Luminescence dating of Würmian (Weichselian) proglacial sediments from Switzerland: methodological aspects and stratigraphical conclusions     

FRANK PREUSSER  REAS BLEI  HANSRUEDI GRAF  CHRISTIAN SCHLÜCHTER 《Boreas: An International Journal of Quaternary Research》2007,36(2):130-142

Proglacial deposits from three independently dated sites in the Swiss lowlands were investigated by optically stimulated luminescence (OSL) to test the reliability of the applied dating approach. Using the single-aliquot regenerative-dose technique applied to small aliquots of quartz revealed that in all samples the OSL signal was differentially bleached prior to deposition. A statistical approach is introduced to extract the fraction of aliquots in which the OSL was apparently set to zero at deposition. The statistical treatment provided OSL ages in good consistency with independent age control. However, some uncertainties remain with this approach, since it is difficult to assess the natural scatter caused by dose-rate inhomogeneity exactly. The available data set implies that glaciers reached the Swiss lowlands prior to about 25 000 yr ago. Previously published data from other sites demonstrate that glaciers were present in lowland Switzerland up to about 20000 yr ago. Furthermore, one OSL date of about 70 000 yr for proglacial outwash sediments points to the presence of the Rhône Glacier in the Lake Neuchâtel area during the middle part of the Late Pleistocene.  相似文献   

Chronology of deglaciation based on ¹⁰Be dates of glacial erosional features in the Grimsel Pass region, central Swiss Alps     

MEREDITH A. KELLY  SUSAN IVY-OCHS  PETER W. KUBIK  FRIEDHELM VON BLANCKENBURG  CHRISTIAN SCHLÜCHTER 《Boreas: An International Journal of Quaternary Research》2006,35(4):634-643

Surface exposure dating, using in situ produced cosmogenic ¹⁰Be, is applied to determine the time since deglaciation of bedrock surfaces in the Grimsel Pass region. Nine ¹⁰Be dates from bedrock surfaces corrected for cover by snow are minimum ages for deglaciation of the pass. Four ¹⁰Be dates from surfaces below 2500 meters above sea level (m a.s.l.) on Nägelisgrätli, east of Grimsel Pass, yield ages that range from about 14 000 to 11 300 years. Three ¹⁰Be dates from locations above 2600 m a.s.l. on Nägelisgrätli are between about 11 700 and 10 400 years. Two ¹⁰Be dates from locations at 2560 m a.s.l. below Juchlistock are about 12 100 and 11 000 years. The geographical distribution of ¹⁰Be dates on Nägelisgrätli either may show the timing of progressive deglaciation of Grimsel Pass or may reflect differences in subglacial erosion of bedrock in the pass region. All dates are discussed in the context of deglaciation of the late Würmian Alpine ice cap and deglaciation from Last Glacial Maximum (LGM) ice extents in other regions.  相似文献   

Environmental and climatic reconstructions during Marine Oxygen Isotope Stage 3 from Gossau, Swiss Midlands, based on coleopteran assemblages     

MONIKA JOST-STAUFFER  GEOFFREY RUSSELL COOPE  CHRISTIAN SCHLÜCHTER 《Boreas: An International Journal of Quaternary Research》2005,34(1):53-60

The well-known lower lignite layer at Gossau (15 km SE of Zürich, Switzerland) has been radiocarbon-dated to between 30 000 and 54 000 yr BP. Though these dates may be considered to be beyond the acceptable limit of the technique, there can be little doubt on stratigraphical grounds that the deposits date from some early part of MOI Stage 3. The lower lignite has yielded 49 taxa of beetles from which a detailed palaeoenvironmental picture can be reconstructed. Quantified palaeotemperature estimates using the Mutual Climatic Range method, based on this fossil assemblage, indicate that the climate was cold and considerably more continental than it is today in the Swiss Midlands and close to the thermal limit for the growth of trees. The fauna bears similarities to others from the same general period in northern Europe.  相似文献   

An 8-year record of the seasonal variation of ²H and ¹⁸O in atmospheric water vapour and precipitation at Heidelberg, Germany     

HELMUT JACOB  CHRISTIAN SONNTAG 《Tellus. Series B, Chemical and physical meteorology》1991,43(3):291-300

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Hydrographic changes in the southern Kattegat (Scandinavia) during the early Holocene transgression     

CHRISTIAN CHRISTIANSEN  KELD CONRADSEN  EMIL EMELYANOV  EGIS TRIMONIS  JAN HEINEMEIER  NIELS RUD 《Boreas: An International Journal of Quaternary Research》1993,22(4):349-356

Detailed sedimentological, micropalaeontological, mineralogical and geochemical investigations as well as ¹⁴C datings were carried out on a core from the southern part of the Kattegat Sea. According to the micropalaeontological interpretations, sea level rose by approximately 20 m in the period c. 9610 BP to 8200 BP. The core therefore provides evidence of the hydrographical conditions in the southern Kattegat during the early Holocene transgression. In the sediment there is geochemical evidence of strong stratification in the water column possibly related to inflow of saline water around 9080 BP. After the sediments dated to 8200 BP there is a hiatus followed by very young (<300 BP?) sediments. It is suggested that this hiatus might be associated with the opening of the Danish Straits.  相似文献   

²²²Rn flux and soil air concentration profiles in West-Germany. Soil ²²²Rn as tracer for gas transport in the unsaturated soil zone     

HELMUT DÖRR  KARL OTTO MÜNNICH 《Tellus. Series B, Chemical and physical meteorology》1990,42(1):9-19

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The Ymer-Formation - an interglacial sequence in northeasternmost Greenland     

CHRISTIAN HJORT  ROLF W. FEYLING-HANSSEN 《Polar research》1987,5(3):347-350

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TRENDS IN THE URBANIZATION PROCESS     

CHRISTIAN WICHMANN MATTHIESSEN Ph. D. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):98-101

Matthiessen, Christian Wichmann: Trends in the urbanization process. The Copenhagen case. Geografisk Tidsskrift 80: 98–101. Copenhagen, June 1980.

Within the framework of the international comparative research project (Cost of Urban Growth) new trends in urban development have recently been observed. The object of this article is to discuss the trends and give impirical evidence on Danish data.  相似文献   

Prediction uncertainty of conceptual rainfall-runoff models caused by problems in identifying model parameters and structure     

STEFAN UHLENBROOK  JAN SEIBERT  CHRISTIAN LEIBUNDGUT  ALLAN RODHE 《水文科学杂志》2013,58(5):779-797

Abstract

The uncertainties arising from the problem of identifying a representative model structure and model parameters in a conceptual rainfall-runoff model were investigated. A conceptual model, the HBV model, was applied to the mountainous Brugga basin (39.9 km”) in the Black Forest, southwestern Germany. In a first step, a Monte Carlo procedure with randomly generated parameter sets was used for calibration. For a ten-year calibration period, different parameter sets resulted in an equally good correspondence between observed and simulated runoff. A few parameters were well defined (i.e. best parameter values were within small ranges), but for most parameters good simulations were found with values varying over wide ranges. In a second step, model variants with different numbers of elevation and landuse zones and various runoff generation conceptualizations were tested. In some cases, representation of more spatial variability gave better simulations in terms of discharge. However, good results could be obtained with different and even unrealistic concepts. The computation of design floods and low flow predictions illustrated that the parameter uncertainty and the uncertainty of identifying a unique best model variant have implications for model predictions. The flow predictions varied considerably. The peak discharge of a flood with a probability of 0.01 year^?1, for instance, varied from 40 to almost 60 mm day^?1. It was concluded that model predictions, particularly in applied studies, should be given as ranges rather than as single values.  相似文献   

The Purple Saxifrage, Saxifraga oppositifolia, in Svalbard: two taxa or one?     

ANNE K. BRYSTING  TOVE M. GABRIELSEN  OVE SØRLIBRÅTEN  ODDMUND YTREHORN  CHRISTIAN BROCHMANN 《Polar research》1996,15(2):93-105

Several studies have demonstrated high levels of genetic (DNA), ecophysiological, ecological, and morphological variation within the species Purple Saxifrage, Saxifraga oppositifolia , in Svalbard. It has recently been proposed that S. oppositifolia is represented by two conspicuously different subspecies in this archipelago: ssp. reptans , a late-flowering, prostrate ecotype of snow-protected, damp habitats, and ssp. pulvinata , an early-flowering, cushion-like ecotype of dry, wind-exposed heaths and ridges. It has also been suggested that the subspecies may be differentiated at the tetraploid and diploid levels, respectively, which would promote reproductive isolation. These hypotheses are tested by examining variation in morphology, ecology, and pollen size and stainability in 150 plants of S. oppositifolia growing in 50 vegetation samples at four sites in the Kongsfjorden area. Although analyses of the various data sets demonstrated the large variation within the species, the material could not be separated into distinct groups. The morphological variation was continuous along local ecological gradients. The pollen grains were fully stainable and the pollen diameter data showed a unimodal distribution, suggesting that the plants analysed represent only one ploidal level. These results reject a hypothesis that the morphologically intermediate plants are hybrids between two taxa at different ploidal levels. Thus, the conspicuous variation in S. oppositifolia in Svalbard probably results from local, in situ ecoclinal differentiation. Although this variation clearly is without taxonomic significance, it is important in the broader context of arctic conservation biology and the potential impact of global warming on arctic vegetation.  相似文献