GeolCarp_Vol67_No4_329

www.geologicacarpathica.com

GEOLOGICA CARPATHICA, AUGUST 2016, 67, 4, 329–345

doi: 10.1515/geoca-2016-0021

Shallow-water benthic foraminiferal assemblages and their

response to the palaeoenvironmental changes — example

from the Middle Miocene of Medvednica Mt.

(Croatia, Central Paratethys)

ÐURÐICA PEZELJ, JASENKA SREMAC and VLADIMIR BERMANEC

Department of Geology and Paleontology, Faculty of Science, University of Zagreb, Horvatovac 102a, 10000 Zagreb, Croatia;

djurdjica.pezelj@geol.pmf.hr, jsremac@geol.pmf.hr, vberman@public.carnet.hr

(Manuscript received November 26, 2015; accepted in revised form June 7, 2016)

Abstract: During the Middle Miocene, the northern Croatian Medvednica Mt. was an island within the Pannonian
Basin System, situated on the SW margin of the Central Paratethys Sea. Miocene sedimentary rocks (the Late Bade-
nian Bulimina–Bolivina Zone and Ammonia beccarii ecozone), from the SW slopes of Medvednica Mt. clearly re ect
a transgressive-regressive cycle with emersion during the Badenian/Sarmatian boundary. After the initial phase of
transgression, the pioneer Elphidium–Asterigerinata–Ammonia benthic foraminiferal assemblage is present in bioclas-
tic limestones, such as those at the Borovnjak locality. This marginal marine assemblage from a highly energetic,
normally saline environment is characterized by poor preservation of foraminiferal tests, low diversity and strong
domination. Advanced transgression is followed by establishment of the Elphidium–Asterigerinata assemblage, which
is found in biocalcsiltites from the laterally deeper and more sheltered environment at Gornje Vrap e. This diverse
assemblage is typical for inner/middle shelf environment with suf cient oxygen content. A general shallowing upward
trend can be recognized at both localities, followed by visible interchange of different sedimentological and biotic
features. Successive and oscillatory regression in the marginal marine environment was followed by salinity  uctua-
tions and  nal brackish conditions with Ammonia–Elphidium assemblage. The laterally deeper environment reacted to
regressive trends on  ner scale with almost regular changes of benthic foraminiferal assemblages in the laminae
(Heterolepa–Bolivina assemblage/Bolivina–Cassidulina assemblage/Elphidium–Asterigerinata assemblage). It might
re ect sea-level oscillations with periodically increased siliciclastic and nutrient input from land or in uence of sea-
sonality on benthic assemblages, which occurred in the advanced phase of the regression near the Badenian/Sarmatian
boundary.

Key words: Middle Miocene, Late Badenian, Central Paratethys, palaeoecology, benthic foraminifera.

Introduction

The north-western part of Croatia during the Middle Mio-
cene belonged to the south-western margin of the Pannonian
Basin System (Central Paratethys)  ooded by the Paratethys
Sea (Fig. 1A, B). Flooding was a consequence of extensional
processes between the Alpine-Carpathian and the Dinaride
tectonic units (Paveli  2001; Vrsaljko et al. 2006;  ori  et al.
2009). The upper part of the Middle Miocene is a particularly
interesting period in the development of the Paratethys,
because it represents the end of the fully marine regime in the
basin, due to the global regression and sea-level fall
(Harzhauser & Piller 2007; Hohenegger et al. 2014). During
the Late Badenian, equivalent of the lower part of the Middle
Serravalian Mediterranean substage (Fig. 2), the Central
Paratethys-Mediterranean corridor via Slovenia was proba-
bly closed (Rögl 1999; Ková  et al. 2007), although some
authors believe that the marine connection was still open
(Selmeczi et al. 2012; Bartol et al. 2014). The Badenian/Sar-
matian Paratethys substage boundary can be traced through
emersion and unconformity at many localities, but the exact

timing of this event and palaeoenvironmental conditions are
still the subject of debate of many geologists (Ri nar et al.
2002; Sopková et al. 2007; Radivojevi et al. 2010; Gedl &
Peryt 2011

;

Hy n et al. 2012;

liwi ski et al. 2012

The Upper Badenian deposits are exposed along the SW

slopes of the Medvednica Mt. and have been under research
for many years (Kochansky 1944; Šiki  1967; Pezelj & Sre-
mac 2007; Pezelj et al. 2014), but detailed quantitative ana-
lyses of foraminiferal assemblages were not yet published.
These deposits represent transgressive-regressive trends,
with pronounced discontinuity at the Badenian/Sarmatian
boundary (Avani  et al. 2005; Vrsaljko et al. 2006). This
paper offers detailed analyses of shallow-marine benthic
fora miniferal assemblages, particularly sensitive to sea-level
oscillations. Triggers of these changes can be of different ori-
gin, from eustatic changes, to global and regional tectonic
transtension/transpression phases. Special attention was paid
to the laminated marls in the upper part of the Gornje Vrap e
section. Such occurrence was observed at several localities
within the Central Paratethys (Mihajlovi  & Kne evi  1989;

Báldi 2006; Crihan & M run eanu 2006; Bartol 2009), but

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laminae were sterile or poor in fossils, and their stratigraphic
position is uncertain. Some authors regard laminated sections
as lithological markers of the Badenian/Sarmatian boundary
(Bartol 2009), while others assign them to the Sarmatian
(Crihan & M run eanu 2006). Laminated deposits at Gornje
Vrap e locality are extremely fossiliferous, with clear almost
regular exchange of benthic foraminiferal assemblages,
enabling both: stratigraphic and palaeoecological
interpretation.

The aim of this paper is to apply the results of benthic fora-

miniferal assemblage analyses to reconstruct the Late Bade-
nian palaeoenvironments present on the south-western slopes
of the Mt. Medvednica and explain events and environmental
conditions at the Badenian/Sarmatian boundary. We will try
to follow the respond of the Late Badenian benthic foramini-
feral assemblages to stressful regressive trends, recognize
the timing of these changes and establish a model of the
Bade nian/Sarmatian boundary, which could be applied to the
wider Paratethys region.

Geological settings and description of sections

Medvednica Mt. is a prominent topographical unit in

north-western Croatia occupying an area of ca. 300 km

(Fig. 1A). Its core is predominantly composed of Palaeozoic
and Mesozoic rocks of varied origin, surrounded by younger,
Palaeogene, Neogene and Quaternary sedimentary rocks
(Šiki 1995). The Middle Miocene shelf deposits represent
an elongated ring-shaped belt around the recent Medved-
nica Mt., reflecting the shape of the depositionary area
around the former Medvednica island within the Paratethys
Sea (Fig. 1B). A specific development of the Late Badenian
deposition in SW part of the Medvednica Mt. was recognized
by Kochansky (1944) who described it as “Dolje sedimen-

tary type”. These deposits represent a transgressive-regres-
sive sequence, with final emersion at the Badenian/Sarmatian
boundary (Fig. 3). Basal Upper Badenian deposits in this
area are transgressive breccia and conglomerate deposited
over the Mesozoic sedimentary rocks. Along the beaches
clastic deposition continued in form of sandstones (biocal-
crudite and biocalcarenite) but in areas away from the terres-
trial input, coralgal biolithites (Lithothamnium limestone)
are present. Bryozoans are often significant coproducers of

Fig. 1. A — Geographical position of studied area in Croatia and simpli ed geological map of Medvednica Mt. with geographic range of
the Middle Miocene (Badenian and Sarmatian) sediments (modi ed after Šiki 1995). Analyzed sections are marked with arrows.
B — Paleogeographical setting showing position of Medvednica Mt. in the southern Pannonian Basin System of Central Paratethys during
the Late Badenian (modi ed after Ková et al. 2007).

Fig. 2. Miocene chronostratigraphic stages of Paratethys and Medi-
terranean (modi ed after Lourens et al. 2004; Strauss et al. 2006;
Hilgen et al. 2009; Pezelj et al. 2013) with highlighted age of ana-
lysed sections.

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biolithites. Diverse benthic fauna, including bivalves Luci-
noma borealis (Linnè), Ostrea and pectinids lived on and
within the coralgal buildups. Echinoids, corals and benthic
foraminifera are also common, with taxa typical for the Late
Badenian (Vrsaljko et al. 1995, 2006). One short episode of
sediment coarsening is visible at the Borovnjak locality
(Fig. 3), but a generally transgressive trend is typical for the
greater part of the Late Badenian. At the locality Gornje
Vrap e deposition of biocalcisiltites indicates further deepe-
ning of the sedimentary basin. Global sea level drop in the
uppermost Badenian, (Fig. 2) can be recognized from shal-
lowing upward sequences and increase of siliciclastic input
in the depositionary basin (Vrsaljko et al. 2006). At the loca-
lity Gornje Vrap e regression results with deposition of lami-
nated biocalcisiltites, and then biolithites. The sequence from
the Borovnjak locality shows a different depositionary

pattern, marked by biocalcirudites. The approximate thick-
ness of the Upper Badenian deposits is ca. 65 m at the Gornje
Vrap e locality, and 25 m in the Borovnjak sequence. Some
shallow marginal areas were finally emerged, and the Sarma-
tian beds transgressively overlay the Upper Badenian depo-
sits in SW part of the Medvednica Mt. (Fig. 3).

Borovnjak section

The Borovnjak section (Lat: 45°50’24.772” Lon: 15°54’

52.141”), (also known as Krvari ; Figs. 3, 4) is situated along
the forest road Gornja Kustošija–Risnjak, above the Kus-
tošija creek. It was sedimentologically studied by Avani et
al. (1995) and discussed by Vrsaljko et al. (2006). The sec-
tion’s length is 28.5 m, and the following rock types can be
recognized: conglomerates, biolithites, biocalcirudites,

Fig. 3. A — Schematic geological column through the Middle Miocene rocks in SW part of the Medvednica Mt. with visible increase of
siliciclastic input. B — Reconstructed palaeoenvironment of localities Gornje Vrap e (V) and Borovnjak (B). Total thickness of the Late
Badenian sequence is estimated to be 65 metres at Gornje Vrap e (West) and 25 meters at Borovnjak (East).

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Fig. 4.

Detailed sections at the localities Borovnjak (

) and Gornje

rap

e (

) with position of samples, and graphic trends of dif

ferent palaeoecological proxies.

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biocalcarenites and biocalcisiltites within the Upper Bade-
nian part of the section, and sandy oolitic calcarenites within
the Sarmatian part of the section. Biocalcrudites and biocal-
carenites are coarse-grained to fine-grained deposits, often
weathered into sands with destroyed primary textures. Frag-
ments of molluscs, crinoids, corals, coralline algae and echi-
noids were collected at this locality.

Probe analyses emphasized the potentially interesting cen-

tral and upper part of the section, while the basal and lower
parts of the section were almost sterile. Therefore a more
detailed sampling was performed within the upper 15 metres
of the section (Figs. 3, 4), dominated by biocalcarenites. The
first sample, (B1), was taken within the biocalcrudite, directly
above the conglomerate and strongly weathered coralgal bio-
lithite, and the last sample, (B14), was taken in the topmost
part of the section, directly below the emersion. Intercala-
tions of biocalcsiltite are also present in the central and upper
part of the section.

Section with grey fine-grained clastic deposits in Gornje

Vrap e (Lat: 45°50’21.12” Lon: 15°54’2.514”) was first
described by Gorjanovi -Kramberger (1882) as “Spongite
marl”, due to the high content of sponge spicules (from
Kochansky 1944). Section is subvertical, ca. 13 10 m large
(Figs. 3, 4). Vrsaljko et al. (1995, 2006) proposed the deposi-
tion from suspended material in the basal part of the section,
and suggested climatic changes as the main trigger for lami-
nation in the upper part of the section. Besides the abundant
microfossils (Šiki 1967), numerous macrofossils (molluscs,
echinoids, crabs, coralline algae and other fossils) can be
found within these siltites (Kochansky 1944).

Greyish-brown siltites in the lower part of the section are

variably consolidated, with no visible textures (sample V1).
The upper part of the section exhibits clear cyclic alteration
of three types of thin laminae (average thickness from 0.5 to
1 cm, some of them are up to 2 cm). Grey-coloured
calcitic-siltose laminae (Type A) are sampled as V2, V5 and
V8; brownish argillaceous-siltose laminae (Type B) are sam-
pled as V3, V6 and V9, and greyish-brown siltose laminae
(Type C) are sampled as V4 and V7 (Fig. 4). In order to
reveal the succession of environmental change, laminae are
separated into three groups. The first group was collected
directly above the basal massive siltite, with no visible tex-
tures (samples V2 and V3). The second group (samples V4,
V5 and V6) was taken in the central part of the profile, and
the third group (samples V7, V8 and V9) was collected from
the upper part of the section (Fig. 4).

Methods

All together twenty-three samples were micropalaeonto-

logically analysed and their foraminiferal and ostracod con-
tent was studied. For each sample, 300 g of sediment was

soaked, treated with hydrogen peroxide and washed over
0.063 mm sieve. The dried material was repeatedly split by
Retsch microsplitter, until standard samples with 300 ran-
domly chosen foraminiferal specimens were obtained. After
that, the plankton/benthos (P/B) ratio was calculated for
each sample. Benthic foraminifera species were identified
according to Papp et al. (1978), Papp & Schmid (1985),
Loeb lich & Tappan (1987a,b) and Cicha et al. (1998), while
palaeoecological proxies were co-opted from Kaiho (1994,
1999); Den Dulk et al. (2000), Hohenegger (2005), Van
Hinsbergen et al. (2005), Báldi (2006), Pezelj et al. (2007),
Holcová & Zágoršek (2008), Pippèrr & Reichenbacher
(2010), De & Gupta (2010), Grunert et al. (2012), Pérez-Asen-
sio et al. (2012) and Pezelj et al. (2013). Each standardized
sample was carefully checked (the presence of size-sorting,
fragmentation, abrasion, corrosion, and the incongruence of
stratigraphic ranges and palaeoecological preferences), in
order to exclude redeposited and transported specimens of
benthic foraminifera from statistical analysis (Murray 1991;
Holcová 1999). The number of species (N) was defined and
relative abundance of benthic species within the assemblage
was estimated according to Murray (1991). In order to quan-
tify the species diversity of benthic foraminifera, Fisher  -in-
dex ( ), Shannon-Wiener index (H), and Dominance (D)
were determined by means of PAST (PALaeontology STatis-
tic) Program (Hammer et al. 2001). Epifaunal/infaunal ratio
and environmental stress markers (Van Hinsbergen et al.
2005) were also calculated. In order to illustrate variations of
oxygen content on the sea bottom during the deposition we
calculated the Benthic Foraminiferal Oxygen Index (BFOI)
for each sample (Kaiho 1999), and determined oxic, suboxic
and disoxic indicators (Kaiho 1994). The number of benthic
foraminifera in 1 g of dried sediment (Foraminiferal number
— NBF) was also determined for each sample. The depth of
the depositional basin was estimated through three indepen-
dent methods: the plankton/benthos ratio (P/B) (Murray
1991); modified plankton/benthos ratio (D1; Van Der Zwaan
et al. 1990, 1999), and gradient analysis (D2; Hohenegger
2005; Báldi & Hohenegger 2008).

The Cluster Analysis (Ward’s method) and Non-metric

Multidimensional Scaling (Bray-Curtis Similarity Index)
were conducted by means of PAST (PALaeontology STatis-
tic) Program (Hammer et al. 2001). They were applied to all
identified species of benthic foraminifera to determine the
differences between benthic foraminiferal assemblages and
their distribution in different samples. Such analyses group
the samples with homogenous foraminiferal assemblages
typical for different palaeoenvironments.

Additionally, the number of ostracod species and their rela-

tive abundance within each standardized sample were deter-
mined. Ostracod/foraminifera ratio (O/F ratio — number of
ostracod specimens/number of foraminifera specimens in 1g
of dried sediment) was also calculated. Whole carapaces were
calculated as two valves (Danielopol et al. 2002). Ostracoda
were determined according to Brestenská & Ji í ek (1978),
Gross (2006) and Hajek-Tadesse & Prtoljan (2011).

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Two different methods of measuring carbonate content

were applied to samples V1, V2 and V3 from three lithologi-
cally different horizons in the Gornje Vrap e section. Deter-
mination of carbonate content in soil by volumetric measu-
ring by Scheibler calcimeter, standard method: HRN ISO:
10693:2004 and Complexometric determination of Calcium
and Magnesium. These analyses were done in the Chemical
laboratory, Department of Mineralogy and Petrology, Uni-
versity of Zagreb.

Palaeontological samples are stored in the collection of the

Department of Geology and Palaeontology (Faculty of
Science, University of Zagreb).

Results

Borovnjak locality

At the Borovnjak locality eight analysed rock samples

were palaeontologically sterile or did not contain enough
specimens of benthic foraminifera for further statistical ana-
lysis. Microfossil assemblages are generally poorly pre-
served. Foraminiferal tests are often broken into particles,
encrusted with calcite crystals and/or abraded or partly dis-
solved. Diagenetic overprint complicates the process of
determination. Besides foraminifera and ostracoda, bryozoan
fragments and echinoid spines are present in these samples
(Fig 5. A–G). Foraminifera are rather scarce and show low
species diversity. The best preserved specimens were
recorded in the central part of the section. Planktonic and
agglutinated foraminifera were not recorded. A total of

10 genera and 14 species of benthic foraminifera (Table 1)
were determined. Benthic foraminifera with perforated tests
dominate in all samples, while imperforated foraminifera are
slightly more common in the lower part of the profile.

Cluster I unites the samples from the Borovnjak section

(Fig. 6). The most important environmental features are high
oxygen values at the bottom (BFOI 100), small depth varia-
bility (D1 36 m; D2 11–12 m) and total lack of planktonic
foraminifera, disoxic and stress indicators (Table 2). Clus-
ter I is subdivided into two subclusters Ia and Ib.
Subcluster Ia. Elphidium–Asterigerinata–Ammonia assem-
blage: This subcluster includes samples from the lower and
the middle part of the Borovnjak section (samples B2, B6
and B9) taken from biocalcarenite. Dominant species are
Elphidium crispum (23.3–27.6 %), Asterigerinata planorbis
(20.9–28.6 %), Ammonia vienennsis (16.3–20.3 %) and
Elphidium macellum (11.9–15.6 %). This is a low biodiver-
sity assemblage (N 10;

2.07; H 1.97) with highly

expressed domination (D 0.17). Within the assemblage the
most prominent features are oxic indicators (98.5 %) and epi-
faunal taxa (97.4 %). The average number of benthic fora-
minifera individuals (BFN) within the 1 g of sediment is 77.
Subcluster Ib. Ammonia–Elphidium assemblage: This
subcluster includes the samples from the middle (B7, B8)
and the upper part of the Borovnjak section (B11), collected

from biocalcsiltites. It is characterized by pronounced domi-
nation of the species Ammonia vienennsis (30.2–37.0 %).
Other dominant species are Elphidium crispum (13.8–25.9 %)
and Asterigerinata planorbis (10.8–21.0 %). The medium
represented species is Elphidium macellum (2.6–11.0 %).
Compared with Subcluster Ia this subcluster shows a higher
number of taxa and biodiversity (N 11;

2.20; H 1.83),

and particularly an increase of the number of individuals
BFN 221. Slight increase of suboxic indicators (4.6 %) and
infaunal taxa (5.8 %) within the benthic assemblage are also
visible, while the domination (D 0.22) is more prominent
than in the previous subcluster.

A total of 7 species of ostracoda were determined at the

Borovnjak locality. Ostracoda/foraminifera ratio varies from
5.6 % (sample B2) to 12.7 % (sample B7) (Table 1). In the
lower part of the section a few specimens of Aurila sp., Loxo-
concha hastata (Reuss), Costa edwardsi (Roemer

)

, Xestole-

beris glabresans (Brady) and Cytheridea pernota Oertly &
Key were recorded. Within the central and the upper part of
the section the ostracod role in the assemblage becomes more
important. Dominant taxa are Phlyctenophora farkasi
(Zalány), L. hastata, Neocyprideis (Miocyprideis) sp. and
Aurila sp. The species C. pernota and X. glabresans are also
common. A significant number of specimens was found with
closed complete valves (almost 50 %), and adult individuals
and the last larval stages prevail within the assemblage.

Fine-grained laminated siltites from the section Gornje

Vrap e contain rich, diverse and well preserved microfossil
assemblage (Fig 5. H–N). This habitat was characterized by
an extremely rich assemblage of siliceous sponges. At least
eight morphotypes of spicules can be clearly recognized
(Fig 5. N1, N2), and deserve further attention. Planktonic
foraminifera are scarce, while benthic foraminifera are
extremely rich and diverse. A total of 31 genera with 44 spe-
cies of benthic foraminifera were determined (Table 1). Ben-
thic foraminifera with perforated tests dominate in all sam-
ples from this locality. Imperforated foraminifera are less
common, while the percentage of agglutinated foraminifera
is almost negligible. There are no signs of transportation or
redeposition of benthic foraminifera.

Cluster II groups the samples from the locality Gornje

Vrap e. Subclusters can be clearly recognized, considering
the dominant benthic foraminifera and palaeoecological indi-
cators (Fig. 6; Table 2).
Subcluster IIa. Elphidium-Asterigerinata assemblage:
Sample V1 collected from the massive siltite in the base of
the section is grouped with siltose laminae (Type C) from the
central (V4) and the upper part of the section (V7). The
domi nant species are Elphidium crispum (11.6–19.5%) and
Asterigerinata planorbis (13.5–17.6%). Medium represented
species are Heterolepa dutemplei, Cibicidoides ungerianus
and E. macellum. Planktonic foraminifera are present in
small numbers (P 6.24 %), and the estimated depth of the

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Fig. 5. Typical microfossils from Borovnjak (A-G) and Gornje Vrap e section (H-N). A — Asterigerinata planorbis (d Orbigny), sample
B6; A1, spiral side, A2, umbilical side. B — Borelis melo (Fichtel & Moll), sample B6; apertural view. C — Ammonia viennensis (d Orbigny),
sample B11; C1, spiral side, C2, umbilical side. D — Elphidium crispum Linne, sample B2; side view. E — Bryozoa, sample B2.
F — Echinoid radiola, sample B6. G — Neocyprideis sp., sample B11; left valve, external Lateral view. H — Asterigerinata planorbis
(d Orbigny), sample V1; H1, spiral side, H2, umbilical side. I — Elphidium crispum Linne, sample V4; side view. J — Cassidulina
laevigata d Orbigny, sample V3; apertural side. K — Pappina neudorfensis (Toula), sample V2; side view. L — Bolivina dilatata Reuss,
sample V6; side view. M — Heterolepa dutemplei d Orbigny, sample V5; spiral side. N1–N2 — Spicule, sample V1.

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Table 1. A — List of determined species of benthic foraminifera from the localities Gornje Vrap e and Borovnjak, their absolute number in
samples and ecological/palaeoecological requirements. Bolded taxa were represented with more than 5 % in at least one sample. Lower part
of the table: Percentage of planktonic taxa, estimated depths of sedimentary basin, number of species and number of individuals (BFN) of
benthic foraminifera, diversity indices, BFOI, oxic, suboxic and disoxic indicators, epifauna/infauna ratio, stress markers and ostracoda/
foraminifera ratio. B — List of determined species of ostracoda from the localities Gornje Vrap e and Borovnjak.

A. BENTHIC FORAMINIFERA

Oxic

efer

ence

Mode

of life

Str

ess

marker

V5 V6

xtularia

gramen

000

10000

Quinqueloculina akneriana

117

00000

Quinqueloculina

020

20000

iloculina

000

1445

Bor

elis melo

(Fichtell & Moll)

Lenticulina inornata

Orbigny)

/SI

10000

Globulina gibba

000

00006

Fissurina

120

20000

Bolivina dilatata

Reuss

0000

Bolivina plicatella

(Cushman)

00000

Bolivina pokorny

010

20000

Cassidulina laevigata

d'Orbigny

0000

Globocassidulina oblonga

(Reuss)

50000

Bulimina elongata

d'Orbigny

100000

Bulimina gutsulica

100

70000

Bulimina insignis

004

00000

Praeglobobulimina pyrula

(d'Orbigny)

816

0000

Pappina neudorfensis

)

1597

110000

Uvigerina bellicostata

200

30000

Uvigerina brunnensis

Karrer

004

00000

Uvigerina semiornata

200

00000

Reusella spinulosa

)

200

00000

Fursenkoina acuta

Orbigny)

10000

Cancris auriculus

(Fichtell & Moll)

00000

lvulineria complanata

Orbigny)

40000

Neoconorbina ter

quemi

(Rzehak)

000

00000

Rosalina obtusa

650

00000

Cibicidoides ungerianus

(d'Orbigny)

0000

Cibicidoides

230

00000

Cibicides

000

Lobatula lobatula

alker & Jacob)

Asterigerinata planorbis

(d'Orbigny)

Nonion commune

Orbigny)

Melonis pompilioides

l &

1426

60000

Pullenia bulloides

(d'Orbigny)

156

0000

Heterolepa dutemplei

d'Orbigny

0000

Hanzawaia boueana

Orbigny)

4001

Ammonia viennensis

(d'Orbigny)

011

117

Por

osononion granosum

Orbigny)

00000

Elphidium aculeatum

Orbigny)

E/SI

00000

Elphidium crispum

(Linné)

Orbigny)

/SI

Orbigny)

E/SI

Elphidium macellum

(Fichtell & Moll)

E/SI

Elphidium rugosum

Orbigny)

E/SI

10000

Elphidium

sp.

000

1190

302

298

318

301

295

306

289

292

301

305

303

291

274

309

293

337

MIDDLE MIOCENE SHALLOW-WATER BENTHIC FORAMINIFERS, MEDVEDNICA MT. (CROATIA)

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Table 1 (continuation): A. List of determined species of benthic foraminifera from the localities Gornje Vrap e and Borovnjak, their abso-
lute number in samples and ecological/palaeoecological requirements. Bolded taxa were represented with more than 5 % in at least one
sample. Lower part of the table: Percentage of planktonic taxa, estimated depths of sedimentary basin, number of species and number of
individuals (BFN) of benthic foraminifera, diversity indices, BFOI, oxic, suboxic and disoxic indicators, epifauna/infauna ratio, stress
markers and ostracoda/foraminifera ratio. B. List of determined species of ostracoda from the localities Gornje Vrap e and Borovnjak.

V5 V6

P/B ratio (%)

5.22

1.34

2.72

4.38

2.03

3.14

9.12

5.43

6.6

50000

1 (

)

453

434

425

513

2 (

)

173

284

492

111

BFN

7392

214

9896

6733

192

8007

502

246

1128

121

352

269

Number of species

Fisher

index

9.44

4.52

8.5

7.18

4.85

8.24

8.03

5.85

7.18

1.74

1.99

2.52

2.57

2.48

1.52

Shannon-W

iener index

2.87

2.73

2.95

2.83

2.64

2.71

2.9

2.91

2.85

1.92

1.91

2.01

1.94

2.07

1.54

Dominance

0.09

0.08

0.07

0.08

0.1

0.09

0.08

0.07

0.08

0.17

0.19

0.18

0.22

0.16

0.27

BFOI

88.3

68.3

59.2

87.3

73.8

56.5

81.2

62.6

100

Oxic (%)

82.5

58.4

44.7

66.5

64.1

41.2

74.7

49.3

38.2

100

94.8

95.9

95.5

95.6

Suboxic (%)

6.6

14.4

24.5

23.9

13.2

27.1

7.9

21.2

26.6

5.2

4.1

4.5

4.4

Disoxic (%)

10.9

27.2

30.8

9.6

22.7

31.7

17.3

29.5

35.

20000

Epifauna (%)

81.1

51.7

43.4

67.4

64.8

35.6

67.5

44.9

37.5

100

94.8

93.9

92.2

93.8

Infauna (%)

18.9

48.3

56.6

32.6

35.2

64.4

32.5

55.1

62.5

5.2

6.1

7.8

6.2

Stress markers (%)

11.6

27.2

29.9

24.8

31.4

17.7

29.5

35.

20000

O/F ratio (%)

2.6

1.9

3.7

0.7

1.3

2.1

0.7

5.6

4.6

12.7

9.5

2.9

6.8

B. OSTRACODA

Phlyctenophora farkasi

(Zalány)

Callistocyther

e canaliculata

(Reuss)

Cnestocyther

e lamellicostata

riebel

Aurila haueri

(Reuss)

Aurila

sp.

××××

Carinocyther

eis carinata

(Roemer)

××

Costa edwar

dsi

(Roemer)

××

Cytheridea pernota

Oertly & Key

××

Neocyprideis

(

Miocyprideis

) sp.

××

Semicytherura

cf.

acuticostata

Sars

Hemicytherura

sp.

Loxoconcha hastata

(Reuss)

×××

Loxoconcha punctanella

(Reuss)

Xestoleberis glabr

esans

(Brady)

××

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sedimentary basin ranges from D1 47 m to D2 23 m. Within
this assemblage the highest oxygen amount at Gornje Vrap e
locality is calculated (BFOI 85.6), the highest number of
species (N 30), highest biodiversity (

8.22; H 2.87), and

average domination (D 0.08). Within the assemblage oxic
indicators prevail (74.6 %) as well as epifaunal taxa (72.0 %),
while the amounts of suboxic and disoxic indicators are equal
(around 13 %). The amount of stress markers is small (13.1 %),
and number of individuals of benthic foraminifera (BFN)
is 4876.
Subcluster IIb. Heterolepa-Bolivina assemblage: This sub-
cluster groups the samples taken from the solid grey calcsil-
tite laminae (Type A; V2, V5 and V8) laying directly above
the base, and above the siltose laminae (Subcluster IIa). The
dominant species are Heterolepa dutemplei (14.1–23.4 %)
and Bolivina dilatata (9.9–11.9 %). Medium represented spe-
cies are Bulimina elongata, Cassidulina laevigata, Asteri-
gerinata planorbis and Cibicidoides ungerianus. Within this
subcluster, an abrupt decrease in number of species can be
observed (N 21) as well as a decrease of the number of indi-
viduals (BFN 217). Indices re ect the decrease in diversity
of benthic foraminifera (

5.07; H 2.76). Domination is

still unchanged and the amount of planktonic foraminifera
slightly decreases (P 2.93 %). Compared to Subcluster IIa
infaunal taxa increase in number (46.2 %), as well as suboxic
(16.3 %) and particularly disoxic (26.5 %) indicators. The
amount of stress markers is doubled (27.2 %). Indices re ect
the decrease of oxygenation at the bottom (BFOI 68.2),
while the estimated depth of the sedimentary basin remains
the same as in the previous subcluster (D1 42m) or slightly
increases (D2 38 m).
Subcluster IIc. Bolivina-Cassidulina assemblage: Samples
V3, V6 and V9 collected within the argillaceous-siltose
laminae (Type B), directly above the grey marly laminae are

grouped within this subcluster. The dominant species are
Bolivina dilatata (11.6–18.0 %) and Cassidulina laevigata
(10.3–16.7 %), while the medium represented species are
Elphidium crispum, Bolivina elongata, Cibicides ungerianus
and Heterolepa dutemplei. Within this assemblage extreme
increase of number of individuals is present (BFN 6344),
there is restoration of diversity (N 29;

7.94; H 2.84),

while the domination remained unchanged. Decrease of oxy-
genation of the sea bottom is still in progress (BFOI 55.9)
and amount of planktonic foraminifera is increasing
(P 4.17 %). Estimation of depth is almost the same as in the
previous subcluster (D1 45 m; D2 42 m). Within this
assemblage infaunal taxa are dominant (61.2 %). The amount
of suboxic (26.0 %), disoxic (32.6 %) and stress markers
(32.2 %) is still increasing.

The number of ostracods (Table 1) within the microfossil

assemblages varies from 0 % (samples V2, V8) to maximally
3.7 % (sample V4). A total of 8 species were recognized,
including the most common species Aurila haueri (Reuss),
Cnestocythere lamellicostata Triebel, Callistocythere cana-
liculata (Reuss) and Semicytherura cf. acuticostata Sars.
Ostracod species Carinocythereis carinata (Roemer), Phlyc-
tenophora farkasi (Zalány), Loxoconcha punctanella (Reuss)
and Hemicytherura sp. occur with small numbers of indivi-
duals. The number of complete ostracod carapaces is very
low (around 2 %), and assemblage comprises adult, as well as
larval stages.

Three lithologically different samples from the Gornje

Vrap e section were analysed by calcimetric and complexo-
metric methods. The results are very similar (Table 3) and
clearly exhibit excursions of calcite content. The calcite con-
tent in sample V1 from the basal massive marl is 56.60 %
(56.38 %). Carbonate component increases in the first over-
lying lamina (Type A) up to 75.00 % (73.89 %) and again

Fig. 6. Results of Cluster Analysis (Ward’s method, Bray-Curtis Similarity Index) and Non-metric-Multidimensional Scaling analyses
(Bray-Curtis Similarity Index) of the Middle Miocene foraminiferal benthic communities from localities Borovnjak and Gornje Vrap e
in SW Medvednica Mt.

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MIDDLE MIOCENE SHALLOW-WATER BENTHIC FORAMINIFERS, MEDVEDNICA MT. (CROATIA)

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decreases in the next overlying lamina (Type B) to 41.98 %
(41.54 %). Such oscillations are probably present up to the
top of the laminated portion of the section. Three-valent
metal (probably iron) also exhibits variations (R

, Table 3).

Biostratigraphy

Biostratigraphic analysis of the studied sections is based

upon standard biozonations for Central Paratethys (Papp et
al. 1978; Papp & Schmid 1985; Cicha et al. 1998). Two Late
Badenian zones Bulimina–Bolivina Zone (biozone) and
Ammonia beccarii Zone (ecozone) can be recognized on the
basis of detailed microfossil study.

Samples from the locality Borovnjak belong to the Ammo-

nia beccarii ecozone. Benthic foraminiferal assemblage
shows low diversity, with a dominant role for Ammonia
(A. viennensis),  Elphidium  (E. crispum,  E. macellum) and
rather common occurrence of miliolids (Borelis melo, Trilo-
culina inflata). The Elphidium–Ammonia assemblage was
observed at several localities within the Central Paratethys in
different Miocene stratigraphic horizons (Bakra  et al. 2010;
Pippèrr 2011; Nehyba et al. 2016), and similar shallow-water
environments at the Late Badenian/Early Sarmatian boun-
dary were described from Slovakia (Hy n  et al. 2012). The
Late Badenian age was proven by ostracods Phlyctenophora
farkasi (Zalány) and Neocyprideis (Miocyprideis) sp., which
are typical for the uppermost part of the Badenian (Bres-
tenská & Ji í ek 1978; Ji í ek 1983). Another criterion is
superposition — after the short emersion, the Sarmatian clas-
tic sediments were deposited in this area.

Samples from the locality Gornje Vrap e belong to the

Late Badenian Bulimina–Bolivina Zone. Age is presumed on
the basis of benthic foraminifera Pappina neudorfensis
(Toula), Bulimina insignis Luczkowska and Uvigerina belli-
costata Luczkowska (indicative for the Late Badenian) and
Bulimina gutsulica Livental and Uvigerina brunnensis
Karrer (Middle to Late Badenian), (Cicha et al. 1998). Addi-
tional proofs are the presence of marine ostracod Carino-
cythereis carinata (Roemer), typically present in the Late
Badenian of the Paratethys and the Badenian ostracod taxa
Cnestocythere lamellicostata Triebel, Aurila haueri (Reuss)
and Loxoconcha punctanella (Reuss) (Brestenská & Ji í ek
1978; Nascimento & Riha 1996; Hajek-Tadesse & Prtoljan
2011).

Discussion

Miocene rocks in both investigated sections reflect three

different phases of deposition within TB 2.5 global 3

order

sequence (Hilgen et al. 2009; Fig. 2): initial Late Badenian
transgression and establishment of shallow marine environ-
ments, start of regression and environmental stress in the
uppermost Late Badenian and final regression and emersion
at the Badenian/Sarmatian boundary. During wet periods
marginal shelf deposits of the Paratethys are characterized by
coarse clastics, while the carbonate-siliciclastic complexes
are known only in some intervals which were dry (Moissette
et al. 2007; Holcová et al. 2015). Marginal facies are present
at the Borovnjak locality and they are assigned to the
Ammonia beccarii ecozone. Along with transgression, more

Table 2: Mean values of paleoecological indices for

different benthic foraminiferal assemblages at analysed sections
Borovnjak and Gornje Vrap e.

Cluster

IIa

IIb

IIc

Community

Elphidium–Asterigerinata–

Ammonia

Ammonia–Elphidium

lphidium–Asterigerinata

Heterolepa–Bolivina

Bolivina–Cassidulina

range

ean

range

mean

range

ean

range

mean

range

ean

P (%)

4.38–9.12

6.24

1.34–5.43

2.93

2.72–6.65

4.17

D1 (m)

36–36

43–53

39–47

41–51

D2 (m)

42715

11.5

42715

11.5

17–28

33–41

33–49

BFOI

100

81.2–88.3

85.6

62.6–73.8

68.2

52.0–59.2

55.9

Number of species (N)

42713

42712

27–33

19–23

27–31

BFN

53–121

42–352

221

502–7392

4876

192–246

217

1128–9896

6344

Fisher

index (

)

1.74–2.48

2.07

1.52–2.57

2.2

7.18–9.44

8.22

4.52–5.85

5.07

7.18–8.50

7.94

Shannon–

iener index (H)

1.91–2.07

1.97

1.54–2.01

1.83

2.83–2.90

2.87

2.64–2.91

2.76

2.71–2.95

2.84

Dominance (D)

0.16–0.19

0.17

0.18–0.27

0.22

0.08–0.09

0.08

0.07–0.10

0.08

0.07–0.09

0.08

Oxic (%)

95.5–100

98.5

94.8–95.9

95.4

66.5–82.5

74.6

49.3–64.1

57.2

38.2–44.7

41.4

Suboxic (%)

0–4.5

1.5

4.1–5.2

4.6

6.6–23.9

12.8

13.2–21.2

16.3

24.5–27.1

Disoxic (%)

9.6–13.3

12.6

22.7–29.5

26.5

30.8–35.2

32.6

Epifauna (%)

92.2–100

97.4

93.8–94.8

94.2

67.4–81.1

44.9–64.8

53.8

35.6–43.4

38.8

Infauna (%)

0–7.8

2.6

5.2–6.2

5.8

18.9–32.6

35.2–55.1

46.2

56.6–64.4

61.2

Stress markers (%)

10.0–17.7

13.1

24.8–29.5

27.2

29.9–35.2

32.2

O/F ratio (%)

2.9–5.6

4.4

6.8–12.7

9.7

2.1–3.7

2.8

0–0.7

0.2

0.7–1.9

1.3

PEZELJ, SREMAC and BERMANEC

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GEOLOGICA CARPATHICA

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specialized taxa appear, indicative for Bulimina–Bolivina
Zone such as those present at the Gornje Vrap e locality.

The Late Badenian transgression

The initial transgression along the SW slopes of Medved-

nica Mt. took place over the pronounced palaeorelief develo-
ped in the Mesozoic carbonate basement (Fig. 3). Encrusting
coralline algae were the first sessile inhabitants of clastic
shelf, stabilizing the substrate and enabling colonization by
other benthic biota. The first additional frame-building meta-
zoans were bryozoa, producing compound reef buildups —
suitable habitats for diverse benthic assemblage of thick-
shelled taxa (e.g. ostreids, echinoids, corals) (Gorka et al.
2012). Reef buildups, in most cases patch-reefs composed of
coralline algae and/or corals, are common in the Badenian
deposits of Paratethys (Pisera, 1996; Reuter et al. 2012).
Small reef buildups at the locality Borovnjak were produced
in shallow, relatively warm, agitated, normally saline envi-
ronments. Corals and vermetids were not collected during
this study, but scarce findings were reported by previous
authors in Croatia (Avani et al., 1995; Vrsaljko et. al. 2006).

Laterally, bioherms are replaced with coarse-grained bio-

clastic limestones (calcrudite/calcarenite) with typical mar-
ginal marine Elphidium-Asterigerinata-Ammonia assem-
blage (Subcluster Ia). The depth of this facies estimated by
two methods ranges between 11 and 36 metres. Laboratory
experiments have shown that foraminifera from Elphi dium–
Ammonia assemblage are active colonizers of sterile sub-
strates, and are in many cases the pioneer biota in marginal
marine environments during the initial transgression
(Debenay et al. 2009).

Poor preservation of specimens with

visible traces of destruction, abrasion and corrosion, suggest
highly energetic environments. The analysed assemblages
exhibit low number of species, low diversity and pronounced
domination (Fig. 4, Table 2), which is typical for stress envi-
ronments, sometimes with brackish or hypersaline water, but
also for normal marine habitats with high domination of one
or several species (Murray 1991). Lack of planktonic fora-
minifera, highly oxic conditions (BFOI 100), with domi-
nance of oxic proxies and epifaunal taxa definitely indicate
a typical shallow-marine habitat. Such conditions are also
favourable for organic carbonate growth, particularly of reef
structures and reef-building biota. Typical marine species of
Elphidium (E. crispum, E. macellum and E. fichtelianum)
represent more than 45 % of the basal Borovnjak assem-
blages. Recent keeled elphidia are in most cases herbivorous,
epifaunal, preferring sandy substrates and often attached to
rhizomes of sea-grasses (Murray 1991, 2006). Together with

other epiphytic foraminifera (Asterigerinata, Triloculina,
Borelis) they point to the environment with algal/sea-grass
meadows in the Late Badenian of Borovnjak. A particularly
indicative genus is Borelis (present up to 4 %), recently com-
mon in the Red Sea and Gulf of Aquaba, with fossil species
B. schlumbergeri typical for fore-reef assemblages (Parker et
al. 2012). It is a shallow-marine genus (up to 40 metres
depth), typical for warm seas. The tolerance of benthic fora-
minifera to clastic influx is variable and it seems that Borelis
at the Borovnjak locality could tolerate such temporary epi-
sodes. Ostracod assemblages comprise scarce stenohaline
marine taxa Aurila sp., Loxoconcha hastata, Costa edwardsi,
Xestoleberis cf. glabresans and Cytheridea pernata (Table 1,
2) which are typical for littoral and epineritic environment
(Smith & Horne 2002). Their carapaces are in most cases
strongly calcified and with coarse ornamentation, except the
smooth-surfaced epiphytic Xestoleberis (

Triantaphyllou et

al. 2010

). A significant amount of carapaces were preserved

complete, with closed valves, which is a consequence of
selective sorting due to the high-energy conditions. Adult
specimens and last larval stadia predominate, which is also
typical for agitated shallow marine environments. Minute
carapaces in such environments can be disturbed by turbu-
lences and later transported by currents (Danielopol et al.
2002).

The open section at the locality Gornje Vrap e begins with

similar marginal marine stressed facies (Fig. 3). Advancing
transgression results with a deeper inner shelf, more stable
environment and very rich (44 species) and diverse Elphi-
dium-Asterigerinata assemblage (Subcluster IIa) and
increase of siltose and argillaceous component in marls.
Planktonic foraminifera are scarce (<10 %), as is typical for
the inner shelf (Murray 1991). The values of the Fisher

index (Table 1) additionally point to the normal salinity

shelf environment or marine lagoon. The estimated depth of
the basin according to Van der Zwann (1999) (39–53 m), and
gradient analysis (17–49 m) confirm the shallow inner/mid-
dle shelf environment. Within the assemblage oxic and epi-
faunal indicators prevail, with dominant shallow water spe-
cies Elphidium crispum, Asterigerinata planorbis and
Elphidium macellum. Compared to the precursor Elphi dium–
Asterigerinata–Ammonia assemblage, this assemblage with
average domination lived in a significantly more stable envi-
ronment with abundant oxygen (BFOI 85.6). The accompa-
nying ostracod taxa Aurila haueri, Cnestocythere lamelli-
costata and Semicytherura acuticostata are typical for a shal-
low marine environment (Smith & Horne 2002). The shel-
tered habitat of Gornje Vrap e was also inhabited with an
extremely abundant and diverse siliceous sponge

CALCIMETRY

COMPLEXOMETRY

Sample

CaCO

[%]

CaO [%]

CaCO

[%]

recalculated to carbonate [%]

Undissolved residue [%]

Total [%]

V-1

56.60

31.25

56.38

1.68

3.08

40.00

99.46

V-2

75.00

41.51

73.89

1.41

2.61

23.92

100.42

V-3

41.98

23.34

41.54

3.49

6.38

51.91

99.84

Table 3: Results of calcimetric and complexometric analyses of three different samples from Gornje Vrap e section.

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assemblage. Loose spicules are so numerous that geologists
named these deposits “Spongite marls” or “Spongite siltites”.
Findings of the Miocene sponges in Paratethys deposits are
extremely scarce. A nice sponge assemblage from basinal
Karpatian deposits of the Vienna Basin (Pisera & Hladilova
2003; ukowiak et al. 2014) contain a significant number of
transported shallow-marine spicules. Most of the collected
spicules from Gornje Vrap e are monaxone, or simple
trienes, probably belonging to demosponges, but it is very
hard to determine them in detail. Some of the collected
amphitrianes spicules, short-shafted dichotriaenes can be
well compared with Karpatian samples. Rich and well pre-
served spicules deserve further attention.

Shallowing upward trend and environmental stress

The Borovnjak locality is a good example of a stressed

marginal marine environment, particularly in the middle part
of the section, which is characterized by cyclic alteration of
foraminiferal assemblages (Subcluster Ia and Subcluster Ib)
and final establishment of Ammonia–Elphidium assemblage
(Subcluster Ib) in the upper part of the column. The benthic
foraminifera Ammonia and Elphidium frequently dominate
recent foraminiferal assemblages in the lower reaches of
estuaries, and in normal marine lagoons and bays (Leckie &
Olson 2003). Compared to the previous Elphidium–Asteri-
gerinata–Ammonia assemblage, decrease in abundance of
stenohaline elphidiids and species Asterigerinata planorbis,
and pronounced domination of the species A. viennensis
(more than 30

%) can indicate temporary fresh-water

influence in the sedimentary basin and seasonal oscillation
between normal and decreased salinity. The genus Ammonia
is common in both, brackish (Amarossi et al. 2013; Reymond
et al. 2013) and marine assemblages, as it can quickly adapt
to variable salinity, oxygen and temperature oscillations
(Donnici & Serandreo Barbero 2002). They are also common
in deposits with highly variable organic component (TOC)
and they can become facultative anaerobes (Murray 2006).
Reduction in abundance of imperforate foraminifera and
complete lack of Borelis in the upper part of the section sup-
ports the theory of fresh-water input. These foraminifera
diminish in brackish lagoons and estuaries and completely
vanish in brackish marshes (Murray 1991). A higher number
of specimens, slightly higher amount of infaunal taxa and
suboxic proxies (Table 2), and somewhat better preservation,
indicate the environment with increased mud support. At the
same time, the number of ostracods increases (average rate
9.7 %) within the microfossil assemblage and brackish genus
Neocyprideis (Miocyprideis) sp. appears (Brestenská and
Ji í ek 1978; Olteanu 1997). Common taxa are Cytheridea
pernata and Xestoleberis glabresans. Some species within
the genera Cytheridea, Xestoleberis and Loxoconcha can be
well adapted to low-salinity habitats (Ruiz et al. 2000;

Pipík

2007

). We can presume that Ammonia–Elphidium assem-

blage reflects a phase of increased siliciclastic and nutrient
input from land, which can be caused by local regression. On

the other hand, seasonal or periodical fresh-water influx
could cause the oscillations of salinity in the habitat.

Almost regular exchange of three different types of lami-

nae in the upper part of the profile from the laterally deeper
and more sheltered environment at Gornje Vrap e also indi-
cates temporary instabilities. Laminae differ in colour and
are characterized by almost regular interchanges of benthic
foraminiferal assemblages, carbonate content, and high-
valent metal content. Evident increase of environmental
stress can be recognized at the beginning of the upper part of
the section (Type A lamina) with abruptly decreased diversity
and number of specimens of benthic foraminifera, while
amount of stress markers is doubled (Table 1, 2). The amount
of oxygen in bottom waters decreases (BFOI 68.2) and the
Heterolepa–Bolivina assemblage (Subcluster IIb) is typical
for this lamina. Oxygen depletion in bottom waters generally
influences the quantity and quality of available food for ben-
thic foraminifera, and is usually followed by increase of
organic particles within the substrate (Duijnstee et al. 2004).
At the Gornje Vrap e locality this leads to the diminishing of
oxic and epifaunal taxa, while suboxic, disoxic and infaunal
taxa flourish, additionally supported by ample food supply.
Environmental needs of the abundant species Heterolepa
dutemplei dominantly depend on the food supply, and this
foraminifera preferably lives on organic-rich substrates
(Debenay & Redois 1997). The opportunistic species
Bolivina dilatata also positively responds to the increased
input of fresh phytodetritus and is extremely tolerant to oxy-
gen depleted environments (Bartels-Jonsdotir 2006; Diz &
Francès 2008). A further trend of oxygen depletion in bottom
waters (BFOI 55.9) can be observed in an argillaceous
lami na (Type B) with Bolivina–Cassidulina assemblage
(Subcluster IIc). Infaunal biota predominate, and suboxic,
disoxic and stress proxies further increased in number. Com-
pared to the previous Heterolepa–Bolivina assemblage, the
number of species and diversity increase, while the domi-
nance remains unchanged. Some opportunistic species (espe-
cially Cassidulina laevigata and Bolivina dilatata) very
quickly adapted to the new conditions and increased their
number of specimens more than 29 times, due to their rapid
reproduction. The genus Cassidulina is well adapted to oxy-
gen depletion (suboxic proxy) and abundance of the species
Cassidulina laevigata is strongly dependent on high nutrient
influx (De Stigter et al. 1999). Amount of high-valent metal
(probably iron) is twice as high in this type of lamina than in
types A and C, which points to the available source of metal
(possible bacterial activity). The overlying siltite lamina
(Type C) with Elphidium–Asterigerinata assemblage repeats
environmental conditions from the basal part of the section
and indicates reoxidization of bottom waters. Alteration of
all three types of laminae and associated benthic foramini-
feral assemblages occurs regularly up to the top of the lami-
nated sequence. Similar values of domination in all three
types of laminae point to abrupt changes of environmental
conditions, and particular taxa did not have enough time to
take the dominant role within the benthic assemblage.

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Ostracods are very scarce in the laminated section of the
Gornje Vrap e profile (average rate 1.3 %). Slightly more
abundant are the taxa Cnestocythere lamellicostata, Aurila
haueri, Hemicytherura sp. and Callistocythere canalliculata.
Like the Borovnjak locality, the analysed section at Gornje
Vrap e fits into the generally proven regressive trend. In
newly established nearshore environments the influence of
sea level oscillations can be much better observed. In the
same time periodical (seasonal) input of detritus and nu trients
from land strongly influences the biota and mode of deposi-
tion. In most inner and middle shelf environments (enclosed
systems), seasonal hypoxia (decrease in oxygen content in
bottom water) during the summer season is very common
(Jorissen 1999; osovi et al. 2002). If bottom water oxygen
concentration fluctuates on a shorter seasonal or interannual
timescale, the composition of the benthic foraminiferal
assemblage may be highly variable depending on the dura-
tion and intensity of successive oxygen minima and maxima,
and reproductive rate of certain foraminiferal groups under
the variable environmental conditions (Den Dulk et al. 2000).
Although microfossil assemblages of Gornje Vrap e show
similarities with seasonally controlled recent assemblages,
direct comparisons are not fully possible. We must take into
consideration taphonomic processes and known fact that fos-
sil assemblage only partly reflects the composition of ancient
biocoenosis. Nevertheless, the Heterolepa–Bolivina assem-
blage (Subcluster IIb) can be assigned to the period spring–
early summer, with pronounced freshwater discharge, which
influences the start of the spring phytoplankton bloom, and,
consequently, oxygen depletion at sea-bottom. Opportunistic
foraminiferal taxa increase in number responding to the
newly available nutrients. The Bolivina–Cassidulina assem-
blage (Subcluster IIc) can be assigned to the summer–early
autumn period. The summer phytoplankton bloom, increased
temperature, high organic matter degradation and maximal
stratification of the water-column cause the disoxic/anoxic
conditions at the sea-bottom. The Elphidium–Asterigerinata
assemblage (Subcluster IIa) reflects the late autumn–early
spring period. Re-established vertical water circulation again
supplies the bottom waters and benthic assemblage with
oxygen.

End-Badenian regression and emersion

Sedimentary features, deposition of massive biocalcrudites

with visible coarsening-upwards in the upper part of the
Borovnjak locality, undoubtedly indicate a regressive trend.
These deposits, unfortunately, do not comprise microfossils
and therefore we cannot reach any conclusions on eventually
full freshwater conditions before the final emersion. During
the emersion the Upper Badenian biocalcrudites were inten-
sively weathered and karstified, producing a pronounced
palaeorelief as the base for the Sarmatian transgression
(Vrsaljko et al. 2006).

The End-Badenian regression is also evident in the upper

part of the Gornje Vrap e section. The laminated portion of

the section is overlain by biolithites, and, finally, emersion
occurs before the deposition of the Sarmatian clastic sedi-
mentary rocks.

Conclusions

The Upper Badenian shallow marine sediments on the

SW slopes of the Medvednica Mt. were transgressively
deposited over the Mesozoic carbonate basement. The mar-
ginal marine highly oxygenated environment of normal
salinity is represented by the pioneer Elphidium–Asterigeri-
nata–Ammonia benthic foraminiferal assemblage, with low
diversity and strong domination. The relatively rich and
diverse Elphi dium–Asterigerinata assemblage appears with
an advanced transgression, visible in the Gornje Vrap e
section. This assemblage is typical for high-oxygenated
inner/middle shelf environments. Shallowing upward
sequences with increase of siliciclastic and nutrient input in
a depositional basin are present in the middle and upper part
of the studied sections. In the marginal shoal area (Borov-
njak locality) fluctuations in salinity appear, finishing with
brackish conditions and an Ammonia–Elphidium assem-
blage. The deeper and more sheltered inner/middle shelf
environment (locality Gornje Vrap e) bears evidence of
environmental changes in lamination. Laminae differ in
colour, calcium content and benthic foraminiferal assem-
blages. The dominant controlling factors in this part of the
section were fluctuations in bottom oxygen content and
changes in quantity and quality of food supply. In the
Heterolepa–Bolivina assemblage opportunistic taxa in crease
in number responding to the newly available nutrients and
oxygen depletion. The Bolivina–Cassidulina assemblage is
typical for periods of minimal oxygen concentrations, while
the Elphidium–Asterigerinata assemblage reflects the
period of recovery of vertical water circulation and oxyge-
nation of bottom waters. Similar almost regular changes
and distribution of foraminiferal assemblages is known
from modern seasonally controlled shelf environments. The
uppermost part of both sections is represented by massive
biocalcrudite or coralgal biolitite, and, finally, emersion
between the Upper Badenian and the Sarmatian depo sits.
Ostracod assemblages generally comprise scarce taxa
which are typical for shallow marine environments while in
the middle and upper part of Borovnjak section, amount of
ostracods increases within the microfossil assemblage. The
occurrence of the brackish ostracod Neocyprideis (Miocy-
prideis) sp. indicates fresh water inflows into a marine
environment.

Acknowledgements: Our thanks go to reviewers Katarina
Holcová and Stjepan ori for critical suggestions that
helped to improve the manuscript. Financial support for this
study was provided by scienti c project (119-1951293-
1162) of the Croatian Ministry of Science, Education and
Sports.

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, 2016, 67, 4, 329–345

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