Jökull - 01.12.1987, Page 63

descriptions give locations as the distance in m from the
northernmost point of the cliffs, point 0 in Fig. 2.
THE ÁSBAKKAR DIAMICTON: A
GLACIOMARINE FACIES ASSOCIATION
The lowermost stratigraphical unit in the sequence, rest-
ing on striated bedrock, is composed of two major litho-
facies of diamicton (Dms, Dmu) and a number of in-
trabedded units of diamictons, sands and gravels (Logs
A and H, Fig. 3). The Ásbakkar diamicton makes up the
bulk of the cliffs over long stretches (Fig. 2). All its
lithofacies can be seen in the Ásbakkar-part of the sec-
tion.
Facies Dms
Description:
The lowest lithofacies is a fossiliferous, matrix supported,
vaguely to clearly stratified silty diamicton with occásional gran-
ule and pebble clasts (Fig. 10A). The stratification is due to
occasional laminae and thin interbeds of medium sorted to
nonsorted sand (Sl, Ss). The diamicton is light gray to slightly
bluish gray in color, compact to lithified. The grain size of the
matrix (samples 1 and 2, Fig. 4) is silt with a minor content of
sand. A thin section study of a third sample showed that 85% of
the matrix was silt with interstitial altered volcanic glass frag-
ments, and 15% sand grains and granules. Facies Dms is rich in
subfossil marine molluscs and barnacles, which are not in situ,
primarily due to postdepositional deformation of the sediments.
Sand
Fig. 4. Grain size distribution for selected samples from
the sequence. Samples from (1) Ásbakkar diamicton,
(2) Látrar beds, (3) Melabakkar silts and sands, (4) Ás
beds, (5) Ásgil gravels, (6) Melagil gravels and sands.
Samples described in the text refer to figures within the
triangle.
4. mynd. Kornastcerðardreifing nokkurra sýna frá bökk-
unum.
The shells are evenly distributed in the sediments, except in the
random beds of gravelly sand (sample 6, Fig. 4) where concen-
trations of shells that have been subject to transport occur. The
transport has probably only been slight as paired valves were
found, and external ornamentation, siphon sheath, periostra-
SPECIES GLACIOMARINE UNIT RECENT DISTRIBUTION
Lusi- tanian Boreal Arctic
* o -1 T3 i | High| |Low| Mid 1 High|
1 2 3
Natica (Tectonatica)affinis Trophon (Boreotrophon) truncatus Colus fusiformis Buccinum undatum Nucula (Leionucuia) tenuis Chlamys(Chlamys) islandica Tridonta (Tridonta)elliptica Tridonta (Nicania)montagui Macoma (Macoma) caicarea Hiatella (Hiatella) arctica Mya (Mya)truncata Balanus (Balanus) balanus Balanus sp. • • • • • •• • •• • ••• • • • • • • • • • • •

• •• • ••

—'

• •• • • • • • •
REGIONAL DIVISION OF THE EUROPEAN SEAS
• Rare, fragments only; •• Present; • •• Common; •••• Very common
TABLE II.
Molluscs and barnacles collected from the Melabakkar-Ásbakkar glaciomarine sediments. Stratigraphical position
and Recent geographical distribution. Glaciomarine units: 1: Ásbakkar diamiction, 2: Látrar beds, 3: Melabakkar
silts and sands. Location of samples in the cliffs: see Fig 2. Regional division of the European seas from
Feyling-Hansen (1955). Taxonomical nomenclature and recent geographical distribution of species from Simonar-
son (1981).
TAFLA II: Fornskeljar úr mela- og Ásbökkum: Tegund, staðsetning, landfræðileg dreifing í dag.
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