Lateglacial and early Holocene vegetation ... - geo.edu.ro

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L. Bj .orkman et al. / Quaternary Science Reviews 21 (2002) 1039–1059
The second site, Steregoiu (47148 0 48 00 N; 23132 0 41 00 E),
is situated at a somewhat higher altitude than Preluca
Tiganului, at c. 790 ma.s.l. It has a roughly elongated
surface (c. 50 100 m) of c. 0.5 ha. The site is drained by
a small stream towards the east. It is surrounded by
fairly steep slopes to the south <strong>and</strong> west, where a small
streamenters the basin. Towards the northeast fairly
steep slopes lead down to the Talna valley. The
surrounding <strong>vegetation</strong> is dominated by young Fagus
(approximately 30–50 years) <strong>and</strong> Picea st<strong>and</strong>s. The site
can be described as a eutrophic to mesotrophic mire
with a field layer dominated by grasses, sedges <strong>and</strong>
herbs.
There are no climate records directly available for
the study area, but records fromweather stations
in Satu Mare <strong>and</strong> Baia Mare (Fig. 1), <strong>and</strong> fromthe
eastern (Ocna Sugutag) <strong>and</strong> northern (Sighetu Marmatiei)
part of the Gutaiului Mountains, may be used
as a good approximation. Highest mean annual air
temperatures of 9.51C are recorded at Satu Mare
<strong>and</strong> Baia Mare, while temperatures range slightly
lower at 7.81C <strong>and</strong> 8.51C east <strong>and</strong> north of the
mountain chain. Mean annual precipitation is lowest
in Satu Mare (c. 600 mm). It rises towards the east
to c. 850 mm around Baia Mare <strong>and</strong> then decreases
slightly to c. 700 <strong>and</strong> 750 mm towards the east <strong>and</strong> the
north.
Froma <strong>geo</strong>logical point of view, the area represents
the northwestern termination of a volcanic arc, situated
in the inner part of the Eastern Carpathians. The
volcanic activity in this region took place during the
Late Pliocene, generating a large range of intermediary
<strong>and</strong> acidic rocks, in particular dacites, <strong>and</strong>esites <strong>and</strong>
rhyolites (Borcos et al., 1979). The main bedrock type in
the study area is <strong>and</strong>esite. There is no published
information about Quaternary deposits in the area,
but our own field observations in, for instance road cuts,
indicate that most of the soil cover is derived from slope
processes. It is also assumed that alpine glaciers did not
reach below 1800 ma.s.l. in the Carpathians during the
Last Glacial Maximum (LGM) (Balteanu et al., 1998).
The low elevation of the Gutaiului Mountains makes it
unlikely that the area was glaciated during the
Weichselian, but is however, likely that the area has
been subjected to periglacial conditions during the
LGM.
3. Methods
Sediment cores were taken in the centre of each basin
in May 1999, where the organogenic deposits were
thickest (Table 1). Coring was performed with a
strengthened Russian corer (diameter: 5 cm, length:
1 m), <strong>and</strong> each core was taken with an overlap of
50 cm, in order to obtain enough material for analyses.
Table 1
Simplified lithostratigraphic descriptions of the analysed profiles from
Preluca Tiganului <strong>and</strong> Steregoiu
Depth (m)
Description
(A) Preluca Tiganului. The pollen analysed levels extend between
9.89 <strong>and</strong> 4.01 m
0–6.13 Fen peat
6.13–8.70 Carr peat
8.70–8.78 Peaty gyttja
8.78–8.89 Gyttja peat
8.89–9.10 Peat
9.10–9.14 Gyttja peat
9.14–9.33 Clay gyttja
9.33–9.49 Peaty gyttja
9.49–9.59 Clay gyttja
9.59–9.68 Fine detritus gyttja
9.68–9.84 Coarse detritus gyttja
9.84–9.90 Fine detritus gyttja
(B) Steregoiu. The pollen analysed levels extend between
5.92 <strong>and</strong> 2.83 m
0–1.25 Fen peat
1.25–2.80 Carr peat
2.80–4.28 Coarse detritus gyttja
4.28–4.57 Gyttja
4.57–5.26 Clayey gyttja
5.26–5.44 Gyttja clay
5.44–5.70 Silty clay (partly laminated)
5.70–5.84 S<strong>and</strong>y silt
5.84–5.92 Silty clay
The cores were described in the field, <strong>and</strong> thereafter
wrapped in plastic film<strong>and</strong> placed in half PVC tubes.
Subsequently they were transported to the Department
of Quaternary Geology in Lund, Sweden, where they
were stored at 41C. Prior to sub-sampling all cores were
carefully cleaned, described again <strong>and</strong> visually correlated
with each other.
The profiles were continuously sub-sampled at c.
2.5 cmintervals for pollen analysis. The preparation of
the samples (1 cm 3 ) follows st<strong>and</strong>ard methods (Berglund
<strong>and</strong> Ralska-Jasiewiczowa, 1986; Moore et al., 1991). To
enable the calculation of pollen concentration, tablets
with a known content of Lycopodium spores were added
to each subsample (Stockmarr, 1971). Microscope slides
were prepared fromthe residue <strong>and</strong> scored for pollen. At
least 450–500 grains were counted in each subsample,
except when pollen concentration was low, a minimum
of 300 grains was accepted. Pollen counts were made at
400 magnification, but 1000 was used for some
critical determinations. Pollen keys <strong>and</strong> illustrations in
Moore et al. (1991) <strong>and</strong> Reille (1992) were used for
pollen identification. Pollen slides in the reference
collection at the Department of Quaternary Geology,
Lund University, were also used to check some pollen
types. Pollen nomenclature follows Moore et al.
(1991).