Jökull - 01.12.1981, Blaðsíða 18

TABLE 3. Particle size distribution. — TAFLA 3. Kornastœrðardreifing
% OF TOTAL SAMPLE % OF MATRIX (■ 2 mm)
Sample Silt Silt
Gravel Sand Silt Clay + Clay Sand Silt Clay + Clay
1 28.9 33.2 37.2 0.7 37.9 46.7 52.3 1.0 53.3
2 19.7 50.3 27.2 2.8 30.0 62.7 33.8 3.5 37.3
3 36.8 26.7 27.5 9.0 36.5 42.2 43.5 14.3 57.8
4 29.0 42.2 25.6 3.2 28.8 59.5 36.1 4.4 40.5
5 29.1 33.7 32.8 4.4 37.2 47.5 46.3 6.2 52.5
6 42.1 33.8 20.7 3.4 24.1 58.4 35.7 5.9 41.6
7 62.4 35.4 1.9 0.3 2.2 94.1 5.0 0.9 5.9
8 21.7 53.3 21.7 3.2 24.9 68.1 27.8 4.1 31.9
9 45.3 28.6 22.9 3.2 26.2 52.2 41.9 5.9 47.8
Note: The following particle size categories were used: Gravel -2 mm; Sand 2 mm — 63 um;
Silt 63 — 2 (im; Clay < 2 txm.
Its glaciological and climatological signifi-
cance cannot be determined from the present
evidence but further survey of the position of
the ice margin and the character of the ice
front will be undertaken in 1981.
ii) The Moraine Ridges — The complex pat-
tern of ridges between the immediate vicinity
of the glacier snout and the downvalley limit
of the map (Fig. 1) clearly resolves itself into
elongated ridges whose crests trend obliquely
down the valley sides, approximately mirror-
ing the trends of the present glacier snout.
There can therefore be little doubt on
morphological grounds that they are pre-
dominantly morainic in origin, although some
modification by avalanches and snowmelt
drainage is apparent in places. The ridges are
more numerous on the western, less steeply
sloping, valley side than on the eastern side.
Their relief amplitude ranges from about 2 m
up to 10 m, and the complexity of their pat-
tern varies from the simple, single linear ridge
as exemplified by ridges 36 and 40,_ to the
closely packed system of sometimes sinuous
ridges, with ridges joining and crossing, that
occurs near Station 6. In this latter complex,
some small mounds between the main ridges
were not mapped because of difficulty in
identifying a mappable crest.
In some cases it is possible to discern former
ice-margin positions quite clearly across the
valley, most notably in the case of the outer-
most ridges (36 and 40)j often termed the
T750’ moraine in earlier expedition reports,
which probably mark the culmination of a
significant advance, for together they form a
major feature, up to 10 m high, that coincides
with a marked change in the vegetation cover.
Other likely cross-valley demarcations include
38-41, 31-34-42, 30-32-33-43, 3-4-5-53 and 2-
59, but further correlations would be highly
speculative.
The surface composition of the ridges varies
from coarse blocky till to much finer till in
which silt and clay are more evident and
stones much smaller. Both coarser and finer
facies are present at different locations on the
same ridge, but some ridges have a notably
finer surface composition than most, includ-
ing 9, 10, 15, 17, 18, 19, 20, 25 and 26 on the
16 JÖKULL 31. ÁR