GEOLOGICA CARPATHICA, 50, 2, BRATISLAVA, APRIL 1999
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST
BIOEVENTS AND INTEGRATED BIOCHRONOLOGY
OF THE TITHONIAN TO VALANGINIAN
IN THE WESTERN BALKANIDES, BULGARIA
ISKRA LAKOVA, KRISTALINA STOYKOVA and DARIA IVANOVA
Geological Institute, Bulgarian Academy of Sciences, Acad. G. Bonchev Str. Bl. 24, 1113 Sofia, Bulgaria
(Manuscript received January 26, 1998; accepted in revised form December 9, 1998)
Abstract: This joint study on calpionellids, calcareous nannofossils and calcareous dinocysts of the Tithonian, Berriasian
and Valanginian sediments in the Western Balkanides allowed detailed documentation of the stratigraphic ranges and
selection of reliable diagnostic bioevents, within the parallel microfossil successions. The individual zonations based on
calpionellids, nannofossils and dinocysts are made more precise, refined and directly correlated to each other. The calpionellid
zones and subzones recorded in Bulgaria are widely accepted for the Mediterranean. The proposed nannofossil zonation is
considered as a regional one for the Western Balkanides. Ten dinocyst zones are recognized three of them being introduced
here: Stomiosphaera wanneri, Colomisphaera conferta and Carpistomiosphaera valanginiana. A number of intrinsic coin-
ciding bioevents between two or all the three planktonic microfossil groups are documented and interpreted related to
certain stage and substage boundaries. This approach of direct correlation of three fossil groups enhances the argumenta-
tion and resolution of the zonation. It may represent a basis for a reference biochronology of the Tithonian to Valanginian,
applicable to various lithologies in the Tethyan Realm.
Key words: Bulgaria, Western Balkanides, Tithonian, Berriasian, Valanginian, integrated biochronology, calpionellids,
calcareous nannofossils, calcareous dinocysts.
vides an uninterrupted stratigraphic Kimmeridgian to Hau-
terivian succession. We sampled the uppermost 20 m of the
Gintsi Formation, the whole Glozhene Formation (37 m) and
the lower part of the Salash Formation (108 m) (Figs. 2, 4, 6).
Introduction and sections studied
The thick and continuous Upper Jurassic and Lower Creta-
ceous pelagic carbonate sequence outcropping extensively in
the area of the West Balkan Mountains and West Fore-Bal-
kan, Bulgaria, provides excellent material for detailed, com-
prehensive biostratigraphic studies on several planktonic mi-
crofossil groups and working out of a joint scale of
successive bioevents and integrated zonations.
This study encompasses the individual biostratigraphic re-
sults on the following microfossil groups: calpionellids, cal-
careous nannofossils and calcareous dinocysts (cadosinids
and stomiosphaerids) from successions of pelagic nodular,
pure micritic and clayey limestones of Tithonian, Berriasian
and Valanginian age in the Western Balkanides (West Balkan
Mountains and West Fore-Balkan) (Fig. 1). Three formations
have been studied: the Gintsi Formation (pink and grey nod-
ular limestones), Glozhene Formation (grey hard micritic
limestones) and Salash Formation (alternation of micritic
limestones, clayey limestones and marls).
A detailed combined sampling has been carried out of
three reference sections Barlya, Gorno Belotintsi 1 and
Gorno Belotintsi 2 (Figs. 28). Calpionellids and calcare-
ous dinocysts are determined in thin-sections, and calcare-
ous nannofossils in smear slides. The section of Barlya is lo-
cated at the northern end of the village of Barlya, Sofia
District, very close to the Bulgarian-Yugoslavian border, in
the area of the West Balkan Mountains. This section pro-
Fig. 1. Outcrops of the Gintsi, Glozhene and Salash Formation in
the West Balkan Mountains and West Fore-Balkan and location of
the sections studied.
152 LAKOVA, STOYKOVA and IVANOVA
The sections of Gorno Belotintsi 1 and Gorno Belotintsi 2
are situated 3 km to the north of the village of Gorno Be-
lotintsi, Montana District, in the area of the West Fore-Bal-
kan. In Gorno Belotintsi 1 section we sampled the upper part
of Gintsi Formation (20 m) and the Glozhene Formation, its
thickness there being 240 m, and in Gorno Belotintsi 2 sec-
tion the lowest 40 m of the Salash Formation. These two
sections are positioned stratigraphically one over another but
the lithological transitions between the Glozhene and Salash
Formations and the Berriasian-Valanginian boundary are ob-
scured by some absences of exposures.
The calpionellids were studied by I. Lakova, calcareous
nannofossils by K. Stoykova and calcareous dinocysts by D.
In the last four decades, the taxonomic and bio-
stratigraphic studies on calpionellids proved that these
planktonic microfossils are essential for the fine division,
precise dating and reliable long-distance correlation of Mid-
dle Tithonian to Valanginian pelagic carbonates throughout
the Mediterranean Realm. The advantages of the calpionel-
lids in biostratigraphy are their relatively rapid evolution
consisting of distinguished steps, the unequivocal succes-
sion of numerous bioevents (first and last occurrences, phyl-
etic transitions and dramatic increases in abundance) which
are used to define the boundaries of 7 interval-zones and to-
tal-range zones and at least 12 interval subzones, as well as
the common geographical distribution, the lack of provin-
cialism and quantitative abundance.
The originally proposed calpionellid zonal schemes by Re-
mane (1971) and Alleman et al. (1971) were progressively
refined, divided into subzones, completed and the criteria of
placing the boundaries were specified (Pop 1974, 1976;
Borza 1984; Remane et al. 1986; Trejo 1980; Altiner & Öz-
kan 1991; Lakova 1993). Previously, Tithonian and Berria-
sian calpionellids of the Western Balkanides were studied by
Bakalova-Ivanova (1986). We apply here a slightly modified
version (Lakova & Stoyanova 1997) of the zonal and sub-
zonal subdivisions by Pop (1994, 1997) and Reháková &
Michalík (1997) which differs significantly in terms of sub-
zones from Blau & Grüns (1997) zonation.
Middle and Late Tithonian
The first occurrence (FO) of Chitinoidella dobeni and re-
lated species (Chitinoidella colomi, Chitinoidella tithonica,
Chitinoidella slovenica) which are the first representatives
of the family Codonellidae with microgranular wall indicate
the base of the Chitinoidella Zone. This level coincides with
the Lower/Middle Tithonian boundary. The zone is divided
into two subzones Chitinoidella dobeni and Chitinoidella
boneti, the base of the latter being marked by the FO of
Chitinoidella boneti (Grandesso 1977; Borza 1984).
The Praetintinnopsella Zone is defined between the FO of
Praetintinnopsella andrusovi and the FO of representatives
of the family Calpionellidae with hyaline calcite wall
(Grandesso 1977). This zone corresponds to the Middle/Up-
per Tithonian boundary interval.
The standard Crassicollaria Zone is restricted between the
FOs of calpionellids with hyaline wall and the explosion of
Calpionella alpina. In most of the sections studied else-
where in the West Balkan Mountains three species appear si-
multaneously at the lower boundary of the zone Tintin-
nopsella carpathica, Tintinnopsella remanei and
Crassicollaria intermedia. The Crassicollaria Zone cor-
responds to the Late Tithonian.
There is no agreement on the subzonal division of this
zone. We follow the bipartite division proposed at the
Sümeg Meeting (Remane et al. 1986), the name of the upper
Intermedia Subzone being replaced by Crassicollaria
massutiniana because of the controversial and confusing
use of the Intermedia Subzone. The base of the Crassicol-
laria massutiniana Subzone is marked by the FO of Calpi-
onella grandalpina, i.e. the large-sized elongated Tithonian
form of Calpionella alpina s.l.
There is, indeed, a potential to define a third, uppermost
subzone within the Crassicollaria Zone on the basis of the
FO of Crassicollaria brevis, which is usually later than the
FO of Calpionella grandalpina. We do not accept, however,
the Colomi Subzone erected by Pop (1994) and Reháková
& Michalík (1997) since our studies have proved that Cras-
sicollaria colomi occurs only in the lower part of the over-
laying Calpionella Zone and has nothing to do with the Cras-
sicolaria Zone. An additional criterion to determine the
upper boundary of the Crassicollaria Zone is the last occur-
rence (LO) of Calpionella elliptalpina, the so-called ho-
meomorph of Calpionella elliptica. This event coincides
with the explosion of C. alpina (Figs. 2, 3).
The Standard Calpionella Zone is defined between two
easily determinable biostratigraphic events the explosion
of Calpionella alpina s.s., i.e. the medium-sized spherical
form of C. alpina s.l., and the FO of Calpionellopsis sim-
plex. The boundary between the Crassicollaria and Calpi-
onella zones was recommended as boundary between the Ti-
thonian and Berriasian stages at the LyonNeu Châttel
Colloquium in 1973. In terms of ammonite zones and sub-
stages, the Calpionella Zone corresponds to the Berriasella
jacobi Zone (Early Berriasian) + Tirnovella occitanica Zone
The zone has been divided into three subzones. Within the
Calpionella Zone, two successive bioevents are used for def-
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 153
Fig. 2. Range chart of calpionellids and zonation of Barlya section, West Balkan Mountains.
inition of subzones. The FOs of Remaniella ferasini and/or
Remaniella duranddelgai indicate the lower boundary of
Remaniella ferasini Subzone, and the FO of Calpionella el-
liptica the base of Calpionella elliptica Subzone. In addi-
tion, we documented in many sections another two bioevents
within the Calpionella alpina Subzone which offer a tool for
further refining the division of the Early Berriasian. These
are the FO of Crassicollaria colomi in the lower portion and
the FO of Calpionella minuta, the so-called small degener-
ative Berriasian form of Calpionella alpina s.l., in the up-
per half of the Calpionella alpina Subzone (Fig. 3). In the
uppermost part of the Calpionella Zone, within the Calpi-
onella elliptica Subzone, the FO of Tintinnopsella longa en-
ables the definition of a forth subzone, the Tintinnopsella
longa Subzone, as proposed by Pop (1994) but this subzone
is still not widely accepted.
The Standard Calpionellopsis Zone is defined between the
FOs of Calpionellopsis simplex and Calpionellites darderi.
It is divided into three subzones: Calpionellopsis simplex,
Calpionellopsis oblonga and Praecalpionellites murgeanui.
The lower boundary of the Calpionellopsis oblonga Subzone
is placed at the FO of Calpionellopsis oblonga, and the base
of the Praecalpionellites murgeanui Subzone at the FO of
The Calpionellopsis Zone coincides totally with the am-
monite Fauriella boissieri Zone (Late Berriasian) according
to Blau & Grün (1997) and Bulot (1996). The cited authors
changed the definition of the lower boundary of the Valang-
inian at the base of the ammonite Pertransiens Zone. How-
ever, Pop (1994, 1997) followed the classical definition of
the base of the Valanginian at the lower boundary of the am-
monite Otopeta Zone; in this case the uppermost Prae-
calpionellites murgeanui Subzone of the Calpionellopsis
Zone belongs to the basal part of the Valanginian.
Within the Calpionellopsis oblonga Subzone the diversity
of calpionellid species reached its culmination thus enabling
a recognition of additional bioevents. In the section of Bar-
lya, the successive FOs of Calpionellopsis oblonga, Loren-
ziella hungarica and/or Lorenziella plicata and Remaniella
filipescui are documented. This series of successive bioev-
ents may represent an additional tool for finer subdivision
The Standard Calpionellites Zone is a total-range zone of
the genus Calpionellites. The FO of Calpionellites darderi is
the criterion for its lower boundary, whereas the LO of spe-
cies of genus Calpionellites (Calpionellites coronata, Calpi-
onellites major, Calpionellites caravacaensis) indicates the
upper boundary. The zone is divided into two subzones
the Calpionellites darderi Subzone and Calpionellites major
154 LAKOVA, STOYKOVA and IVANOVA
Fig. 3. Range chart of calpionellids and zonation of Gorno Belotintsi 1 section, West Fore-Balkan: 1 nodular limestones (Gintsi Forma-
tion); 2 micritic and/or intraclastic limestones (Glozhene Formation); 3 marly limestones and marls (Salash Formation); 4 no ex-
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 155
Subzone, as proposed by Pop (1994) and widely accepted
and confirmed in many areas of the Mediterranean Bioprov-
ince. The lower boundary of the Calpionellites major Sub-
zone is placed at the FO of Calpionellites major.
The Calpionellites Zone corresponds to the ammonite
Pertransiens and Campylotoxum zones (Early Valangin-
ian except its base).
We have also documented the FO of Calpionellites coro-
nata within the Calpionellites darderi Subzone, as well as
the FO of Calpionellites caravacaensis within the Calpion-
ellites major Subzone (Fig. 8). These two bioevents may be
used for further subdivision of the Calpionellites Zone.
The disappearance of genus Calpionellites at the Early/Late
Valanginian boundary marks a significant decline of calpi-
onellids in both diversity and abundance. After this event, the
calpionellid associations consist only of a small number of
species of the genera Tintinnopsella and Lorenziella. The up-
permost Tintinnopsella Zone is defined between the LO of
Calpionellites and the total extinction of calpionellids.
This zone corresponds to the Late Valanginian and to a
great part of the Hauterivian, too, according to Pop (1994)
and Reháková (1995). In the Western Balkanides, only the
Late Valanginian part of the Tintinnopsella Zone has been
studied so far. In this lower part, the successive LOs of
Lorenziella hungarica, Lorenziella plicata and Tintinnopsel-
la longa represent a potential for definition of subzones.
Calcareous nannofossil studies of the TithonianValangin-
ian interval in Bulgaria have been done since 1995. The first
work does not appear to have reached a satisfying degree of
biostratigraphic resolution (Stoykova 1995). Detailed nan-
nofossil studies both in the Tethyan and Boreal Bioprovinces
were done by Thierstein (1971, 1973, 1976) and Roth
(1983). Recently, Bralower et al. (1989) and Gardin &
Manivit (1993) published refined nannofossil biostratigra-
phy for this interval (JurassicCretaceous). In conclusion,
there is no one widely accepted nannofossil scheme yet. In
this work we propose five calcareous nannofossil biozones
for the KimmeridgianValanginian interval considered as a
regional zonation for the area of the Western Balkanides.
This zonation is comparable to some extent to the zonal
schemes mentioned above.
The main advantage of the present joint study is the direct
correlation of the recorded nannofossil events with calpi-
Fig. 4. Range chart of calcareous nannofossils and zonation of Barlya section, West Balkan Mountains.
156 LAKOVA, STOYKOVA and IVANOVA
onellid and calcareous dinocyst ones. The samples originating
from the section of Barlya yielded relatively diverse and mod-
erately well preserved nannofloras (Fig. 4), whereas in the
Gorno Belotintsi sections the assemblages are less diverse and
preservation is poorer (Figs. 5, 8). Taking into account these
preservation problems affecting nannofossil occurrence we
have compiled a series of nannofossil bioevents (Fig. 9).
When selecting events for zonation, we attempted to
choose the most reliable, clearly distinctive and repeatable
ones in all sections. Bioevents within the zones are consid-
ered of less biostratigraphic importance because they are not
recognizable in each section.
The zonation proposed here consists of five interval-zones
based on successive FOs of the index-species, spanning the
Late Kimmeridgian to Valanginian interval: Parhabdolithus
embergeri Zone (Late Kimmeridgian), Conusphaera mexica-
na Zone (Early to Late Tithonian), Microstaurus chiastius
Zone (Latest TithonianEarly and Middle Berriasian), Nan-
noconus steinmannii Zone (Late BerriasianEarly Valangi-
nian) and Tubodiscus verenae Zone (Late Valanginian).
Fig. 5. Range chart of calcareous nannofossils and zonation of Gorno Belotintsi 1 section, West Fore-Balkan (for legend see Fig. 3).
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 157
Only the uppermost part of the Kimmeridgian is studied in
Parhabdolithus embergeri Zone
The zone is defined as an interval between the FO of Par-
habdolithus embergeri and the FO of Conusphaera mexica-
na mexicana. The nannofossil assemblages of this zone are
of low diversity and are dominated by Ellipsagelosphaera
and Cyclagelosphaera representatives. The FO of Conus-
phaera mexicana minor, the immediate precursor of Conus-
phaera mexicana mexicana, is documented within this zone
in the section of Barlya (Fig. 4).
Conusphaera mexicana mexicana Zone
The zone is regarded as an interval between two clearly
determinable bioevents: the FO of Conusphaera mexicana
mexicana at the beginning of Tithonian and the FO of Mi-
crostaurus chiastius in the Late Tithonian. In addition, the
FO of Faviconus multicolumnatus is another reliable event,
approximating to the base of this zone (Figs. 4, 5). The nan-
nofossil assemblages change significantly starting from the
base of this zone. They are dominated by Conusphaera mex-
icana mexicana, Conusphaera mexicana minor and ellip-
sagelosphaerids. In the lower part of the zone, the stepwise
FOs of Polycostella beckmannii and Polycostella senaria
are recorded (Fig. 4). The FO of Umbria granulosa in the
upper part of this zone requires further specification.
Microstaurus chiastius Zone
The interval from the FO of Microstaurus chiastius to the
FO of Nannoconus steinmannii. The zone equates to the
topmost Tithonian and Early and Middle Berriasian. The FO
of Microstaurus chiastius at the base of the zone is a suitable
diagnostic event, occurring in all the sections studied (Figs.
Within this zone, a succession of first occurrences is ob-
served, some of them representing the early evolution of the
nannoconids group: Nannoconus sp.n., N. compressus, N.
globulus minor. The last occurrence of Polycostella beck-
mannii is a less reliable event, but it could also be helpful
and needs further elucidation. Cretarhabdus angustiforatus,
another commonly used marker-species has its FO restricted
at the middle of the Calpionella elliptica calpionellid zone.
Fig. 6. Range chart of calcareous dinocysts and zonation of Barlya section, West Balkan Mountains.
158 LAKOVA, STOYKOVA and IVANOVA
Nannoconus steinmannii Zone
This zone is considered to be an interval between the FOs
of Nannoconus steinmannii minor and Tubodiscus verenae.
Nannoconids are the major dominant component of the as-
semblages. The base of this zone corresponds to the explo-
sion in nannoconid abundance, a prominent broadly recog-
nizable event (Figs. 4, 5).
It should be noted that the FO of Micrantholithus speeton-
ensis is recorded in the lower part of the zone. Micran-
tholithus speetonensis is usually regarded as an Late Valang-
inian Boreal marker-species. Recently, Gardin (in Bulot
1996) has shown its FO during the Late Berriasian and earli-
est Valanginian in the NW Tethyan basin. These data are
consistent to our finds (Figs. 4, 5).
The nannofossil data in the present study enable a good
biostratigraphic resolution in the middle and upper part of
this zone. Therefore, it should be further examined in other,
more suitable localities.
Tubodiscus verenae Zone
The base of this zone is marked by the FO of Tubodiscus
verenae an event which approximates to the Lower/Upper
Valanginian boundary in terms of calpionellids. A couple of
additional first co-occurrences makes the base of the zone
easily determinable: the FOs of Nannoconus cornuta, N.
quadratus, etc. Other stratigraphically important species ap-
pearing within this zones are Calcicalathina oblongata,
Nannoconus bermudezii and Diadorhombus rectus (Fig. 4).
The interest in the study of calcisphaerids concentrated in
the past mainly on its biostratigraphic implication, was direct-
ed in the last 1520 years to another aspect elucidation of
Fig. 7. Range chart of calcareous dinocysts and zonation of Gorno Belotintsi 1 section, West Fore-Balkan (for legend see Fig. 3).
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 159
their biological affinities and taxonomical identification of
species belonging to the calcareous dinocysts. In spite of the
new approaches and tendencies in the study of calcisphaerids,
their stratigraphic importance for the Late KimmeridgianEar-
ly Valanginian time interval remains significant.
On the basis of the succession of vertical ranges of ca-
dosinid and stomiosphaerid species proved in several sec-
tions, Nowak (1968) proposed 6 zones from the Late Kim-
meridgian to the Hauterivian: Moluccana, Pulla, Malmica,
Cieszynica-carpathica, Minutissima-carpathica and Echina-
ta. Later on, Nowak (1976) revised his first zonation. Further
contributions to the biostratigraphy of calcisphaerids were
made by Borza (1969, 1984), Borza & Michalík (1986), Øe-
hánek (1992), Øehánek & Heliasz (1993), Øehánek & Cecca
(1993), Vaíèek et al. (1994).
The detailed and parallel microfossil studies carried out on
the Tithonian to Valanginian of the Western Balkanides allow
a series of successive FOs of calcareous dinocyst species to be
recorded (Figs. 6, 7). These FOs are directly correlated to the
calpionellid events and to the stratigraphic time scale. The cal-
careous dinocyst zonation here recorded consists of 10 inter-
val-zones, the bases of all being defined by the FO of index-
species (Fig. 9). The following dinocyst zones previously
proposed by different authors are confirmed in the West Bal-
kan and West Fore-Balkan: Carpistomiosphaera borzai, Carp-
istomiosphaera tithonica, Parastomiosphaera malmica, Colo-
misphaera tenuis, Colomisphaera fortis, Stomiosphaerina
proxima and Stomiosphaera echinata. In this study, the defini-
tion of their bases and the chronostratigraphic assignment of
these zone are specified. Three new dinocyst interval-zones
are introduced within the Uppermost BerriasianValanginian
interval: Stomiosphaera wanneri, Colomisphaera conferta and
Carpistomiosphaera valanginiana zones (Figs. 6, 7, 8).
Carpistomiosphaera borzai Zone
The lower boundary is defined at the FO of Carpistomi-
osphaera borzai. The index-species is associated with Cado-
sina parvula, Colomisphaera pieniniensis, C. lapidosa and C.
carpathica. The zone corresponds partly to Parhabdolithus
embergeri nannofossil zone and to the Late Kimmeridgian
(Figs. 6, 7).
Carpistomiosphaera tithonica Zone
The FO of Carpistomiosphaera tithonica at the base of the
Tithonian marks the lower boundary of this zone. The suc-
Fig. 8. Range chart and zonations of calpionellids, calcareous nannofossils and calcareous dinocysts of Gorno Belotintsi 2 section, West
160 LAKOVA, STOYKOVA and IVANOVA
Fig. 9. Bioevents and integrated zonations of the Tithonian, Berriasian and Valanginian of the Western Balkanides.
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 161
cessive first occurrences of Cadosina semiradiata semiradi-
ata, C. fusca fusca and Committosphaera pulla are docu-
mented within the zone. The Carpistomiosphaera tithonica
Zone spans the Kimmeridgian-Tithonian boundary interval
Parastomiosphaera malmica Zone
The base of this zone is defined at the FO of Parastomi-
osphaera malmica. The zone corresponds to the Early Titho-
nian. Its upper boundary is placed in the basal part of the
calpionellid Chitinoidella Zone thus the top of Parastomi-
ophaera malmica Zone slightly overlaps the very base of
Chitinoidella Zone (Figs. 6, 7).
Colomisphaera tenuis Zone
The FO of the index-species Colomisphaera tenuis marks
the base of this zone. Colomisphaera tenuis Zone corre-
sponds exactly to the calpionellid Chitinoidella Zone (Mid-
dle Tithonian). Our combined calpionellid and dinocyst
studies proved the coeval FOs of Chitinoidella dobeni and
Colomisphaera tenuis (Figs. 6, 7).
Colomisphaera fortis Zone
The lower boundary of this zone is defined by the FO of
Colomisphaera fortis in the middle of the Praetintinnopsella
Zone. Within the Colomisphaera fortis Zone, the abundance
and diversity of calcareous dinocysts significantly de-
creased. This zone coincides with the upper part of the calpi-
onellid Praetintinnopsella Zone and the Tintinnopsella rema-
nei Subzone of Crassicollaria Zone (earliest Late Tithonian)
(Figs. 6, 7).
Stomiosphaerina proxima Zone
The lower boundary of this zone is defined by the FO of Sto-
miosphaerina proxima an event coinciding with the FOs of
Calpionella grandalpina and Microstaurus chiastius in the
middle of the Upper Tithonian (Fig. 9). It suggests that Øe-
háneks (1992) proposal to place the Tithonian-Berriasian
boundary at the FO of Stomiosphaerina proxima is not applica-
ble. This is a relatively longer-ranging zone which is compara-
ble to the sum of the calpionellid Crassicollaria massutiniana,
Calpionella alpina, Remaniella ferasini, Calpionella elliptica,
Calpionellopsis simplex subzones and the lower part of the
Calpionellopsis oblonga Subzone (latest Late Tithonian and the
whole Berriasian except its very top) (Figs. 6, 7).
Stomiosphaera wanneri Zone
The FO of the index-species Stomiosphaera wanneri marks
the base of this zone and the FO of Colomisphaera conferta
its top. The zone is here proposed as a new one. Within the
Stomiosphaera wanneri Zone, Colomisphaera heliosphaera
makes its FO. This zone corresponds approximately to the up-
per third of the calpionellid Calpionellopsis oblonga Subzone
and the Praecalpionellites murgeanui Subzone (latest Berria-
sian and Early Valanginian) (Figs. 6, 7).
Colomisphaera conferta Zone
This zone is the interval between the FO of Colomisphaera
conferta and the FOs of Carpistomiosphaera valanginiana
and/or Colomisphaera vogleri. The zone is introduced in this
paper. In terms of calpionellid zonation, the Colomisphaera
conferta Zone corresponds to the calpionellid Calpionellites
darderi and Calpionellites major subzones (Early Valanginian)
(Figs. 6, 7, 8).
Carpistomiosphaera valanginiana Zone
The FO of the index-species Carpistomiosphaera valangini-
ana defines the lower boundary of the zone. The zone is first
defined in this study. It is comparable to the calpionellid Tintin-
nopsella Zone in its Late Valanginian part (Figs. 6, 8)
Stomiosphaera echinata Zone
The FO of the index-species marks the lower boundary of
this zone, whereas the upper boundary is still not deter-
mined. The studied part of Stomiosphaera echinata Zone is
tentatively assigned to the Late Valanginian and Early Hau-
terivian on the basis of diagnostic ammonite finds in the top-
most part of the section of Barlya (Fig. 6).
Microfossil bioevents, zonations and
The chronostratigraphic assignment of the calpionellid
zones from Chitinoidella to Tintinnopsella (Middle Titho-
nianHauterivian) is given according to Pop (1994) and the
bioevents and zonations on nannofossils and calcareous di-
nocysts are correlated to those on calpionellids (Fig. 9). The
Kimmeridgian-Tithonian boundary is fixed on the basis of
diagnostic FO of nannofossil and calcareous dinocyst spe-
The FOs of nannofossils Faviconus multicolumnatus and
Conusphaera mexicana mexicana (the lower boundary of Co-
nusphaera mexicana nannofossil zone) and the simultaneous
FO of dinocyst species Committosphaera pulla in the middle
portion of Carpistomiosphaera tithonica dinocyst zone mark
the Kimmeridgian-Tithonian boundary (Figs. 4, 6).
At the Lower/Middle Tithonian boundary, the almost co-
eval first occurrences of the calpionellid Chitinoidella dobe-
ni and dinocyst Colomisphaera tenuis are documented, thus
determining the bases of Chitinoidella dobeni calpionellid
subzone and Colomisphaera tenuis dinocyst zone, respec-
162 LAKOVA, STOYKOVA and IVANOVA
tively. Later in the Tithonian, the FO of Praetintinnopsella
andrusovi (i.e. the base of Praetintinnopsella calpionellid
zone) coincides with the FO of the nannofossil Umbria
granulosa granulosa close to the Middle/Upper Tithonian
boundary. Within the Late Tithonian (Crassicollaria Zone)
there are a clearly documented simultaneous FOs of repre-
sentatives of calpionellides, nannofossils and dinocysts:
Calpionella grandalpina, Microstaurus chiastius, Nannoco-
nus sp.n., Stomiosphaerina proxima. This gives ground to
define the coinciding lower boundaries of three biostrati-
graphic units: Crassicollaria massutiniana calpionellid sub-
zone, Microstaurus chiastius nannofossil zone and Stomio-
sphaerina proxima dinocyst zone (Fig. 9).
The Tithonian/Berriasian boundary is easily determinated
in terms of calpionellids at the base of the Calpionella Zone
on the explosion of Calpionella alpina and the LO of C. el-
liptalpina, events occurring together with the FOs of nanno-
fossil species Cruciellipsis cuvillieri and Nannoconus com-
pressus (Figs. 2, 4).
Another coinciding microfossil events to be mentioned are
the FOs of calpionellid Calpionellopsis simplex (base of the
Calpionellopsis Zone) and the nannofossils Nannoconus
steinmannii minor and N. dolomiticus (base of the N. stein-
mannii nannofossil zone). The base of Calpionellopsis Zone
corresponds to the boundary between the T. occitanica and F.
boissieri ammonite zones commonly regarded as Middle/Up-
per Berriasian boundary (Blau & Grün 1997), even though
there is no final agreement on the substage division of the
Berriasian. Later on, Calpionellopsis oblonga and Nannoco-
nus steinmannii steinmannii make their first co-occurrences
(at the base of the Calpionellopsis oblonga Subzone). In the
upper portion of this subzone there is a coincidence of the
FOs of calpionellid Remaniella filipescui and the dinocyst
Stomiosphaera wanneri, the latter event defining the base of
the St. wanneri dinocyst zone (Fig. 9).
The Berriasian/Valanginian boundary remains hardly de-
terminable in terms of microfossil bioevents and zonations
because the only criterion to place this boundary is the FO of
Praecalpionellites murgeanui (the lower boundary of Pr.
murgeanui calpionellid subzone), a species which is very
rare indeed. On the other hand, within the basal Valanginian
it is much easier to recognize the lower boundary of the
Calpionellites Zone (FO of Calpionellites darderi), coincid-
ing with the lower boundary of the Colomisphaera conferta
dinocyst zone defined by the FO of C. conferta (Fig. 9).
At the Lower/Upper Valanginian boundary or a little low-
er, the FOs of two dinocyst species, Carpistomiosphaera va-
langiniana and Colomisphaera vogleri, are used to define
the base of the C. valanginiana Zone. The LO of representa-
tives of the genus Calpionellites which approximates this
event is much more difficult to recognize because the extinc-
tion is rather gradual and slow. In the Late Valanginian (low-
er part of Tintinnopsella Zone) the first co-occurrences of
the nannofossil species Diadorhombus rectus and the calcar-
eous dinocyst Stomiosphaera echinata are recorded (the
base of the St. echinata Zone) (Figs. 4, 6). A Late Valangin-
ianEarly Hauterivian age is suggested for this zone on the
basis of diagnostic ammonite finds.
Apart from the coinciding events in the evolution of calpi-
onellids, nannofossils and calcareous dinocysts reviewed
above, there is a number of non-coinciding events which
can be helpful for finer and more precise subdivision and
correlation of the Tithonian, Berriasian and Valanginian
stages (Fig. 9). Moreover, this triple common study of strati-
graphic ranges, bioevents and zonations may serve as a ref-
erence biochronology of the Tithonian to Valanginian age
and provides a background for further application of inde-
pendent studies on nannofossils and/or dinocysts in different
lithologies lacking calpionellids.
Acknowledgements: We would like to thank Prof. I.
Sapunov and Prof. P. Tchoumatchenco, Geological Institute,
Sofia, for their kind advices on the regional geology of the
Western Balkanides and their critical notes on the text. This
work was undertaken in the framework of Project 72/95-96
Mesozoic correlations of the Moesian Platform funded by
the Peri-Tethyan Program and Project 515/95 of the Bulgari-
an Scientific Fund.
Plate I: Calpionellids of the Western Balkanides, Bulgaria. (All
figures 500×). Fig. 1. Chitinoidella dobeni Borza, Middle Titho-
nian, Chitinoidella Zone, Ch. dobeni Subzone, Gorno Belotintsi 1
section, sample 15. Fig. 2. Chitinoidella boneti Doben, Middle Ti-
thonian, Chitinoidella Zone, Ch. boneti Subzone, Barlya section,
sample 0302. Fig. 3. Tintinnopsella remanei Borza, Upper Titho-
nian, Crassicollaria Zone, T. remanei Subzone, Barlya section,
sample 301. Fig. 4. Calpionella minuta Houa, Middle Berriasian,
Calpionella Zone, C. elliptica Subzone, Gorno Belotintsi 1 section,
sample 48. Fig. 5. Lorenziella hungarica Knauer & Nagy, Lower
Valanginian, Calpionellites Zone, Ctes major Subzone, Gorno Be-
lotintsi 2 section, sample 70. Fig. 6. Crassicollaria brevis Remane,
Upper Tithonian, Crassicollaria Zone, Cr. massutiniana Subzone,
Gorno Belotintsi 1 section, sample 27. Fig. 7. Calpionella gran-
dalpina Nagy, Upper Tithonian, Crassicollaria Zone, Cr. massutini-
ana Subzone, sample 28. Fig. 8. Calpionella elliptalpina Nagy,
Upper Tithonian, Crassicollaria Zone, Cr. massutiniana Subzone,
Gorno Belotintsi 1 section, sample 26. Fig. 9. Calpionella alpina
Lorenz, Middle Berriasian, Calpionella Zone, C. elliptica Subzone,
Gorno Belotintsi 1 section, sample 48. Fig. 10. Remaniella ferasini
(Catalano), Middle Berriasian, Calpionella Zone, C. elliptica Sub-
zone, Gorno Belotintsi 1 section, sample 51. Fig. 11. Calpionella
elliptica Cadisch, Middle Berriasian, Calpionella Zone, C. elliptica
Subzone, Gorno Belotintsi 1 section, sample 51. Fig. 12. Calpi-
onellopsis simplex (Colom), Upper Berriasian, Calpionellopsis
Zone, Csis simplex Subzone, Barlya section, sample 332. Fig. 13.
Calpionellites darderi (Colom), Lower Valanginian, Calpionellites
Zone, Ctes major Subzone, Gorno Belotintsi 2 section, sample 75.
Fig. 14. Tintinnopsella longa (Colom), Upper Berriasian, Calpi-
onellopsis Zone, Csis oblonga Subzone, Barlya section, sample
334. Fig. 15. Calpionellopsis oblonga (Cadisch), Upper Berria-
sian, Calpionellopsis Zone, Csis oblonga Subzone, Barlya section,
sample 335. Fig. 16. Praecalpionellites murgeanui (Pop), Lower
Valanginian, Calpionellites Zone, Ctes darderi Subzone, Barlya
section, sample 340. Fig. 17. Calpionellites major (Colom), Lower
Valanginian, Calpionellites Zone, Ctes major Subzone, Gorno Be-
lotintsi 2 section, sample 67.
PLATE I 163
164 LAKOVA, STOYKOVA and IVANOVA
Plate II: Calcareous nannofossils from the Western Balkanides, Bulgaria. (All figures 2000
, except otherwise stated). Fig. 1. Parhabdo-
lithus embergeri (Noël) Stradner, Upper Kimmeridgian, P. embergeri Zone, Barlya section, sample 59. Figs. 2, 3. Faviconus multicolum-
natus Bralower, Lower Berriasian, M. chiastius Zone, Barlya section, sample 319. Fig. 4. Conusphaera mexicana mexicana Trejo, Lower
Berriasian, M. chiastius Zone, Barlya section, sample 320. Fig. 5. Cyclagelosphaera deflandrei Manivit, Lower Valanginian, N. steinman-
nii Zone, sample 339. Fig. 6. Cyclagelosphaera deflandrei Manivit, Upper Valanginian, Gorno Belotintsi 2 section, sample 80. Fig. 7.
Cruciellipsis cuvillieri (Manivit) Thierstein, Lower Valanginian, N. steinmannii Zone, Gorno Belotintsi 2 section, sample 67. Fig. 8. Nan-
noconus globulus globulus Brönnimann, Lower Valanginian, N. steinmannii Zone, Barlya section, sample 339. Fig. 9. Nannoconus com-
pressus Bralower & Thierstein, Lower Berriasian, M. chiastius Zone, Barlya section, sample 310. Fig. 10. Nannoconus steinmannii minor
Deres & Achéritéguy, Upper Berriasian, N. steinmannii Zone, Barlya section, sample 332. Fig. 11. Nannoconus steinmannii steinmannii
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 165
List of taxa recorded
Chitinoidella dobeni Borza
Chitinoidella slovenica Borza
Chitinoidella colomi Borza
Chitinoidella tithonica Borza
Chitinoidella boneti Doben
Praetintinnopsella andrusovi Borza
Tintinnopsella carpathica (Murgeanu & Filipescu)
Tintinnopsella remanei Borza
Tintinnopsella longa (Colom)
Tintinnopsella subacuta (Colom)
Tintinnopsella dacica Filipescu & Dragastan
Crassicollaria intermedia (Durand Delga)
Crassicollaria massutiniana (Colom)
Crassicollaria brevis Remane
Crassicollaria parvula Remane
Crassicollaria colomi Doben
Calpionella alpina Lorenz
Calpionella grandalpina Nagy
Calpionella elliptalpina Nagy
Calpionella minuta Houa
Calpionella elliptica Cadisch
Remaniella ferasini (Catalano)
Remaniella duranddelgai Pop
Remaniella cadischiana (Colom)
Remaniella filipescui Pop
Calpionellopsis simplex (Colom)
Calpionellopsis oblonga (Colom)
Lorenziella hungarica Knauer & Nagy
Lorenziella plicata Remane
Sturiella oblonga Borza
Sturiella dolomitica Grün & Blau
Praecalpionellites murgeanui (Pop)
Praecalpionellites siriniaensis Pop
Calpionellites darderi (Colom)
Calpionellites coronata Trejo
Calpionellites uncinata Cita & Pasquaré
Calpionellites major (Colom)
Calpionellites caravacaensis Allemann
Assipetra infracretacea (Thierstein) Roth
Calcicalathina oblongata (Worsley) Thierstein
Conusphaera mexicana mexicana Trejo
Conusphaera mexicana minor Bralower
Cretarhabdus angustiforatus (Black) Bukry
Cruciellipsis cuvillieri (Manivit) Thierstein
Cyclagelosphaera deflandrei Manivit
Diadorhombus rectus Worsley
Faviconus multicolumnatus Bralower
Micrantholithus hoschultzii (Reinhardt) Thierstein
Micrantholithus speetonensis Perch-Nielsen
Microstaurus chiastius (Worsley) Grün in Grün & Allemann
Nannoconus bermudezii Brönnimann
Nannoconus compressus Bralower & Thierstein
Nannoconus cornuta Deres & Achéritéguy
Nannoconus dolomiticus Cita & Pasquaré
Nannoconus globulus globulus Brönnimann
Nannoconus globulus minor Bralower
Nannoconus quadratus (No
l) Deres & Achéritéguy
Nannoconus steinmannii steinmannii Kamptner
Nannoconus steinmannii minor Deres & Achéritéguy
Parhabdolithus embergeri (No
Polycostella beckmannii Thierstein
Polycostella senaria Thierstein
Tubodiscus verenae Thierstein
Umbria granulosa granulosa Bralower & Thierstein
Cadosina fusca fusca Wanner
Cadosina fusca cieszynica Nowak
Cadosina minuta Borza
Cadosina parvula Nagy
Cadosina semiradiata olzae Nowak
Cadosina semiradiata semiradiata Wanner
Carpistomiosphaera borzai (Nagy)
Carpistomiosphaera tithonica Nowak
Carpistomiosphaera valanginiana Borza
Colomisphaera carpathica (Borza)
Colomisphaera cieszynica Nowak
Colomisphaera conferta Øehánek
Colomisphaera fortis Øehánek
Colomisphaera heliosphaera (Vogler)
Colomisphaera lapidosa (Vogler)
Colomisphaera lucida Borza
Colomisphaera minutissima (Colom)
Colomisphaera nagyi (Borza)
Colomisphaera pieniniensis (Borza)
Colomisphaera tenuis (Nagy)
Colomisphaera vogleri (Borza)
Committosphaera pulla (Borza)
Committosphaera sublapidosa (Vogler)
Parastomiosphaera malmica (Borza)
Stomiosphaera alpina (Leischner)
Stomiosphaera echinata Nowak
Stomiosphaera moluccana Wanner
Stomiosphaera wanneri Borza
Stomiosphaerina proxima Øehánek
Kamptner, Upper Berriasian, N. steinmannii Zone. Fig. 12. Nannoconus steinmannii steinmannii Kamptner, Upper Berriasian, N. stein-
mannii Zone, Gorno Belotintsi 1 section, sample 52. Fig. 13. Microstaurus chiastius (Worsley) Grün in Grün & Allemann, Upper Titho-
nian, M. chiastius Zone, Barlya section, sample 307, 1000×. Fig. 14. Micrantholithus speetonensis Perch-Nielsen, Upper Berriasian, N.
steinmannii Zone, Barlya section, sample 335, 1000×. Fig. 15. Micrantholithus speetonensis Perch-Nielsen, Upper Valanginian, T. verenae
Zone, Barlya section, sample 107, 1000×. Fig. 16. Micrantholithus speetonensis Perch-Nielsen, Upper Berriasian, N. steinmannii Zone,
Gorno Belotintsi 1 section, sample 53, 1000×.
Continuation of the text to Plate II
166 PLATE III
CALPIONELLID, NANNOFOSSIL AND CALCAREOUS DINOCYST BIOEVENTS 167
in Bulgaria. Acta Geol. Hung., 29, 12, 8992.
Blau B. & Grün J., 1997: Late Jurassic/Early Cretaceous revised
calpionellid zonal and subzonal division and correlation with
ammonite and absolute time scales. Miner. slovaca, 29, 45,
Borza K., 1969: The microfacies and microfossils of the Upper Ju-
rassic and Lower Cretaceous of the Klippen Belt of the Western
Carpathians. Sbor. Slov. Akad. Vied, 1301 (in German).
Borza K., 1984: The Upper JurassicLower Cretaceous parabios-
tratigraphic scale on the basis of Tintinninae, Cadosinidae, Sto-
miosphaeridae, Calcisphaerulidae and other microfossils from
the West Carpathians. Geol. Zbor. Geol. Carpath., 35, 5, 539
Borza K. & Michalík J., 1986: Problems with delimitation of the
Jurassic/Cretaceous boundary in the Western Carpathians.
Acta Geol. Hung., 29,12, 133149.
Bralower T., Monechi S. & Thierstein H., 1989: Calcareous nanno-
fossil zonation of the Jurassic-Cretaceous boundary interval
and correlation with the geomagnetic polarity timescale. Mar.
Micropaleontology, 14, 153235.
Bullot L. (Ed.), 1996: The Valanginian Stage. Bull. Inst. Roy. Sci.
Natur. Belg., Sci. de la Terre, Supp., 66, 1118.
Gardin S. & Manivit H., 1993: Upper Tithonian and Berriasian cal-
careous nannofossils from the Vocontian Trough (SE France):
biostratigraphy and sequence stratigraphy. Bull. Cent. Rech.
Expl. Prod. Elf-Aquit., 17, 277289.
Grandesso P., 1977: Gli strati a prealpionellidi del Titoniano e i
loro rapporti con il Rosso Ammonitico Veneto. Mem. Sci.
Geol., 32, 114.
Lakova I., 1993: Middle Tithonian to Berriasian praecalpionellid
and calpionellid zonation of the Western Balkanides, Bulgar-
ia. Geologica Balcan., 23, 6, 324.
Lakova I. & Stoyanova D., 1997: Calpionellid zonation of Titho-
nian-Valanginian carbonate successions in the West Fore-Bal-
can (Montana Region). Proc. Conf. 50 years of Geology,
Sofia University, 710 (in Bulgarian).
Nowak W., 1968: Stomiosphaerids of the Cieszyn Beds (Kim-
meridgian-Hauterivian) in the Polish Cieszyn Silesia and their
stratigraphical value. Rocz. Pol. Tow. Geol., 38, 23, 275
Nowak W., 1976: Parastomiosphaera malmica (Borza) from the
Polish Carpathians and their stratigraphical value for Lower Ti-
thonian deposits. Rocz. Pol. Tow. Geol., 46, 12, 89134 (in
Pop G., 1974: Calpionellid zones from the Tithonian-Valanginian
of the Resita belt (Southern Carpathians). Rev. Roum. Géol.
Géophys. Géogr., Geol., 18, 109125 (in French).
Pop G., 1976: TithonianValanginian calpionellid zones from Cuba.
D. S. Inst. Geol. Geofiz., 62, 237266.
Pop G., 1994: Calpionellid evolutive events and their use in bios-
tratigraphy. Rom. J. Stratigraphy, 76, 724.
Pop G., 1997: Tithonian to Hauterivian praecalpionellids and calpi-
onellids: bioevents and biozones. Miner. slovaca, 29, 45,
Reháková D., 1995: New data on calpionellid distribution in the
Upper Jurassic/Lower Cretaceous formations (Western Car-
pathians). Miner. slovaca, 27, 308318 (in Slovak).
Reháková D. & Michalík J., 1997: Evolution and distribution of
calpionellids the most characteristic constituents of Lower
Cretaceous Tethyan microplankton. Cretaceous Research, 18,
Øehánek J., 1992: Valuable species of cadosinids and stomio-
spherids for determination of the Jurassic-Cretaceous bound-
ary (vertical distribution, biozonation). Scripta, 22, 117122.
Øehánek J. & Cecca F., 1993: Calcareous dinoflagellate cysts bios-
Plate III: Calcareous dinocysts from the Western Balkanides, Bul-
garia. (All figures 400
, except otherwise stated). Fig. 1. Colo-
misphaera nagyi Borza, Upper Kimmeridgian, C. borzai Zone,
Gorno Belotintsi 1 section, sample 5. Fig. 2. Colomisphaera pien-
iniensis (Borza), Upper Kimmeridgian, C. borzai Zone, Gorno Be-
lotintsi 1 section, sample 8. Figs. 3, 4. Stomiosphaera moluccana
Wanner, Upper Kimmeridgian, C. borzai Zone, Gorno Belotintsi 1
section, samples 3, 10. Fig. 5. Colomisphaera carpathica (Borza),
Lower Tithonian, C. tithonica Zone, Gorno Belotintsi 1 section,
sample 11. Figs. 6, 7. Carpistomiosphaera borzai Borza, Lower
Tithonian, C. borzai Zone, Gorno Belotintsi 1 section, samples 5, 9.
Figs. 8, 9. Carpistomiosphaera tithonica Nowak; 8 Lower Ti-
thonian, C. tithonica Zone, Gorno Belotintsi 1 section, sample 10;
9 Middle Tithonian, C. tenuis Zone, Gorno Belotintsi 1 section,
sample 16. Fig. 10. Colomisphaera tenuis (Nagy), Middle Titho-
nian, C. tenuis Zone, Gorno Belotintsi 1 section, sample 17. Figs.
11, 12. Parastomiosphaera malmica (Borza), Lower Tithonian, P.
malmica Zone, Gorno Belotintsi 1 section, samples 12, 14. Figs.
13, 14. Cadosina fusca fusca Wanner; 13 Middle Tithonian, C.
tenuis Zone, Gorno Belotintsi 1 section, sample 18; 14 Lower
Berriasian, St. proxima Zone, Gorno Belotintsi 1 section, sample
38. Fig. 15. Colomisphaera fortis Øehánek, Upper Tithonian, C.
fortis Zone, Gorno Belotintsi 1 section, sample 23. Fig. 16. Cado-
sina minuta Borza, Upper Berriasian, St. wanneri Zone, Gorno Be-
lotintsi 1 section, sample 54. Fig. 17. Stomiosphaera wanneri Bor-
za, Upper Berriasian, St. wanneri Zone, Gorno Belotintsi 1 section,
sample 53. Figs. 18, 19. Stomiosphaerina proxima Øehánek; 18
Upper Berriasian, St. proxima Zone, Gorno Belotintsi 1 section,
sample 52; 19 Lower Berriasian, St. proxima Zone, Gorno Be-
lotintsi 1 section, sample 42. Fig. 20. Stomiosphaera alpina
Leischner, Middle Berriasian, St. proxima Zone, Gorno Belotintsi 1
section, sample 49. Fig. 21. Colomisphaera vogleri (Borza), Low-
er Valanginian, C. valanginiana Zone, Gorno Belotintsi 2 section,
sample 75. Figs. 22, 23. Cadosina semiradiata semiradiata Wan-
ner; 22 Lower Tithonian, C. tithonica Zone, Gorno Belotintsi 1
section, sample 10; 23 Lower Valanginian, C. conferta Zone,
Gorno Belotintsi 2 section, sample 65, 300
. Figs. 24, 25. Cadosi-
na semiradiata olzae Nowak, Lower Valanginian, C. conferta
Zone, Gorno Belotintsi 2 section, samples 65, 69, 300
. Figs. 26,
27. Colomisphaera conferta Øehánek; 26 Lower Valanginian,
C. conferta Zone, Gorno Belotintsi 1 section, sample Sal 1; 27
Lower Valanginian, C. conferta Zone, Gorno Belotintsi 2 section,
sample 61, 300
. Fig. 28. Colomisphaera heliosphaera (Vogler),
Lower Valanginian, C. conferta Zone, Gorno Belotintsi 2 section,
sample 58, 300
. Figs. 29, 30. Carpistomiosphaera valanginiana
Borza; 29 Lower Valanginian, C. valanginiana Zone, Gorno Be-
lotintsi 2 section, sample 73, 300
; 30 Upper Valanginian, C.
valanginiana Zone, Gorno Belotintsi 2 section, sample 84, 300
Alleman F., Catalano R., Fares F. & Remane J., 1971: Standard
calpionellid zonation (Upper Tithonian-Valanginian) of the
Western Mediterranean province. Proc. II Plankt. Conf.,
Roma, 1970, 13371340.
Altiner D. & Özkan S., 1991: Calpionellid zonation in North-West-
ern Anatolia (Turkey) and calibration of the stratigraphic ranges
of some benthic foraminifers at the Jurassic-Cretaceous bound-
ary. Geologica Romana, 27, 215235.
Bakalova-Ivanova D., 1986: Peculiarities of the Calpionella Zone
168 PLATE III
tratigraphy in Upper Kimmeridgian-Lower Tithonian pelagic
limestones of Marches Apennines (Central Italy). Rev. Micro-
paléont., 36, 2, 143163.
Øehánek J. & Heliasz Z., 1993: Microfacies and microbiostratigraphy
of the OxfordianLower Kimmeridgian on the basis of Ca-
dosinids and Stomiosphaerids in the Czestochowa region of Po-
land. Geol. Carpathica, 44, 2, 8193.
Remane J., 1971: The calpionellids, plankton Protozoa from the
Mesozoic Mediteranean seas. Ann. Guébhard, 47, 369432
Remane J., Bakalova-Ivanova D., Borza K., Knauer J., Nagy I., Pop
G. & Tardi-Filacz E., 1986: Agreement on the subdivision of
the standard calpionellid zones defined at the II plankton con-
ference, Roma 1970. Acta Geol. Hung., 29, 12, 514.
Roth P., 1983: Jurassic and Lower Cretaceous calcareous nanno-
fossils in the Western Nord Atlantic (Site 534): biostratigra-
phy, preservation and some observations on biogeography and
paleoceanography. In: Sheridan R.E. et al. (Eds.): Init. Rept.
DSDP, 76, US Gouvernment Printing Office, Washington,
Stoykova K., 1995: Calcareous nannofossil occurrence across the
Jurassic-Cretaceous boundary interval in West Bulgaria. Rev.
Bulg. Geol. Soc., 56, 2, 7786 (in Bulgarian).
Thierstein H.R., 1971: Tentative Lower Cretaceous calcareous nan-
noplankton zonation. Eclogae Geol. Helv., 64, 459488.
Thierstein H.R., 1973. Lower Cretaceous calcareous nannoplankton
biostratigraphy. Abh. Geol. Bundesanst., 29, 152.
Thierstein H.R., 1976: Mesozoic calcareous nannoplankton biostratig-
raphy of marine sediments. Mar. Micropaleontology, 1, 325362.
Trejo M., 1980: Stratigraphic distribution of the Mesozoic Tinntinids
from Mexico. Rev. Inst. mex. Petroleo, 12, 413 (in Spanish).
Vaíèek Z., Michalík J. & Reháková D., 1994: Early Cretaceous
stratigraphy, paleogeography and life in Western Carpatians.
Beringeria, 10, 1108.
LAKOVA, STOYKOVA and IVANOVA