Age determination of fossil ice-wedge polygons in Nordic areas
DOI:
https://doi.org/10.26485/BP/1982/29/2`1Keywords:
frost structures, relative age determination, radiocarbon dating, tephrochronology, Norway, Sweden, IcelandAbstract
In the Nordic areas there are indications of fossil ice-wedge polygons in the ground surface, e.g. as: (1) a pattern of shallow furrows, (2) crop marks in cultivated areas. Where the original ground pattern has been destroyed, the existence of a former polygon pattern is indicated by ice-wedge casts which are observable in vertical sections, for instance in gravel pits.
The paper intends to give a survey of and to discuss applicable methods for dating the formation or fossilization of such ice-wedge polygons. The examples have been chosen from those areas in northern Norway which are included in the excursion program, but experiences from two other areas are also referred to, namely the Swedish west coast and Iceland.
Two aspects are treated in the chronological discussion: relative and absolute dating. For an absolute dating of polygons in coastal areas a reliable shoreline diagram is a very valuable tool. Moreover C-14 datings are a possible means of estimating the age of polygon furrows.
In Iceland, tephro-chronology offers a unique possibility for discussing geomorphological sequences; in this case, not only to determine the age, but also to analyse the material supplied and the structural details at the infilling of frost fissures.
Finally it is pointed out that an age determination of polygon patterns are not only of interest for producing a time scale of ice-wedge development or fossilization, but also to yield information on the climatic conditions prevailing in late-glacial time.
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