Jökull - 01.12.1984, Blaðsíða 124

modified the results of Kjartansson in the area
between Borgarfjördur and Hvalfjördur. Kjart-
ansson (1960, 1968) showed localities where sub-
fossil marine molluscs are preserved in the sedi-
ments. More recently Fridriksdóttir (1978) and
Ingólfsson (1981) have added to his compilation
(Fig. 1). Jónsson (1972) and Gunnlaugsson et al.
(1973) dealt with the sediments of Melasveit and
Leirársveit from a hydrogeological point of view,
and suggested that the surface sediments in the
vicinity of the ridge Skorholtsmelar were of flu-
vioglacial origin. Gíslason (1973) measured the
thickness of the Melasveit and Leirársveit sedi-
ments by geophysical methods. He reported a
maximum thickness of about 60 m at the ridge
Skorholtsmelar. An estimated mean thickness of
about 25 m for these sediments can be deduced
from Gíslason’s data. Hafstad (1974) studied the
stratigraphy of the Mela- and Ásbakkar cliffs and
came to conclusions similar to Bárdarson’s
(1923). Torfason (1974) investigated the sedi-
ments in the Andakíll-Skorradalur area. He
described sections through the sediments and
mapped their surface coverage. Torfason recog-
nized outcrops of tills at several localities in Skor-
radalur and described two sets of marine terraces
in the area, one being at approximately 70 m and
the other at 40 m. He proposed fluvioglacial
origin for the terrace sediments, and suggested
that possibly some of the higher terraces are at
least partially composed of stratified tills.
Ashwell (1967, 1975) investigated the Anda-
kíll-Skorradalur area, and published radiocarbon
dates for shells collected from the deposits (Table
1). He recognized three major types of sediments
which he termed as cobble drift, glacial marine
drift and fluvioglacial deposits. Ashwell observed
the glacial marine drift in two main types of
localities: (1) rather thin, usually massive
deposits on the rock floor of the lowlands, and
(2) thicker deposits generally showing some
layered structures, sometimes contorted, in and
near the entrances to the valleys, at a higher
elevation than those on the lowlands. He did not
suggest any temporal difference between the two
sets of deposits. Ashwell published cumulative
frequency curves and scattergrams for mean size,
standard deviation and skewness for samples col-
lected from the sediments. He suggested that
much of the material ultimately derived from
subglacial or englacial transport and deposition.
Ashwell concluded that deltaic sediments in the
Fig. 4. Composite vertical section of sedimentary
strata of Melasveit and Leirársveit. Slightly mod-
ified from Ingólfsson (1981). Mynd 4. — Samsett
jarðlagasnið er sýnir jarðlagaskipan setlaga í
Melasveit og Leirársveit.
area were subglacially deposited, and contra-
dicted Bárdarson (1923) by stating that recog-
nized forms of moraines, lateral or terminal,
were lacking in the tributary valleys of Borgar-
fjördur. Sigbjarnarson (1976) and Hafstad (1980)
briefly described the sediments of Melasveit and
Leirársveit. They both recognized the sequence
to be constituted chiefly of marine and glacioge-
nic sediments.
lngólfsson (1981) investigated the lithostra-
tigraphy in the area between Borgarfjördur and
Hvalfjördur. He studied the stratigraphy of the
Melabakkar and Ásbakkar cliffs, and disting-
uished between three major silt units on the basis
of their lithology and fossil content. He consi-
dered the silt units to be of glaciomarine origin.
Ingólfsson also recognized fluvioglacial and
littoral sediments in the sequence and found evi-
dence of a glacial advance from the Svínadalur
valley subsequent to the deposition of the lower-
most silt unit. He also presented a composite
122 JÖKULL 34. ÁR