GeolCarp_Vol58_No4_367

GEOLOGICA CARPATHICA, AUGUST 2007, 58, 4, 367—381

www.geologicacarpathica.sk

Introduction

The specific paleogeographical position of the Balkan
Peninsula which was located between Tethys and Para-
tethys during the Neogene is important in terms of under-
standing the evolution of the recent flora and vegetation
of this region. The territory of Bulgaria, with its numerous
Miocene freshwater basins, appears as a key region to un-
derstand the Neogene evolution of the connection be-
tween Central and Eastern Europe and Asia Minor (Rögl
1998; Meulenkamp & Sissingh 2003), and the migration
pathways and exchange routes for many plant and animal
species. Apparently, this area plays a major role in the
evolution and migration of the Mediterranean vegetation,
in the survival of numerous Paleogene taxa in refugia, and
in the processes of plant speciation (e.g. Palamarev 1989;
Palamarev et al. 1999; Palamarev & Ivanov 1998, 2001,
2004). This region is also important for comprehending
Neogene climate dynamics, the transition from green-
house to icehouse climate, the appearance of arid habitats,
and evolution of open landscapes.

During the last decade, palynological studies on the

Neogene of the territory of Bulgaria have been undertaken
to elucidate the evolution of vegetation and climate (e.g.
Ivanov 1995, 1997a, 2003; Ivanov et al. 2002). The
present paper provides an analysis of Late Miocene vege-
tation-climatic evolution based on the interpretation of
palynological data in the area of the Beli Breg Coal Basin
(West Bulgaria) using quantitative methods.

Late Miocene vegetation and climate of the Balkan region:

palynology of the Beli Breg Coal Basin sediments

DIMITER IVANOV

, A. RAHMAN ASHRAF

, TORSTEN UTESCHER

, VOLKER MOSBRUGGER

and EUGENIA SLAVOMIROVA

Bulgarian Academy of Sciences, Institute of Botany, Acad. G. Bonchev Str. 23, BG-1113 Sofia, Bulgaria;

dimiter@bio.bas.bg

University of Tübingen, Institute of Geosciences, Sigwartstrasse 10, D-72076 Tübingen, Germany

Geological Institute, Nußallee 8, D-53115 Bonn, Germany

Senckenberg Research Institute and Natural History Museum, Senckenberganlage 25, D- 60325 Frankfurt am Main, Germany

(Manuscript received March 3, 2006; accepted in revised form December 7, 2006)

Abstract: The results of palynological studies of Neogene freshwater deposits of the Beli Breg Graben (West Bulgaria)
are presented. We analysed pollen and spores with the aim of obtaining data about the composition and structure of
fossil vegetation and climate conditions. The main vegetation paleocommunities, which existed during the fossiliza-
tion process, are characterized as mixed mesophytic and swamp forests, communities of aquatic plants, and herba-
ceous paleocoenoses. The climate data reconstructed by the Coexistence Approach indicate a warm temperate climate
with mean annual temperatures around 16

ºC and with mean temperature of at least 4 ºC during the coldest month.

With annual precipitation rates commonly above 1000 mm climatic conditions were overall humid, although partly
seasonally drier conditions are evident from the data.

Key words: Pliocene, Late Miocene, Bulgaria, climate, vegetation, pollen analysis.

Notes on geological settings

The Beli Breg Coal Basin is located within a graben

structure that is a part of the Sredna Gora tectonic unit in
West Bulgaria, close to the village of Gaber, about 50 km
west of Sofia (Fig. 1). It is a part of the so-called “Burrell
fault zone” (Gochev et al. 1970), and in older literature it
is also known as the Burrell Basin (e.g. Konjarov 1932).
The Beli Breg Basin is an elongated NW—SE tending

Fig. 1. Geological map of Beli Breg Basin (redrawn after Petrov &
Drazheva-Stamatova 1974, with corrections).

368

IVANOV, ASHRAF, UTESCHER, MOSBRUGGER and SLAVOMIROVA

structure, with a maximal length of ca. 9 km and a width of
2 to 5 km (Vatsev & Zdravkov 2004). It is surrounded by
Jurassic (Polaten and Slivnitsa Formations: Ivanova et al.
2000; Ivanova & Koleva-Rekalova 2004) and Lower Cre-
taceous rocks as well as Upper Cretaceous volcano-clastic
sediments and lavas with andesites, trachyandesites and
tuffs. The Neogene sediments are represented by sand-
stones, carbonates, sandy clays and up to five browncoal
seams, of which only one has a constant thickness and dis-
tribution within the basin.

The lithological subdivision of the sediments in the

Beli Breg Basin is still controversial. Yovchev (1960) rec-
ognized 5 informal litostratigraphic units (horizons) in the
basin: the first (from bottom to top) is represented by
green sandy clays, sands and conglomerates (up to 50 m in
thickness), the second (coal-bearing) is represented by a
thick browncoal seam, and the III, IV, and V units lie on
top of the above-mentioned units, and are represented
mainly by unevenly distributed dark green and green
clays and sandy clays.

Problems with the lithological subdivision arise from

the fact that the basin is located in close proximity to the
Sofia Basin, which is the main sedimentary structure in
this region. There are two different approaches regarding
the lithology of the sediments. The first one relies on the
close geographical proximity to the Sofia Basin and ap-
plies the same lithostratigraphic units as defined by Ka-
menov & Kojumdgieva (1983) for the lithological
sequence of the Sofia Basin to sediments from the Beli
Breg, and other small basins in this area (e.g. Nikolov
1985; Zagorchev et al. 1995). This approach also suggests
that all the small basins of the area were part of the Sofia
Basin, or at least were connected to it in more or less pre-
cisely defined time slices. However, assigning lithostrati-
graphic units from the Sofia Basin to the Beli Breg Basin
causes some inconsistencies, for example, according to Ni-
kolov (1985), the coal-bearing horizon is an analogue of
the Balsha Member belonging to the Gniljane Formation
(Kamenov & Kojumdgieva 1983), while Zagorchev at al.
(1995) recognized the same layer as the Lozenets Forma-
tion, and Palamarev (in Mai & Palamarev 1997) assigned
these sediments from the Beli Breg Basin to the Noviiskar
Formation (Kamenov & Kojumdgieva 1983).

The other approach considers the Beli Breg Neogene

Basin as isolated with its own specific lithostratigraphic
units and geological history. From this point of view, Vat-
sev & Zdravkov (2004) introduced three official lithos-
tratigraphic units (from bottom to top): the Nedelishte,
Kaisiinitsa and Tranerska Formations. The Kaisiinitsa For-
mation, which includes the main coal seam with the III
and IV units on top, established by Yovchev (1960), is the
subject of our study.

The age of the sediments is also under discussion, and

according to different authors it varies within a wide
frame. Konjarov (1932) proposed a Pontian age for the
sediments from the Beli Breg Basin, while Yovchev
(1960) regarded them as Lower Pliocene (Dacian). The
Pliocene age (Dacian—Romanian) was accepted by
Zagorchev et al. (1995). Palamarev (1972) supposed the

presence of Pontian sedimensts in the first and partly in
the second horizon, but for clays on top of the main coal
seam (III and IV units after Yovchev 1960) Palamarev &
Kitanov (1988) accepted an Early Pliocene (Dacian) age,
mainly on interpretations of the floristic composition. Ni-
kolov (1985) determined the age of the coals as Pontian,
based on the mammal record that indicates the MN13
mammal Zone. From the analysis of the diatom flora re-
corded in the succession, there is also evidence for a Pon-
tian age (Ognjanova-Rumenova & Yaneva 2000).

Vatsev & Zdravkov (2004) attempted to summarize all

available data and stated a Pontian to early Dacian age
for the Kaisiinitsa Formation. In this study we will keep
on this last proposed age frame until more detailed
stratigraphic information becomes available from
ongoing biostratigraphic (mammal fauna) and magneto-
stratigraphic studies.

Materials and methods

The sediments studied originate from core 670 (Fig. 1)

drilled in the Beli Breg open cast mine (formerly known as
the Bolshevik mine – see Palamarev 1972; Petrov &
Drazheva-Stamatova 1974). The profile comprises brown-
coals (58.90—34.00 m and 33.60—26.00 m), grey clays
(34.00—33.60 m), marly clays (26.00—13.00 m), interbed-
ded with thin browncoal seams (at 15, 21, 23 and 26 m),
and yellow clays up to the top of the core (13.00—0.50 m)
with thin beds of green sandy clays (Fig. 2). The lignites
are typical xylite-rich coals (Zdravkov & Kortenski 2003,
2004) containing weakly altered xylitic fragments (e.g.
wood fragments at 42.0 and 44.0 m – Fig. 2) mixed with
detritic material. The main coal seam is interbedded with
carbonaceous and clay sediments, and in some layers (e.g.
at 50.5, 52.5 and 57.5 m) numerous shells of freshwater
molluscs occur.

The samples were processed according to the standard

technique for disintegrating Cenozoic sediments. On the
basis of pollen/spore counts a percentage pollen diagram
was plotted (Fig. 3) showing the palynological record of
the complete section. The percentage of each pollen taxon
identified in the pollen spectra was calculated with respect
to the total sum of aboreal (AP) and non-aboreal (NAP)
pollen (AP + NAP = 100 %), with spores excluded. Local
elements (L), such as spores, aquatic plants, were calculated
on the basis of the sum AP + NAP + L = 100 %. Some sam-
ples did not provide enough pollen for a correct calcula-
tion of palynomorph percentages (or some were barren). In
this case, the presence of pollen/spores is indicated with
the symbol “

”, not with a percentage proportion. This is

done in order to present the complete palynomorph record
for the studied section while at the same time avoiding er-
roneous interpretations from low quantities. For all the
other samples, the quantities of taxa are illustrated on the
diagram as bars responding to their percentage proportion
in the pollen spectra.

To reconstruct paleoclimate from the palynological

record of the Beli Breg Coal Basin, the Coexistence Ap-

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PALYNOLOGY OF THE BELI BREG COAL BASIN SEDIMENTS (BALKAN REGION)

proach (CA) was applied (Mosbrugger 1995; Mosbrugger
& Utescher 1997). This method uses the climate tolerances
of all Nearest Living Relatives known for a given fossil
flora to determine a coexistence interval for each consid-
ered climate variable which allows the majority of Nearest
Living Relatives of a fossil flora to co-exist. The resulting
intervals obtained for the different climate variables were
then interpreted as the most probable ranges of paleocli-
mate parameters for the fossil flora analysed. The climatic
resolution of the method and the significance of the re-
sults obtained mainly depend on the diversity of the fossil
flora analysed, and on the taxonomic level of identifica-
tion of Nearest Living Relatives for a given fossil taxon
(Mosbrugger & Utescher 1997).

In the present study, five climatic parameters are consid-

ered and discussed below, namely mean annual tempera-
ture (MAT), mean temperature of the coldest month
(CMT), mean temperature of the warmest month (WMT),

mean annual precipitation (MAP), and mean monthly pre-
cipitation in the driest month (MMPdry). These are the pa-
rameters which most reliably represent changes in
paleoclimatic conditions because their effect on plant dis-
tribution is most important. As shown by previous paleo-
climate reconstructions for the Bulgarian Neogene,
significant changes primarily involve mean annual tem-
perature, temperature of the coldest month and mean an-
nual precipitation, while temperatures of the warmest
month are more constant and show smaller fluctuations
(Ivanov et al. 2002).

For the analysis, 30 microfloras were selected providing

climate data for 8 to 33 extant plant taxa at a mean diver-
sity of 17 taxa. Fourteen samples were excluded because
their diversity was below the limit of the method to pro-
duce reliable results (Mosbrugger & Utescher 1997). The
climate data obtained for the different variables are sum-
marized in Table 1.

Fig. 2. Lithological column of core 670, Beli Breg Basin (redrawn after Petrov & Drazheva-Stamatova 1974, with corrections). 1 – Brown-
coals with interbedded calcareous clays, shells, and wood fragments; 2 – Green clays; 3 – Marl clays; 4 – Yellow clays; 5 – Grey clay;
6 – Soil.

372

IVANOV, ASHRAF, UTESCHER, MOSBRUGGER and SLAVOMIROVA

Results and discussion

Plant diversity and vegetation

Core 670 had already been a subject of palynological

studies by Petrov & Drazheva-Stamatova (1974). The au-
thors identified and described 21 pollen taxa belonging to
14 genera, namely Ephedra distachya type, Thalictrum cf.
aquilegifolium L., Thalictrum cf. simplex L., Eucommia ul-
moides Oliv. foss., Humulus cf. lupulus L., Pterocarya cf.
insignis Rehd. et Wils., Pterocarya sp., Juglans cinerea
type, Juglans regia type, Carya ovata type, Carya sp.1,
Carya sp.2, Engelhardtia acerifolia type, Apocynum cf.
venetum L., Periploca cf. graeca L., Plantago cf. lan-
ceolata L., Alisma cf. plantago L., Typha cf. latifolia L.,

Table 1: Climate data calculated for the single microfloras of core 670. Ntaxa – number of taxa contributing climate data; min/max – lower/
upper limit of climate range. For samples with Ntaxa < 7 no data are given. Samples with Ntaxa 14 are highlighted in grey; for all these
microfloras more specific climate data are obtained from the coexistence approach.

Typha cf. angustifolia L., Sparganium sp., and Stratiotes
cf. aloides L. In the present study we have re-analysed all
samples from this core, including identification of all
spores and pollen recorded and quantitative counts. As a
result, more than 65 additional pollen and spore taxa were
identified for the first time in the core section (see Fig. 3,
and Figs. 4—7), and thus results are obtained allowing for
conclusions with respect to vegetation and climate.

The recognized fossil spore and pollen flora in the

course of this study on the Beli Breg Basin comprise
plants from different taxonomic groups: pteridophytes,
gymnosperms, and angiosperms. The latter produces the
highest taxonomic diversity, namely about 70 % of the
taxonomic composition of the flora. Pollen spectra from
the lower part of the section (meaning from brown coals)

374

IVANOV, ASHRAF, UTESCHER, MOSBRUGGER and SLAVOMIROVA

were very poor in fossil palynomorphs, and only few sam-
ples (41.0, 52.0, 52.5 m) provided enough grains for pol-
len counts. In the samples with a lower pollen content
(Fig. 3a,b)  Tsuga, Betula, Corylus, Quercus, Fagus, Ul-
mus,  and Carya (Figs. 4, 5, and 6)  occur most commonly,
and in rarer cases also Zelkova, Tilia, Eucommia, Ptero-
carya, Juglans, Ephedra,  and  Oleaceae. Most of these are
components of mesophytic forests. Taxodiaceae, Alnus,
and Salix originate  from wetland vegetation, Chenopodi-
aceae,  Asteraceae,  and Artemisia (Fig. 7) from herbaceous
communities. The results obtained from studies on the
composition and environmental conditions of the coal for-
mation (Zdravkov & Kortenski 2003, 2004) suggest oxy-
gen-rich conditions during the deposition of the peat
(oxygenated upper layer of the peat). This assumption ex-
plains the low content (or even lack) of palynomorphs in
the coal samples studied, because their exine is sensitive
and can easily be destroyed in oxygen-rich environments.
The low quantity of palynomorphs from coal-bearing sedi-
ments restricts us to confirm the conclusion of Zdravkov
& Kortenski (2003, 2004) that coals were deposited in an
environment with predominantly herbaceous vegetation
mixed with woody plants and with limited development
of open-water surfaces within the mire.

The upper part of the core (mostly clayey sediments)

provides more complete pollen spectra permitting quanti-
tative calculations and thus providing data not only for
the taxonomic composition of fossil vegetation, but also
for the quantitative participation of individual pollen
taxa. Thus, the vegetation reconstruction presented herein
is largely based on these samples.

Quercus, Fagus, Carya and Ulmus are most abundant

among all the angiosperm pollen recorded, especially in
the upper part of the profile (Fig. 3a,b). The percentage
proportions of most taxa vary in narrow ranges, mainly be-
tween 1—5 % and the pollen of Betula,  Corylus,  Carpinus,
Ostrya,  Eucommia, Zelkova, Fraxinus, Tilia, Acer, Engel-
hardia, Pterocarya, Juglans,  etc.  is more abundant
(Figs. 5, 6, and 7).

The mosaic character of the vegetation, composed of

different plant associations, grew in the hinterland and
lowlands – these were mainly deciduous mixed meso-
phytic forest types with evergreen components. Thermo-
phillous taxa are of comparatively minor importance in
these plant communities – only small quantities of paleo-
tropical elements are recorded in the pollen spectra stud-
ied. The dominant taxa in mesophytic forest paleocoenoses
(which formed the zonal vegetation) were Quercus, Fagus,
Carya, and Ulmus,  accompanied by Betula,  Carpinus,
Ostrya, Corylus, Zelkova, Fraxinus, Eucommia, Acer,
Juglans, Engelhardia, Tilia, Buxus, Ilex,  etc.  The
taxonomic diversity of these forests was due mainly to
floristic elements growing in temperate and/or warm-
temperate climatic conditions, while the subtropical
elements (like Engelhardia,  Platycarya,  Symplocos,  Sapo-
taceae,  Arecaceae etc.) appeared in low quantity in the
pollen spectra. Macrofloristic studies in the Beli Breg coal
mine (Palamarev & Kitanov 1988; Palamarev et al. 2002)
point out the importance of Fagaceae-species, which

formed the forest canopy, and an undergrowth of ever-
green shrubs such as Buxus, Ilex and Daphne.

A high percentage of Pinus pollen is present and domi-

nates all the pollen spectra. P. diploxylon prevails over P.
haploxylon (including Cathaya  –  Fig. 4.9,10). It should
also be mentioned that conifer pollen, mainly Pinus, can
be particularly abundant, presumably because of the ca-
pacity of saccate pollen for a long-distance transport. The
other gymnosperms (Picea, Abies, Tsuga, Keteleeria) are
represented in small quantities, usually about 3—5 %. Thus
their presence testifies to the existence of mid- and/or
high-altitude forests (composed by Tsuga,  Cedrus, Ca-
thaya,  Abies,  Picea  and some flowering plants) that were
also important in the regional vegetation.

Swampy and marshy elements are comparatively scarce

in the pollen spectra. Taxodiaceae is poorly presented in
all the pollen spectra, commonly reaching less than 2 %.
While macroremains of Glyptostrobus (branches with
leaves or cones) are very common in the clayey sediments
(see Palamarev & Kitanov 1988; Palamarev et al. 2002),
pollen that can be identified as the Glyptostrobus type is
very rare. The same is true for Sequoia pollen (Fig. 4.15—19)
and, in rarer cases, also for Sciadopitys, Nyssa, Myrica,
and Salix. Only Alnus reaches higher percentages (up to
10—15 %) suggesting the domination of these trees in
flooded forests (Fig. 3a,b). Some pteridophytes appeared
as undergrowth of these communities or in partly open
places, for example, Osmunda and Laevigatosporites (cf.
Thelypteridaceae, Ivanov 1997b; Barthel 1976). Ptero-
carya, Platanus, Liquidambar and Itea were part of these
plant communities or of riparian forests closely connected
to the swamp. From the pollen spectra originating in clay
sediments (meaning a high stand of the water table and a
lake environment) we can conclude that the distribution
of this vegetation type was limited to the shore-side of the
lake or some small marshy ponds, respectively.

Aquatic plants were more or less closely connected to

swamp areas, but they are poorly represented in the pollen
spectra and their spatial distribution was limited, as is ob-
vious from their low percentage proportion (e.g. Nuphar,
Potamogeton, Typha, Sparganium, Alisma, Stratiotes
(Fig. 5.5—6; Fig. 7.12—15) and other inhabitants of open
water and shoreline). The presence of algae (Pediastrum,
Botryococcus, and cysts of unknown algae Fig. 7.16—23)
indicates open water conditions.

Pollen of trees and shrubs dominate the pollen spectra,

while herbs are represented in small quantity, thus testi-
fying to the dominance of forest-type vegetation in the
areas surrounding the paleo-lake. Herbs (mainly Poaceae,
Chenopodiaceae, Artemisia, Caryophyllaceae, Polygal-
aceae, Apiaceae, and Asteraceae – Fig. 7.4, 6—11) do not
exceed 6—7 % NAP (Fig. 3). Because of the absence of
significant changes in the frequency of herbs it is not
possible to draw conclusions about the dynamics of this
vegetation type. Probably open landscapes and herba-
ceous communities had only a limited distribution and
did not play a significant role in the vegetation structure.
Mesoxerophytic shrubs and forests (Ephedra, Olea, Celt-
is, Rhus, Quercus ilex-coccifera type, Carpinus orientalis/

379

PALYNOLOGY OF THE BELI BREG COAL BASIN SEDIMENTS (BALKAN REGION)

Ostrya type – Fig. 5.11—12; Fig. 6.10—19) were also quite
limited in distribution, depending on local, edaphic and/or
microclimatic conditions. Macrofloristic data (Palamarev &
Kitanov 1988) also support this assumption.

Climate reconstruction

The climate data calculated for 30 palynomorph sam-

ples from core 670 (cf. Table 1) are shown in Fig. 8 where
they are plotted together with the lithological profile. As
it is shown by the analysis, microfloras with less then 15
taxa yield very broad, unspecific coexistence intervals of
almost ten degrees for the temperature variables, and
about 1000 mm for mean annual precipitation. More pre-
cise data are obtained when only the more diverse samples
are selected (Fig. 8).

A MAT of 17.2 ºC to 17.6 ºC obtained for the lower part

of the brown coal section (50.2 m) is among the highest in
this reconstruction. In the upper part of the brown coal and
in the overlying clays, the lower limits of MAT ranges are
at 15.6 ºC not exceeding 16.6 ºC at 15 and 23 m in the
profile. CMT ranges between 4 ºC and 9 ºC for most of the
selection of diverse microfloras, in the upper part of the
section, the upper CMT limit may decline to 7 ºC (at 15 m
and 23 m in the profile). WMT stays at the same level
ranging between ca. 25 ºC and 26.5 ºC although slightly
cooler values can be admitted for the basal part of the sec-
tion (22.8 ºC—26.4 ºC at 52.2 m). Annual precipitation to-
tals were well above 1000 mm in the lower part of the
profile (at 50.5 m), and in the upper part, between 29 m
and 15 m. Between 30 m and 41 m, slightly lower totals of
800 mm are possible. This trend to drier conditions in the
middle part of the section is supported by the results ob-
tained for MMPdry where, at 34 m, a range of 8 mm to
24 mm is obtained while MMPdry rates of at least 25 mm
result for the lowermost part of the section (52.5 m), and
also for parts of the clays on top.

Summarizing the results obtained it can be stated that a

warm temperature climate persisted during the studied
time period. Temperatures stayed at about the same level.
Towards the upper part of the profile a slight decreasing

trend can be detected, affecting MAT and CMT. In most of
the cases, MAP totals above 1000 mm with MMPdry
above 25 mm point to a permanently humid climate (Cfa-
type). However, data obtained for one sample from the
middle part of the section (at 24 m) indicate seasonally
drier conditions.

The paleoclimate data reconstructed using the NLR

technique are over all supported by the broader vegetation
data. For instance in most cases warm temperate and per-
manently humid conditions coincide with the presence of
forest cover (mixed mesophytic forest with warmth-loving
evergreens in the undergrowth; see above). The calculated
MAP total, commonly above 1000 mm, explains the rare-
ness of xerophytic elements in the pollen spectra. Howev-
er, the more pronounced seasonality of precipitation
calculated for the middle part of the section is not clearly
reflected by the frequency of xerophytic pollen types (see
above).

So far uncertainties of stratigraphical dating of the stud-

ied section do not allow correlation with climate curves
available for other continental parts of Europe or global
records, but work is in progress. However, if a latest Mi-
ocene age (Pontian) can be assumed for at least the basal
part of the section, the data can be discussed in a Europe-
an context. When compiling paleoclimate data for the lat-
est Miocene from various sources for different parts of
Europe (Table 2) it is clear that the Beli Breg region was
characterized by favourable climate conditions with com-
paratively high MAT and mild winter temperature. When
comparing temperatures (MAT, CMT) calculated for the
Pontian of the nearby Forecarpathian Basin of NW Bulgaria
values obtained for the Beli Breg Basin tend to be higher
by a few degrees (Table 2). This can be explained by a
more southerly latitudinal position and/or a favourable
microclimate caused by a small-scale relief. In the study
area, MAP was apparently high when compared to other
European regions (Table 2). However, precipitation rates
of the driest month were among the lowest. As in the Fore-
carpathian Basin where the climate record displays cycles
of more humid and drier conditions (Ivanov et al. 2002)
there is also evidence for fluctuations in precipitation
rates in the present data.

Table 2: Paleoclimate data for the W Bulgarian latest Miocene compared to other European regions.

380

IVANOV, ASHRAF, UTESCHER, MOSBRUGGER and SLAVOMIROVA

Conclusions

As a summary of the results from the research we can

stated that mixed mesophytic forest dominated the vegeta-
tion. It can be characterized as mainly deciduous forest
with evergreen components while swamp forests were
comparatively scarce. In addition, local vegetation types
such as aquatic communities have been recorded. Floristic
data evidence that a dense forest cover existed in the
study area while the distribution of grasslands and open
landscapes was limited. The minor importance of xero-
phytic plants observed in the pollen spectra argues against
a Mediterranean type climate.

Climate data support the results obtained from vegeta-

tion analyses. A warm temperature climate with high rain-
fall and mild winter temperatures persisted in the time
period considered. Temperatures stayed about at the same
level, although towards the upper part of the profile, a
slight decreasing trend can be detected which involved
mean annual temperature (MAT) and mean temperature of
the coldest month (CMT). Ongoing studies in the Beli
Breg Basin will provide more precise stratigraphic dating.
Additional pollen records will provide a significantly
higher resolution, and the analysis of the sedimentary cy-
cles displayed in the sections will considerably increase
our knowledge about vegetation and climate evolution in
the Late Miocene of West Bulgaria.

Acknowledgments: We thank N. Doláková and Z. Kvaček
for thorough reviews of the manuscript, critical comments
and valuable suggestions. We are grateful to M. Pole
(Brisbane, Australia) for revising the English. This work is
a contribution to the Projects 436 Bul. 113/139/0-1 (DFG,
Germany) and B-1525 (NSF, Bulgaria).

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