Jökull

Issue

Jökull - 01.12.1993, Page 43

Jökull - 01.12.1993, Page 43
cm h 50 Stratified eolian sand - 40 - 30 - 20 - 10 - 0 ö . -o Palaeosoil Black tephra layer The Miöfjöröur Tephra Stratified sand and fine sand Cross-bedded sand and gravel Figure 8. The sediment succession at the boundary between the fluvioglacial terrace sediments and the discordantly overlying channel fill with tephra layers (cf. Figure 7). — Jarðlagasnið er sýnir skipan jarð- laga í brún sethjallans við Miðfjörð. 30 m shoreline must be situated roughly parallel to the isobases and that the main glacial overburden load was situated to the south-west of there. The final part of the deglaciation history in the area comprises a regression of sea-level and withdrawal of the glaciers towards a few ice-divides or ice-centres in the mountainous inland parts of the area (Figure 9). Kjartansson (1955) and later Pétursson (1986, 1991) reconstructed a major Lateglacial ice-divide above the central and southern parts of the Melrakkasléttapenin- sula and the neo-volcanic zone. However, glacial striae in the southeastern part of the studied area indi- cate that another ice-divide was situated on the present water-divide between the Bakkaflói and Vopnafjörður areas and also in the mountainous southern part of the Langanes peninsula (Figure 9). Consequently, these elevated parts of the area most likely hosted the last remains of the Lateglacial glaciers. As relevant 14C-datable material has not yet been found in the study area, the apparent age of the events Figure 9. Main Lateglacial and early Holocene ice- divides, regional marine limit and ice-marginal forma- tions in northeast Iceland. Glacial striae are fromKjar- tansson (1955), K. Sæmundsson (1977) and Pétursson (1986). — Helstu ísaskil, fjörumörk og lega jökul- jaðra á síðjökultíma og í upphafi nútíma á Norðaust- urlandi. Stefna jökulráka er samkvæmt ritum Guð- mundar Kjartanssonar (1955), Kristjáns Sœmunds- sonar (1977) og Halldórs G. Péturssonar (1986). outlined above can only be suggested by comparison with 14C-dated events in adjacent areas. The earliest part of the Lateglacial deglaciation history of northeast Iceland has been 14C-dated to about 12,700 BP on the western Melrakkaslétta peninsula (Pétursson, 1991). We, therefore, assume that present-day dry land in the study area was first deglaciated at a similar or even a later date, when scattered shoreline features were formed at 65 m and 50-40 m a.s.l. in the outer coastal parts of the area. A readvance or a standstill of the glacier mar- gin in the Vopnafjörður area, some 25 km south of the Bakkaflói bay, has been 14C-dated to about 9700 BP (Norðdahl and Hjort, 1987; Th. Sæmundsson, 1994). At that time the glaciers in the Vopnafjörður area reached a position some distance inland from the JÖKULL, No. 43, 1993 41

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