Jökull


Jökull - 01.12.1984, Side 121

Jökull - 01.12.1984, Side 121
area and to point out the most important aspects of future research. It is hoped that the literature survey will also give some insight into the present position of Late Weichselian studies in Iceland in general. In this paper the term Weichselian substitutes the term Last Glaciation, and Late Weichselian is used for Late Glacial. This is in agreement with the proposal of Mangerud et al. (1974) for the terminology and classification of the Quaternary stratigraphy of Norden. The lower boundary of the Late Weichselian is taken to be 25.000 years BP as proposed by Mangerud and Berglund (1978). This terminology has previously been applied in Iceland by Th. Einarsson (1967), Norddahl (1979, 1981, 1983) and Andersen (1981). RESEARCH HISTORY Earliest research During the years 1753—57 the Icelandic naturalist Eggert Ólafsson visited the Borgarfjör- dur region. Ólafsson (1772) made the first stra- tigraphical observation in the area when he dis- tinguished three clay units in the lowlands of Leirársveit, one of which he considered to be of marine origin. He also discovered localities at the Leirá- and Laxá rivers where subfossil marine molluscs are preserved in the sediments. Ólafs- son concluded that the oceans were diminishing, resulting in the emergence of land from the sea. Ólafsson’s localities at Leirá and Laxá became somewhat classic in the 19th century geological literature on Iceland, and were frequently refer- red to (Paijkull 1867, Mörch 1871, Keilhack 1884, 1886, Thoroddsen 1892, Hallgrímsson 1934). The Icelandic geologist and poet Jónas Hallgrímsson and the Danish zoologist Japetus Steenstrup visited the Borgarfjördur region in 1840. Hallgrímsson (1934) briefly described a bluish marine clay he observed at a few localities on the lowland south of the Hafnarf- jall-Skardsheidi massif. He suggested fluviogla- cial origin for laminated deposits he observed in the vicinity of the River Hvítá. Hallgrímsson was the first investigator to visit the Melabakkar cliffs, where a roughly five km long coastal sec- tion of sediments is exposed. He was convinced that the marine sediments had emerged from the sea because of land upheaval, which he consi- dered still to be active. Although Steenstrup never published any of the results from his research in Iceland, he contributed considerable data to later workers (Thoroddsen 1902, 1911, 1913). Bárdarson (1923) published and discussed a list of mollusc species collected in the Borgarf- jördur region by Jónas Hallgrímsson and identi- fied by Japetus Steenstrup. The first geological maps of Iceland were pub- lished by Paijkull (1867) and Keilhack (1886). They both remarked on the fossiliferous sedi- ments in Leirársveit. Paijkull was one of the first geologists to point out the importance of glacial erosion in the sculpturing of the Icelandic land- scape. Helland (1882) referred to Paijkull on glacial erosion in Iceland, and added that Lake Skorradalsvatn occupies an ice-scoured hollow. The contributions of Keilhack and Thoroddsen Keilhack (1884) wrote an important paper on the postglacial marine deposits of Iceland. He published a compiled map of Iceland showing areas formerly submerged, which included the Borgarfjörður region. This map is more accurate than the corresponding map published by Thor- oddsen (1892), and it was not matched in details until Th. Einarsson (1961, 1963) presented a similar map with isobases. Keilhack determined the upper limit of marine clay in western Iceland to be at about 40 m above present sea level. He concluded that the clay had been deposited by glacial rivers at the end of the glaciation, and pointed out that similar clay is still being depo- sited off the coasts of Iceland. Keilhack (1884) discussed a list of mollusc species which he col- lected from clay deposits at many localities in Iceland, and suggested that arctic conditions were prevalent during the deposition of the clay. Pjetursson (1905) pointed out that Keilhack had not distinguished between Late Weichselian and Interglacial sediments found in the vicinity of Reykjavík. However, Keilhack’s general conclu- sions on the arctic character of the fossil fauna were later confirmed by Bárdarson (1923), Áskelsson (1934) and Kjartansson (1943). Keilhack (1884, p. 160) correlated the clay deposits with the “upper drift deposits of Scot- land, the Yoldia clay of Scandinavia and the Champlain-Formation of North America”. Keilhack (1886) mapped the Melasveit and Leirársveit sediments as fluvioglacial deposits, thereby suggesting the existence of glaciers in the near vicinity at the time of their deposition. JÖKULL 34. ÁR 119
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