共查询到20条相似文献，搜索用时 312 毫秒
1.
The regularities of Sr absorption by different Quaternary fluvioglacial sediments, containing groundwater within the Khibiny massif, have been studied. The studied sediments have been shown to adsorb Sr as a result of the cation exchange and complexing on the solid phase surface, which is responsible for the absorbing capacity of the sediments in the wide range of natural water pH. The base exchange capacity of Sr has been established to largely depend on the concentration of the macrocomponents (Ca2+ and Mg2+) in the groundwater. It has been noted that the migration mobility of Sr is low under the conditions of almost neutral water typical of the soil horizon in the studied area. 相似文献
2.
3.
The Chisone Valley is located in the internal NW Alps, in the Pinerolese District, an area characterized by present low to medium seismicity. Fine-grained sediments (sand, silt and clay with interbedded gravel) crop out in the lower Chisone Valley: they were first interpreted as glaciolacustrine deposits, and then as a lacustrine infilling of the valley floor probably due to differential uplifting of the valley mouth. Review of this data, together with new field and palynological observations, lead us to refer the lacustrine deposits to approximately the Lower Pleistocene (Villafranchian). In many outcrops, the lacustrine deposits show strong soft-sediment deformation such as convolute laminations, water-escape structures and disrupted beds, some of them associated with folds and faults (cm to dm in size); only two sites show metric to decametric folds and faults trending E-W and N-S. Detailed structural analysis conducted along a recently exposed section (Rio Gran Dubbione site) shows several soft-sediment deformation features on the limbs of mesoscale folds. Because of their intimate structural association, the origin of these minor structures seems to be connected to synsedimentary activity on reverse and normal faults (m to dm in size) affecting the lacustrine deposits in the same locality. Soft-sediment deformation features can be interpreted as possible paleoseismites. If so, the present seismicity of the Pinerolese District, which is the major area of such activity in NW Italy, cannot be considered an isolated episode in the geological evolution of the region; even if there is no supporting evidence for continuous seismicity, the deformations in the lacustrine sediments of the Chisone Valley testify to Early Pleistocene seismic activity, probably related to the recent tectonic evolution of the internal side of the NW Alps. 相似文献
4.
Earthquake-induced soft-sediment deformation structures in the Mesoproterozoic Wumishan Formation,North China,and their geologic implications 总被引：2，自引：0，他引：2
Soft-sediment structures are key to defining seismites. Two soft-sediment deformation horizons, bounded by undeformed carbonate strata, have been found in the Wumishan Formation in the Jumahe region, 175 km southwest of Beijing. One is in the lowest part of Wumishan Formation; and the other is in the uppermost part of Litho-member I. The soft-sediment structures in these two horizons fall into three categories: mould-and-sag structures, hydraulic shatterings and liquefaction dikes. The mould-and-sag structures are divided into two types: one developed in tidal-flat sediments, accompa-nied by many liquefaction-related structures and characterized by autochthonous post-earthquake sediments in sags, and the other type developed in deep-water environments, is not associated with liquefaction structures, and is overlain immediately by seismogenic tsunamites. The hydraulic shat-terings are composed of pockets of fluidization conglomerate, sand intrusions, and syndepositional faults. The liquefaction dikes fall into two categories: hydraulic-fracturing dikes and lateral-spreading dikes. The former are steep, planar, and pinch out upwards. The latter are snake-like and characterized by no diapir-related drag structures in surrounding rocks. Examination of the attitudes and strati-graphic positions of these structures suggests that these soft-sediment structures are seismogenic, and consequently, are seismites. Most seismites in the Wumishan Formation are developed near the former western, margin fault of Yanliao rift. This occurrence suggests that they could be related to movements on this fault. Other geological implications are discussed. 相似文献
5.
6.
岷江上游堰塞湖沉积中软沉积物变形构造成因讨论 总被引：3，自引：0，他引：3
对在岷江上游及其支流河谷中的晚第四纪古堰塞湖地层中发现的大量软沉积物变形构造的类型、特征和成因进行了分析,发现这些软沉积物变形构造分为两类:一类是小型的层内变形构造,如液化卷曲变形、泄水构造、负荷构造、阶梯状微断裂等,其形成与软沉积物的塑性变形、液化和流动作用相关;另一类是崩(滑)塌体对软沉积物的扰动形成的大型褶曲构造.通过与其它成因的软沉积物变形构造的对比以及对区域构造环境的分析,得出地震、崩塌和滑坡等灾害性地质事件是造成河谷区古堰塞湖地层中软沉积物变形构造发育的最可能的驱动机制. 相似文献
7.
P. A. Lelyaev 《Izvestiya Physics of the Solid Earth》2011,47(12):1083-1085
Prediction of the material composition of deep crustal horizons in the Earth from the geophysical data requires an algorithm
to classify the rocks according to their petrophysical properties. In the present work, we propose a classification algorithm
that is based on the membership function and describe the computer program, which is based on this algorithm and intended
for visualization of the most typical crystalline rocks of the Voronezh massif. 相似文献
8.
Kazuya Shiraishi Masako Robb Karl Hosgood Yasuhiro Yamada 《Geophysical Prospecting》2019,67(2):317-330
To better image deformation structures within the inner accretionary wedge of the Nankai Trough, Japan, we apply common reflection angle migration to a legacy two-dimensional seismic data set acquired with a 6 km streamer cable. In this region, many seismic surveys have been conducted to study the seismogenic zone related to plate subduction. However, the details of the accreted sediments beneath the Kumano forearc basin are still unclear due to the poor quality of seismic images caused by multiple reflections, highly attenuated signals, and possibly complex geological structures. Generating common image gathers in the subsurface local angle domain rather than the surface offset domain is more advantageous for imaging geological structures that involve complex wave paths and poor illumination. By applying this method, previously unseen structures are revealed in the thick accreted sediments. The newly imaged geometric features of reflectors, such as the folds in the shallow part of the section and the deep reflectors with stepwise discontinuities, imply deformation structures with multiple thrust faults. The reflections within the deep accreted sediments (approximately 5 km) are mainly mapped to far angles (30°–50°) in the common reflection angles, which correspond to the recorded offset distances greater than 4.5 km. This result indicates that the far offset/angle information is critical to image the deformation structures at depth. The new depth image from the common reflection angle migration provides seismic evidence of multiple thrust faults and their relationship with the megathrust fault that is essential for understanding the structure and evolution of the Nankai Trough seismogenic zone. 相似文献
9.
南北地震带区域形变异常特征与地震关系研究 总被引：1，自引：0，他引：1
利用南北地震带及附近地区20世纪70年代以来的区域水准网和90年代以来的GPS监测网资料, 结合地质构造和监测区发生的多次6级左右及以上震例, 分析了震前区域性形变场异常的基本特征。 进而根据资料支持程度, 分别以GPS、 区域水准观测位移为地表约束, 以“973”项目活动地块划分结果为地质依据, 进行非震负位错模型反演计算, 研究了数值模拟结果反映的活动块体和边界断裂构造变形状态与地震的关系。 在此基础上, 定性与定量相结合分析研究了强震前区域性水平、 垂直构造形变异常特征及可能的机理, 初步总结了基于区域水准、 GPS观测与数值模拟的强震前区域构造形变异常的一些判据。 相似文献
10.
Xuemei Cheng Shuyun Cao Junyu Li Zunpu Yu Yanlong Dong Meixia Lv Junlai Liu 《中国科学:地球科学(英文版)》2018,61(8):1023-1041
Diancangshan metamorphic massif is one of the four metamorphic massifs developed along the Ailaoshan-Red River strike-slip fault zone, Yunnan, China. It has experienced multi-stage metamorphism and deformation, especially since the late Oligocene it widely suffered high-temperature ductile shear deformation and exhumation of the metamorphic rocks from the deep crust to the shallow surface. Based on the previous research and geological field work, this paper presents a detailed study on deformation and metamorphism, and exhumation of deep metamorphic rocks within the Diancangshan metamorphic massif, especially focusing on the low-temperature overprinted retrogression metamorphism and deformation of mylonitic rocks. With the combinated experimental techniques of optical microscope, electron backscatter diffraction attachmented on field-emission scanning electron microscopy and cathodoluminescence, our contribution reports the microstructure, lattice preferred orientations of the deformed minerals, and the changes of mineral composition phases of the superposition low-temperature retrograde mylonites. All these results indicate that: (1) Diancangshan deep metamorphic rock has experienced early high-temperature left-lateral shear deformation and late extension with rapid exhumation, the low-temperature retrogression metamorphism and deformation overprinted the high-temperature metamorphism, and the high-temperature microstructure and texture are in part or entirely altered by subsequent low-temperature shearing; (2) the superposition of low-temperature deformation-metamorphism occurs at the ductile-brittle transition; and (3) the fluid is quite active during the syn-tectonic shearing overprinted low-temperature deformation and metamorphism. The dynamic recrystallization and/or fractures to micro-fractures result in the strongly fine-grained of the main minerals, and present strain localization in micro-domians, such as micro-shear zones in the mylonites. It is often accompanied by the decrease of rock strength and finally influences the rheology of the whole rock during further deformation and exhumation of the Diancangshan massif. 相似文献
11.
Climate variability during the Mid‐Late Holocene has influenced the activity of geomorphic processes in the current periglacial belt of the Sierra Nevada. We studied two types of sedimentary records that reveal a synchronous timing for slope instability in this high semi‐arid massif: solifluction landforms and mountain lake sediments. Lithological and sedimentological properties of both records have recorded numerous cycles of different magnitude of slope processes in the massif. Solifluction deposits record seven phases of solifluction activity and soil development during the last 7 ka bp and lake sediments show evidence of eight periods with increased geomorphic activity in the catchments over the last 6 ka bp . Although present‐day climate conditions do not promote active solifluction processes in the Sierra Nevada, colder and wetter periods during the Holocene triggered solifluction and transported coarse‐grained sediments into the lakes. By contrast, warm phases favoured soil formation and spread an incipient vegetation cover over the headwaters of the highest valleys, diminishing the grain size of the particles reaching the lakes. Lake sediments record an aridification trend in the massif intensifying since 4·2 ka bp that has conditioned solifluction activity to shift gradually to higher elevations. During major cooler phases such as the Little Ice Age active solifluction was recorded back down to 2500 m altitude. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
12.
V. G. Bakhmutov V. Ya. Yevzerov V. V. Kolka 《Izvestiya Physics of the Solid Earth》2009,45(7):567-582
The genesis, varve, and paleomagnetic informativeness of glaciolacustrine sediments are considered based on paleomagnetic and lithological studies. The magnetic properties of varved clays from periglacial basins have been considered using the sedimentological model of formation of varved clays as products of glacial turbidity currents, which explains the differences in the magnetic characteristics and degree of paleomagnetic informativeness of these clays. The distal zone sediments (formed due to precipitation from glacial turbidity currents, suspension, and sometimes along the periphery of the proximal zone) are most successfully used to study secular variations. The possible errors of the secular variation records in varved clays and such errors in estimating annual bedding of these clays have been analyzed. It has been indicated that information about the composition, concentration, and magnetic fraction size should be completed with detailed lithological studies, which make it possible to reconstruct the character of clastic material income into a basin and to decipher a paleomagnetic record. An analysis of the magnetic susceptibility anisotropy parameters and the magnetization formation in a sediment makes it possible to take into account disturbances caused by the sedimentation process and, thereby, to detect a pure geomagnetic signal 相似文献
13.
Abstract We present backscattered scanning electron microscope and petrographic microscope observations of deformed sediments from Ocean Drilling Program (ODP) Site 808 in order to better understand the dewatering and deformation history of the Nankai accretionary complex. This synthesis of deformation textures has three implications. First, the early structures that dominate the Nankai prism, small faults and kink bands, have very different electron microscope versus optical microscopic expressions. This observation is important to investigations of fine-grained sediment in both stable and active tectonic settings, in part, because these materials have often been studied almost exclusively by electron microscope methods. In sediments of this type, investigators often forego petrographic analysis because of the relative opacity of samples at normal (i.e. 30 pm) thin section thicknesses. Second, the textural observations we have compiled suggest that these deformation structures acted as 'single-event' pathways that contributed to diffusive dewatering of the prism. Third, our observations serve as a reference frame for the early tectonic structures that are important to the dewatering history of a 'sandy' accretionary prism. 相似文献
14.
Composition and origin of a lithalsa related to lake‐level recession and Holocene terrestrial emergence,Northwest Territories,Canada 
下载免费PDF全文
下载免费PDF全文 Lithalsas of the Great Slave Lowland, Northwest Territories, occur within fine‐grained glaciolacustrine, lacustrine, and alluvial deposits. Detailed investigations of a lithalsa revealed that it is composed of ice‐rich sediments with ice lenses up to 0.2 m thick below 4 m depth. The observed ice accounted for about 2 m of the 4 m between the top of the lithalsa and adjacent terrain. The ice is isotopically similar to modern surface water, but enriched in δ18O relative to local precipitation. Total soluble cation concentrations are low in the basal, Shield‐derived and unweathered glaciolacustrine sediments of the lithalsa. Higher concentrations in the overlying Holocene‐aged lacustrine and alluvial deposits may be due to greater ion availability in Holocene surface waters. Increasing Cl‐ and Na+ concentrations in clays at depth likely relate to exclusion and migration of these dissolved ions in pore water during ice lens formation though total soluble cations remain comparatively low. The lithalsa developed 700 to 300 cal yr BP. A conceptual model of lithalsa formation and landscape evolution illustrates that this feature and more than 1800 other lithalsas in the region have developed in association with Holocene terrestrial emergence following lake‐level recession. Copyright © 2017 John Wiley & Sons, Ltd. 相似文献
15.
《Journal of Applied Geophysics》1999,41(1):75-91
Ground penetrating radar (GPR) was used in a programme of geological and hydrogeological investigations into the Quaternary of west Cumbria, UK. The investigations were part of an extensive programme to determine the suitability of the area for a deep radioactive waste repository. The hydrogeological characteristics of the drift deposits are important since they affect both recharge and discharge. The glacially derived Quaternary sediments include a variety of deformation structures related to their mode of deposition and subsequent modification by glacial and periglacial processes. These deformation structures range from variable scale thrusts (centimeter to tens of meter displacement due to proglacial thrusting) to small to medium scale faults, folds and collapse structures which are early or syn-sedimentary adjustments. From the GPR data a number of dipping reflectors, having dip angles in the range of 8–23°, were interpreted as thrust planes and related faults and folds have been clearly observed. Inwardly dipping reflectors, having a maximum dip angle of 36°, creating a characteristic `V' shaped anomaly, were also observed and interpreted to be linear collapse structures where glacitectonically emplaced slices of ice melted out causing sediments to slump. Lateral continuations, up to 90 m, of GPR-interpreted dislocations were mapped between survey lines, suggesting that such features could be laterally continuous on the scale of hundreds of metres. 相似文献
16.
EARTHQUAKE-CAUSED SEISMIC VOLCANIC ROCKS AND THIXOTROPIC DEFORMATION OF SOFT SEDIMENTS IN THE UPPER CRETACEOUS SHIJIATUN MEMBER,JIAOZHOU CITY 下载免费PDF全文
下载免费PDF全文 A lot of seismic volcanic rocks and strong earthquake-induced thixotropic deformation structures in soft mud-sandy sediments(seismites)were identified from the Upper Cretaceous Shijiatun Member of the Hongtuya Formation for the first time in Jiaozhou City of the Zhucheng Sag, eastern China. Seismic volcanic rocks are volcanic rocks with co-seismic deformation structures which were produced by major earthquakes destroying volcano ejecta. Seismites are sediment layers with soft-sediment deformation structures formed by strong earthquake triggering saturated or semi-consolidated soft sediments to produce liquefaction, thixotropy, faults, cracks and filling and so forth. The Shijiatun Member of the Hongtuya Formation mainly consists of basaltic volcano rocks interbedded with mud-sandy(muddy sand and sandy mud)deposition layers of the river-lake facies. In the Shijiatun Member, main types of seismic volcanic rocks are shattered basalts with co-seismic fissures and seismic basaltic breccias. The thixotropic deformations of soft mud-sandy sediments mainly include thixotropic mud-sandy veins and thixotropic mud-sandy layers with tortuous boundaries. Under the strong earthquake action, saturated mud-sandy sediments could not be liquefied, instead resulting in thixotropy, i.e. their texture can be damaged and their flow-ability or rheology becomes strong. Because basaltic volcano rocks were damaged(shattered, seismic broken), a major earthquake can lead to thixotropic mud-sandy sediments flowing along seismic fissures in basalts, resulting in the formation of deformation structure of thixotropic veins, and boundaries between volcano rock and mud-sand layer became quite winding. Under the koinonia of gravity and vibration force, seismic breccia blocks sunk into thixotropic mud-sandy layers, resulting in the formation of inclusions of thixotropic mud-sandy sediments. Seismic intensity reflected by these strong earthquake records during the end stage of the Late Cretaceous was about Ⅶ to more than X degrees. The Shijiatun Member is mainly distributed in the south of the Baichihe fault in the northern Zhucheng Sag, and the fault has generated many strong tectonic and earthquake activities at the end of the late Cretaceous, also provided the channel for intrusion and eruption of basaltic magma then. At the end of the late Cretaceous, intermittent intrusion and eruption of basaltic magma took place along the Baichihe fault, meanwhile the volcano earthquakes took place or tectonic earthquakes were generated by the Baichihe fault which caused the deformation of the volcano lava and underlying strata of red saturated muddy-sand, resulting in the formation of various seismo-genesis deformations of volcanic rocks interbedded with mud-sandy sediment layers. Therefore, strong seismic events recorded by them should be responses to strong tectonic taphrogenesis of the Zhucheng Sag and intense activity of the Baichihe fault in the end of Late Cretaceous. In addition, these seismogenic deformation structures of rock-soil layers provide new data for the analysis of the failure effect produced by seismic force in similar rock-soil foundations. 相似文献
17.
Jasper Knight 《地球表面变化过程与地形》2016,41(2):277-288
Interpretation of subglacial processes and environments can be usefully informed by the stratigraphy and structures of sediments preserved within drumlins, and the down‐ice variability of these sediments. Drumlins in Clew Bay, western Ireland, were formed by westward late Pleistocene ice flow onto the Atlantic shelf, but the depositional processes and environments of these sediments remain uncertain. This study describes and interprets the drumlin stratigraphy and sediment properties and structures from two drumlins on the south side of Clew Bay. Drumlin sediments are dominated by massive to stratified diamicton deposited subglacially by deformation of flows of varying rheology. Folds, shears and clastic dikes within the sediments suggest active subglacial water flow related to variations in ice flow and ice‐bed coupling. The distal ends of the drumlins are dominated by stratified diamicton and gravel units with sandy interbeds. These sediments reflect deposition in a leeside subglacial cavity formed coevally with bedform development. A model is proposed that can account for sediment stratigraphic patterns and drumlin formation. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
18.
本文通过对航磁异常资料进行向上解析延拓、垂向不同阶导数及磁性体边界确定新方法等处理,并结合地震震中分布对鄂尔多斯块体及邻区不同深度场源磁异常特征加以分析研究.结果表明,鄂尔多斯块体虽具有整体刚性的特征,但其内部也存在非均质性;块体东缘的华北克拉通地区经后期改造,产生近SN向的基底软弱带;青藏高原地壳缩短增厚的同时,其东北缘下地壳韧性物质分别沿秦岭、祁连两个软弱带向周缘塑性流动,而且青藏高原巨大的NE向挤压应力造成鄂尔多斯块体逆时针旋转;鄂尔多斯块体及其边界多样化的构造特征反映了不同刚性程度的地质体在外部不同应力作用下产生了显著差异的地质构造形态,这种构造形态具有继承性和叠加性. 相似文献
19.
Pseudo velocity logs can be obtained by seismogram inversion, using true amplitude processing and detailed investigation of move-out velocities. The precision of the results depends on the quality of the seismic data and on the possibility of deconvolving without increasing the noise. An investigation is made of the deformation of pseudo logs due to seismic signal variations and to imperfections of deconvolution. Both marine and land examples are shown, in some cases with adjustment on well logs. When the dips are large, time sections must be migrated and pseudo velocity logs must be computed from migrated sections. Comparison of sonic logs with pseudo velocity logs obtained in the same area is usually good enough to obtain information on lithological parameter variations by adjustment of pseudo velocity logs on sonic logs. Even when no well is available, pseudo velocity logs can give some indications on the nature of sediments between seismic horizons. 相似文献
20.
Kurazhkovskii A. Yu. Kurazhkovskaya N. A. Klain B. I. Zakonnov V. V. 《Water Resources》2002,29(5):506-509
Physical properties of cores taken from sediments in the channel zone of the Volga Stretch in the Rybinsk Reservoir are studied. The physical properties of the sediments are shown to be related to the evolution of geomorphological processes and the amount of organic matter in the sediment. Variations in the physical properties were used to recognize synchronous formation of sediment horizons corresponding to certain formation stages of the reservoir soil complex and anomalous environmental and climatic events. Three stages of channel sedimentation are established based on characteristic behavior of magnetic parameters and organic matter content. The magnetic parameters of sediments are shown to allow data reconstruction on some environmental and hydrological processes. 相似文献