophysics》2008,49(12):963-970

An improved technique is suggested for quantifying seismic activity over averaging areas of an arbitrary size. The example of the Altai-Sayan seismic zone is used to substantiate the choice of a 1° N × 2° E averaging area instead of the traditional one of 40×40 km². Maps compiled with averaging areas of different sizes can be spliced and correlated using a correction coefficient estimated in different models. The new seismicity map of the Altai-Sayan area covers more than 90% of the territory and provides a generalized image of activity being advantageous over the classic maps as it allows better correlation of regional seismicity with the tectonic setting. With larger averaging areas and, correspondingly, a greater amount of data in each area, one can obtain time series of seismic activity to be analyzed using mathematical statistics as a basis for mathematical modeling and simulation of the seismic process.  相似文献   

Tjörnes fracture zone. New and old seismic evidences for the link between the North Iceland rift zone and the Mid-Atlantic ridge   总被引：1，自引：1，他引：0  

Ragnar Stefansson  Gunnar B. Gudmundsson  Pall Halldorsson 《Tectonophysics》2008,447(1-4):117

The Tjörnes facture zone (TFZ) connects the EW extension of the Mid-Atlantic ridge north of Iceland to the extension of the North volcanic zone (NVZ) of Iceland. Earthquakes up to magnitude 7 (Ms) can occur in TFZ, volcanic eruptions have been observed and large crustal deformations are expected in similar way as have been observed in the NVZ. Most of the zone is below ocean, which limits the historical information and geological observations. For studying the dynamics of the zone we must rely on interpretation and modelling based on seismic observations, especially on microearthquake observations for the last 10 years. In this paper we demonstrate how microearthquakes can be applied to map the details of the plate boundary, and how this information can be applied to find epicenters and fault planes of large historical earthquakes, also how seismic information can be applied in dynamic modelling and to infer spatial and temporal interplay in activity, and to enhance hazard assessment.  相似文献   

Hydrogen incorporation in enstatite in the system MgO–SiO2–H2O–NaCl     

Roland Stalder  Andreas Kronz  Klaus Simon 《Contributions to Mineralogy and Petrology》2008,156(5):653-659

The incorporation of hydrogen in enstatite in a hydrous system containing various amounts of NaCl was investigated at 25 kbar. The hydrogen content in enstatite shows a clear negative correlation to the NaCl-concentration in the system. The most favourable explanation is the reduction of water fugacity due to dilution. Other reasons for the limited hydrogen incorporation at high NaCl levels, such as a significant influence of Na⁺ on the defect chemistry or an exchange between OH^- and Cl⁻in enstatite, appear much less important. A partition coefficient D _Na ^En/Fluid = 0.0013 could be determined, demonstrating that Na is less incompatible in enstatite than H. The new results support the idea that dissolved components have to be considered when the total hydrogen storage capacity in nominally anhydrous minerals is estimated, especially in geological settings with high levels of halogens, such as subduction zones.  相似文献   

Geochronology of Pliocene volcanism in the Dzhavakheti Highland (the Lesser Caucasus). Part 2: Eastern part of the Dzhavakheti Highland. Regional geological correlation     

V. A. Lebedev  S. N. Bubnov  O. Z. Dudauri  G. T. Vashakidze 《Stratigraphy and Geological Correlation》2008,16(5):553-574

The results of isotopic-geochronological study of the Pliocene volcanic rocks in reference sections and volcanic edifices of eastern part of the Dzhavakheti Highland (the northwestern Lesser Caucasus) are considered. The isotopic-geochronological data obtained here are correlated with data on western part of the Dzhavakheti Highland, which have been considered in previous part of this work. Based on correlation, time spans of principal volcanic events of the Pliocene in the study region as a whole are determined, and general trends of the young magmatism evolution within the region are established. In sum, the isotopic-geochronological dates evidence that the Pliocene magmatism of the Dzhavakheti Highland developed practically without essential breaks during the period of about 2 Ma long, from 3.75 to 1.75–1.55 Ma ago. The areal basic volcanism that was most widespread at that time is divisible into five discrete phases according to the isotopic dates obtained. Comparatively short pauses, which separated these phases of magmatic activity, were a few hundreds thousand years long, not more. Chemical composition of moderately acidic to silicic volcanics, which are of a limited distribution in the Dzhavakheti Highland, and their age relations with basic lavas of the region suggest that they are most likely the differentiation products of parental basic mantle-derived magmas. The analyzed distribution of volcanic centers, which erupted basic lavas of the Dzhavakheti Highland, evidence that first two phases of basic magmatism were connected here with volcanic activity in southwestern part of the region (northern termination of the Egnakhag Ridge), whereas activity of volcanoes situated on the east, predominantly in water-shed part and on slopes of the submeridional Dzhavakheti Ridge, controlled development of the third and fourth phases. Consequently, magmatic activity of the Pliocene stage in history of the Neogene-Quaternary magmatism of the Dzhavakheti Highland laterally migrated from the west to the east, being controlled by development of regional submeridional extension zones. Volcanic ridges marking the latter are formed by volcanic edifices, which are amalgamated at their bases and have erupted lavas of close age and composition. The migration of volcanic activity can be described in terms of the “domino effect,” when cessation of volcanism in one zone led to formation of the other submeridional zone of extension and magmatic activity displaced from the west eastward in sublatitudinal direction. In general, evolution of the Pliocene magmatism of the Dzhavakheti Highland, was similar, despite the essential regional peculiarities, to the generalized trend of magmatism evolution in the continental rifts and intraplate zones of the “hot-spot” type.  相似文献   

Focal parameters of seismic sources during the 1981 and 1983 eruption at Mt. Etna volcano (Sicily,Italy)     

Sebastiano Imposa 《Environmental Geology》2008,55(5):1061-1073

In this study 50 seismic events, preceding and accompanying the eruptions occurring in 1981 and 1983, have been considered. Seismic moments, fault radii, stress drops and seismic energies have been calculated using Brune’s model (J Geophys Res 75:4997–5009, 1970; J Geophys Res 76:5002, 1971); site, anelastic attenuation along the propagation path, geometrical spreading and interaction with the free surface effects are taken into account. For each event we have also estimated the equivalent Wood–Anderson magnitude (MWAeq) (Scherbaum and Stoll in Bull Seism Soc Am 73:1321–1343, 1983); relations among all these source parameters have been determined. Furthermore, the hypothesis of self-similarity (Aki in J Geophys Res 72:1217–1231, 1967) is not verified for events with seismic moments <10¹² N-m: in fact the relationship between log-stress drop and log-moment is linear up to a moment of 10¹² N-m (events of 1981 eruption), while for higher moments (events of 1983 eruption) the slope of the regression line is not significantly different from zero. We suppose that such a behaviour is related to a heterogeneous medium with barriers on the faults. Finally, the main conclusion is that eruptions of 1981 and 1983 differ from one another both in eruptive and seismic aspects; analysis of seismic energies indicates an increase in Mt. Etna’s activity, confirmed by studies performed on the following lateral eruption of 1991–1993 (Patanè et al. in Bull Volcanol 47:941–952, 1995), occurring on the same structural trend.  相似文献