Jökull


Jökull - 01.12.1982, Page 10

Jökull - 01.12.1982, Page 10
difierent glacial streams nunataks might have exist- ed. Kjartansson’s map (1969) of Nordvesturland con- tains numerous observations of glacial striae from different parts of the peninsula, giving a more de- tailed view of ice movement. My own observations only cover the southwest- ernmost peninsula, with the well known Látra- bjarg, the westemmost point of Europe. They were made during a stay from 6 to 9 July, 1976. The higher parts of the peninsula consist of bare rock, often heavily frostshattered.. Till is present only at lower elevations. Thoroddsen (1906, p. 325) made an interesdngobservation in the small bay of Keflavík, which he considered to be part of an old glacial cirque. He observed ,,a terrace, 66 m high, with striated pebbles, which seems to be an old moraine, reworked by the sea”. The “terrace” (Fig. 6) is about 400x400 m, in its eastern part divided by a creek. It has a core of bedrock. What Thoroddsen did not observe is that the terrace is beautifully drumlinized, with 8 to 10 ridges oriented north- south and up to 2 m high. The ridges have been modified by frost processes, and their surfaces are covered by stone stripes. The drumlins were not necessarily formed by a cirque glacier. Glacial striae were observed at several places, well preserved, however, only when protected by a cover of till. At the road to the Látrabjarg light- house not only is the bedrock surface striated, but also the boulders in the till are striated in the same direction. The striae of the peninsula, observed to eleva- tions of at least 200 m, demonstrate ice flow in all directions from its central highlands. In accordance with earlier interpretations the icemovements were largely inherited from the ice retreat in the sur- rounding sea, the level of which reached several tens of m higher in the area than now. It is very probable that the whole of this very peripheral peninsula was covered by an isolated ice cap, at the end of the glaciation. Some observations from the sea bottom outside of Vestfirdir may be added. In his Ph.D. thesis Kjartan Thors (1974) came to the conclusion that the shelf outside of Vestíirdir was shaped predominantly by glacial processes. “Glacial outwash was attacked by a transgressing sea and redistributed, although the coarsest gravels were left more or less in situ. The relict shelf surface has seen no terrigenous sedi- mentation during the Holocene, but biological pro- ductivity has continued to the present day.” (Letter from Dr. Thors of 14.11. 1974). NORTHEASTERN ICELAND Thoroddsen (1906) recorded traces ofglaciation at several localities in northeastern Iceland, such as the impressive glaciofluvial terraces in the Vopna- fjördur valley, tills and erratics on Langanes, and glacial striae on Langanes, Fagranes and Melrakka- slétta. Kjartansson (1955) added some new observa- tions of glacial striae from Melrakkaslétta. Finally the geological map oflceland, Sheet 7, compiled by Saemundsson (1977) records a great number of striae in the whole coastal area from Melrakkaslétta in the northwest to Vopnafjördur in the southeast. My own observations in the area were made on July 10 to 11, 1972, on Melrakkaslétta and Langanes and in the Vopnafjördur district on August 21, 1974, this time in the company with Sigurdur Thorarinsson. My striae observations seem in the main to appear on the geological map, to which the reader is referr- ed. The observations indicate that the whole north- east coast of Iceland between Axarfjördur and Hér- adsflói was inundated by the inland ice sheet. 'Fhe radiating pattern of striae on Melrakkaslétta once again reflects the pattern of deglaciation typical of ice retreat in the sea. Langanes was overridden by ice flowing from the south; this indicates a sign- ificant ice thickness even in this northeasternmost corner of Iceland. SOUTHEASTERN ICELAND Thoroddsen (1906) did not pay much attention to traces of glacial activity in this region. However, he gives some information about glacial striae from the inner parts of the Berufjördur, Hamarsfjördur, Alftafjördur and Hornafjördur areas. Kjartansson (1962), in his comments on Trausti Einarsson’s paper „An unglaciated area in Eastern Iceland” refers to own observations of glacial striae on a headland between Berufjördur and Hamarsfjördur and on promontories in Alftafjördur and Lón. “In all this area the fjord glaciers extending from the inland ice-sheet seem to have coalesced in front of the interjacent mountain ridges, to form an almost uninterrupted brim of a piedmont glacier on the coastal plain. The possibility that the glacial traces referred to might be older than the last (or Wurm) glaciation, is discussed and rejected.” My own observations in the area were made during several visits, starting in 1952. Roches mout- 8 JÖKULL 32. ÁR
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