Fróðskaparrit - 01.01.1998, Page 264

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MACROFOSSIL STUDIES OF LACUSTRINE SEDIMENTS FROM SKÁLAFJØRÐUR,
THE FAROEISLANDS, PRELIMINARY RESULTS
Sediments Magnetic susceptibility (CGS)
ItzitiI Silty clay I - I Shell, -fragment
I, 'I Sand, gravel I ~ I Bioturbation
| • | Pebble ||!|||||“|||| Ash layer
j////////j Organic detritus
Fig. 3. Sedimentological log and magnetic
susceptibility profile ofcore SKPCI8. Forfurther
explanation, see text.
Mynd 3. Aløgufrøðilig skrá og magnetiskur
árinstvørskurður av kjarna SKPC18. Gjøllari
frágreiðing í tekstinum.
Fig 1 shows the location of the coring site,
where the water depth is 61 m. Due to the
presence of the threshold, bottom water ex-
change in the fjord is limited. A stratifíca-
tion of the water masses is present most of
the year, and it only disappears during the
winter months (DHI, 1986; Hansen et ai,
1990) .
Results from the shallow seismic survey
made in Skálafjørður in 1991 (Larsen,
1991) indicate the presence of two larger
depositional basins, where the maximum
thickness of sediments deposited after
deglaciation is between 15 and 20 m. The
sediments cored here are predominantly
dark olive gray marine silty clays. The core
discussed here was sampled from the mar-
gin of the innermost depositional basin,
where the shallow seismic (boomer) record
shows the presence of only a few rnetres of
postglacial sediments (fíg. 2).
Material and methods
The core (SKPC18) was sampled by R/V
Skagerak of Goteborg University on Octo-
ber 5, 1995, using a piston corer with an in-
side PVC liner (diameter 75 mm). The lo-
cation of the core is at 62°09.4’N,
6°45.8’W. After retrieval, the core was cut
into two sections, which were split length-
wise, and the core was visually described
(fig. 3), and subsampled in the laboratory.
Magnetic susceptibility was measured at 3
cm intervals using a portable Bartington
MS2 Meter. Only the lowermost core sec-
tion was subsampled for the present study.
The volume of most of the macrofossil
samples was 2 ml, but larger samples were
collected at 154 and 140 cm (20 ml) and at
148 cm (5 ml), where layers of organic de-
tritus were present. The sediment samples
were wet sieved on 0.4, 0.2 and 0.1 mm
sieves, and the residue left on the sieves
analyses using a dissecting microscope. In
the somewhat simplified diagram (fig. 4),