摘要:

AbstractIn a pilot study three samples of diamictons from boreholes in the Dutch sector of the North Sea have been thin sectioned. In the thin sections the granulometry, structure and plasmic fabric of the diamictons have been studied. On the basis of this study two of the samples have been interpreted as flow tills, while one sample has been interpreted as a basal (lodgement) till.

ISSN:0267-8179    

DOI:10.1002/jqs.3390050202

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPollen data are the most important source of information with respect to late Quaternary vegetation history. Broad‐scale palaeovegetation patterns have been subjectively inferred from mapped pollen data by previous authors. In this study, multivariate classification was applied to European pollen data for the last 13 000 yr. The resulting clusters are mapped at millennial intervals and can be equated with vegetation units. The maps portray the changing vegetation of Europe since the last glacial. They reveal the impermanence of the assemblages of species that ecologists recognise as communities. The dominant patterns in the maps also change through time, indicating important changes in palaeoenvironmental conditions and in the alignment of major environmental gradients. Human impact upon European vegetation history is seen to be relatively unimportant when the vegetation is viewed at a continental scal

ISSN:0267-8179    

DOI:10.1002/jqs.3390050203

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractData from 92 postglacial pollen sequences are used to map the spread and increase of alder (Alnus glutinosa) across the British Isles between 9000 and 5000 years ago. The spread is found to be patchy and erratic in space and time. Consideration of the habitat requirements and reproductive ecology of alder suggest that it spread within Britain and Ireland after about 10 000 yr BP, when suitable habitat for it was scarce. Alder spread across most of Britain and Ireland early in the postglacial but only increased in abundance as (i) suitable habitat became available through changing sea levels, hydroseral successions, and floodplain development, and as (ii) rare weather events produced the necessary conditions for reproduction. Alder is unique among British and Irish trees in its requirement for a suitable habitat isolated among expanses of unsuitable habitats. Because of this, maps of its postglacial population spread and increase do not show the spatial coherence of maps for other forest tree taxa.

ISSN:0267-8179    

DOI:10.1002/jqs.3390050204

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractRadiocarbon dates are described from a section through Lateglacial and early Flandrian sediments at Llanilid, Mid‐Glamorgan, South Wales. Comparisons between age determinations on the alkali soluble (humic) and alkali insoluble (humin) organic fractions from 12 biostratigraphic horizons reveal the extent of contamination by both older and younger carbon residues. The Llanilid time‐scale suggests that for the Lateglacial, the earliest organic sediments date from around 13 200 yr BP, the early InterstadialJuniperusmaximum occurred at ca. 12 400‐12 500 yr BP with a marked decline some 200 years later, the mainBetulaphase lasted only from ca. 11 700 to 11 400 yr BP and the end of the Interstadial occurred around 11 100 yr BP. The beginning of the Flandrian dates from ca. 10 000 yr BP, theJuniperusmaximum occurred approximately 200 years later, the expansion of birch woodland began around 9600 yr BP, while the first hazel arrived in the area at ca. 9300 yr BP. These age determinations are discussed in the context of radiocarbon dates from comparable biostratigraphic horizons in western Britain and the dating of Lateglacial events in the ocean core records from the North Atl

ISSN:0267-8179    

DOI:10.1002/jqs.3390050205

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPleistocene sediments and soils exposed at Stebbing in central Essex, England are described, analysed and interpreted. The sand and gravel units above Eocene London Clay and Upper Pliocene Red Crag are shown to be a high level member of the Kesgrave Formation, with a surface immediately beneath that of the Westland Green Gravels, which are tentatively assigned to the Pre‐Pastonian ‘a’ Stage of the British Quaternary succession. The rubified, argillic soil developed in the surface of these fluvial deposits is a composite of the Valley Farm and Barham Soils and displays micromorphological evidence of several phases of clay illuviation, gleying and clay coating disruption. Originally truncated and buried beneath Anglian gelifluction deposits, cover sand and till, the soil has been exhumed in most places by subsequent erosion. The full succession, however, is preserved within large gulls that formed by periglacial cambering prior to this erosion. More recent loess incorporation and pedogenesis have modified the exhumed soil and the materials within the

ISSN:0267-8179    

DOI:10.1002/jqs.3390050206

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390050208

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390050210

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390050211

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390050213

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY

ISSN:0267-8179    

DOI:10.1002/jqs.3390050214

出版商:John Wiley&Sons, Ltd    

年代:1990

数据来源: WILEY