Evolution of orogenic wedges and continental plateaux: insights from crustal thermal–mechanical models overlying subducting mantle lithosphere     

O. Vanderhaeghe  S. Medvedev  P. Fullsack  C. Beaumont  R. A. Jamieson 《Geophysical Journal International》2003,153(1):27-51

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Dynamic modelling of passive margin salt tectonics: effects of water loading, sediment properties and sedimentation patterns   总被引：1，自引：0，他引：1  

Lykke Gemmer  Christopher Beaumont  Steven J. Ings† 《Basin Research》2005,17(3):383-402

We investigate the evolution of passive continental margin sedimentary basins that contain salt through two‐dimensional (2D) analytical failure analysis and plane‐strain finite‐element modelling. We expand an earlier analytical failure analysis of a sedimentary basin/salt system at a passive continental margin to include the effects of submarine water loading and pore fluid pressure. Seaward thinning sediments above a weak salt layer produce a pressure gradient that induces Poiseuille flow in the viscous salt. We determine the circumstances under which failure at the head and toe of the frictional–plastic sediment wedge occurs, resulting in translation of the wedge, landward extension and seaward contraction, accompanied by Couette flow in the underlying salt. The effects of water: (i) increase solid and fluid pressures in the sediments; (ii) reduce the head to toe differential pressure in the salt and (iii) act as a buttress to oppose failure and translation of the sediment wedge. The magnitude of the translation velocity upon failure is reduced by the effects of water. The subsequent deformation is investigated using a 2D finite‐element model that includes the effects of the submarine setting and hydrostatic pore pressures. The model quantitatively simulates a 2D approximation of the evolution of natural sedimentary basins on continental margins that are formed above salt. Sediment progradation above a viscous salt layer results in formation of landward extensional basins and listric normal growth faults as well as seaward contraction. At a later stage, an allochthonous salt nappe overthrusts the autochthonous limit of the salt. The nature and distribution of major structures depends on the sediment properties and the sedimentation pattern. Strain weakening of sediment favours landward listric growth faults with formation of asymmetric extensional depocentres. Episodes of low sediment influx, with partial infill of depocentres, produce local pressure gradients in the salt that result in diapirism. Diapirs grow passively during sediment aggradation.  相似文献   

Continental margin syn‐rift salt tectonics at intermediate width margins          下载免费PDF全文

Janice Allen  Christopher Beaumont 《Basin Research》2016,28(5):598-633

This paper examines interactions among syn‐rift continental margin extension, evaporites, particularly rocksalt (halite), deposited in the overlying sedimentary basins, and clastic sediment loading. We present dynamically evolving 2D numerical models that combine syn‐rift lithospheric extension, with salt (viscous halite, 10¹⁸–10¹⁹ Pa s) and clastic (frictional‐plastic) sediment deposition to investigate how salt is distributed and subsequently mobilized during syn‐rift extension. Example results are shown, contrasting salt deposition in the early, mid and late syn‐rift phases of a single lithospheric extension model. The lithospheric model is chosen to give depth‐dependent extension and intermediate width margins with proximal grabens and a hyperextended distal region. The models exhibit diachronous migration of extension towards the rift axis and this is reflected in the faulting of overlying sediments. The models illustrate the roles of timing of salt deposition, relative to rifting and subsequent sedimentation, in defining the location and deformation of syn‐rift salt, with post‐salt sediment progradation in some models. Late deposition of salt leads to increased lateral extent of the original salt body and decreased variation in salt thickness. Seaward flow of salt increases with later deposition; early syn‐rift salt is deposited and trapped in the grabens, whereas mid and late syn‐rift salt tends to flow towards the distal margin or even over the oceanic crust. Prograding clastic post‐salt sediments drive more substantial seaward movement of mid and late syn‐rift salt. A numerical model of the Red Sea with evaporite deposition during the mid to late syn‐rift period, preceded and followed by aggrading and prograding clastic sediment, shows reasonable agreement with observations from the central Red Sea.  相似文献   

Graben generation of major sedimentary basins     

C. Beaumont  J.F. Sweeney 《Tectonophysics》1978,50(1):T19-T23

Regional isostatic adjustment to the load that fills the trough of a large graben will produce a surface depression that extends far beyond the boundaries of the load. Sediment infilling of this depression can lead to the development of a major sedimentary basin as the regional adjustment mechanism approaches isostatic equilibrium.  相似文献   

Primordial non-Gaussianity from LAMOST surveys     

Yan Gong    Xin Wang  Zheng Zheng  Xue-Lei Chen    National Astronomical Observatories  Chinese Academy of Sciences  Beijing  China  Graduate University of Chinese Academy of Sciences  Beijing  China Institute for Advanced Study  Einstein Drive  Princeton  NJ  USA Center of High Energy Physics  Peking University  Beijing  China Kavli Institute for Theoretical Physics China  CAS  Beijing 《中国天文和天体物理学报》2010,10(2)

The primordial non-Gaussianity (PNG) in the matter density perturbation is a very powerful probe of the physics of the very early Universe. The local PNG can induce a distinct scale-dependent bias on the large scale structure distribution of galaxies and quasars, which could be used for constraining it. We study the detection limits of PNG from the surveys of the LAMOST telescope. The cases of the main galaxy survey, the luminous red galaxy (LRG) survey, and the quasar survey of dif- ferent magnitude limits...  相似文献   

Geology and regional significance of the Sarnoo Hills,eastern rift margin of the Barmer Basin,NW India          下载免费PDF全文

Andrew J. Bladon  Stuart D. Burley  Stuart M. Clarke  Hazel Beaumont 《Basin Research》2015,27(5):636-655

The Barmer Basin is a poorly understood rift basin in Rajasthan, northwest India. Exposures in the Sarnoo Hills, situated along the central eastern rift margin of the Barmer Basin, reveal a sedimentary succession that accumulated prior to the main Barmer Basin rift event, and a rift‐oblique fault network that displays unusual geometries and characteristics. Here, we present a comprehensive study of Lower Cretaceous sedimentology on the basin margin, along with a detailed investigation of rift‐oblique faults that are exposed nowhere else in the region and provide critical insights into Barmer Basin evolution. Lower Cretaceous sediments were deposited within a rapidly subsiding alluvial plain fluvial system. Subsequent to deposition, the evolving Sarnoo Hills fault network was affected by structural inheritance during an early, previously unrecognised, rift‐oblique extensional event attributed to transtension between India and Madagascar, and formed a juvenile fault network within the immediate rift‐margin footwall. Ghaggar‐Hakra Formation deposition may have been triggered by early rifting which tectonically destabilised the Marwar Craton prior to the main northeast–southwest Barmer Basin rift event. The identification of early rifting in the Barmer Basin demonstrates that regional extension and the associated rift systems were established throughout northwest India prior to the main phase of Deccan eruptions. Inheritance of early oblique fault systems within the evolving Barmer Basin provides a robust explanation for poorly understood structural complications interpreted in the subsurface throughout the rift. Critically, the presence of syn‐rift sedimentary successions within older oblique rift systems obscured beneath the present‐day Barmer Basin has significant implications for hydrocarbon exploration.  相似文献   

Water resource management in the USA: a case study of large dams     

Peter Beaumont 《Applied geography (Sevenoaks, England)》1983,3(4):259-275

The construction of large dams in the USA reveals a rapid growth in activity in the post-Second World War period, with the largest number of dams being inaugurated in the mid-1960s. Texas, with 823 dams, is the state with the largest number, followed in turn by California, Oklahoma, Pennsylvania and Colorado. At the other extreme some states have fewer than a dozen dams. Although there are large variations in the number of dams between states nearly all of them record peak constructional activity between the late 1950s and early 1970s. Surprisingly, most dams have relatively small reservoirs with about 70 per cent of the total having capacities of less than 10⁶ m³. Over two-thirds of all dams have been constructed with a single aim in view, with flood control being the most important reason. Only 1.5 per cent of all dams are utilized for four or more purposes. The objectives behind dam construction reveal changes since the 19th century. In the early years of the 20th century irrigation, hydro-electric power generation and water supply were the most important reasons for dam construction, whereas in the post-1950 period flood control stands out as the dominant activity. Changing technology, the introduction of specific legislation and changing attitudes to the environment have been the major influences on dam-building activity over the period studied.  相似文献   

Intraspecific cleaning by juvenile Cape white seabream Diplodus capensis (Sparidae) off eastern South Africa     

PC Sikkel  NJ Smit 《African Journal of Marine Science》2018,40(1):97-99

Juveniles of the Cape white seabream Diplodus capensis were observed cleaning adult conspecifics in a large tidepool off Sodwana Bay, South Africa. Although nine other tropical fish species were present and interacted with a nearby pair of Labroides cleaner wrasses, only adults of D. capensis posed for and were cleaned by the D. capensis juveniles. Such cleaning interactions have not been reported previously for this species or among marine fishes off South Africa, and thus add to the growing list of facultative cleaners globally.  相似文献   

Identification, definition and quantification of goods and services provided by marine biodiversity: implications for the ecosystem approach     

Beaumont NJ  Austen MC  Atkins JP  Burdon D  Degraer S  Dentinho TP  Derous S  Holm P  Horton T  van Ierland E  Marboe AH  Starkey DJ  Townsend M  Zarzycki T 《Marine pollution bulletin》2007,54(3):253-265

This paper identifies and defines ecosystem goods and services provided by marine biodiversity. Case studies have been used to provide an insight into the practical issues associated with the assessment of marine ecosystem goods and services at specific locations. The aim of this research was to validate the definitions of goods and services, and to identify knowledge gaps and likely difficulties of quantifying the goods and services. A validated theoretical framework for the assessment of goods and services is detailed, and examples of the goods and services at a variety of case study areas are documented. These results will enable future assessments of marine ecosystem goods and services. It is concluded that the utilisation of this goods and services approach has the capacity to play a fundamental role in the Ecosystem Approach, by enabling the pressures and demands of society, the economy and the environment to be integrated into environmental management.  相似文献   

Experiments and geochemical modelling of CO₂ sequestration by olivine: Potential,quantification     

B. Garcia  V. Beaumont  E. Perfetti  V. Rouchon  D. Blanchet  P. Oger  G. Dromart  A.-Y. Huc  F. Haeseler 《Applied Geochemistry》2010

Aqueous solutions equilibrated with supercritical CO₂ (150 °C and total pressure of 150 bar) were investigated in order to characterize their respective conditions of carbonation. Dissolution of olivine and subsequent precipitation of magnesite with a net consumption of CO₂ were expected. A quantified pure mineral phase (powders with different olivine grain diameter [20–80 μm], [80–125 μm], [125–200 μm] and [>200 μm]), and CO₂ (as dried ice) were placed in closed-batch reactors (soft Au tubes) in the presence of solutions. Different salinities (from 0 to 3400 mM) and different ratios of solution/solid (mineral phase) (from 0.1 to 10) were investigated. Experiments were performed over periods from 2 to 8 weeks. Final solid products were quantified by the Rock-Eval 6 technique, and identified using X-ray diffraction, Raman spectroscopy, electron microprobe and scanning electron microscopy. Gaseous compounds were quantified by a vacuum line equipped with a Toepler pump and identified and measured by gas chromatography (GC). Carbon mass balances were calculated.  相似文献