摘要:

Examination two peat samples collected at Kep København, Peary Land, Northgreenland, revealed the presence fo fossils ofBetula nana, Menyanthes trifoliataand other plants which do not occur as fao north today. likewise, remains fo Cladocera (e.g.Alonella excisa), beetles (e. g.Gyrinus opacusandBembidion grapi) and other animals, none of which live in the area today, are present. The occurrence of these fossils, coupled with a radiocarbon date giving an infinite age, suggest that the peat is an interglacials deposit

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00713.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Relative a absolute (pollen concentration) diagrams are presented from Bergebyvatnet, Holmfjellvatnet and Stjernevatnet on Varanger peninsula. All three sites are outside the younger Dryas (Main substage) moraines and the pollen assemblage zones are correlated biostratigraphically with chronozones from Allerød to Middle Flandrian. Radiocarbon dates from Bergebyvatnet appear to have been affected by hard water error, but dates from the other two sites agree will with the inferred chronostratigraphy. Pollen diagrams from Varanger peninsula suggest broadly similar vegetational histories, the longest record beign that from Østcrvatnet (H. C. Prentice 1981,Boreas, Vol. 10, pp. 53–70). Open tundra‐like conditions prevailed throughout the Late Weichselian, withSalixdominance interrupted by unstable vegetation with abundantArtemisiaduring the Older and Younger Dryas zones. Major vegetational and floristic changes began just before 10,000 B.P., the rapid scquence from herb pollen flora was rich and varied, including a mixture of floristic clements similar to that found during the Late Weichselian in southern Scandinavia. Basiphilous herbs were particularly abundant at Østervatnet and Bergebyvtnet.Betula nandand species of Ericales became locallydominant just before the full establishment ofB. pubescens, which rapidly spread beyond its present limit. Later immigrants includedAlnus incana; Juniperus communis; andPinus sylvestris, which reached the south wester

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00714.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Pollen, macrofossils and matrix composition are described for a 221 cm core from a polygonal peatland overlying a late‐Wisconsin lakebed. A hydroseral succession of wetland communities occurred at the site, and included a submerged assemblage withChara, aCarex aquatilis ‐ Eleocharismarsh, a fen, and finally aSphagnum ‐ Ledumbog. A transition about 9,600 B.P. to a wetterS. balticum ‐ Andromedacarpet is attributed to formation of permaforst and polygonal ice wedges. This community, sometimes withS. compactumandChamaedaphne, prevailed until about 3,000 B.P. when the polygon became high centered, and peat growth declined. Peat growth rate is determined from 1114C dates, and is used to calculate pollen influx. Apparent periodic oscillations every 2,000 years, in total influx, are not accepted as sufficient evidence of treeline fluct

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00715.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

A difference in the size of Neoglacial lateral moraines on either side of a valley axis (within‐valley asymmetry of lateral moraine development) is described. Analysis of clast roundness has revealed subangular material in latero‐terminal and terminal moraines; lateral moraines, however, exhibit a compositional gradient of increasing angularity with distance from the former glacier snout. Comparisons with clasts of known origin suggest that this ‘roundness gradient’ may be explained with reference to either or both of two hypotheses: (1) a variable proportion of supraglacial (or englacial) to subglacial transported material; and (2) the variable composition of regolith incorporated by a push mechanism from the valley sides. Within‐valley asymmetry is inferred to result where the supply of debris to lateral moraines from these sources is unequal either side of a valley axis. Both interpretations are also consistent with the relatively large size of latero‐terminal sections of end moraines. In order to account for the discrepancy between moraine size and apparent debris supply rates, it is suggested that the largest lateral moraines may have been formed over a longer time scale than the ‘Little Ice Age’, and that reworking of deposits may have occurred. The supply of debris to the north‐facing lateral moraine at Nordre Illåbreen has been so great that it has developed into a rock glacier; this suggests the possibility that subglacial material and valley‐side regolith, as well as supraglacial material, contributes to the formation of ice

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00716.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Three kinds of end moraines, depending most probably on climatic conditions affecting depositional environments, are characterized: (1) fluvioglacial end moraines ‐ built of gravels and sands froming fans superimposed on one another, and accumulated by abundant melt water during intense melting of an ice front in a comparatively warm environment; (2) ‘Glacial’ end moraines ‐ built of flow tills accumulated during slow melting in a comparatively cold environment; and (3) fluvioglacial‐and‐glacial end moraines, the most widespread ones in Polish lowlands – built of fluvioglacial stratified gravels and sands and of glacial ‘flow’ deposits; zones of considerable prevalence of glacial deposits over fluvioglacial ones may probably point to comparatively cold stages during deposition, and vice versa. The question of deposition of end moraines in distal and proximal direction, and their geological and geomorphological features is also

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00717.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Deposition of till by melt‐out was described as early as a hundred years ago, and today the criteria which provide evidence to support an interpretation of melt‐out till are available. The most important criteria are (P1) the presence of unlithified, sorted and stratified sediments within or interstratified with the till(s). (P2) the presence of a statistically preferred orientation of stone axes closely related to ice‐flow condition, and (P3) a configuration of till with a recognizable textural or lithological property closely related to the configruation of englacial debris with regard to P1. Based on P1and P2and on regional aspects, tills composing ridges transverse to the dircetion of ice flow are interpreted as mult‐out till and flow till. The interpretation of till genesis must be based on the balnce of probability, as absolute proof is unrealistic in mos

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00718.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Book reviewed in this article:A stratigraphic study of Late Weichselian de‐glaciation, shore displacement and vegetation history in southeastern Swede

ISSN:0300-9483    

DOI:10.1111/j.1502-3885.1982.tb00719.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY