Jökull


Jökull - 01.12.1984, Side 128

Jökull - 01.12.1984, Side 128
and concluded that the moist south-westerly winds and the short distance from the sea enabled glacier growth below 1000 m altitude in Skardsheidi. Keilhack (1886) described large snowfields at the locality described by Ólafsson (1772), and found it interesting that a cirque-gla- cier should begin to grow prior to any visible signs of glacier growth at the higher elevated plateaux. He suggested that the Skardsheidi plateau was large enough to sustain its own ice- cap, given favourable circumstances. Thoroddsen (1891, 1958) described two small glaciers in Skardsheidi above Skorradalur and discussed their sensitivity to climatic variations. According to Thoroddsen (1958) the glaciers were very small during the warm and dry summer of 1888, but grew considerably during the wet summer of 1890, at which time the glaciers reached down below 300 m altitude. During the first decade of the 20th century the Skardsheidi glaciers seem to have melted rapidly. According to Bárdarson (1934) the Skardsheidi glaciers had retreated to above 800 m altitude by 1910. Eythorsson (1931) only found traces of these glaciers. Bárdarson (1934) and Thorarinsson (1943) surveyed the literature concerning the glaciers and commented on their oscillations. DISCUSSION When reviewing the geological literature on the Late Weichselian of the Borgarfjördur region, it is evident that many problems have remained unsolved or controversial. The lithos- tratigraphy of the area is not well known, and formal lithostratigraphical division of the sedi- ments has not been proposed for any part of the sequence. The work of Bárdarson (1923) does not meet modern requirements for quantitative methods or precision. The sections described by Ashwell (1967, 1975) and Ingólfsson (1981) need to be reexamined with the aim of lithostra- tigraphical correlation between different parts of the region. Most workers have only visited the region briefly, and their observations are often casual and difficult to correlate in order to form a concise picture of the Late Weichselian glacia- tion. The chronostratigraphy of the region can only be considered preliminary as the radiocar- bon dates on which it is based (Table 1) only date a small part of the sequence. A detailed chronos- tratigraphical scheme for the sequence is there- fore lacking. The sea level changes in the region are not well known and only a few careful levell- ings of ancient shore lines have been carried out. Bárdarson’s evidence for two transgressions in the region has not been reexamined, and correla- tions of sea levels with sections of the strata are fragmentary and often controversial. Reconstruc- tions of palaeoenvironments are contradictory and have not been integrated with any facies analysis of the sediments. The existence of tills or other glacial deposits is a matter of dispute. A detailed geological map of the region has not been compiled, and the surface extent of the various sediments is not well known. CONCLUSIONS The literature reviewed in this paper gives clear indication of the vast sedimentary deposits in the Borgarfjördur region, and some insight into the many aspects involved concerning the interpretation of their formation and environ- ments of deposition. The lack of detailed know- ledge of the stratigraphy allows for various interpretations of the Late Weichselian processes in the region. Further research has potential significance in two interconnected fields of research: Firstly it can contribute to a more solid model of the Late Weichselian glaciation than presently exists for Western Iceland, and can as such have implica- tions for the general picture of glacial geology in Iceland. Secondly it can contribute to the intense scientific debate on the Weichselian glacier varia- tions in the North Atlantic region (for discussion see e.g. Andrews and Barry 1978, Boulton 1979, Hughes et al. 1981, Hjort 1981, Andersen 1981, Ruddiman and Mclntyre 1981, Funder 1982, Boulton et al. 1982, Salvigsen and Österholm 1982). As Iceland lies geographically in the mid- dle of the North Atlantic region, it could be expected to contribute valuable evidence on the topic of Late Weichselian glaciations in the region. But the incomplete stratigraphical control of the available data in Iceland renders the value of the Icelandic contribution somewhat limited. ACKNOWLEDGEMENTS 7 arn indebted to the following people for their assistance: Professor Th. Einarsson, for initiating the research project of which this paper is a part, 126 JÖKULL 34. ÁR
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