GEOLOGICA CARPATHICA, AUGUST 2005, 56, 4, 347358
Upper Neogene siliceous microfossils from Pelagonia Basin
Department of Paleontology and Stratigraphy, Institute of Geology, Bulgarian Academy of Sciences, Acad. G. Bonchev Street 24,
1113 Sofia, Bulgaria; firstname.lastname@example.org
(Manuscript received March 15, 2004; accepted in revised form December 9, 2004)
Abstract: This paper presents data from an investigation of the Late Miocene-Pliocene siliceous microfossils (diatoms
and chrysophycean stomatocysts) from borehole V-466, east of the city of Bitola, southern Macedonia. The diatom flora
consists of 127 species, varieties, and forms of diatoms of thirty genera, eighteen families, five orders, and two classes.
Four associations are distinguished in the development of the diatomaceous flora, as confirmed by cluster analysis.
Ecological data for the diatom taxa and the frustule/chrysophycean stomatocysts ratio are used in an attempt to recon-
struct in detail the paleoecological conditions at the time of sediment deposition in detail.
Key words: Late Neogene, Balkan Peninsula, Pelagonia Basin, paleoenvironment, biostratigraphy, continental sediments,
diatoms, chrysophycean stomatocysts.
Introduction and geology of the study area
The Pelagonia Basin, measuring 1500 km
is a part of the tec-
tonic basins created after the Savian orogeny and the Early
Miocene intense peneplenization in the Balkan Peninsula (Du-
murdzanov et al. 1997). This led to the formation of a set of
sub-grabens within the Pelagonia Basin and the faults running
from NW to SE. The Neogene sediments of the basin are in di-
rect contact with the basement, consisting of metamorphic
rock, limestones, dolomites, flysh and ophiolites (Dermitzakis
& Papanikolaou 1981). Several major sub-basins can be dis-
tinguished: the Bitola and Prilep areas (Republic of Mace-
donia) and the areas of Florina, Ptolemais and Servia parts
(Greece) (Fig. 1). Three lithostratigraphic units are recognized
only within sub-basins in the territory of Greece (Koufos &
Pavlides 1986), namely: 1 a lower, unnamed formation
composed of basal conglomerates; 2 a middle unit, the Ve-
gora Formation composed of marls, sandy marls, sands, and
lignite (xylite type) (Upper Miocene, according to its macrof-
lora and palynomorphs: Van de Weerd 1983; Knobloch &
Velitzelos 1986; Velitzelos & Gregor 1986, 1990; Riegel et al.
1993; Velitzelos & Kvaèek 1999); 3 the upper, Ptolemais
Formation composed of argillaceous layers, marls, sands, lig-
nite beds, and lacustrine calcareous muds in alternating se-
quence (Lower Pliocene, according to its macroflora, palyno-
morphs and small mammalia: Van de Weerd 1979; Velitzelos
& Gregor 1986, 1990; Riegel et al. 1993; Bosch et al. 1996).
The Ptolemais Formation is composed of two members: the
lower Kardia Member (lower group of lignite beds), and the
upper Anagiri Member (upper set of lignite beds).
The Neogene sediments from the Macedonian area can be
subdivided into the following informal lithostratigraphic
sandy-gravel-clay series with maximum thickness of 400
500 m, discordantly covering the pre-Neogene formation.
terrigeneous coal-bearing series with sandy-silty unit,
which in the Prilep part has a maximum thickness of 100 m.
gravel-sandy-silty series, which in the Macedonian area has
a thickness of 150 m.
sandy-silty coal-bearing series, which in the Bitola part of
the basin has a thickness of more than 200 m (Suvodol mine,
These sediments correspond to two sedimentary cycles (Du-
murdzanov 1997). The first sedimentary cycle (MiddleUpper
Miocene/SarmatianMeotian) included the first two series. Dur-
ing the second sedimentary cycle (MiocenePliocene) the sec-
ond two series were formed. The upper part of the second sedi-
mentary cycle in the Macedonian part is referred to the Upper
Pontian on the basis of correlation by vertebrate fossils. The
mammalian fauna in the lignite bed corresponds to zones
MN1213 (Dumurdzanov 1997). Recent paleobotanical studies
(Kitanov 1996; Mihajlovic & Lazarevic 2004) have confirmed
the age of the second sedimentary cycle as Late Miocene
Pliocene. During the third sedimentary cycle (Pleistocene) the
basin was in its final phase of disappearance and this stage is
presented by coarse molasses (Dumurdzanov 1997).
Until now, diatom-bearing sediments from the Pelagonia
Basin have been studied only from the Ptolemais sub-basin
(Gersonde & Velitzelos 1977) and the Servia sub-basin
(Economou-Amilli 1991). Here I present the first study of the
diatom flora from the sediments in the Bitola sub-basin
(Macedonia). The aim of this research is to trace the develop-
ment of the siliceous microfossils (diatom and chrysophycean
stomatocysts), to define the corresponding chronostratigraphy
and to reconstruct the paleoecological conditions in the basin
during the sediment deposition.
Fig. 1. Schematic map of the Pelagonia Basin with location of the
borehole V-466, Bitola. The map is redrawn from outlay maps by
Van de Weerd (1983) and Dumurdzanov (1997).
Material and methods
Borehole V-466 in the village of Vranjevci, east of the city
of Bitola, is located on the far eastern margin of the Pelagonia
Basin (Fig. 1). In an unpublished report of 1986 (Suvodol
Coal Mine documentation) N. Krstiæ (Geoinstitute, Belgrade)
described the sedimentation sequence in V-466 as follows:
0.70 to 7.05 m: Diluvial bed (from the top downward):
red sand-gravelly detritus; white silty sand with gravel at the
7.05 to 11.85 m: Lacustrine siltstone with a sand inter-
bed (8.858.90 m).
11.85 to 78.00 m: Light grey diatomite, silty at some lev-
els; an interbed of micaceous sand (24.5524.70 m); vivianite
pellets, particularly abundant in interval 14.0514.85 m.
78.00 to 104.00 m: Lignite.
104.00 to 175.00 m: Whitish coarse silty sand with yel-
lowish sand bed (115.00119.00 m).
175.00 to 178.00 m: Paleorelief and/or paleorelief blocks
The present diatom analysis was carried out on 17 samples
taken from borehole V-466, Bitola area, Pelagonia Basin.
Fourteen samples contained siliceous microfossils.
The diatoms were cleaned by the procedure described by
Ognjanova-Rumenova (1991). The relative abundance of dia-
toms was estimated according to Schraders scale (Schrader
1973). An amplival microscope was used for the light micros-
copy. Photographs were taken on ORWO films, 15
aration for scanning electron microscopy was as described in
Hasle & Fryxell (1970) and samples were examined with a
Jeol Superprobe 733 and Jeol JSM T300. Terminology fol-
lows Anonymous (1975) and Ross et al. (1979) with a few ad-
ditions. For all taxa mentioned, authors names are given in
the list of taxa observed (Appendix). Ecological spectra were
composed on the basis of studies of recent diatoms by the
method of Abbott & Van Landingham (1972). The basic envi-
ronmental factors interpreted in the paleoecological analysis
were the active water reaction, temperature, nutrient, type of the
habitat and halobity. The minimum variance clustering (Wards
method) based on Squared Euclidean distance was used for the
paleoecological subdivision and classification of diatom thana-
tocenoses. Sample clustering included all samples used in the
diatom analysis (14). The ratio of diatom frustules to chryso-
phycean stomatocysts was applied (Smol 1985).
Results and discussion
Species composition, taxonomic structure and analysis of
the diatom flora
The diatom flora from the profile V-466, Bitola sub-basin,
consists of 127 species, varieties and forms of diatoms, be-
longing to 30 genera. They are referred to 18 families, 5 orders
and two classes. There are 9 species for which no definite
identification was possible and one species for which only a
tentative, but likely, specific identification can be given. The
diatom flora is composed almost entirely (85.9 %) of recent
species. The fossil species amount to 14.1 %, but in their rela-
tive abundance they show considerable dominance. The spe-
cies list of the community is given in Appendix.
The species diversity in the studied flora is attributable to
the class Pennatophyceae (78.12 %). Most of these species oc-
cur sporadically and they are characterized as rare (2
according to Schraders scale). Among the araphid diatoms,
the genus Fragilaria is the most abundant (15 species, variet-
ies and forms), whilst among the raphid diatoms (order
Raphales) the genus Navicula (sensu lato) displays the largest
species diversity in the material examined (21 species and va-
The development of the different genera of the class Centro-
phyceae, Bacillariophyta, in the continental deposits has been
used for the diatom biostratigraphic subdivision. The investi-
gated profile is generally dominated by the genera Cyclotella,
Actinocyclus and Aulacoseira of the class Centrophyceae. The
genus Cyclotella is represented in the sediments of borehole
V-466, by 11 species and varieties. Most of these have been
examined in both the light- and scanning-electron micro-
scopes. Similar species of this genus have been found in lacus-
UPPER NEOGENE SILICEOUS MICROFOSSILS FROM PELAGONIA BASIN (BALKAN) 349
Fig. 2. 1 Melosira undulata (Ehr.) Kütz., V-466, depth 25.00 m. 2 M. undulata (Ehr.) Kütz., V-466, depth 40.00 m. 3 Aulacoseira
ambigua (Grun.) Sim., V-466, depth 65.00 m. 4, 5 Cyclotella castracanei Eulenst., V-466, depth 20.00 m. 6, 7 C. castracanei Eulenst.,
V-466, depth 15.00 m. 8, 9 Cyclotella iris Brun et Hérib., V-466, depth 30.00 m. 10, 11 C. iris Brun et Hérib., V-466, depth 33.94 m.
12 C. iris Brun et Hérib., V-466, depth 70.00 m. 13 C. iris var. ovalis Brun et Hérib., V-466, depth 33.94 m. 14 C. iris var. ovalis
Brun et Hérib., V-466, depth 50.00 m. 15 C. iris var. cocconeiformis Brun et Hérib., V-466, depth 33.94 m. 16 Cyclotella sp. 1, V-466,
depth 33.94 m. 17 Cyclotella sp. 1, V-466, depth 70.00 m. 18 Cyclotella sp. 1, V-466, depth 65.00 m. 19 Cyclotella sp. 1, V-466,
depth 45.00 m. 20 Cyclotella sp. 1, V-466, depth 40.00 m. 21 Cyclotella sp. 1, V-466, depth 70.00 m. 22 Cyclotella sp. 1, V-466,
depth 45.00 m. 23, 24 Cyclotella elymaea Econ.-Am., V-466, depth 70.00 m. 25 Tetracyclus glans (Ehr.) Mills, V-466, depth 33.94 m.
26 Fragilaria leptostauron var. fossilis (Pant.) Rehák., V-466, depth 75.00 m. 27 Diploneis elliptica (Kütz.) Cl., V-466, depth
70.00 m. 28 Gomphonema grovei var. herrmanniana (Patrik) Koc., Stoerm., Yang., V-466, depth 70.00 m. 29 Cymbella ehrenbergii
Kütz., V-466, depth 61.00 m. 30 Amphora libyca Ehr., V-466, depth 75.00 m. Scale bar = 5 µm.
trine deposits throughout Southern Europe (Ognjanova-Ru-
menova 2000). On the basis of their infrageneric classification
and the ultrastructural features they may be classified into
three informal groups:
1. Cyclotella castracanei group This forms a separate
phylogenetic range (Loginova 1989). This group also includes
C. scrobicula and C. schambica. These species have been de-
scribed from maar sediments of Armenia (Aleshinskaya &
Pirumova 1982; Loginova et al. 1990) (Fig. 2.47; Fig. 5.56;
2. Cyclotella iris group The presence of almost all variet-
ies of Cyclotella iris in the investigated profile is a very inter-
esting discovery. Similar infraspecific variations of this spe-
cies had been identified only in the Upper Miocene sediments
in the Massif Central (Heribaud 1893; Serieyssol 1981, 1984)
and in the Sofia Neogene Basin (Ognjanova-Rumenova 1991,
1996) (Fig. 2.815; Fig. 3.16).
3. Cyclotella andancensis group The only member of
this group isolated was C. elymaea Economou-Amilli. It is a
rockforming species in the Neogene sediments, belonging to
the Servia sub-basin, Pelagonia Basin (Economou-Amilli
1991) (Fig. 2.2324; Fig. 6.34).
Among the Cyclotella species, there is one very interesting
dominant form in the profile Cyclotella sp. 1. This form is
very similar to Cyclotella ocellata Pantocsek in the main char-
acteristics (Lowe 1975; Kiss et al. 1996; Hakansson 2002):
simple alveoli, a single rimoportula in the submarginal zone of
the valve, the marginal fultoportulae appear on every second
to sixth valve mantle costa, the ornamentation pattern of the
central zone is typical with large depressions and granuls
on the valve face. But there are some differences: the marginal
fultoportulae have three (not two) satellite pores (Fig. 4.4); the
central fultoportulae are missing; spines are present on some
and absent on other valves. On the basis of differences in size
range, shape of the valve and some morphological characters,
two morphotypes of Cyclotella sp. 1 could be distinguished
Small valves, clearly elliptical in outline with a length/
width ratio of 5.917.6 µm/4.917.6 µm. There are 1420
striae in 10 µm (Fig. 5.14).
Large valves, circular outline with a diameter of 6.86
22.54 µm and 1220 striae in 10 µm (Fig. 4.15).
The above-described isomorphic populations of Cyclotella
sp. 1, occurring at various levels up the stratigraphic column
V-466, Bitola might be explained by paleoecological parame-
ters in the paleoenvironmental interpretation.
Another characteristic feature of the diatom flora from the
Bitola sub-basin is the development of the genus Actinocyclus,
Fig. 3. 1, 2 Cyclotella iris var. ovalis Brun et Hérib., valve exterior, V-466, depth 65.00 m. 3 C. iris var. ovalis Brun et Hérib.,
valve interior with spacing of the marginal fultoportulae, V-466, depth 65.00 m. 4 Cyclotella iris Brun et Hérib., valve exterior, V-
466, depth 65.00 m. 5 C. iris Brun et Hérib., valve interior with spacing of the marginal fultoportulae (with three satellite pores; a
and the single rimoportula, b V-466, depth 61.00 m. 6 Cyclotella iris Brun et Hérib., valve exterior, V-466, depth 61.00 m.
UPPER NEOGENE SILICEOUS MICROFOSSILS FROM PELAGONIA BASIN (BALKAN) 351
represented by various species among which the Late Miocene
and Miocene-Pliocene representatives have a high relative
abundance (45 according to Schraders scale 1973). There is
a concurrence of all representatives belonging to the genus Ac-
tinocyclus and determined as index species for Upper Miocene
sediments of the Sofia and Karlovo Basins, SW Bulgaria: A.
makarovae, A. fungiformis, Actinocyclus sp. 1 (Temniskova-
Topalova & Ognjanova-Rumenova 1997).
The genus Aulacoseira is found across a wide geographical
area throughout the Neogene, with massive development in
the Miocene and Early Pliocene. All over the world the Neo-
gene flora of Aulacoseira species consists of identical or simi-
lar species, including A. granulata, A. ambigua, A. distans, A.
islandica, etc. In general the species composition of Aula-
coseira does not differ from the above in the material from the
Bitola sub-basin investigated here. In addition, A. distans var.
scala an extinct variety with limited stratigraphic distribution,
is present and this can used in diatom biostratigraphy as an in-
All taxa (species, varieties and forms) ranking as 45 ac-
cording to Schraders scale, even if found in only one level in
the sequence, are included in the succession diagram. Plank-
tonic diatoms belonging to the class Centrophyceae prevail in
depth. Four associations can be distinguished in the develop-
ment of the diatom flora (Fig. 7) and they are demonstrated by
the multivariate cluster analysis (Fig. 8).
At the beginning of the investigated succession (65.00
77.00 m) diatoms are very abundant in the deposits. The wid-
est distribution is observed for species of Cyclotella and Acti-
nocyclus. The deposit is marked by a significant increase in
the number of specimens of C. elymaea, C. iris, Cyclotella
sp. 1 (only circular forms) and Actinocyclus makarovae, Acti-
nocyclus sp. 1. At 70.00 m Aulacoseira ambigua appears and
develops in mass. The accompanying species from the class
Pennatophyceae are species of the genus Fragilaria: F. con-
struens, F. construens f. venter., F. construens f. binodis, F.
pinnata, F. heidenii. Among the subdominant pennate species
Tetracyclus glans is established with single occurrence. The
mass development of Cymbella silesiaca in the uppermost part
of this interval is also remarkable. This diatom association
corresponds to cluster group A
in the cluster dendrogram.
Above the level of 61.00 m C. elymaea decreases consider-
ably and at 45.00 m it disappears completely. Other species of
the genus Cyclotella develop continually, but their abundance
is estimated at 34 according to Schraders scale with the ex-
Fig. 4. 1 Cyclotella sp. 1, circular morphotype, valve exterior, V-466, depth 75.00 m. 2 Cyclotella sp. 1, circular morphotype,
valve exterior, with spines at the end of the interstrial strips, V-466, depth 75.00 m. 3 Cyclotella sp. 1, circular morphotype, valve ex-
terior, V-466, depth 75.00 m. 4 Cyclotella sp. 1, detail of the valve interior with the marginal fultoportula (with three satellite pores; a
and the single rimoportula, b V-466, depth 65.00 m. 5 Cyclotella sp. 1, valve interior, V-466, depth 70.00 m.
ception of C. iris and Cyclotella sp. 1. At 50.00 m the latter
species is established in the form of the clearly elliptical mor-
photype. The abundance of Aulacoseira ambigua decreases
and the species then disappears. The majority of Pennato-
phyceae species occur singly or are absent. This second dia-
tom association corresponds to cluster group A
in the cluster
Between 25.0040.00 m Cyclotella schambica appears and
at some certain levels (25.00 m and 40.00 m) it develops in
mass. More abundant are also the varieties of C. iris: C. iris
var. cocconeiformis and C. iris var. ovalis. C. scrobicula de-
scribed by Aleshinskaya & Pirumova (1982) from Pliocene
maar sediments in Armenia also appears. The elliptical forms
of Cyclotella sp. 1 prevail over the circular ones only in the
uppermost part of the interval (25.00 m). The frequency of
species of Actinocyclus decreases considerably. During this
interval the abundance of Aulacoseira ambigua increases
again. This diatom association corresponds to the cluster
in the cluster dendrogram.
After this interval, the abundance of Cyclotella sp. 1 and C.
iris decreases, but C. castracanei becomes dominant (ranking
as 5 according to Schraders scale). The species diversity of
the diatom flora decreases and more of the subdominant taxa
belonging to the genus Actinocyclus disappear. This fourth di-
atom association corresponds to cluster group A
in the cluster
Comparison with diatom biostratigraphic zones in South
Bulgaria (Sofia and Karlovo Basins), where the paleolimno-
logical conditions are similar to those in the Bitola sub-basin
and the type of the diatom flora is also Actinocyclus (Temni-
skova-Topalova & Ognjanova-Rumenova 1997; Ognjanova-
Rumenova 2001) shows that the beginning of the Pliocene is
characterized by the disappearance of the fossil species of the
genus Actinocyclus. The extinction of the Miocene Actinocy-
clus species and the appearance of Cyclotella castracanei, de-
veloping in mass in the upper part of the borehole V-466 indi-
cate that the Miocene-Pliocene boundary probably lies in the
uppermost level of the investigated profile (15.0020.00 m).
Ecological analysis of diatom flora
Of the defined 127 species, varieties and forms of diatoms
identified, 93 (72.7 %) have a known ecology. Analysis of the
ecological spectra (Fig. 9) shows the following:
Periphytic (epiphytic) diatoms predominate (58.8 %) in al-
most all diatom thanatocoenoses, followed by periphytic
(benthic deep water form) 29.4 % and planktonic elements
(11.8 %). The planktonic representatives have a higher abun-
Fig. 5. 1 Cyclotella sp. 1, elliptical morphotype, valve exterior, V-466, depth 70.00 m. 2, 3 Cyclotella sp. 1, elliptical morphotype,
valve exterior, V-466, depth 25.00 m. 4 Cyclotella sp. 1, elliptical morphotype, valve interior, V-466, depth 70.00 m. 5 Cyclotella
castracanei Eulenst., valve exterior, V-466, depth 20.00 m. 6 C. castracanei Eulenst., valve exterior with a small frustule of Cyclotel-
la scrobicula Alesch. et Pirum. on the valve face, V-466, depth 20.00 m.
UPPER NEOGENE SILICEOUS MICROFOSSILS FROM PELAGONIA BASIN (BALKAN) 353
Fig. 6. 1 Cyclotella castracanei Eulenst., valve exterior with spines in the marginal zone, V-466, depth 20.00 m. 2 C. castracanei
Eulenst., valve interior with alveolar structure, V-466, depth 20.00 m. 3 Cyclotella elymaea Econ.-Am., V-466, depth 70.00 m. 4 C. ely-
maea Econ.-Am., V-466, depth 70.00 m.
dance and they compose the rock-forming complex. The ratio
of planktonic to periphytic diatom (Fig. 10) shows a decline
over the lowermost level (77.0065.00 m), reflecting mainly a
decline in varieties of the infraspecific group of Cyclotella
iris. Above this level and up to 50.00 m the ratio increases as
the plankton component, particularly Aulacoseira ambigua,
increases. A greater variability in valve form of Cyclotella
sp. 1 appears at the top of the stratigraphic column (20.00
30.00 m). The distinct dominance of periphyton shows that
these diatom sediments most probably represent a shallow-
The diatoms represent a fresh-water flora. Besides oligoha-
lobous (halophobous and indifferent) diatoms, a small per-
centage of halophilous (3.4 %), mesohalobous (3.4 %) and
marine (2.3 %) forms occur. Their quantitative proportion in
the communities varies in a vertical direction (Fig. 10). A rela-
tively weak salinity increase is observed in the interval be-
tween 77.0061.00 m, but above this level the percentage of
halophilous and mesohalobous diatoms decreases and finally
they disappear. A peak in marine, mesohalobous and halophil-
ous species occurrence appears again at 33.94 m and this coin-
cides with a high abundance of the elliptical form of Cyclotel-
la sp. 1. This increased infraspecific variability could be
caused by salinity changes, which are directly controlled by
the hydrological and hydrochemical regimes of the basin.
Grouping of diatoms according to their pH-preferences
shows that alkaliphilous (52.3 %) and pH-indifferent (29.5 %)
diatoms clearly predominate. In the levels of lower mineraliza-
tion (40.00 m) the number of indifferent diatoms increases
(Fig. 10). Some acidophilous diatoms like Tetracyclus glans,
Navicula kotschii, Eunotia minor, E. pectinalis etc., appear to-
gether with pH-indifferent species, but their percentages in
depth are always below 10 %.
As regards geographical distribution the cosmopolitan
group (69.3 %) is predominant, followed by boreal (18.2 %)
and north-alpine species (10.2 %). Tropical species, that is Cy-
clotella iris var. charetonii and Melosira undulata, constitute
2.3 % of the assemblage.
Results of the relative proportions of diatom
Where lacustrine conditions are concerned, chrysophytes
can provide additional and complementary information to that
Fig. 8. Samples clustering, including all investigated samples from
borehole V-466. Var1 (15.00 m), Var2 (20.00 m), Var3 (25.00 m),
Var4 (30.00 m), Var5 (33.94 m), Var6 (40.00 m), Var7 (45.00 m),
Var8 (50.00 m), Var9 (55.00 m), Var10 (61.00 m), Var11
(65.00 m), Var12 (70.00 m), Var13 (75.00 m), Var14 (77.00 m).
Fig. 7. Diatom diagram from borehole V-466, Bitola. 1 diatomaceous clays, 2 sandy clays, 3 coal deposits.
UPPER NEOGENE SILICEOUS MICROFOSSILS FROM PELAGONIA BASIN (BALKAN) 355
of diatoms alone. Chrysophytes are a group of predominantly
flagellated and planktonic algae that occur most abundantly in
circumneutral pH, low-alkalinity, low-phosphorus, low-pro-
ductivity lakes. A characteristic feature of this algal group is
the production of endogenously formed siliceous resting cysts
or statospores, which are well-preserved in many continental
sediments. Diatoms, however, also occur in more eutrophic
lakes, and include both planktonic and benthic forms. As a
group, cysts have been analysed in relation to diatoms (Smol
1985): the ratio of cysts to diatoms has been proposed as a
trophic indicator in the succession.
Tracing the ratio of diatom frustules/chrysophycean stoma-
tocysts we observed two peaks in the development of the latter
(Fig. 10). The lower part of the profile (77.0040.00 m) is
Fig. 9. Histograms Percentage ratio of the ecological diatom groups. pH spectrum: 1 alkaliphilic, 2 acidophilic, 3 alkalibion-
tic, 4 indifferent. Halobion spectrum: 1 halophobous, 2 halophilous, 3 indifferent, 4 mesohalobous, 5 marine. Habitat
spectrum: 1 planktonic, 2 periphytic (epiphytic), 3 periphytic (deep water form). Geographical distribution: 1 cosmopolitans,
2 north-alpine forms, 3 boreal forms.
Fig. 10. Percentage diagrams of the different ecological diatom groups in the depth of borehole V-466, Bitola.
characterized by a relatively lower abundance of chryso-
phytes. At the beginning of this stage, the plankton contains a
low concentration of eutrophic indicators, but these decrease
rapidly with the growth of large populations of Cyclotella spp.
If the genus is accepted as an indicator of oligotrophic condi-
tions, this would indicate that the trophic level of the pelagic
zone had decreased. Chrysophyte abundances generally in-
crease from 33.94 m to 20.00 m and then decrease dramatical-
ly to level at 15.00 m. At the top of the core, the eutrophic in-
dicators appear to decrease again in both the periphyton and
the plankton components.
This paper presents the first biostratigraphic study of the
Late MiocenePliocene lacustrine diatom flora from the
Macedonian part of the Pelagonia Basin. The lower part of the
Pliocene is marked by the extinction of Miocene Actinocyclus
species and the first appearance of Cyclotella castracanei de-
veloping in mass in the uppermost part of the sequence.
A diverse taxonomical composition is reported for the
genus Cyclotella. Similar species of the genus have been iden-
tified from lacustrine deposits throughout Southern Europe.
The Cyclotella sp. 1 present in the studied material has a high
infraspecific variability as regards the valve outline, which
might be explained by the variable ecological conditions in
the paleolake during the sediment deposition.
There is a concurrence of all representatives belonging to
the genus Actinocyclus and determined as index species for
Upper Miocene sediments of the Sofia and Karlovo Basins,
SW Bulgaria: A. makarovae, Actinocyclus fungiformis, Acti-
nocyclus sp. 1.
The results of the diatom analyses presented here allow a
reconstruction of the paleoecological conditions of the Bitola
sub-basin, Pelagonia Basin, at the end of the Miocene and the
beginning of the Pliocene.
Acknowledgments: This study was financially supported by
the Bulgarian Ministry of Science and Education under Grant
NZ 903/1999 and it is a contribution to the Project IGCP 449:
Global correlation of Late Cenozoic fluvial deposits. I am
thankful to Dr. N. Krstiæ for the borrowed unpublished report
including the geological section of borehole V-466 and to Dr.
D. Mihajlovic for providing the samples and for helpful dis-
List of the diatom taxa found in the sediment sequence of borehole
Family: Thalassiosiraceae Lebour emended Hasle
Family: Stephanodiscaceae Makarova
Cyclotella castracanei Eulenstein, 1868
C. elymaea Economou-Amilli, 1991
C. iris Brun et Héribaud, 1893
C. iris var. charetonii (Héribaud) Serieyssol, 1982
C. iris var. cocconeiformis Brun et Héribaud, 1893
C. iris var. integra Peragallo et Héribaud, 1893
C. iris var. ovalis Brun et Héribaud, 1893
C. schambica (Eulenstein) Aleschinskaya et Pirumova, 1981
C. scrobicula Aleschinskaya et Pirumova, 1990
Cyclotella sp. 1
Cyclotella sp. 2
Family: Melosiraceae Kützing
Melosira undulata (Ehrenberg) Kützing, 1844
M. undulata var. normannii Arnott, 1882
Ellerbeckia kochii (Pantoscek) Valeva et Temniskova, 1993
Family: Aulacoseiraceae Moisseeva
Aulacoseira ambigua (Grunow) Simonsen, 1979
A. distans (Kützing) Simonsen, 1979
A. distans var. scala (Ehrenberg) Ognjanova-Rumenova, 1998
A. granulata (Ehrenberg) Simonsen, 1979
A. granulata var. angustissima (O. Müller) Simonsen, 1979
A. islandica (O. Müller) Simonsen, 1979
A. valida (Grunow) Krammer, 1990
Family: Hemidiscaceae Hendey emended Simonsen
Actinocyclus fungiformis Temniskova, Khursevich, Valeva, 1993
A. gorbunovii (Sheshukova) Moisseeva et Sheshukova, 1981
A. aff. kutzingii (A. Schmidt) nov. comb.
A. makarovae (Temniskova et Ognjanova) Temniskova et
Actinocyclus sp. 1
Actinocyclus sp. 2
Family: Fragilariaceae (Kützing) De Toni
Fragilaria bituminosa Pantoscek, 1889
F. brevistriata Grunow, 1885
F. capucina Desmazieres, 1925
F. construens (Ehrenberg) Grunow, 1862
F. construens f. binodis (Ehrenberg) Hustedt, 1957
F. construens f. venter (Ehrenberg) Hustedt, 1957
F. heidenii Østrup, 1910
F. leptostauron (Ehrenberg) Hustedt, 1931
F. leptostauron var. dubia (Grunow) Hustedt, 1931
F. leptostauron var. fossilis (Pantocsek) Reháková, 1965
F. martyi (Héribaud) Lange-Bertalot, 1993
F. pinnata Ehrenberg, 1843
F. pinnata var. trigona (Brun et Héribaud) Hustedt, 1913
F. transylvanica Pantocsek, 1892
F. virescens Ralfs, 1843
Family: Diatomaceae Dumortier
Meridion circulare var. constrictum (Ralfs) Van Heurck, 1881
Family: Tabellariaceae Schutt
Tetracyclus emarginatus (Ehrenberg) W. Smith, 1856
T. glans (Ehrenberg) Mills, 1835
Family: Naviculaceae Kützing
Navicula anglica var. minuta Cleve, 1895
N. arenariaeformis Pantocsek, 1889
N. arenariaeformis var. major Gasse, 1980
N. capitata var. lueneburgensis (Grunow) Patrick et Reimer, 1966
N. digitoradiata (Gregory) Ralfs, 1861
N. gastrum (Ehrenberg) Kützing, 1844
N. gastrum var. signata Hustedt, 1936
N. hasta Pantocsek, 1892
N. kotschyi Grunow, 1860
N. laterostrata Hustedt, 1925
N. menisculus Schumann, 1867
N. placentula (Ehrenberg) Kützing, 1844
N. platystoma Ehrenberg, 1838
N. platystoma var. pantocsekii Wislouch et Kolbe, 1927
N. porifera var. opportuna (Hustedt) Lange-Bertalot, 1985
N. protracta (Grunow) Cleve, 1894
N. pseudoanglica Lange-Bertalot, 1985
N. radiosa Kützing, 1844
UPPER NEOGENE SILICEOUS MICROFOSSILS FROM PELAGONIA BASIN (BALKAN) 357
N. scutelloides W. Smith, 1856
N. tuscula Ehrenberg, 1841
Navicula sp. 1
Sellaphora bacillum (Ehrenberg) Mann, 1989
S. pupula var. capitata (Hustedt) nova comb.
Stauroneis anceps Ehrenberg, 1843
S. phoenicenteron (Nitzsch) Ehrenberg, 1843
S. smithii Grunow, 1860
Gyrosigma acuminatum (Kützing) Rabenhorst, 1853
Pinnularia borealis Ehrenberg, 1843
P. esox Ehrenberg, 1843
P. viridis (Nitzsch) Ehrenberg, 1843
P. viridis var. leptogongyla (Grunow) Cleve, 1895
Caloneis schumanniana (Grunow) Cleve, 1894
Diploneis carpathorum (Pantocsek) Pantocsek, 1913
D. elliptica (Kützing) Cleve, 1891
D. marginestriata Hustedt, 1922
D. papula (A. Schmidt) Cleve, 1894
Neidium iridis (Ehrenberg) Cleve, 1894
Family: Achnathaceae Kützing
Cocconeis neodiminuta Krammer, 1991
C. minimus Loseva, 1982
C. placentula Ehrenberg, 1838
C. placentula var. euglypta (Ehrenberg) Grunow, 1884
Achnanthes conspicua Mayer, 1919
A. delicatula (Kützing) Grunow, 1880
A. delicatula ssp. hauckiana (Grunow) Lange-Bertalot, 1985
A. dispar Cleve, 1891
A. lanceolata var. elliptica Cleve, 1891
Family: Eunotiaceae Kützing
Eunotia minor (Kützing) Grunow, 1881
E. pectinalis (Dillw.? Kützing) Rabenhorst, 1864
Family: Rhoicospheniaceae Mann
Rhoicosphenia abbreviata (Agardh) Lange-Bertalot, 1980
Family: Cymbellaceae (Kützing) Grunow
Cymbella affinis Kützing, 1844
C. cuspidata Kützing, 1844
C. ehrenbergii Kützing, 1844
C. helvetica Kützing, 1844
C. leptoceros (Ehrenberg) Kützing, 1844
C. naviculiformis (Auerswald) Cleve, 1894
C. parva (W.Smith) Wolle, 1890
C. silesiaca Bleisch, 1864
C. subcuspidata Krammer, 1982
Amphora bornetti Héribaud, 1903
A. delphinea var. jamalinensis (Cleve et Grunow) Cleve, 1895
A. delphinea var. minor Cleve, 1895
A. libyca Ehrenberg, 1840
A. pediculus (K
tzing) Grunow, 1880
Family: Gomphonemataceae (K
Gomphonema angustatum (K
tzing) Rabenhorst, 1864
G. grovei var. herrmanniana (Patrik) Kociolec, Yang et Stoermer,
Family: Epithemiaceae Grunow
Epithemia sorex Kützing, 1844
E. turgida (Ehrenberg) Kützing, 1844
E. turgida var. granulata (Ehrenberg) Brun, 1880
E. zebra var. porcellus (Kützing) Grunow, 1862
E. zebra var. saxonica (Kützing) Grunow, 1862
Family: Rhopalodiaceae Topatschevski
Rhopalodia gibba (Ehrenb.) O. Müller, 1895
Family: Nitzschiaceae Grunow
Nitzschia heufleriana Grunow, 1881
N. sinuata var. tabellaria Grunow, 1881
Hantzschia amphioxys (Ehrenb.) Grunow, 1880
Family: Surirellaceae Kützing
Surirella bifrons Ehrenberg, 1843
S. biseriata f. punctata (Meister) Krasske, 1925
Cymatopleura elliptica var. constricta Grunow, 1862
C. solea (Brébisson) W. Smith, 1851
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