ISSN:0267-8179    

DOI:10.1002/jqs.3390060102

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractIn this paper we use the mineral magnetic data (χ and χfd) to stratigraphically correlate different loess‐palaeosol profiles in Kashmir Valley. The two available thermoluminescence (TL) chronologies on the Kashmir loess profiles have been reinterpreted to identify the soil of the Last Interglacial (ca. 125 000 yr BP). We show that the mineral magnetic data correlates well with the global marine δ18O record. This correlation has revealed the well‐known Milankovich periodicities of 40 ka and 20 ka in the loess‐palaeosol record. On the basis of this study, we conclude that loess deposition in the Kashmir Valley started around 200 ka and not 350 ka ago as suggested by earlier workers, and that magnetic susceptibility variations provide a tool to decipher climatic changes from loess‐palaeosol

ISSN:0267-8179    

DOI:10.1002/jqs.3390060103

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractEmploying an average vertical sampling interval of 20 cm, oriented samples were collected from 26 m of the loess section at Liujiapo, near Xian, China in order to refine the existing magnetostratigraphic record. Palaeomagnetic results reveal two short reversed‐polarity subzones within a profile of predominantly normally magnetised sediments, an interpretation that is at variance with previous results from this section and from other studies of Chinese loess. Investigation of sediment mineral‐magnetic properties indicates a close correspondence between down‐section variations in intensity of magnetisation, susceptibility and saturation isothermal Journal of Quaternary Science remanence (SIRM), and lithology. The ratios IRM‐100mT/SIRM and SIRM/ susceptibility appear to be particularly sensitive indicators of the degree of soil development and hence of palaeo

ISSN:0267-8179    

DOI:10.1002/jqs.3390060104

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractAeolian sand transport during winter and the snow‐free season was assessed quantitatively by direct year‐round field measurements along transects on the lee side of parabolic dunes in subarctic Québec. In 1987–1988, niveo‐aeolian deposition was more important than aeolian sedimentation in three of the four study sites, and contributed>75% of the total annual accumulation in exposed sites and<25% in protected forest sites. The maximum depth of interstratified snow and sand deposits (3.5 m) was recorded in March. Semi‐permanent snow lenses may persist longer than 2 years in the aeolian sediments. After dissipation of snow, 22 cm of sand (as a maximum) accumulated on the slipface of the most active dunes, whereas only minor sand accumulation occurred in distant areas from active sand erosion. Wind‐driven sand was dispersed over 7.4 km2in the Whapmagoostui‐Kuujjuarapik area. The acumulation of snow and sand during the snow season, together with spring thaw and collapse of the niveo‐aeolian deposit, caused different types of injuries to trees, especially in 1985 and 1987 when a maximum of torn branches was recorded over the las

ISSN:0267-8179    

DOI:10.1002/jqs.3390060105

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe Baginton Sand and Gravel is traced along the lower Wreake Valley as a continuous water‐laid stratum at the base of the drift succession. Its properties closely resemble those previously described from the proto‐Soar valley, namely an upward fining sequence and a composition dominated by pebbles of Triassic and Carboniferous origin. Such a provenance is consistent with the idea that the proto‐Soar once followed a route eastwards past Melton Mowbray, and that the drainage along the lower Wreake Valley has been reversed in the course of Pleistocene times. However, the slope of the sand and gravel train appears to be to the west rather than the east, and the rockhead relief is also inconsistent with an eastward‐flowing proto‐Soar. Until this enigma is resolved, it would be imprudent to use the Baginton Sand and Gravel as the basis for inter‐regional correlations. The issue is further complicated by the preservation at Brooksby of earlier interglacial or interstadial deposits whose temporal affinities rem

ISSN:0267-8179    

DOI:10.1002/jqs.3390060106

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractExcavation of peat and clay filling a sink hole has provided a relatively long late glacial to Holocene pollen/vegetation record for the King Valley. The record shows a change from alpine herbland,Microstrobosscrub and heath at 13 ka BP toEucalyptussubalpine woodland.Phyllocladus‐Nothofagusrainforest succeeded after 12.5 ka BP but degenerated to scrub rainforest after 11 ka BP, whenLagarostrobos frankliniiexpanded. The sequence of local changes occurred while the sink‐hole lake was being rapidly infilled and converted to topogenous peat around 12 ka BP.Examination of the timing of changes in vegetation associations in other pollen profiles from different altitudes in western Tasmania indicates that many of the changes are non‐synchronous and cannot be related directly to climatic events. They probably reflect the effects of both biological and local environmental factors.The major regional climatic change from alpine to temperate conditions on the lowlands occurred ca. 13 ka BP. Demonstration of non‐synchronous changes in the late glacial to early Holocene pollen/vegetation associations at several sites contrasts with the view of Markgrafet al., who infer synchronous changes related to climate. There are no indications in the pollen/vegetation sequence of either Allerød or Younger Dryas events in western

ISSN:0267-8179    

DOI:10.1002/jqs.3390060107

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

摘要:

AbstractThe nature and origin of glacial sediments at Wylfa Head are described, and their significance with regard to sedimentary environments during Late Devensian deglaciation of the Irish Sea Basin is discussed. Recent models of deglaciation under glaciomarine conditions are challenged. The Quaternary sequence at Wylfa consists of eroded and glaciotectonically deformed bedrock, locally derived lodgement till, calcareous silt‐rich lodgement till containing northern erratics, discontinuous units of orange‐brown silty sand of possible aeolian origin, and grey laminated freshwater silts filling a small kettle hole. The till units thicken to the south where the surface is drumlinised. It is concluded that the landforms and deposits result from a warm‐based Irish Sea glacier, which moved towards the southwest. Spatial variation in basal water pressure resulted from localised drainage through zones of more heavily jointed bedrock. Rapid glacial erosion occurred in areas where subglacial water pressure was relatively high, while deposition of the resulting basal sediment took place where water pressures were reduced. The glacier also carried basal calcareous silty till onshore, which was deposited by lodgement processes. None of the deposits at Wylfa are interpreted as glaciomarine in origin, and there is no evidence at this site for an isostatically induced marine transgression prior to deglaci

ISSN:0267-8179    

DOI:10.1002/jqs.3390060108

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390060109

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390060110

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390060112

出版商:John Wiley&Sons, Ltd    

年代:1991

数据来源: WILEY