Wind tunnel and field testing of a simple sand catcher for sampling inhomogeneously saltating sand in desertified environments

Problems of vertical alignment and vibrations of disposable coffee cups used in a modified version of the De Ploey saltating sand catcher were solved. The new version was tested in a sediment wind tunnel. Its catches appeared linearly related to amounts of eroded sand, largely independent of wind speed and wind direction, and depended logarithmically on height. The catch efficiency may therefore be taken to be approximately independent of wind speed and direction. The instrument performed well under conditions of inhomogeneously saltating sand in a strongly desertified environment in Central Sudan. Use and results show the improved simple catcher to be easy to assemble, reproducible and cheap, suitable for multipoint use to cover all inhomogeneities in outdoor saltating sand fields.     

Optical dating of relict sand wedges and composite-wedge pseudomorphs in Flanders, Belgium

We report on quartz Optically Stimulated Luminescence (OSL) dating of the infill of 14 relict sand wedges and composite-wedge pseudomorphs at 5 different sites in Flanders, Belgium. A laboratory dose recovery test indicates that the single-aliquot regenerative-dose (SAR) procedure is suitable for our samples (measured to a given dose ratio 0.980 ± 0.005; n =139). Completeness of resetting of the wedge infill of two samples was confirmed by single-grain analyses. The suite of optical ages indicates that repeated thermal contraction cracking, degradation and infilling with wind-blown sediment appear to have been commonplace in Flanders during the Late Pleniglacial (Oxygen Isotope Stage 2; OIS2); more specifically, around the Last Glacial Maximum (LGM, ∼21 kyr ago) and the transition period between the LGM and the start of the Lateglacial (∼15 kyr ago). Optical dating at one site has revealed two significantly older wedge levels, the younger inset into the older; the younger wedge has an age of 36 ± 4 kyr (Middle Pleniglacial; OIS3), the older wedge 129 ± 11 kyr, which points to formation during the Late Saalian (OIS6). Our OSL ages of the wedges and host sediments bracket formation of the BGB (Beuningen Gravel Bed: a widespread deflation horizon in northwestern Europe) at between ∼15 and 18 kyr; this is in good agreement with previous OSL dating studies. We conclude that optical dating using quartz SAR OSL establishes an absolute chronology for these periglacial phenomena and allows secure palaeoenvironmental reconstructions to be made.     

The Role of Advective Fluid Flow and Diffusion during Localized, Solid-State Dehydration: Sondrum Stenhuggeriet, Halmstad, SW Sweden

A localized dehydration zone, Söndrum stone quarry, Halmstad,SW Sweden, consists of a central, 1 m wide granitic pegmatoiddyke, on either side of which extends a 2·5–3 mwide dehydration zone (650–700°C; 800 MPa; orthopyroxene–clinopyroxene–biotite–amphibole–garnet)overprinting a local migmatized granitic gneiss (amphibole–biotite–garnet).Whole-rock chemistry indicates that dehydration of the graniticgneiss was predominantly isochemical. Exceptions include [Y+ heavy rare earth elements (HREE)], Ba, Sr, and F, which aremarkedly depleted throughout the dehydration zone. Systematictrends in the silicate and fluorapatite mineral chemistry acrossthe dehydration zone include depletion in Fe, (Y + HREE), Na,K, F, and Cl, and enrichment in Mg, Mn, Ca, and Ti. Fluid inclusionchemistry is similar in all three zones and indicates the presenceof a fluid containing CO₂, NaCl, and H₂O components. Water activitiesin the dehydration zone average 0·36, or X_H2O = 0·25.All lines of evidence suggest that the formation of the dehydrationzone was due to advective transport of a CO₂-rich fluid witha minor NaCl brine component originating from a tectonic fracture.Fluid infiltration resulted in the localized partial breakdownof biotite and amphiboles to pyroxenes releasing Ti and Ca,which were partitioned into the remaining biotite and amphibole,as well as uniform depletion in (Y + HREE), Ba, Sr, Cl, andF. At some later stage, H₂O-rich fluids (H₂O activity >0·8)gave rise to localized partial melting and the probable injectionof a granitic melt into the tectonic fracture, which resultedin the biotite and amphibole recording a diffusion profile forF across the dehydration zone into the granitic gneiss as wellas a diffusion profile in Fe, Mn, and Mg for all Fe–Mgsilicate minerals within 100 cm of the pegmatoid dyke. KEY WORDS: charnockite; fluids; CO₂; brines; localized dehydration; Söndrum     

Lithology and palynology of Weichselian alluvial fan deposits near Eerbeek, The Netherlands

In a sandpit in an alluvial fan in the central Netherlands, four interstadials could be recognized. The upper two are ¹⁴C-dated and assigned to Hengelo and Moershoofd, while the lower two belong to either Odderade or Brorup. Lithological evidence suggested the existence of two zones indicative of permafrost separated by a zone in which running water was more important. The lower permafrost zone was found to be situated between the Moershoofd and Odderade interstadials, the younger zone to belong to the Upper Pleniglacial.     

具有VRL8350静电反馈装置的拉科斯特重力仪性能的研究

1983年,美日科学家Harrison和Sato发展的一种静电反馈技术成功地用于拉科斯特流动重力仪,使这一技术迅速推广到世界各国。本文将讨论具有VRL 8350静电反馈装置的拉科斯特重力仪的线性问题,研究拉科斯特重力仪在非反馈和反馈条件下,仪器纵水泡对重力仪的灵敏度、固有周期和阻尼的影响。     

MATHEMATICAL DENOTATION OF STANDARD-GRAPHS FOR RESISTIVITY PROSPECTING IN VIEW OF THEIR CALCULATION BY MEANS OF A DIGITAL COMPUTER*

This paper is the follow-up of an earlier paper by the same author on the calculation of standard-graphs for horizontally stratified subsoils. The method which was developed in that earlier paper was destined for handwork; it was laid down in master-tables. The present paper deals with the presentation of similar methods to the computer expert in purely mathematical denotation. Two different denotations are described for the calculation of the image pole strengths involved. The first denotation is an improved version of Watsons formulae; it gives the total strengths. The second denotation preserves the character of successive approximations as described in the previous paper. Both denotations have been worked out until a six layer resistivity profile, but actually there is no limitation to the number of layers. There is no restriction to the resistivities of any layer. The only condition is now that all interface depths must be integers. This paper is followed by a paper on the relevant computer program by Argelo in this same issue     

Lateglacial and early Holocene vegetation and climate gradients in the Nordfjord–Ålesund area,western Norway

Birks, H. H. & van Dinter, M. 2010: Lateglacial and early Holocene vegetation and climate gradients in the Nordfjord–Ålesund area, western Norway. Boreas, Vol. 39, pp. 783–798. 10.1111/j.1502‐3885.2010.00161.x. ISSN 0300‐9483. Modern climate in western Norway shows a strong west–east gradient in oceanicity–continentality (coast to inner fjord) and altitudinal temperature gradients that control the regional and altitudinal zonation of vegetation. To discover if similar gradients existed during the Lateglacial and early Holocene, plant‐macrofossil analyses were made from five lacustrine sediment sequences in the Nordfjord–Ålesund region selected to sample the present climatic gradients. The macrofossil assemblages could be interpreted as analogues of the present vegetation, thus allowing reconstruction of past vegetation and climates. When the five sites were compared, climatic gradients could be detected. During the Lateglacial interstadial, mid‐alpine assemblages with Salix herbacea and S. polaris occurred at the lowland coast and upland inland sites, whereas the inland lowland site had low‐alpine dwarf‐shrub heath dominated by Betula nana, demonstrating a strong west–east gradient in temperature and precipitation and an altitudinal gradient inland. During the Younger Dryas stadial, assemblages at the lowland coast and upland inland sites resembled high‐alpine vegetation, whereas the inland lowland site was warmer with mid‐alpine vegetation, demonstrating west–east and altitudinal temperature gradients. Gradients became less pronounced in the Holocene. The early abundance of Betula nana in the inner fjord sites but its rarity at the coast is striking and reflects the oceanicity gradient. All sites became forested with Betula pubescens a few centuries into the Holocene. This forest was probably close to tree line at 370 m a.s.l. at the coast. Inland, there was no detectable altitudinal gradient, with the tree line well above 400 m a.s.l. reflecting the present pattern of tree‐line elevation.     

Time-Series Modeling and Prediction of Global Monthly Absolute Temperature for Environmental Decision Making

A generalized,structural,time series modeling framework was developed to analyze the monthly records of absolute surface temperature,one of the most important environmental parameters,using a deterministicstochastic combined(DSC) approach.Although the development of the framework was based on the characterization of the variation patterns of a global dataset,the methodology could be applied to any monthly absolute temperature record.Deterministic processes were used to characterize the variation patterns of the global trend and the cyclic oscillations of the temperature signal,involving polynomial functions and the Fourier method,respectively,while stochastic processes were employed to account for any remaining patterns in the temperature signal,involving seasonal autoregressive integrated moving average(SARIMA) models.A prediction of the monthly global surface temperature during the second decade of the 21st century using the DSC model shows that the global temperature will likely continue to rise at twice the average rate of the past 150 years.The evaluation of prediction accuracy shows that DSC models perform systematically well against selected models of other authors,suggesting that DSC models,when coupled with other ecoenvironmental models,can be used as a supplemental tool for short-term(～10-year) environmental planning and decision making.     

Optimizing sampling strategy for radiocarbon dating of Holocene fluvial systems in a vertically aggrading setting

In this paper we address the question of how to determine the period of activity (sedimentation) of fossil (Holocene) fluvial systems in vertically aggrading environments. Our data base consists of almost 100 ¹⁴C ages (partly AMS) from the Rhine–Meuse delta in the central Netherlands. Radiocarbon samples from the tops of lithostratigraphically correlative organic beds underneath overbank deposits (sample type 1) yield consistent ages, indicating a synchronous onset of overbank deposition over distances of at least up to 20 km along channel belts. Similarly, ¹⁴C ages from the base of organic residual channel fills (sample type 3) generally indicate a clear termination of within-channel sedimentation. In contrast, ¹⁴C ages from the base of organic beds overlying overbank deposits (sample type 2), commonly assumed to represent the end of fluvial sedimentation, show a large scatter reaching up to 1000 ¹⁴C years. This setting usually produces ¹⁴C ages significantly younger than residual channels of the same fluvial system, indicating the presence of non-depositional unconformities. These usually occur on top of slightly elevated sediment bodies (especially natural levee deposits), which often contain palaeosols. Such hiatuses appear to be much more abundant than hitherto supposed. We conclude that a combination of sample types 1 and 3 generally yields a satisfactory delimitation of the period of activity of a fossil fluvial system. The problems associated with ¹⁴C samples of type 2 may also be present in coastal areas with an alternation of tidal deposits and organic beds.