Jökull - 01.12.1978, Blaðsíða 48

Fig. 4. Shipek sampling stations and con-
tours of weight of samples obtained, measured
in grammes of dry sample.
Mynd. 4. Botnsýnastöðvar (punktar). A kortið eru
dregnar jafngildislínur fyrir punga botnsýna, mœldan
í grömmum.
crescentic shapes described by the boundary
consistently facing west. Along the
northeastern border of the map the
sand/gravel boundary defines elongate strips
of sand and gravel, trending N—S and
NW—SE. The strips of gravel are seen here to
have negative relief in some places.
Grab samples show the sand to be mainly
made up of shell fragments with some com-
plete shells.
Unit 4. The southernmost part of the
study area is floored by dark-toned material
(gravel) of variable character. The eastern-
most part of this area is characterised by long
and narrow stripes of light material (sand) set
in a darker background. These stripes are seen
to have two orientation trends, at right angles
to one another. Farther to the west this pattern
is replaced by more irregular, diffuse patches
of fine-grained sediment. Rock outcrops in a
few places.
Grab samples of gravel from this unit reveal
a terrigenous component of pebbles and
grains of well rounded basalt, and a biogenic
component commonly of worn and disco-
loured shell fragments.
Size of samples
The amount of sediment recovered at the
various sampling stations varied greatly. To
illustrate this variation, the dry weight of the
samples has been charted on Fig. 4., and con-
tours drawn for sample weight, expressed in
grammes. The pattern observed is difficult to
a.
Fig. 5. a) Histograms showing percentage of
gravel (coarser than 2 mm) plotted against
percentage of stations in units 1, 2, 3 and 4b)
Histograms of mean size (Mz) of sediments
from units 1, 2, 3 and 4.
a) Malarinnihald setsýna (% G) á móti prósentu af
stöðvafjölda af hinum ýmsu einingum botngerðar-
kortsins.
46 JÖKULL 28. ÁR