Jökull - 01.12.1982, Side 20

probably in part a gravel bar enclosing a shallow
lagoon. These raised beaches may be attributed to
adjustments at the end of the last glacial period
rather than to the kind oflong-term uplift ofeastem
Iceland which is recorded by the high level erosion
surfaces of the Austfirðir.
THE RIVER PATTERN
The main watershed of the Austfirðir lies on aver-
age 5 to 10 km west of the axis of the main moun-
tains mass, Fig. 4. It is likely that originally the
main watershed coincided with the mountain axis,
but at a later stage vigorous down-cutting by the
shorter and steeper east-ílowing streams resulted in
capture of the headwaters of many of the westem
streams, so shifting the watershed westwards. Ex-
amples of river capture are evident for example
north of the head of Reyðarfjörður, Fig. 5, and the
resulting dry cols or “wind gaps” lie at or below 650
m, suggesting that river capture followed uplift of
the 650 m surface and was due to the cycle of erosion
which was thereby initiated.
One consequence of this rejuvenation was the
capture of many of the northílowing rivers of the
Eyvindará system. An east-flowing river in what is
now Reyðarfjörður successively captured the head-
waters of the following:
1. The Tunguá - now the Eskifjarðará (with wind
gap at 645 m)
2. The Eyvindará- now the Búðará (607 m)
3. The Fagradalsá — now the Geithúsaá and
Stuðlaá (445 m)
4. The Skógdalsá and southern part of the Fagra-
dalsá (325 m)
5. The Skógdalsá — captured by a tributary of the
Stuðlaá (325 m)
The headwaters of the Eyrarteigsá, Brúðardalsá
Fig. 6. Series of schematic west-east profiles across the Austfirðir and inland plateau showing
evolutionary stages.
Mynd 6. Þróun landslags á þversniði gegnum Austjirði.
18 JÖKULL 32. ÁR