Middle Miocene palynoflora of the Legnica lignite deposit complex ...

the Middle Miocene and caused signifi cant
extension of deposits in fl uvial, lacustrine and
swampy environments in the Polish Lowland
area. Humid and warm-temperate climate close
to subtropical one in Middle Miocene favoured
the peat-producing vegetation, forming the 2 nd
Lusatian group of seams (the Lusatian lignite
seam in the studied area). Origin of this seam
is connected with extensive swamps occurring
on coastal plains surrounded a bay of the
then North Sea, extended far to the East. In
western and partially central Poland, where
this group of seams has a continuous range,
the brown coal is of paralic origin, whereas
in isolated basins in south-western, central
and eastern Poland it is of limnic or limnofl
uvial origin. The Lusatian group of seams is
a marker of the great lithostratigraphical correlative
importance, composed of 1–4 horizons
usually making together more than 3 m thick
seam (Piwocki 1992, 1998).
Presence of this seam in the Legnica deposit
complex has been confi rmed in boreholes from
the west fi eld – Legnica 5/53, 7/49, 7/58, and
8/59 (Sadowska et al. 1976), as well as the
east fi eld – Legnica 33/56, 41/52, 41/56, 41/64,
47/55, 47/62, 47/68, and 53/56 (Sadowska et al.
1981, Nowak 1998, Wacnik & Worobiec 2001).
Two of these cores (33/56 and 41/52) were
subjects of current study. In all profi les from
the Legnica deposit results of pollen analysis
were similar. Pollen grains of conifers were
numerous (mainly Taxodiaceae/Cupressaceae
– up to 50%, with a signifi cant contribution
of Sequoia, as well Pinus – up to 50%, with
domination of Pinus sylvestris type). Among
the angiosperms, pollen grains of Tricolporopollenites
pseudocingulum (in previous studies
misidentifi ed as Rhus), Quercoidites henrici
(up to 15–25%), Araliaceoipollenites edmundi
(=Tricolporopollenites edmundi), and other
Araliaceae (up to 8–10%), as well as Myrica,
Ilex, Alnus, Liquidambar, Nyssa, Quercus,
Engelhardia, Ericaceae, and palms (usually
less than 10%) prevailed. There were also found
Abies, Sciadopitys, Betula, Fagus, Castanea,
Ulmus, Carya, Rosaceae, Fabaceae (=Leguminosae),
Symplocos, Celtis, and single pollen
grains of other plants. Tricolporopollenites
liblarensis (+ T. fallax) and T. cingulum were
present in all profi les (Sadowska et al. 1976,
1981, Nowak 1998, Wacnik & Worobiec 2001).
In the Legnica deposit (for example in Legnica
47/68 profi le) the Lusatian seam is divided into
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two horizons, what was caused by the situation
of the deposit in the marginal zone of the
basin and strong lability of this zone during
the sedimentation time (Sadowska et al. 1981).
At Ruja it has a form of one compact seam in
central part, and 2–3 (or more) horizons at the
western and northern margins (Dyląg 1995).
Plant communities, both the swamps and
the mesophilous forests growing outside the
swampy basins, were fl oristically rich and had
a relatively signifi cant contribution of plants
of the palaeotropical geofl ora, which contained
the tropical (P1) and subtropical (P2) elements
of large taxonomic differentiation (Tab. 1), with
a considerable role of warm-temperate plants
(A1). Picture of vegetation shown by the pollen
diagrams (Figs 3–5) implies a warm and humid
climate, favourable for abundant peat-producing
vegetation. This was the warmest phase of
the Legnica profi les, when swamp and peat-bog
vegetation dominated. Large areas were constantly
covered by shallow water or marshes.
Only on elevations there existed patches of
riparian and mesophilous vegetation. Swamp
forests were luxuriant and dominated by Taxodium,
Glyptostrobus, Nyssa, and Alnus. In the
upper part of the bottom section of Legnica
33/56 profi le the contribution of bush swamp
elements: Cyrillaceae, Clethraceae, Ericaceae,
Ilex, and Myrica, as well as Sequoia increases,
what indicates more mesophilous conditions
during the sedimentation.
Results of palynological investigations of
the Legnica profi les are similar to spectra
from the 2 nd group of seams correlated with
the V spore-pollen zone – Quercoidites henrici
phase, distinguished by several authors
(Ziembińska-Tworzydło & Ważyńska 1981,
Piwocki & Ziembińska-Tworzydło 1995, 1997,
Ziembińska-Tworzydło 1998, Słodkowska
1998). Deposits of this phase occur on large
areas of the Polish Lowland, mainly in western,
south-western (Nowe Czaple, Zielona Góra
– Sadowska 1977), north-western and central
(Wyrzysk region – Kohlman-Adamska 1993,
Bełchatów B seam – Stuchlik et al. 1990, Lubstów
near Konin – Ciuk & Grabowska 1991),
as well as northern parts (Grabowska 1987,
Grabowska & Ważyńska 1997).
Upper part of the bottom section of the Legnica
33/56 profi le refers to the VI spore-pollen
zone – Tricolporopollenites megaexactus
phase, previously distinguished as the Cyrillaceae
phase by Raniecka-Bobrowska (1970)