Jökull - 01.12.1986, Blaðsíða 49

Taxon KEl/l KEI/2 KE2/2 KE3/2 BRI/2 KEI/5 KEI/3 KEI/6 KEI/4 KEl/7 KEI/14
Selaginella selaginoides (L.) Link. 82.0 9.3 2.6 190.8 24.1 24.0 74.5 — 6.5 — 1.4
Rumex sp. — — — — 0.2 — — — — — —
Montia fontana L. — — — — — — — — — 0.1 —
Stellaria media L. — — — — 0.5 — — — — — —
Cerastium sp. — — — — 2.0 — — — — 0.1 —
Ranunculus cf. acris L. 0,3 0.4 — — 0.1 — — — — — —
dlchemilla sp. 9.5 35.8 — 0.2 1.2 1.5 10.4 — — — —
Empetrum nigrum L. — — — — 1.0 — — — — — —
Menyanthes trifoliolata L. — — — — — — — — — — 4.9
Gramineae (indet.) — — — — 0.9 — — — — — —
cf. Alopecurus geniculatus L. — — — — - - - - - 0.3 -
Carex spp.(indet.) 13.8 5.1 — 2.0 66.9 59.8 89.4 — — 1.9 3.3
Juncus spp. (indet.) — 0.1 — 0.1 8.1 0.3 0.7 - - — -
Luzula cf. multiflora (Retz.) Lej 0.4 0.7 - 0.1 3.8 1.5 2.2 8.4 - 0.3 -
TOTAL seeds/100 g 106.0 51.4 2.6 192.3 108.8 77.1 177.2 8.4 6.5 2.7 9.6
Number of taxa. 5 6 1 5 12 5 5 1 1 5 3
' » ' Post 1357 ^ Pre-1357 Pre-Landnám
Table 1:
Plant macrofossils from Ketilsstadir, southern Iceland (numbers expressed per 100 g of sample).
Det. D. Savory.
the more richly vegetated parts of the ditches occurred
Trechus obtusus, Stenus carbonarius and Lesteva
longoelytrata (within vegetation zone 1).
SAMPLING
In 1979, after detailed examination of the strati-
graphy, a section was selected in one of the more re-
cently cut ditches (fig. 5) for sampling. Taking due
fegard of the tephra stratigraphy, a sequence of 22
samples (BRl/1—22) was taken in slices roughly
lOOmm thick. Each sample, of about 2.5kg, was
bagged in polythene and returned to Birmingham for
processing. Separate samples were taken for tephro-
chronological study. Since it was important to ex-
amine spatial as well as temporal variation in flora
and fauna, an additional sequence of samples, imme-
diately adjacent to the 1979 samples, was taken in the
following year (KEl/1 —15), overlapping with the
earlier samples and extending the succession to above
the —1357 horizon and to the base of the ditch. In
addition, using the tephra horizons as isochrones
(time stratigraphic markers, Buckland et al., 1981),
further samples (KEl suppl.; KE2; KE3; KE4) were
collected from elsewhere in the bog (fig. 3) from above
and below the -1357 Katla ash (KE2-4/1-2) and
from beneath the Landnám ash (KE2—4/3).
Processing of samples
The recovery of macrofossils from Quaternary sedi-
ments has been considered in some detail by Kenward
et al. (1980) and the kerosene (paraffin) flotation
technique, devised by Coope and Osborne (1968) for
the recovery of insect remains has been discussed by
Coope (1985) and Sveinbjarnardóttir et al. (1981).
Samples are disaggregated in water over a 300 pm
sieve, drained and kerosene added. This adsorbs onto
the fragments of insect cuticle and these float with the
kerosene when water is added; a reasonable sub-
sample of the seed flora may also be obtained by this
technique but it is necessary to sort a subsample of the
whole, separated further into >2mm and >lmm frac-
tions, before a representative flora can be obtained.
For the Ketilsstadir samples, this was a tedious pro-
cess and it was not possible to process as many
samples for plant macrofossils as for insects. After
flotation, both flotant and residue are separately
washed in detergent and alcohol to remove the kero-
sene and are sorted in alcohol under a binocular
microscope. Identification is carried out using exten-
sive modern reference collections. Table 1 lists the
number of seeds and macrospores per lOOg of sample
and table 2 lists the insect taxa recovered from the
Ketilsstadir samples. The number of individuals is
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