Jökull


Jökull - 01.12.1982, Side 9

Jökull - 01.12.1982, Side 9
in the Reykjavík area show an ice movement from the south-southeast, while in the Akranes area they are oriented from the northeast. Another conclusion, once again based on much experience from Scandinavia and exemplified by the situation on Grímsey, is that in coastal areas with irregular topography both above and below sea level the direction of the receding ice front and thereby also of the glacial striae changed contin- uously. This is the reason why double sets of striae appear now and then. VVell known examples are from Arbaer on the outskirts of Reykjavík and from the surroundings of Borgarnes. BREIDAFJÖRDUR (Fig. 5) Thoroddsen (1906, p. 327) having observed traces of glaciation both on the northern side of Snaefells- nes and on the southern side of the Vestfirdir pen- insula as well as in the innermost tributary fjords to Breidaljördur (Hvammsfjördur and Gilsfjördur), considered it „very interesting to know if the islands tn Breidaljördur south of Bardastrandarsýsla were glacially striated and, ifso, what was the direction of the striae“. He mentions that these islands never had been visited by geologists. Kjartansson (1955) states that he had great difli- culty in finding glacial striae on the islands of Breidafjördur, because ofwave abrasion which has attacked all the islands, forming a beautiful strand- flat. However, he made a few observations of striae on Látralönd and Skáleyar, showing ice movements from northeasterly directions. I was able to visit some of the outer islands of Breidafjörduron June 29—30, 1973. OnHeigilsey a bedrock surface was uncovered from under 0.5 m of humus and pebbles. It did not show any clear striae but was most probably affected by glacial activity, as the outcrop exhibited a stoss side to the north- northeast and a small crescentic gouge was present. On the eastern part of Flatey I found two sites with bedrock surfaces bearing definite glacial striae from the east-northeast; both sites were covered by a thin mantle of till. In the Svefneyar complex of islands I found well preserved glacial striae, coarse and thin, at several sheltered places about 2 km northeast of the farm. They showed ice movements from the northeast and east-northeast. These observations show that the ice sheet reach- ed far into theopen sea. In this connection reference should be made to a paper dealing with the same problent. In a B.S. thesis at the University of Ice- land Olajsdóttir (1974) demonstrated the existence of a long ridge, 25 to 30 m high and 800 m wide, situated outside of Breidafjördur and 140 km west of Snaefellsnes at a depth of 250 m. She believed this ridge to be an end moraine showing the outermost position of the ice sheet front during the VVeichsel or Saale glacial period. VESTFIRDIR (Fig. 5) Thoroddsen (1906) observed numerous traces ofan inland ice sheet over Vestfirdir, which he believed was separate from the main ice sheet of Iceland, although the two ice sheets were believed to be in contact at Gilsfjördur— Bitrufjördur. From the inn- er part of the peninsula outlet glaciers extended down the valleys and into the fjords. How far they extended was an open question tohim. Between the Fig. 6. Drumlinized till plateau, at Keflavík, Vestfirdir. Mynd 6. Oldóttur hjalli úr j'ókul- ruðningi í Kejlavík á Vestjjórbum. JÖKULL 32. ÁR 7
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