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Jökull - 01.12.1990, Qupperneq 41

Jökull - 01.12.1990, Qupperneq 41
gional marine limit at 30^40 m a.s.l. Hjartarson et al. (1981) suggested, that the younger Cirque-glacier stage occurred in late Younger Dryas or early Pre- boreal time when relative sea-level had receded below the 10 m level. Furthermore, they proposed that the older Valley-glacier stage might correlate with the pe- riod between 12,000 and 10,000 B.P. Based on the data collected by Norðdahl and Einarsson (1988), the course of deglaciation and sea- level changes in East and Southeast Iceland has been divided into three successive stages. The oldest Fáskrúðsfjörður stage represents the first standstill or readvance of the glaciers recorded on land in East Iceland since their retreat from the Weichselian max- imum position on the shelf. Simultaneously relative sea-level rose to its highest position at about 50 m a.s.l. at the Fáskrúðsfjörður stage moraines (Fig. 7). This stage was subsequently terminated by retreat of the glaciers and regression of relative sea-level. The second Breiðdalur stage is represented by moraines which were formed, either during a standstill or a readvance of the glaciers in the area between Lón and Norðfjörður, when the ice margin had retreated to within the present coastline (Fig. 7). Simultane- ously sea-level rose to a new elevated position at the Breiðdalsvík; stage moraines. Finally the Berufjörður stage comprises the third and youngest set of moraines and raised beaches at the Berufjörður stage moraines (Fig. 7) (Norðdahl and Einarsson, 1988). Comparison with the results of Hjartarson et al. (1981) shows, that the Berufjörður stage correlates with the Cirque-glacier stage, the Breiðdalur stage with the Valley-glacier stage, and consequently that the Fáskrúðsfjörður stage predates the Valley-glacier stage. The stratigraphical position of the Fáskrúðs- fjörður, Breiðdalur and Berufjörður stage moraines and their related marine limits is uncertain so far, as radiometric dates are still lacking. On basis of paral- lelism between the above described course of deglacia- tion and sea-level changes in East Iceland and the one described by Ingólfsson (1988) in West Iceland the Fáskrúðsfjörður stage may correspond to the Skipa- nes event (Older Dryas) and the Breiðdalur stage to the Skorholtsmelar event (Younger Dryas) (Norðdahl and Einarsson, 1988). marine-limit features in South Iceland. Legend: 1) I4C dates. 2)TheBúðimoraine. —Jökulgarðarog sjávar- borðsmenjar frá upphafi nútíma á Suðurlandi. Tákn: 1) Geislakolsaldursákvarðanir. 2) Búðaröðin. SOUTH ICELAND Since the identification of the Búði stage (Kjartansson, 1943; 1958; Th. Einarssoni, 1964), the Búði moraine itself has been subjected to very limited research efforts. Kjartansson (1958) described the Búði moraine (Fig. 8) as ”a belt of terminal moraine ridges“ and later Th. Einarsson (1960) pointed out that the moraine is a complex of several ridges. In a seismic study of the Markarfljót sandur area in central South Iceland an extension of the Búði moraine was detected 25-50 m below the sandur surface (Haralds- son 1981). Jóhannesson (1985) emphasized that the Búði moraine is a complex of up to seven more or less parallel moraine ridges and speculated that the outermost ridges of the Búði moraine were at least of an Older Dryas age (about 12,000 B.P.) and that the innermost ridges were at least of a Younger Dryas age (about 10,000 B.P.). Recently, Hjartarson and Ingólfsson (1988) have, on basis of substantial stratigraphical and chronolog- ical evidence, drawn quite different conclusions con- cerning the age of the complex Búði moraine. Out of twelve 14C dated samples of marine molluscs gathered from raised marine sediments in the South Icelandic JÖKULL, No. 40, 1990 39
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