Jökull - 01.12.1987, Blaðsíða 60

of Borgarfjördur are controversial, and that detailed
studies on the stratigraphy, sedimentology and mor-
phology of the deposits have been lacking. The Mela-
bakkar-Ásbakkar cliffs are sensu strictu the type locality
for Einarsson's (1961,1968) Álftanes Stadial, correlated
with the Older Dryas of Scandinavia (Einarsson 1979) as
the Álftanes glacial advance was radiocarbon dated by a
mollusc sample from these cliffs (Einarsson 1971).
I have studied the Melabakkar-Ásbakkar cliffs in or-
der to identify glacial episodes, by investigating sedi-
mentological and structural properties and stratigraph-
ical relations of the sediments, to provide a depositional
model for the sequence. Because of the long, almost
continuous section, the geomorphic setting and the pre-
served subfossil marine molluscs and barnacles in the
sediments, the Melabakkar-Ásbakkar cliffs could give
Fig. 2. Melabakkar-Ásbakkar coastal profile. Legend:
(1) bedrock, (2) Ásbakkar diamicton, (3) Ás beds, (4)
units of interbedded sands and diamictons, intrabedded
in the Ásbakkar diamicton, (5) the Látrar beds cross
stratified sand facies, (6) the Látrar beds interbedded
silt and sand facies, (7) Melar diamicton, (8) boulders,
(9) Landhólmi sands, (10) Ásgil gravels, (11) Melabakk-
ar silts and sands, (12) Melagil gravels and sands, (13)
important information on depositional environments in
a glaciated fjord/bay setting, and also reflect changes in
the proximity of the depositional basin to a glacier mar-
gin. The present study discusses some recent models for
glaciomarine sedimentation and for glaciotectonism. A
preliminary report on the glacial stratigraphy and chro-
nology was given by Ingólfsson (1985).
The field work was carried out in 1980,1983 and 1984.
The cliffs are actively eroded by the sea during high tides
and westerly storms, which causes difficulties when
mapping them, due to their nearly vertical stand and the
risk of large scale slumping. The field mapping was thus
partly conducted on photographs covering the cliffs in
scale 1:200. This allows the recognition of major lithofa-
cies, stratigraphic boundaries and deformational fea-
tures. Accessible sections were described and measured
location and no. of radiocarbon dated samples in Table
III, (14) section covered, (15) major joints, (16) clastic
wedges, (17) normal faults, (18) glaciotectonic deforma-
tions, (19) major thrust faults, (20) direction of glacio-
tectonic thrust, (21) paleocurrent direction, (22) direc-
tion of glacial striae on bedrock substratum, (23) loca-
tion of logs in Fig. 3.
2. mynd. Strandsnið Mela- og Ásbakka.
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