Jökull - 01.12.1978, Page 45

KII-AS
Fig. 2. Sounding sheet of the study area showing curved survey tracks and broad outlines
of bathymetry. Isobaths are sketched at 20, 30, 40 and 50 m depth. The survey tracks were
curved in order to facilitate navigation (Raydist). Sounding sheet from the Icelandic
Hydrographic survey.
Mynd 2. Mælingakort af svæðinu, sem sýnir m. a. mælingalínur sem siglt var með botnsjá og dýptarmæli.
A kortið eru skissaðar dýptarlínur fyrir 20, 30, 40 og 50 metra. Sjómælingar Islands.
“hraun” areas are characterised by rough
topography (Icel. “hraun” means lava field or
rough, rocky terrain) and depths of less than
ca. 25 m. Minimum depths are about 10
metres.
The “hraun” areas of Faxaflói have been
rich fishing grounds for centuries and topo-
graphic names, like Sydra Hraun and Vestra
Hraun are indicative of fishermen’s knowl-
edge of the nature of the seabed. The knowl-
edge that the flat seabed around the “hraun”
areas is of shell sand and gravel led to a study
of the feasibility of using these shell beds as a
source of lime for the production of Portland
Cement (Vestdal', 1949). This shell material is
now used by the Iceland State Cement Works
for that purpose.
The demand for fuller knowledge of the
occurrence of carbonates in Faxaflói was one
of the reasons for a survey carried out in the
southern part of the bay in June 1975. The
survey covered an qrea of some 500 km2 and
included echo — sounding, side — scanning,
sediment sampling and some Boomer profil-
ing. This was a cooperative venture of the
Icelandic Hydrographic Service and the
Marine Research Institute, Reykjavík, and
was carried out on board the survey launch
TYR. The following report describes the
results of the survey.
INSTRUMENTS AND METHODS
The survey was carried out in three phases.
The first consisted of echo-sounding and
sidescan sonar surveying on parallel tracks,
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