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Jökull - 01.12.1990, Qupperneq 39

Jökull - 01.12.1990, Qupperneq 39
advanced and was probably divided by Akrafjall as the glacier reached out into the mouth of the fjord. The marine limit at 80-90 m a.s.l. was probably reached during this readvance of the glaciers, which is referred t0 as the Skipanes event (Fig. 5). Close to 11,700 B.P., the Borgarfjörðurglacier and the glacier in Hval- fjörður both retreated to an unknown position (Ingólfs- son, 1988). Simultaneously with the recession of the glaciers relative sea-level was lowered, although not falling below the 35 m level. This episode of glacier retreat and regression of relative sea-level is referred to as the Látrar event and has been 14C dated be- tween 11,715 ± 120 B.P. (Lu-2372) and 10,965 ± 80 B-P (Lu-2056) (Ingólfsson, 1988). Some time around 11,000 B .P. the glacier in Borgarfjörður advanced and reached a position similar to the one reached during the Skipanes event, and formed the conspicuous Skor- holtsmelar moraine (Fig. 5). This episode of glacier advance has been named the Skorholtsmelar event and it was terminated close to 10,155 ± 150 B.P. (Lu- 2378). About 10,300 B.P. the glacier retreated from the Skorholtsmelar moraine when relative sea-level was 60-70 m a.s.l. (Fig. 5). Subsequently relative sea-level fell towards present sea-level. This event has been named the Melabakkar event (Ingólfsson, 1988). Additionally, Ingólfsson (1988) assumed that an intermittent 40-50 m raised shorelevel could be of Preboreal age and possibly have been formed concur- rently with a glacial episode in the upper Borgarfjörður tributary valleys. The most important result from these studies in the lower Borgarfjörður region is the occurrence of two Late Weichselian glacier advances and retreats (stadials and interstadials). The stadials, the Skipanes and Skorholtsmelar events culminated about 11,800 and 10,600 B.P. respectively, closely correspond to the Older Dryas and the Younger Dryas stadials, and the Asbakkar and Látrar events consequently corre- spond to the Bplling and the Aileröd interstadials in Northwest Europe. The Melabakkar event covers the latest part of the Younger Dryas Chronozone and the heginning of the Holocene (Ingólfsson, 1988). An- °ther and equally interesting conclusion is that the Icelandic inland ice sheet and its outlet glaciers were ntuch more extensive in Younger Dryas time than Figure 6. Late Weichselian and early Holocene end-moraines and marine-limit features in Northeast Iceland. Legend: 1) 14C dates. 2) Raised beaches. 3) End-moraines. —Jökulgarðar og sjávarborðsmenjar frá síðjökultíma og upphafi nútíma á Norðausturlandi. Tákn: 1) Geislakolsaldursákvarðanir. 2) Fornfjöru- mörk. 3) Jökulgarðar. the previous DAD-model had suggested, and that the glaciers attained approximately the same extent dur- ing the Younger Dryas as they did in Older Dryas time (Ingólfsson, 1988). NORTHEAST ICELAND In his studies of Weichselian sediments in the west- ern part of the Melrakkaslétta peninsula in Northeast Iceland (Fig. 6), Pétursson (1986; 1991) reached a conclusion, which in important aspects differs from the DAD-model conceming the chronological posi- tion of the glacier readvance that overrode the Röndin sediments at Kópasker and the deglaciation history of the area. The sediments in westem Melrakkaslétta were overridden by a glacier that flowed towards the west away from a north-south orientated ice-divide above the central parts of the peninsula and across the present coastline (Fig. 6) (Pétursson, 1986). The JÖKULL,No. 40, 1990 37
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