Jökull - 01.12.1976, Page 6

West of the channel and the ridge end, but is
much eroded and sinks to 78 m above the Braut-
artunga farm. The present form shows a number
of shallow channels running parallel to the
main channel under Tungufell, but only a
metre or so deep. In fact, they are difficult to
pick up on the ground and show better on
photographs (Fig. 3). There is some rounded
debris on tliis part of the platforms, but its
relationship to the channels is not clear.
When examined on air photographs these
small channels seem to be related to the gullies
on the south slope of the Tunguá valley and
in some cases are continuous with them across
the Tunguá. The relationship on the north side
of the valley is not so clear. It appears that we
have liere signs of a double pattern of sub-
glacial drainage, as found elsewhere in the
district (Ashwell, 1975), and as described in the
Introduction.
In the case we are examining the ice-directed
flow seems to have been partly subglacial in its
passage across the valley, and the channels
across Tungufellsflói beyond the tip of Tungu-
fell are thus part of a system following the slope
of the ice across the valiey and the gullies on
the south side of the valley are ‘reverse chutes’
in which water rose over the ridge.
The valley-guided flow is probably represent-
ed here by the two river channels. From the
long profile (Fig. 2), it can be seen that the
Tunguá flows in a ravine between Englandsflói
and Tungufellsflói, below the knickpoint at
about 110 m, and that a further knickpoint
occurs at 140 m some 2 km upstream. There is
no indication that subglacial water, although
generally guided by the lines of the valley, is
constrained into the narrower parts of the river
channel, nor is it certain whether such flow is
controlled by a base-level downstream. If, how-
ever, the narrower parts of the river valley were
blocked by deposits, the subglacial flow in the
present valley would tend to flow over Tungu-
fellsflói, especially if directed to the point of
Tungufell. At the point marked as ‘Leirgróf’
(claypit), (Fig. 1) varved clays are found from
101 to 106 m, just below the edge of the Tungu-
fellsflói platform, covered with about lialf a
metre of consolidated current-bedded sand.
This could be the remnant of a deposit formed
Fig. 3.
Upper Lundarreykjadalur
from northern valley side.
Tungufellsflói in middle
of picture, showing minor
channels. Grímsá flows
this side of Tungufell,
left centre, to foot of
slope, right foreground.
Tunguá flows the other
side of Tungufellsflói.
The Englandsflói plat-
form is visible above the
house and fields of the
Tungufell farm, left cen-
tre. - Photo: Ian Ashwell,
July 1972.
Mynd 3. Horft yfir Efri-Lundarreykjadal frá norðri. Tungufellsflói er i miðri
mynd. Grímsá fellur norðan Tungufells, sem er i miðri mynd til vinstri, og rennur með norður-
hlið. Farvegur hennar sést neðst til hœgri. Tunguá er handan Tungufellsflóa. Englandsflói sést
handan við bœjarhús á Tungufelli.
4 JÖKULL 26. AR