High elevation of low‐relief surfaces in mountain belts: does it equate to post‐orogenic surface uplift?

We present experiments of upraising and relaxing topographies showing that peneplanation can occur above the ultimate base level (sea level). After active uplift, the erosion of a topography bounded by a piedmont generates a final smooth and highly elevated topography. Smoothing at high elevation is even possible during active uplift if the evolution of topography is disrupted by the deposition of the products of erosion on its piedmont which is the case at the transition from underfilled to overfilled conditions in foreland basins.     

面向对象在关系数据库设计中的应用

针对面向对象技术和关系数据库的特点,将两者相结合,探索一种将面向对象思想应用到关系数据库系统设计中的方法,并以图书管理系统为例,对方法的使用详细地进行了阐述.还就对象映射成关系数据库的方式进行了介绍.     

Practitioner training for building capacity in ICZM

Capacity building has been a much promoted principle of Integrated Coastal Zone Management (ICZM) since its advent beginning in the 1970’s. Although the concept of capacity building includes human resource development, organizational development and institutional and legal framework development, in practice it has often become focussed on the transfer of technical knowledge and procedures to managers and decision makers. The effect of this is often to emphasise and promote sectoral approaches rather than a holistic one as advocated by ICZM. Experiences gained during the EU Intereg IIIB COREPOINT project led to the development of a training programme that progressively reduced its formal lecture-style content and increased opportunity for discussion and delegate participation. It also produced a more uniform and systematic style and structure to presentations, in particular the case studies illustrating the eight EU ICZM principles of best practice, and embedded the ICZM principles and European perspectives of coastal management within the context of the work environment.This paper reviews methods for practitioner-oriented capacity building, and details the evolution of a training course to sensitise and familiarise coastal practitioners with the principles and practices of ICZM, working from local to national to trans-national scales. The lessons learnt from the ICZM capacity development in COREPOINT are identified and it is suggested that these are relevant and applicable to many other ICZM initiatives.     

Modelling mean annual sediment yield using a distributed approach

In this paper a spatially distributed model for the calculation of sediment delivery to river channels is presented (SEDEM: SEdiment DElivery Model). The model consists of two components: (1) the calculation of a spatial pattern of mean annual soil erosion rates in the catchment using a RUSLE (Revised Soil Erosion Equation) approach; and (2) the routing of the eroded sediment to the river channel network taking into account the transport capacity of each spatial unit. If the amount of routed sediment exceeds the local transport capacity, sediment deposition occurs. An existing dataset on sediment yield for 24 catchments in central Belgium was used to calibrate the transport capacity parameters of the model. A validation of the model results shows that the sediment yield for small and medium sized catchments (10–5000 ha) can be predicted with an average accuracy of 41 per cent. The predicted sediment yield values with SEDEM are significantly more accurate than the predictions using a lumped regression model. Moreover a spatially distributed approach allows simulation of the effect of different land use scenarios and soil conservation techniques. Copyright © 2001 John Wiley & Sons, Ltd.     

UHF radar observation of strato-tropospheric transfers on the anticyclonic side of a jet streak

An observation by UHF ST radar of a subsidence pattern on the right side of the exit region of a jet streak is reported. The onset of the subsidence pattern occurred at 23:30 UTC on the 29 November 1991, when a downward motion was initiated above 14 km. The injections of stratospheric air in this region seem to have an intermittent nature; they occur during at least three intervals during the lifetime of the subsidence pattern. Comparison of these results with an ECMWF analysis suggests that it is an unfolding case. However, observation of turbulent intensities w’ greater than 60 cm s⁻¹ at the tropopause level also suggests the existence of a turbulent flux between the stratosphere and the troposphere. From the turbulence characteristics measured by the radar and the potential temperature profile obtained by radiosonde data, the eddy diffusivity at the tropopause level has been calculated. An eddy diffusion coefficient ranging between 5 and 7 m² s⁻¹ is found. From these values, and with the assumption of a climatological gradient of the volume mixing ratio of ozone in the lower stratosphere, it is possible to deduce a rough estimate of the amount of ozone injected from the stratosphere into the troposphere during this event. A rate of transfer of 1.5×10²⁰ molecules of ozone per day and per square meter is found.     

U/Pb and Sm/Nd geochronologic studies of the eastern Borborema Province, Northeastern Brazil: initial conclusions

The Borborema Province of NE Brasil comprises the central part of a wide Pan-African-Brasiliano orogenetic belt that formed as a consequence of late Neoproterozoic convergence and collision of the São Luis-West Africa craton and the São Francisco-Congo-Kasai cratons. New Sm/Nd and U/Pb results from the eastern part of this province help to define the basic internal architecture and pre-collisional history of this province, with particular emphasis on delineating older cratonic terranes, their fragmentation during the Mesoproterozoic, and their assembly into West Gondwana during the Pan African-Brasiliano orogeny at ca. 600 Ma.The region can be divided into three major geotectonic domains: a) Rio Piranhas-Caldas Brandão massif, with overlying Paleoproterozoic to Neoproterozoic supracrustal rocks, north of the Patos Lineament; b) the Archean to Paleoproterozoic São Francisco craton (SFC) to the south; and c) a complex domain of Paleoproterozoic to Archean basement blocks with several intervening Mesoproterozoic to Neoproterozoic fold belts in the center (south of Patos Lineament and north of SFC). The northern and central domains comprise the Borborema Province.Archean basement gneiss and Transamazonian granulite of northern SFC are exposed in the southern part of the central domain, underlying southern parts of the Sergipano fold belt. Basement in the Rio Piranhas massif appears to consist mostly of Transamazonian (2.1 to 2.2 Ga) gneissic rocks; Nd model ages (T_DM) of ca. 2.6 Ga for 2.15 Ga gneisses indicate a substantial Archean component in the protoliths to these gneisses. The Caldas Brandão massif to the east yields both Transamazonian and Archean U/Pb zircon and Nd (T_DM) ages, indicating a complex architecture. Metasedimentary rocks of the Jucurutu Formation yield detrital zircons with original crystallization ages as young as 1.8 Ga, indicating that these rocks may be late Paleoproterozoic and correlate with other ca. 1.8 Ga cratonic supracrustal rocks in Brazil such as the Roraima Group and Espinhaço Group.Most metavolcanic and pre-Brasiliano granitic units of the Sergipano (SDS), Pajeú-Paraíba (SPP), Riacho Pontal (SRP), and Piancó-Alto Brígida (SPAB) fold belts in the central domain formed ˜ 1.0 ± 0.1 Ga, based on U/Pb ages of zircons. Nd model ages (T_DM) for these same rocks, as well as Brasiliano granites intruded into them and large parts of the Pernambuco-Alagoas massif, are commonly 1.3–1.7 Ga, indicating that rocks of the fold belts were not wholly derived from either older (> 2.1 Ga) or juvenile (ca. 1.0 Ga) crust, but include mixtures of both components. A simple interpretation of Brasiliano granite genesis and the Nd data implies that there is no Transamazonian or Archean basement underlying large parts of these fold belts or of the Pernambuco-Alagoas massif. An exception is a belt of syenitic Brasiliano plutons (Syenitoid Line) and host gneisses between SPAB and SPP that clearly has a Transamazonian (or older) source. In addition, there are several smaller blocks of Archean to Transamazonian gneiss that can be defined within and among these fold belts. These blocks do not appear to constitute a continuous basement complex, but appear to be isolated older crustal fragments.Our data support a model in which ca. 1.0 Ga rifting was an important tectonic and crust-forming event along the northern edge of the São Francisco craton. Our data also show that significant parts of the Borborema Province are not remobilized Transamazonian to Archean crust, but that Mesoproterozoic crust is a major feature of the Province. There are several small remnants of older crust within the area dominated by Mesoproterozoic crust, suggesting that the rifting event created several small continental fragments that were later incorporated into the Brasiliano collisional orogen. We cannot at present determine if the Rio Piranhas-Caldas Brandão massifs and the older crustal blocks of the central domain were originally part of the São Francisco craton or whether some (or all) of them came from more exotic parts of the Proterozoic Earth. Finally, our data have not yet revealed any juvenile terranes of either Transamazonian or Brasiliano age.     

Results Of An Artificial Recharge Test And A Double Pumping Test As Preliminary Studies For Optimizing Water Supply In The Western Belgian Coastal Plain

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RESUMEN: En la planicie costera occidental de Bélgica, la mayor parte de la demanda de agua se abastece mediante captaciones en lentejones de agua dulce, bajo el cordón de dunas. Debido a la sobreexplotación, especialmente durante el verano, las captaciones están amenazadas por intrusiones de agua salada. Existe la posibilidad de utilizar recarga artificial, ya que en invierno una gran cantidad de agua dulce superficial se vierte al mar. Se presenta una propuesta para mejorar la gestión del agua en dicha región. Los estudios preliminares han consistido en dos ensayos: uno de recarga artificial en la zona de las dunas, y uno de doble bombeo en un cordón arenoso cerca de un canal de drenaje en la zona pantanosa de la planicie costera. La interpretación de los ensayos se realizó mediante modelación inversa. Los resultados del ensayo de recarga artificial han demonstrado la posibilidad de usar recarga artificial en la zona de captación de Koksijde. El ensayo de doble bombeo ha demonstrado que el cordón arenoso de Avekapelle, situado en la zona pantanosa, se puede utilizar como zona de captación.

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RéSUMé: Dans la partie occidentale de la plaine c?tière belge, la demande en eau est pour la plupart satisfaite par des captages d'eau souterraine. Les puits captent l'eau d'une lentille d'eau douce sous le cordon dunaire. Par suite d'une surexploitation, surtout pendant l'été, ces captages d'eau sont menacés par une intrusion d'eau salé. La recharge artificielle de la nappe peut être envisagée parce que, pendant l'hiver, de grandes quantités d'eau douce sont évacuées vers la mer. Une amélioration de la gestion de la ressource en eau est donc proposée. Deux essais ont été réalisés pour une étude préliminaire: un essai de recharge artificielle dans la région des dunes et un essai de double pompage prés d'un canal de drainage dans les polders. Ces deux essais ont été interprétés grace à une méthode inverse. L'essai de recharge artificielle a démontré les possibilités de recharge de la nappe pour le site de captage de Coxyde. L'essai de double pompage a montré que le d?me sableux d'Avekapelle, dans les polders, est une région de recharge qui convient.