共查询到20条相似文献，搜索用时 31 毫秒
1.
A.S. Alekseev A.V. Belonosova I.A. Burmakov G.V. Krasnopevtseva N.N. Matveeva G.L. Nersessov N.I. Pavlenkova V.G. Romanov V.Z. Ryaboy 《Tectonophysics》1973,20(1-4):47-56
Recent seismological studies of low-velocity layers in the U.S.S.R. have led to the development of new methods of investigation. The most important results obtained are presented in this paper. Several new techniques of record treatment and advanced computer programs make it possible to solve two-dimensional problems of seismic wave propagation in complex media and to outline zones of velocity inversion in the crust and mantle of many regions in the U.S.S.R.Zones of this type seem to occur only locally and are typical of some particular geostructures. Lateral inhomogeneities are also found to be closely related to geological features. Their depths sometimes can reach 300–400 km. 相似文献
2.
洞庭盆地的形成与演化对长江中游乃至中国中部的地质环境变迁具有重要意义,但区内的第四纪年代地层研究一直不足.以洞庭盆地沉积中心——沅江凹陷的典型钻孔S3-7孔(孔深255.1 m)为研究对象,在详细的沉积物岩性描述和岩石地层划分的基础上,系统地进行了古地磁、ESR、AMS14C等测试,并建立了S3-7孔的年代地层序列.通过与其他两口典型钻孔的对比分析,初步建立了研究区的区域年代地层格架,结果显示洞庭盆地沉积中心下更新统底界位于各钻孔底部240~300 m,中更新统底界位于90~95 m,上更新统底界位于28~50 m,全新统底界位于1.5~3.1 m.平均沉积速率和分段线性方程的结果表明洞庭盆地覆盖第四纪区岩石地层单位的时代为:华田组的地质年龄为2 590~1 600 ka BP,湘阴组的地质年龄为1 600~920 ka BP,洞庭湖组的地质年龄为920~120 ka BP,安乡组的地质年龄为120~11 ka BP,全新统的地质年龄为11 ka BP至今. 相似文献
3.
第四纪地层年代学格架的建立对区域地层对比及古地理环境演化研究具有重要意义。通过分析河北大厂凹陷北部第四系标准孔S9钻孔岩心沉积物颜色、结构构造、岩性组合特征,应用测井曲线、古地磁、AMS 14C和OSL测年方法,对S9钻孔剖面进行详细地层划分、沉积相分析和地层年代学格架建立。将S9孔揭示的松散沉积物分为4套岩性组合:第1套岩性组合代表洪积扇沉积;第2套岩性组合代表辫状河沉积;第3套岩性组合代表洪积扇沉积;第4套岩性组合代表泛滥平原沉积和河床沉积。通过对古地磁实验结果的分析得出, 0~145.3 m为古地磁极性带的布容正极性时,145.3~212.6 m为古地磁极性带的松山反极性时,212.6~251.8 m为古地磁极性带的高斯正极性时。以磁性地层为主导,以岩性地层特征、14C和OSL测年数据为辅,对S9孔第四纪岩性地层进行初步划分,其第四纪地层的下更新统、中更新统和上更新统的底界对应深度分别为210.9 m、145.4 m和24.05 m。 相似文献
4.
New methods are presented for processing and interpretation of shallow marine differential magnetic data,including constructing maps of offshore total magnetic anomalies with an extremely high resolution of up to 1-2 nT,mapping weak anomalies of 5-10 nT caused by mineralization effects at the contacts of hydrocarbons with host rocks,estimating depths to upper and lower boundaries of anomalous magnetic sources,and estimating thickness of magnetic layers and boundaries of tectonic blocks. Horizontal dimensions of tectonic blocks in the so-called "seismic gap" region in the central Kuril Arc vary from 10 to 100 km,with typical dimensions of 25-30 km.The area of the "seismic gap" is a zone of intense tectonic activity and recent volcanism.Deep sources causing magnetic anomalies in the area are similar to the "magnetic belt" near Hokkaido. In the southern and central parts of Barents Sea,tectonic blocks with widths of 30-100 km,and upper and lower boundaries of magnetic layers ranging from depths of 10 to 5 km and 18 to 30 km are calculated.Models of the magnetic layer underlying the Mezen Basin in an inland part of the White Sea-Barents Sea paleorift indicate depths to the lower boundary of the layer of 12-30 km.Weak local magnetic anomalies of 2-5 nT in the northern and central Caspian Sea were identified using the new methods,and drilling confirms that the anomalies are related to concentrations of hydrocarbon.Two layers causing magnetic anomalies are identified in the northern Caspian Sea from magnetic anomaly spectra.The upper layer lies immediately beneath the sea bottom and the lower layer occurs at depths between 30-40 m and 150-200 m. 相似文献
5.
N.A. Belyaevsky A.A. Borisov V.V. Fedynsky E.E. Fotiadi S.I. Subbotin I.S. Volvovsky 《Tectonophysics》1973,20(1-4):35-45
The compilation of statistical data for 269 seismic crustal sections (total length: 81,000 km) which are available in the U.S.S.R. has shown that the preliminary conclusions drawn on relations between the elevation of the surface relief and Bouguer anomalies on one hand and crustal thickness (depth to the M-discontinuity) on the other hand are not fulfilled for the continental part of the U.S.S.R. The level of isostatic compensation has been found to be much deeper than the base of the earth's crust due to density inhomogeneities of the crust and upper mantle down to a depth of 150 km.
The results of seismic investigations have revealed a great diversity of relations between shallow geological and deep crustal structures:
Changes in the relief of the M-discontinuity have been found within the ancient platforms which are conformable with the Precambrian structures and which can exceed 20 km. In the North Caspian syneclise, extended areas devoid of the “granitic” layer have been discovered for the first time in continents. The crust was found to be thicker in the syneclises and anteclises of the Turanian EpiHercynian plate. In the West Siberian platforms these relations are reversed to a great extent.
Substantial differences in crustal structure and thickness were found in the crust of the Palaeo zoides and Mesozoides. Regions of substantial neotectonic activity in the Tien-Shan Palaeozoides do not greatly differ in crustal thickness if compared to the Kazakhstan Palaeozoides which were little active in Cenozoic time. The same is true for the South Siberian Palaeozoides.
The Alpides of the southern areas in the U.S.S.R. display a sharply differing surface relief and a strongly varying crustal structure. Mountains with roots (Greater Caucasus, Crimea) and without roots (Kopet-Dagh, Lesser Caucasus) were found there.
The Cenozoides of the Far East are characterized by a rugged topography of the M-discontinuity, a thinner crust and a less-pronounced “granitic” layer. A relatively small thickness of the crust was discovered in the Baikal rift zone.
The effective thickness of the magnetized domains of the crust as well as other calculations show that the temperature at the depth of the M-discontinuity (i.e., at depths of 40–50 km) is not higher than 300–400° C for most parts of the U.S.S.R. 相似文献
6.
Robert L Fleischer Howard R Hart Wallace R Giard 《Geochimica et cosmochimica acta》1974,38(3):365-380
Measurements of cosmic ray track densities are presented for soil samples from Apollo 15, 16 and 17. Median track densities are used to infer total effective exposure times within ~15 cm of the lunar surface. Minimum track densities are used to derive the time of the last impact-produced rearrangement of soil grains. For samples from near various craters ages are derived of 40 m.y. for St. George, 6 (±3) m.y. for S. Ray, 25–90 m.y. for Plum, and 20–35 m.y. for Shorty. The material of 15003. the Apollo 15 deep core at depths of 120–160 cm, is inferred to have been deposited at an average rate of ≥0.35 cm/m.y. The Apollo 16 core at 41–47 cm depths. 60007, appears to be well mixed and was covered up by deposition at 0.3 cm/m.y. for the next few m.y. after its deposition. 相似文献
7.
Delaware Bay is one of the largest estuaries on the U.S. eastern seaboard and is flanked by some of the most extensive salt marshes found in the northeastern U.S. While physicochemical and biotic gradients are known to occur along the long axis of the bay, no studies to date have investigated how the fish assemblage found in salt marsh creeks vary along this axis. The marshes of the lower portion of the bay, with higher salinity, are dominated bySpartina spp., while the marshes of the upper portion, with lower salinity, are currently composed primarily of common reed,Phragmites australis, S. alterniflora, or combinations of both. Extensive daytime sampling (n=815 tows) during May–November 1996 was conducted with otter trawls (4.9 m, 6 mm mesh) in six intertidal and subtidal marsh creek systems (upper and lower portions of each creek) where creek channel depths ranged from 1.4–2.8 m at high tide. The fish taxa of the marsh creeks was composed of 40 species that were dominated by demersal and pelagic forms including sciaenids (5 species), percichthyids (2), and clupeids (7), many of which are transients that spawn outside the bay but the early life history stages are abundant within the bay. The most abundant species wereMorone americana (24.3% of the total catch),Cynoscion regalis (15.4%),Micropogonias undulatus (15.3%),Anchoa mitchilli (12.0%), andTrinectes maculatus (10.8%). Non-metric Multi-Dimensional Scaling ordination of catch per unit effort (CPUE) data indicated two fish assemblages that were largely independent of the two major vegetation types, but generally corresponded with spatial variation in salinity. This relationship was more complex because some of the species for which we could discriminate different age classes by size had different patterns of distribution along the salinity gradient. 相似文献
8.
Data on CO, wind velocity and mixing depths collected over a five-year period show a definite association between higher levels of air pollution and SW winds in Calgary (pop. 610,000), a city 110 km E of the Canadian Rockies. The phenomenon most pronounced at wind speeds lower than 3m sec–1 is present during winds of up to 10 m sec–1. The shallow mixing depth associated with southwesterlies in this area appears to be a strong factor in the maintenance of the discrepancy. In addition, a climatological assessment of the distribution of mean mixing depths in the city shows that mixed layers are shallowest and least frequent in the S end of the city thereby increasing the potential for air pollution hazard in that part of the city. 相似文献
9.
《International Geology Review》2012,54(8):1492-1494
A large number of specimens of Seymouriamorph amphibian, family Discosauriscidae, were collected from the south slopes of the Kuramanskiy Khrebet, Mt. Sarytaypan, 10 km northeast of the settlement of Adrasman, Tadzhik S.S.R. Deposits yielding the fossils consist of about 70 m of effusive sedimentary rocks, the top third being tuffs, tuff sandstones, and tuff breccias, and the remainder being alternating fine-grained sandstones, argillites, and siltstones, of gray, greenish, pink, and black colors. The beds overlie 800 m of tuff lavas and tuff breccias and are overlain by 200 m of-tuff breccias. Fossil leaves are abundant in the lower half of the beds in all lithologic types, but the vertebrates are confined to about 1 m of adjoining layers of fine-grained gray to pink sandstone, and almost black argillite. The fossils consist of complete impressions of skeletons, which will yield much anatomical information. Two genera are represented, the most abundant referrable to the Central European form Discosauriscus. The other is related to the European Leptoverpeton but may be new. These specimens permit correlation of the Sarytaypan deposits with Lower Permian' bedsgqn Czechoslovakia and Germany. Larval forms are by far the most abundant, but the presence of adults affords a reliable comparison of growth stages. New and detailed information of the development of the spinal column will also be forthcoming from further study of the growth stages. Presence of gills in the larvae reaffirms the persistence of an aquatic larval stage in the morphologically reptile-like Seymouriamorpha. — N. Hotton III. 相似文献
10.
Selenium was determined in duplicate portions from three bottles of six U.S.G.S. standard rocks by a spect rofluorimetric procedure. The following averages, as p.p.m. Se, were obtained: PCC-1, 0.031; GSP-1, 0.088; BCR-1, 0.12; SCo-1, 0.91; MAG-1, 1.3; and SGR-1, 3.7. One-way analysis of variance of the several sets of data showed no significant differences in the selenium content among bottles of any specific rock; these samples may be accepted as homogeneous for their selenium contents by this analytical method. 相似文献
11.
《Journal of Structural Geology》1988,10(8):813-828
Detailed (1:60 scale) mapping of the Fort Foster Brittle Zone in the mylonitic Rye Formation of southernmost Maine has revealed the intricate internal duplex structure of a system of probable Paleozoic-age dextral strike-slip faults that have produced abundant pseudotachylyte and minor breccia. The internal configuration of this brittle zone consists of a mosaic of individual pseudotachylyte generation zones as slab-duplex structures. Individual duplex zones are up to 100 m in length and 1 m or less in width and are defined by pairs of layer-parallel slip surfaces along which frictional melts were produced. These slab-duplex structures are interpreted as zones of displacement transfer between long, overlapping, layer-parallel en échelon strike-slip fault surfaces. Contractional duplexes develop layer-parallel compressional structures that tend to shorten and thicken the fault-bounded slabs by the formation of lateral ramps and conjugate faults, kinks and asymmetric folds. Extensional duplexes develop layer-parallel stretching and thinning by the formation of oblique dextral shears, high-angle conjugate pairs and localized fault breccias. The production of pseudotachylyte by friction melting along layer-parallel fault surfaces in these exposures is attributed to rapid slip during paleoseismic events. The rupture structures developed during these events may be characteristic of fault structure and mechanics at near-focal depths in a strike-slip seismogenic zone. 相似文献
12.
13.
A fine exposure of perennially frozen ice-rich silt and associated flora and vertebrate fauna of late-Quaternary age exists at Mamontova Gora along the Aldan River in central Yakutia, Siberia, U.S.S.R. The silt deposit caps a 50-m-high terrace and consists of three units. An upper layer 1–2 m thick overlies a 10–15-m-thick brownish to black silt layer. The lower silt layer is greenish to gray and about 15 m thick. All the silt is well sorted with 60% of the particles falling between 0.005 and 0.5 mm in diameter and is generally chemically and mineralogically homogeneous. The middle unit contains may extinct vertebrate mammal remains and ice wedges. The lower unit contains little vegetation and no ice wedges. The silt is widespread and exists as a loamy blanket on terraces at various elevations on both sides of the lower Aldan River. The origin of the silt blanket of late-Quaternary age in central Yakutia has long been controversial. Various hypotheses have been suggested, including lacustrine and alluvial, as well as frost-action origins. It is sometimes referred to as loess-like loam. Péwé believes the silt at Mamontova Gora is loess, some of which has been retransported very short distances by water. The silt probably was blown from wide, braided, unvegetated flood plains of rivers draining nearby glaciers. The silt deposits are late Quaternary in age and probably associated with the Maximum glaciation (Samarov) and Sartan and Syryan glaciations of Wisconsinan age. On the basis of biostratigraphy, 10 radiocarbon dates, and their relation to the nearby glacial record, it is felt that the upper unit at Mamontova Gora is Holocene and the middle unit is Wisconsinan. The youngest date available from the middle unit at this particular location is 26,000 years. Dates greater than 56,000 years were obtained in the lower part of the middle unit. The lower unit is definitely beyond the range of radiocarbon dating and probably is older than the last interglacial. The sediment, fauna, ice wedges, stratigraphy, and age of perennially frozen slit deposits in central Alaska are remarkably similar to those of the deposits exposed in central Yakutia. Both areas consist of unglaciated rolling lowlands and river terraces surrounded by high mountains that were extensively glaciated in Pleistocene time. The glaciers extended from the high mountains to the edges of the ranges. In both regions, extensively braided, silt-charged rivers drained the mountains and flowed through the lowlands on their way to the sea. It follows that there should be a similar late-Quaternary history. 相似文献
14.
Six national-scale, or near national-scale, geochemical data sets for soils or stream sediments exist for the United States. The earliest of these, here termed the ‘Shacklette’ data set, was generated by a U.S. Geological Survey (USGS) project conducted from 1961 to 1975. This project used soil collected from a depth of about 20 cm as the sampling medium at 1323 sites throughout the conterminous U.S. The National Uranium Resource Evaluation Hydrogeochemical and Stream Sediment Reconnaissance (NURE-HSSR) Program of the U.S. Department of Energy was conducted from 1975 to 1984 and collected either stream sediments, lake sediments, or soils at more than 378,000 sites in both the conterminous U.S. and Alaska. The sampled area represented about 65% of the nation. The Natural Resources Conservation Service (NRCS), from 1978 to 1982, collected samples from multiple soil horizons at sites within the major crop-growing regions of the conterminous U.S. This data set contains analyses of more than 3000 samples. The National Geochemical Survey, a USGS project conducted from 1997 to 2009, used a subset of the NURE-HSSR archival samples as its starting point and then collected primarily stream sediments, with occasional soils, in the parts of the U.S. not covered by the NURE-HSSR Program. This data set contains chemical analyses for more than 70,000 samples. The USGS, in collaboration with the Mexican Geological Survey and the Geological Survey of Canada, initiated soil sampling for the North American Soil Geochemical Landscapes Project in 2007. Sampling of three horizons or depths at more than 4800 sites in the U.S. was completed in 2010, and chemical analyses are currently ongoing. The NRCS initiated a project in the 1990s to analyze the various soil horizons from selected pedons throughout the U.S. This data set currently contains data from more than 1400 sites. This paper (1) discusses each data set in terms of its purpose, sample collection protocols, and analytical methods; and (2) evaluates each data set in terms of its appropriateness as a national-scale geochemical database and its usefulness for national-scale geochemical mapping. 相似文献
15.
In this paper we describe an example of travertine fissure-ridge development along the trace of a normal fault with metre
displacement, located in the eastern margin of the Neogene–Quaternary Siena Basin, in the Terme S. Giovanni area (Rapolano
Terme, Italy). This morphotectonic feature, 250 m long, 30 m wide and 10 m high, formed from supersaturated hot waters (39.9°C)
flowing from thermal springs aligned along the trace of the normal fault dissecting travertines not older than Late Pleistocene
(24 ± 3 ka). A straight, continuous fissure with a maximum width of 20 cm occurs at the top of the ridge, along its crest.
Hot fluids flow from cones mainly located at the extremities of the ridge, where travertine is depositing. The travertine
fissure-ridge shows an asymmetrical profile since it buries the fault scarp. The difference in height of slopes corresponds
to the vertical displacement of the normal fault. Fissuring of the recent travertine deposits along the strike of the crestal
fissure, as well as recent hydrothermal circulation, lead us to believe that the Terme S. Giovanni normal fault may be currently
active. On the whole, the Terme S. Giovanni fissure ridge can be defined as a travertine fault trace fissure-ridge, adding
a helpful example for studying the relationship between faulting and travertine deposition. 相似文献
16.
Mid-Cretaceous strata within the Tintina Trench.3 km west of the community of Ross River, contain evidence of deposition in two distinct,alternating,fluvial settings.Coal-bearing,mud-dominated strata are commonly associated with high-constructive sandy channel systems,with extensive overbank. levee and splay deposits.Channels are between 3 and 30 m wide and 0.4-7 m thick.They show repetitive development of side and in-channel bar-forms,as well as up-channel widening of the rivers by selective erosion of associated overbank and levee deposits.Levees extended for several hundred metres away from the channels.In this setting low-angle inclined stratification and epsilon cross stratification may reflect lateral migration of crevasse channels or small streams.The paucity of exposure prevents recognition of the channels as products of multiple channel anastomosed systems or single channel high-constructive systems. Gravel-dominated strata,inter-bedded with,and overlying coal-bearing units,are interpreted as deposits of wandering gravel-bed rivers,with sinuosity approaching 1.4.In most exposures they appear to be dominated by massive and thin planar-bedded granule to small pebble conglomerates,which would traditionally be interpreted as sheet-flood or longitudinal bar deposits of a high-gradient braided stream or alluvial fan.Architectural analysis of exposures in an open-pit shows that the predominance of flat bedding is an artefact of the geometry of the roadside exposures.In the pit the conglomerates are dominated by large scale cross stratification on a scale of 1-5.5 m.These appear to have developed as downstream and lateral accretion elements on side-bars and on in-channel bars in water depths of 2-12 m.Stacking of strata on domed 3rd order surfaces suggests development of longitudinal in-channel bar complexes similar to those observed in parts of the modern Rhone River system.Mudstone preserved in some of the channels reflects intervals of channel abandonment or avulsion.Minimum channel width is from 70 to 450 m. 相似文献
17.
《International Geology Review》2012,54(1):23-26
On October 12, 1962, a joint session of the Presidium of the U.S.S.R. Academy of Sciences and the Collegium of the U.S.S.R. Ministry of Geology and Mineral Reserves adopted a resolution “On the present state of the geological sciences in the U.S.S.R. Academy of Sciences and the U. S. S. R. Ministry of Geology and Mineral Reserves and their prospects for the future.” Important contributions of Russian geologists are acknowledged, but attention is drawn to many shortcomings. Future goals of geological study and work are given in detail. Twenty-one lines of research to be concentrated on are given, covering all phases of geology, geophysics, and geochemistry. In discussing the failings of the geological profession in Russia, it is of interest to note the following comment: “Geological research in other countries is still insufficiently studied and applied, and we are not making adequate use of geologic information from abroad.” The list of the Russian geologists' shortcomings sounds vaguely familiar. —J. R. Hayes 相似文献
18.
Instrumented moorings were deployed during the winter of 1994–95 at three depths (28, 58 and 101 m) in southern Lake Michigan. Storms during the observation period were not unusually severe, so the processes observed are typical of those that occur during an average winter. Time series observations of water temperature, beam attenuation coefficient (a measure of water transparency) and current velocity show that local resuspension of bottom sediment occurred frequently after the breakdown of the thermocline. Resuspension was most frequent close to the shore but was also observed at the 58 m station. Local resuspension did not occur at the 101 m station, but advection to the site of material resuspended at shallower sites was observed. These observations do not support the hypothesis proposed by previous investigators that local resuspension at depths of 100 m or greater occurs during the unstratified period. It is more likely that fine-grained material resuspended by storm action in intermediate water depths (≈ 30–60 m) is transported into the deeper parts of the lake by the general lake circulation. 相似文献
19.
为了区分农作物与野生草类的淀粉粒形态,对现代粟（Setariaitalica）、黍（Panicummiliaceum）和狗尾草（Setariaviridis）的淀粉粒形态进行了比较。观察结果表明,粟的淀粉粒以圆球形单粒为主,脐点位于中央,大部分由脐点向外有1～3条放射线,表面光滑,淀粉粒平均长度约19m。黍的淀粉粒以多角形单粒为主,脐点位于中央,但很多淀粉粒的脐点不是很明显。在一些脐点形成1～3条射线,表面光滑,淀粉粒平均长度约为19m。狗尾草淀粉粒以卵形为主,脐点位于中央,表面可见层纹,边缘凹凸不平且常有裂隙形成,淀粉粒平均长度约为18m。研究证明,利用粟、黍和狗尾草的淀粉粒形态特征,可以有效地对考古遗存中的这几种禾本科植物遗迹进行区分。 相似文献
20.
中国地质学家李四光与当时苏联地学界来往交流紧密,他对地质学的贡献得到了苏联地质学家的高度评价。1958年,苏联科学院全体大会选举李四光为苏联科学院院士,并授予卡尔宾斯基金质奖章;该奖章是1947年由当时的苏联科学院和俄罗斯科学院共同发起的、对地质科学有突出贡献的科学家最高单人奖励,李四光是第六位获奖人,也是至2017年止唯一获此殊荣的外籍地质学家,他的获奖理由是:在地质、古生物、地层和矿产研究工作的综合贡献。李四光有两部著作在苏联被译成俄文出版,分别是1952年的《中国地质学》和1958年的《中国西北部的旋卷构造》,这两部译作对当时的苏联地质界产生了很大影响,极大地推动了李四光学术思想的广泛认知;"地质无国界",中国地调百年的发展历程也有着俄罗斯地学理论、规范、方法实践的烙印,在新的"一带一路"合作倡议和李四光学术精神传承下,中俄、中国与中亚在地学领域的交流合作将不断深化,硕果累累。 相似文献