A review of the ～1600 Ma sedimentation, volcanism, and tectono-thermal events in the Singhbhum craton, Eastern India     

Priyanka Chatterjee  Shuvabrata De  Marinah Ranaivoson  Rajat Mazumder  Makoto Arima 《地学前缘(英文版)》2013,4(3):277-287

The Palaeoproterozoic–Mesoproterozoic transition (～1600 Ma) is a significant event in the Earth history as a global thermal perturbation affected the pre-1600 Ma landmasses. Like other cratonic blocks of the world, lithospheric thinning, sedimentation, magmatism, metamorphism and crustal melting/anatexis are associated with this significant geological event in the Singhbhum cratonic province of India. This paper is a review of sedimentological, magmatic and tectono-thermal events in the Singhbhum craton at ～1600 Ma. The Palaeo-Mesoproterozoic sedimentation and volcanism in the Singhbhum craton took place in a terrestrial intracontinental rift setting. The available geochronological data are indicative of late Palaeoproterozoic to Neoproterozoic tectono-thermal events in the Chhotanagpur Granite Gneissic Complex (CGGC), an east–west trending arcuate belt of granite gneisses, migmatites and metasedimentary rocks. A detailed multidisciplinary geo-scientific investigation of the Dalma volcanic belt and the area to its north (Chandil Formation) and further north in CGGC will enable us to constrain the extant surface processes and crust-mantle interactions, the collision events between the North and South Indian cratonic blocks, and the position of India in the Columbia supercontinent.  相似文献   

Ice raft formation, sediment load, and theoretical potential for ice-rafted sediment influx on northern coastal wetlands     

Brittina A. Argow  Zoe J. Hughes 《Continental Shelf Research》2011,31(12):1294-1305

Ice rafting is an important secondary sedimentation process that redistributes sediment form tidal flats, channel beds, and ponds to the vegetated marsh surface in northern temperate climates. Source location of ice-rafted sediment is identifiable based on distinct sediment properties. In New England salt marsh systems, ice raft thickness and entrained sediment load vary both during the season and interannually as a function of severity and duration of winter conditions; however, 97% of ice rafts carry measurable sediment loads. Thick rafts move sand or peat up to 100 m from source areas, whereas thinner rafts tend to transport mud still further onto the marsh platform, sometimes reaching the upland border. Based on these observations, we present relationships defining the theoretical sediment-carrying potential of ice rafts as well as empirical parameterizations for ice-rafted sediment with respect to ice volume. Our results suggest that ice-rafting deposits a volume of sediment contributing up to 5% of annual vertical accretion, an important input in a region where rates of vertical accretion barely compensate for sea-level rise. We provide conceptual models of ice-raft formation and sediment entrainment linking these processes to the general geomorphic evolution of northern temperate marshes, which must be understood in light of the modern acceleration in rates of sea-level rise.  相似文献   

A new section through the Corallian Group (Oxfordian,Upper Jurassic) rocks of Calne,Wiltshire, southern England     

J.K. Wright 《Proceedings of the Geologists' Association. Geologists' Association》2014

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云南香格里拉图姆沟组硅质岩地球化学特征及意义     

李超民  邓江红  王国芝  任小庆 《云南地质》2014,33(3):295-301

本文就香格里拉地区图姆沟组（T3t）的硅质岩岩石学和地球化学特征进行分析研究,进而揭示出晚三叠世早期研究区属于甘孜—理塘洋盆的深水盆地环境,构造相对稳定,形成具深水沉积特征的正常生物沉积硅质岩;晚三叠世中-晚期,伴随甘孜-理塘洋盆向中咱地块俯冲消减,研究区构造活动强烈,热水来源广泛,则主要形成热水沉积硅质岩.  相似文献   

Characteristics of sedimentation and channel adjustment linked to the Three Gorges Reservoir     

Xiaoya Tang  Sichen Tong  Guoxian Huang  Guangxiang Xu  Xinghua Li  Kun Lei  Shiming Yao 《国际泥沙研究》2021,36(2):177-189

Construction of large dams is attractive because of their great benefits in flood control,hydropower generation,water resources utilization,navigation improvement,etc.However,dam construction may bring some negative impacts on sediment transport and channel dynamics adjustments.Due to the effects of recent water and soil conservation projects,sediment retention in the newly constructed large upstream reservoirs,and other factors,the sedimentation in the Three Gorges Reservoir(TGR)is quite different from the amount previously predicted in the demonstration stage.Consequently,based on the measured data,characteristics of sedimentation and the related channel deformation in the TGR were analyzed.The results imply that sediment transport tended to be reduced after the Three Gorges Project(TGP).Sedimentation slowed dramatically after 2013 and indicated obvious seasonal characteristics.Due to the rising water level in the TGR in the flood season,the yearly sediment export ratio(Eratio)was prone to decrease.The water level near the dam site should be reasonably regulated according to the flow discharge to improve the sediment delivery capacity and reduce sedimentation in the TGR,and to try to avoid situations where the flood retention time is close to 444 h.The depositional belt was discontinuous in the TGR and was mainly distributed in the broad reaches,and only slight erosion or deposition occurred in the gorge reaches.Sedimentation in the broad and gorge reaches accounted for 93.8% and 6.2% of the total sedimentation,respectively.The estuarine reach located in the fluctuating backwater area experienced alternate erosion-deposition,with a slight accumulative deposition in the curved reach.Sedimentation mainly occurred in the perennial backwater area.The insight gained in this study can be conducive to directly understanding of large reservoir sedimentation and mechanism of channel adjustment in the reservoir region in the main channel of large river.  相似文献   

MATHEMATICAL MODEL OF SLUDGE SEDIMENTATION     

ZHOU Kezhao  + 《国际泥沙研究》1999,(3)

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Study of gravitational sedimentation of flexible,permeable circular and planktonic particle applying the immersed boundary method     

《国际泥沙研究》2023,38(5):643-652

The gravitational settling of a flexible, permeable circular and planktonic particle drenched in a fluid which is assumed to be Newtonian and incompressible along with being viscous was studied. A mathematical formulation and numerical simulations of the studied problem were done by applying the Immersed Boundary Method (IBM) in a two-dimensional fluid domain. Parametric studies were done for analyzing the impact of varying flexibilities and permeabilities with reference to settling velocity (terminal velocity) and shape deformation of the particle. The terminal velocity and permeability of the particle are directly proportional. It was observed that for fixed permeability, the terminal velocity increases when increasing the flexibility of the particle.  相似文献   

Marine Sand Resources Offshore Israel     

Gideon Almagor  Dan Gill  Ithamar Perath 《Marine Georesources & Geotechnology》2000,18(1):1-42

The continental margin of northern Sinai and Israel, up to Haifa Bay, is the northeastern limb of the submarine Nile Delta Cone. It is made up predominantly of clastics from the Nile and its predecessors. The continental shelf and coastal plain of Israel are built of a series of shore-parallel ridges composed of carbonate-cemented quartz sandstone (locally named kurkar), a lithification product of windblown sands that were piled up into dunes during the Pleistocene. The drop in global sea level and regression during the last glacial period exposed the continental shelf to subaerial erosion and created a widespread regional erosional unconformity which is expressed as a prominent seismic reflector at the top of the kurkar layers. The subsequent Holocene transgression abraded much of the westernmost kurkar ridges, drowned their cores, and covered the previous lowstand deposits with marine sands, which were in turn covered by a sequence of sub-Recent clayey silts. The Mediterranean coasts of Sinai and Israel are part of the Nile littoral cell. Since the building of the Aswan dams the sand supplied to Israel's coastal system is derived mainly from erosion of the Nile Delta and from sands offshore Egypt that are stirred up by storm waves. The sands are transported by longshore and offshore currents along the coasts of northern Sinai and Israel. Their volume gradually declines northward with distance from their Nile source. The longshore transport terminates in Haifa Bay where some sand is trapped, and the test escapes to deeper water by bottom currents and through submarine canyons, thus denying Nile-derived sand supply to the 40-km-long 'Akko-Rosh Haniqra shelf. The sand balance along Israel's coastal zone is a product of natural processes and human intervention. Losses due to the outgoing longshore transport, seaward escape, and landward wind transport exceed the natural gains from the incoming longshore transport and the abrasion of the coastal cliffs. The deficit is aggravated by the construction of (1) seaward-projecting structures that trap sands on the upstream side and (2) offshore detached breakwaters that trap sands between themselves and the coast. The negative sand balance is manifested by the removal of sand from the seabed and the consequent exposure of archaeological remains that were hitherto protected by it. The sediments that escape seaward from the longshore transport system form a 2.5- to 4-km-wide sandy apron adjacent to the shore that extends to where the water is 30 - 40 m deep. The apron's slope (0.5 - 0.8) is steeper than the theoretical equilibrium slope for the median grain-size diameter in this zone (0.1 - 0.3 mm). The beach sands and the apron's surficial sands are well sorted. Their grain size decreases with distance from shore, from 0.2 - 0.3 mm nearshore to 0.11 - 0.16 mm by the drowned ridge. The coarse-grained fraction consists of skeletal debris (commonly 5 - 12% carbonate matter) and wave-milled kurkar grains (locally named zifzif). In deeper water, the basal sands underlying the fine-grained sediment cover consist of 1- to 30-cm layers whose composition ranges from silty sands to various types of sands (fine, medium, coarse, and gravelly) to zifzif. For the most part, they contain large amounts of skeletal debris (20 - 60%) and small fragments of kurkar. Two types of kurkar rock were encountered offshore: a well-sorted, fine- to medium-grained (0.074 - 0.300 mm) lithified dune sand with variable amounts of carbonate cement, ranging from hard rock of low permeability to loose sand; and a porous sandstone made up predominantly of algal grains and skeletal debris (calcarenite).  相似文献   

Evolution of the Academician Ridge Accommodation Zone in the central part of the Baikal Rift, from high-resolution reflection seismic profiling and geological field investigations   总被引：4，自引：0，他引：4  

V. D. Mats  O. M. Khlystov  M. De Batist  S. Ceramicola  T. K. Lomonosova  A. Klimansky 《International Journal of Earth Sciences》2000,89(2):229-250

 New high-resolution seismic reflection data from the central part of Lake Baikal provide new insight into the structure and stratigraphy of Academician Ridge, a large intra-rift accommodation zone separating the Central and North Baikal basins. Four seismic packages are distinguished above the basement: a thin top-of-basement unit; seismic-stratigraphic unit X; seismic-stratigraphic unit A; and seismic-stratigraphic unit B. Units A and B were cored on selected key locations. The four packages are correlated with a series of deposits exposed on the nearby western shores: the Ularyar Sequence (Oligocene); the Tagay Sequence (Lower to Middle Miocene); the Sasa Sequence (Upper Miocene to Lower Pliocene); the Kharantsy Sequence (Upper Pliocene); and the Nyurga Sequence (Lower Pleistocene). Based on stratal relationships, sedimentary geometries, distribution patterns and principal morphostructural elements – both onshore and offshore – we propose a new palaeogeographic evolution model for the area. In this model progressive tectonic subsidence of the Baikal basins and successive pulses of uplift of various segments of the rift margins lead to: (a) formation of the ridge as a structural and morphological feature separating the Central and North Baikal basins during the Middle to Late Miocene; (b) gradual flooding of the main parts of the ridge and establishment of a lacustrine connection between the two rift basins during the Late Miocene; and (c) total submergence of the top parts of the crest of the ridge during the latest Pleistocene. This new model helps to better constrain numerous phases in the structural evolution of the Baikal Rift, in which the Academician Ridge as an accommodation zone plays a crucial role. Received: 26 November 1999 / Accepted: 12 March 2000  相似文献   

沉积过程分形表达及其冲淤幅度分析应用   总被引：2，自引：1，他引：1  

李炎  陈锡土  夏小明  李伯根 《海洋与湖沼》2000,31(1):84-92

根据１９８２－１９９５年在浙江沿岸椒江口、杭州湾、象山县大目涂取得的沉积柱样层序数据系列和重复沉积界面测量序列,利用分形理论进行沉积过程及冲淤幅度的分析。沉积过程和沉积地层层序存在自相似结构,两者之间在无特征尺度区存在着初始值以及分数维的传递。椒江河口和杭州湾南侧潮汐通道边坡沉积柱样泥层工的分数维在１．２－１．５之间。按潮汐沉积基本单元形成的时间为大小潮周期计算,沉积过程１年重现期的高程均方变幅为  相似文献