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   

Sulfur isotopic signals in two shallow ice cores from Dronning Maud Land, Antarctica     

ULF JONSELL  MARGARETA E. HANSSON  CARL-MAGNUS MÖRTH  PETER TORSSANDER 《Tellus. Series B, Chemical and physical meteorology》2005,57(4):341-350

  相似文献   

Cosmic-ray exposure ages of diogenites and the recent collisional history of the howardite,eucrite and diogenite parent body/bodies     

KEES C. WELTEN  LOUIS LINDNER  KLAAS VAN DER BORG  THOMAS LOEKEN  PETER SCHERER  LUDOLF SCHULTZ 《Meteoritics & planetary science》1997,32(6):891-902

Abstract— We determined the cosmic-ray exposure age of 20 diogenites from measured cosmogenic noble gas isotopes and calculated production rates of ³He, ²¹Ne and ³⁸Ar. The production rates were calculated on the basis of the measured chemical composition and the cosmogenic ²²Ne/²¹Ne ratio of each sample. The shielding conditions of each sample were also checked on the basis of the measured ¹⁰Be and ²⁶AI concentrations. The exposure ages range from 6 to 50 Ma but do not form a continuous distribution: ten ages cluster at 21–25 Ma and four at 35–42 Ma. The two diogenite clusters coincide with the 22 Ma and 38 Ma peaks in the exposure age distribution of eucrites and howardites. After the selection from literature data of 32 eucrites and 11 howardites with reliable ages, we find a total of 23 howardite, eucrite and diogenite (HED) group meteorites at 20–25 Ma and 10 at 35–42 Ma. The shape of the two peaks is consistent with single impact events, and random number statistics show that they are statistically significant at the 99% level. Altogether, this provides strong evidence for two major impact events 22 Ma and 39 Ma ago. Although these two events can explain more than half of all HED exposure ages, it takes at least five impact events to explain all ages <50 Ma. An impact frequency of one per 10 Ma corresponds to projectiles of at least 2–4 km in diameter for Vesta and of 60–300 m for the 100× smaller Vesta-derived “vestoids.” Based on the HED exposure-age distribution, the size distribution of the main-belt asteroids and the difference in size between Vesta and the kilometer size vestoids, we favor Vesta as the major source of HED meteorites, although some of the meteorites may have been ejected from the vestoids rather than directly from Vesta.  相似文献   

A reassessment of the gas transfer velocity — wind speed relationship from the Siblyback Lake data     

JOYCE KWAN  PETER A. TAYLOR 《Tellus. Series B, Chemical and physical meteorology》1993,45(3):296-298

  相似文献   

The Storegga tsunami along the Norwegian coast, its age and run up     

STEIN BONDEVIK  JOHN INGE SVENDSEN  GEIR JOHNSEN  JAN MANGERUD  PETER EMIL KALAND 《Boreas: An International Journal of Quaternary Research》1997,26(1):29-53

The statigraphy in 25 coastal lakes shows that most of the Norwegian coastline was impacted by a large tsunami about 7200 ¹⁴C BP. The methodology has been to core a staircase of lake basins above the contemporary sea level in several areas and to map the tsunami deposit to its maximum elevation. The tsunami was identified in the sedimentary record as an erosional unconformity overlain by graded or massive sand with shell fragments, followed by redeposited organic detritus. The greatest recorded runup along the coast (10–11 m above high tide) is found in areas most proximal to the Storegga slide scar on the Norwegian continental slope (Sunnmøre). To the north and south, runup is less, about 6–7 m at Bjugn (250 km north of Sunnmøre) and about 3–5 m in Austrheim (200 km to the south of Sunnmerre). This runup pattern supports the suggestion that the tsunami was generated by the Second Storegga Slide. The recorded runup heights are consistent within and between the investigated areas, and imply that the tsunami wave was not significantly influenced by the local topography, suggesting a very long wave length. The mapped runup estimates are in good agreement with a numerical model of the tsunami generated by the Second Storegga slide, and indicate that the slide was a single major event rather than a set of smaller slides.  相似文献   

Trends in the composition of wet deposition: effects of the atmospheric rehabilitation in East-Germany     

WOLFGANG MARQUARDT  ERIKA BRÜGGEMANN  PETER IHLE 《Tellus. Series B, Chemical and physical meteorology》1996,48(3):361-371

  相似文献   

Quaternary magnetostratigraphy in Denmark     

NIELS ABRAHAMSEN  PETER W. READMAN 《Boreas: An International Journal of Quaternary Research》1987,16(4):373-380

Magnetostratigraphical results from various historical, Holocene, Lateglacial and Glacial deposits from Central Jutland, Vendsyssel, the Baltic Sea and Schleswig-Holstein are illustrated and discussed. Although only a few archaeomagnetic case studies have yet been made in Denmark, magnetic datings with accuracies of about ±50 years have been obtained on mediaeval kilns by comparing with a dipole transformed modification of the British archaeomagnetic master curve. Furthermore, a study of the expected east–west orientation of some 330 Romanesque churches in Denmark seem to indicate that about 25% of these churches were magnetically orientated; thus some kind of a magnetic compass may have been in common use in the twelfth century in Denmark. Radiocarbon-dated Holocene lake sediments from lake Skanderborg reveal a distinct pattern of magnetic secular variation with fairly short time constants, which may be useful in magnetostratigraphical correlations of other lake sediments. Also Lateglacial and Early Postglacial sediments from the southern Baltic Sea show systematical magnetic patterns, whereas glacial boulder clay at the bottom shows disturbed directions, obviously moulded by the moving ice. Lateglacial Younger Yoldia clay from North Jutland shows well-developed short periodic swings as well as an extreme declination variation of some 80° to 90°, the so-called 'Nørre Lyngby declination excursion' around 14,000 B.P. A sequence of Older Yoldia clay at the same site furthermore shows significantly low inclination values, the so-called 'Rubjerg low inclination excursion' of an age between 23,000 B.P. and 40,000 B.P. Finally, a well-clustering palaeomagnetic direction from a Weichselian glacial boulder clay from Timmerhorn north of Hamburg is discussed from a hierarchical, statistical point of view.  相似文献   

Climatic Influence on Morphology and Chemistry of Nine Loess-Profiles,Argentine     

PETER FREDERIKSEN M.Sc. 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(1):16-24

Frcdcriksen, Peter: Climatic influence on morphology and chemistry of nine loess profiles, Argentine. Geografisk Tiddskrift 81:16–24. Copenhagen, October, 1981.

Nine profiles developed in loess under a subtropical, continental climate with a pronounced climatic gradient (udic to aridicj were investigated morphologically and chemically in order to elucidate the influence of climate on soil genesis. Four morphological types developed: a) A1A2BtC-soils, b) ABC-soils, c) A(B)C-soils and d) AC-soils. Some variations could be related to the climatic variation, others were better related to texture or to palaeoclimatic (periglacial) conditions.  相似文献   

The U.K. Regional Research Laboratory Initiative 1987–1991     

PETER A. BURROUGH  ANDY BODDINGTON 《International journal of geographical information science》2013,27(5):425-440

Abstract

The Economic and Social Research Council in the United Kingdom (U.K.) established the Regional Research Laboratory (RRL) Initiative in 1987 to improve facilities for data processing in the social sciences. The Trial Phase in 1987, which was modestly funded for 18 months, established four trial sites and a National Co-ordinator. The Main Phase of the Initiative, covering 8 laboratories at 10 locations, was launched in October 1988, following submission and selection of proposals. Although not originally planned as such, the initiative became a Geographical Information Systems (GIS) programme because the best proposals came from geographers and planners skilled in the processing of spatial data and because of interest stimulated by the influential Chorley Report. This article reviews the major aims of the Initiative and the progress reached after two years to September 1990. The initiative was highly effective in stimulating new research and development work that had regional, national and international dimensions. Nevertheless, with the exception of one RLL, funding has not been continued beyond 1991 and the initiative has been replaced by a network of University Departments working to continue the academic work with GIS in the U.K. for the next three years.  相似文献   

PLACE INVADERS: CONSTRUCTING THE NOMADIC THREAT IN ENGLAND*     

PETER KABACHNIK 《Geographical review》2010,100(1):90-108

Over the centuries, the image of nomads threatening sedentary ways of life has been a common pejorative representation. In order to understand what geographies underpin narratives about nomads, I examine how social theory and media representations invoke the image of nomads. Both media and academic representations are buttressed by limited understandings of place and space, framing nomads as the quintessential “place invaders.” Focusing on nomadic Gypsies and Travelers in England provides a contemporary example of this process. British media representations construct nomadic Gypsies and Travelers in England as out‐of‐place and threatening. Deconstructing essentialist geographical conceptions allows us to avoid reproducing the common image of placeless nomads, reveals how people utilize place to render others inferior, and highlights the fact that conflicts between nomadic and sedentary ways of life are not intractable and natural. Adopting a more nuanced understanding of place can challenge the dominant trope of nomads as place invaders.  相似文献