ISSN:0267-8179    

DOI:10.1002/jqs.3390100102

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThis is a study of Late Devensian drumlins formed in southern Anglesey and Arvon, northwest Wales. This area was affected by ice sheet coalescence when the Welsh ice sheet met with the lrish Sea ice sheet, and drumlins were formed once the two had coalesced. It is suggested that the drumlins were the result of net subglacial soft‐bed erosion, and that they represent more resistant cores within the subglacial deforming layer. The drumlins have either gravel or till cores, and where the core was deformable, large‐scale compressive glaciotectonic structures were seen (e.g. Dinas Dinlle) with local subglacial compression of –59%. Where the cores were more resistant (e.g. Lleiniog) these were not deformed but remained as more competent masses within the deforming layer. It is suggested that the less competent material flowed around the cores, some remaining as a thin carapace, but most of the material being removed down glacier, leaving the drumlins as erosional remnants.In northwest Wales there is a multi‐till sequence that traditionally has been interpreted as having been deposited as the result of separate ice‐sheet advances and retreats. However, in this study, it is suggested that the different tills were deposited as the result of ice‐sheet coalescence, and that sites such as Dinas Dinlle do not show evidence of a major readvance in the retreat of the Devensian ice, but are indicative of continuously changing conditions within the subglacial de

ISSN:0267-8179    

DOI:10.1002/jqs.3390100103

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractPleistocene deposits containing the disarticulated skeleton of a mammoth, and associated faunal and floral remains, were discovered in July 1990 at Upper Strensham, Worcestershire. The environmental evidence from the fauna and flora together with limited geological evidence, indicates that the deposits accumulated within a low energy fluvial environment with a surrounding marsh and restricted tree cover on, or close to, the floodplain. The patchy occurrence of trees in a species‐rich grassland is discussed, and the climatic significance of the fauna and flora is considered.The Strensham site lies within the valley of the River Avon, which is known to contain at least five altitudinally distinct river terraces. The deposits at Strensham lie beneath a terraced surface that cannot be accommodated within the existing framework of terrace development in the valley, and evidence is presented which may suggest that these deposits form a previously unrecognised fluvial unit, the Strensham Member of the Avon Valley Formation. Amino‐acid age estimates from shells taken from the fossiliferous sediments of the Strensham Member suggest a correlation with Oxygen Isotope Stage 7. This correlation suggests that the temperate deposits at this site should be correlated with the temperate phase recorded at Marsworth, Buckinghamshire and Stoke Goldington in the valley of the Great O

ISSN:0267-8179    

DOI:10.1002/jqs.3390100104

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractIce‐proximal sedimentological features from the northwestern Barents Sea suggest that this region was covered by a grounded ice sheet during the Late Weichselian. However, there is debate as to whether these sediments were deposited by the ice sheet at its maximum or a retreating ice sheet that had covered the whole Barents Sea. To examine the likelihood of total glaciation of the Late Weichselian Barents Sea, a numerical ice‐sheet model was run using a range of environmental conditions. Total glaciation of the Barents Sea, originating solely from Svalbard and the northwestern Barents Sea, was not predicted even under extreme environmental conditions. Therefore, if the Barents Sea was completely covered by a grounded Late Weichselian ice sheet, then a mechanism (not accounted for within the glaciological model) by which grounded ice could have formed rapidly within the central Barents Sea, may have been active during the last glaciation. Such mechanisms include (i) grounded ice migration from nearby ice sheets in Scandinavia and the central Barents Sea, (ii) the processes of sea‐ice‐induced ice‐shelf thickening and (iii) isostatic uplift of the central Barents

ISSN:0267-8179    

DOI:10.1002/jqs.3390100105

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractThe Pliocene‐Pleistocene boundary, defined using pollen analysis, has been recorded in sections at the Belchatów outcrop, Kleszczów Graben, central Poland. The boundary is located at the top of the green clay subunit of the Tertiary Clayey‐sandy unit. A pollen flora of Reuverian C type, dominated by pine, 10–20% of ‘Reuverian elements’ and scarce thermophilous Tertiary trees, was found directly below this subunit. Cold stage floras of Praetiglian type were, in turn, recorded in the Łekińsko Formation, lying directly on the green clays. The Pliocene—Pleistocene transition at Belchatów demonstrates the characteristic features of this boundary in western Europe, that is, the disappearance of Tertiary thermophilous tree pollen taxa, followed by a cooling to open‐forest or forest‐steppe conditions. Both pollen analysis and geological data suggest continuous sedimentation at least from the Upper Pliocene to the Prae‐Tiglian, with no change of sediment sources and no marked hiatuses. The fluvial deposits of the Praetiglian Łekińsko Formation, although Pleistocene in age, mark a final period in the Tertiary evolution of the Kleszczów Graben. Later, there is a hiatus to the deposition of the first glacigenic sediments in the region

ISSN:0267-8179    

DOI:10.1002/jqs.3390100106

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractDetailed palynological analyses, including pollen preservation and charcoal counts, and sedimentological analyses (loss‐on‐ignition, percentage dry weight, dry bulk density and humification), supported by 1514C dates, were applied to a small upland (350 m OD) peat basin near Pitlochry, east‐central Grampians, Scotland. Stratigraphical analyses and radiocarbon dating were also undertaken on the valley peat surrounding the basin.Organic sediment began to accumulate in the basin and on the valley floor at ca. 9800 yr BP. ‘Recurrence surfaces’ within the valley floor peat correlate with the end of a trend to increased aridity in the deep basin, from 8900 to 8500 yr BP. Pine may have colonised the hills, with birch, before the migration of hazel at 9150 yr BP. From around 8000 yr BP elm grew on the base‐rich soils. Alder may have been present by 7000 yr BP but it did not expand until immediately after the first major anthropogenic disturbance, at 4800 yr BP.Above 8000 yr BP silt was commonly deposited in the basin by streams, but several phases of exceptionally intense inwashing are identified, and at least two of these correlate with periods of increased precipitation.Grazing pressure during the elm decline marks the beginning of a long history of generally low intensity pastoralism, interspersed with periods of heightened anthropogen

ISSN:0267-8179    

DOI:10.1002/jqs.3390100107

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

摘要:

AbstractData from the Greenland ice sheet and continental records from Europe have indicated climatic fluctuations during the last interglacial (Eemian: Oxygen Isotope Substage 5e). Similar fluctuations have not, however, been documented previously from marine environments. Here, we show the existence of two cold events during substage 5e in two marine, benthic foraminiferal, shelf records from northwest Europe and suggest that these cooling events are a result of fluctuations in the strength of the North Atlantic surface‐water circulatio

ISSN:0267-8179    

DOI:10.1002/jqs.3390100108

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390100109

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390100110

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390100111

出版商:John Wiley&Sons, Ltd    

年代:1995

数据来源: WILEY