GEOLOGICA CARPATHICA, JUNE 2006, 57, 3, 199—210
Sarmatian biostratigraphy of the Mountain Medvednica at
Zagreb based on siliceous microfossils (North Croatia,
and ZLATAN BAJRAKTAREVIĆ
Croatian Geological Survey, Sachsova 2, HR-10 000 Zagreb, Croatia; email@example.com
Department of Geology, Faculty of Science, University of Zagreb, Horvatovac 102a, HR-10 000 Zagreb, Croatia;
(Manuscript received October 15, 2004; accepted in revised form October 6, 2005)
Abstract: We proposed a biozonation of the Middle and Upper part of the Sarmatian Stage, based on siliceous microfos-
sils (silicoflagellates Distephanopsis soljani—Distephanopsis slavnicii Zone and diatoms Anaulus simplex—Coscinodiscus
doljensis Zone). The new silicoflagellate and diatom zones have been correlated with other already proposed zonations
for the Paratethys Sea and other marine realms. 46 diatom and 3 silicoflagellate taxa have been determined, that were
hitherto not known from the Croatian part of the Sarmatian Paratethys. The boundary between Middle and Upper
Sarmatian is supposed to be indicated by the change within the diatom assemblages and by the complete disapperance of
silicoflagellates. Tuffitic particles, occurring at the boundary, could also be used as a marker. Likewise a drastic decrease
of macrofaunal (molluscs) and microfaunal (foraminifers, ostracods) content is observed. The reason for changes in
species assemblages could be in gradual disconnections between Central Paratethys and other marine realms (Eastern
Paratethys, links through the Mediterranean to the Atlantic and towards the Indopacific) providing more near shore
influence and less saline environment during the Late Sarmatian.
Key words: Sarmatian, Central Paratethys, Medvednica Mt, diatoms, silicoflagellates.
In a paleogeographical sense the investigated area (SW
and S parts of Mt Medvednica comprising the suburbs of
Zagreb), represents the SW part of the Pannonian Basin
System, which was part of the Central Paratethys Sea.
Three sections were systematically sampled. These locali-
ties are: Podsused (Dol-I), Kostanjek (Kst-I), and Markuše-
vec (Mar-I). Isolated outcrops in the Susedgrad-Jarek
Fig. 1. Topographic map of Mt Medvednica with location of investigated areas.
region (Dol-II) have also been sampled (Fig. 1). Accord-
ing to the obtained data, in comparatively deeper areas, far
from land influence, the sedimentation of the Sarmatian
deposits proceeded continuously (Kst-I; Fig. 3), whereas
in the nearshore settings the sedimentation was affected
by tectonic and/or eustatic movements recorded as the
discontinuities in the successions (Mar-I and Dol-I;
Fig. 3). The Sarmatian in the Paratethys is characterized
by endemisms, with numerous endemic taxa (genera and
GALOVIĆ and BAJRAKTAREVIĆ
species) including phytoplankton (Jurilj 1957; Jerković
1963, 1965; Bajraktarević 1983a,b). However, a dense
and systematic sampling (Fig. 3), allowed establishment
of a reliable diatom and silicoflagellate zonation, which
may serve as a base for correlation with other seas (Ta-
Material and methods
Almost every 1.5—5 cm of particular marly horizons
have been sampled (Fig. 3). Total number of samples is
71. From the sample as small as a nut is taken approxi-
mately 1/2 cm
of sediments, than put into the standard
epruvet (16 160 mm) and soaked in distilled water un-
til the sample is completely disaggregated. Samples are
treated with 20 ml of 30 % of hydrogen peroxide (H
solution in order to remove organic matter from sedi-
ments, but some of them are treated with 20 ml of 15%
hydrochloric acid (HCl). Then distilled water is added
and decanted to neutral. Some of the samples have been
put into an ultrasonic tank for approximately 15 sec-
onds to have better disaggregation. After that we pro-
ceed with slide preparation. A few drops of sample are
pipetted to smear slide, dried, and mounted with Cana-
da balsam. The slide is than viewed at a magnification
of 200 to 500 with emersion oil under the light micro-
scope. Paleodepths are given on the basis of the formula
and graph according to Pushkar & Cherepanova (2001).
In a regional geologic sense, Mt Medvednica belongs to
the Supradinaricum geotectonic unit (Herak 1986), and
represents part of the northern marginal zone of the Inner
Dinarides (Šikić 1995). The first geological information
regarding the geological structure and paleontological
contents of the Neogene deposits of Mt Medvednica come
from the second half of the 19
century (Foetterle, Vukoti-
nović, Pilar, Gorjanović-Kramberger, Brusina, Kiseljak,
Franzenau and others). The bulk of the central and oldest
part of Mt Medvednica, ranging in age from the Paleozoic
to the Paleogene, was definitely structurally shaped and
placed almost into its present-day position before the sedi-
mentation of the Neogene deposits. Emersion lasted from
the Paleocene to the Ottnangian. The Ottnangian is repre-
sented by lacustrine sediments, which are topped by ma-
rine Karpatian deposits (Avanić 1997). In the Early
Badenian, a marine transgression spread over the NE and
in the Late Badenian it progressed also over the SW parts
of Mt Medvednica. The Paratethys started to become iso-
lated at the end of the Badenian (Šikić 1995). During the
Sarmatian, marine sedimentation still existed in the west-
ern part of the Central Paratethys but toward the end of the
Sarmatian it became progressively brackish due to re-
duced connection with the Mediterranean (Rögl 1996).
The Pannonian Basin became definitely isolated and a
lacustrine environment formed (Vrsaljko 1999). In the Ear-
ly Pontian, the area of Mt Medvednica becomes more
brackish. The Late Pontian is characterized by shallowing
of environments as a consequence of the basin’s closing
(Avanić et al. 2003). Due to tectonic movements in the
Pliocene and in the Quaternary, Mt Medvednica was up-
lifted, accompanied by reverse movements with N and NW
vergence. Simultaneously, erosional processes became
progressively stronger (Šimunić & Šimunić 1987).
Podsused (Dol-I) and Susedgrad-Jarek (Dol-II) localities
The geological column Podsusedsko Dolje (Dol-I) and
the outcrop Susedgrad-Jarek (Dol-II) are situated on the
southwestern slopes of Mt Medvednica, near the village of
Podsused (Fig. 1). The thickness of the Sarmatian deposits
amounts to 20 m. They are separated from the underlying
Badenian deposits by an erosional and angular unconfor-
mity, and from the overlying, Pannonian, deposits, by a
fault. In the lower parts of the columns calcitic silts pre-
dominate; going upward they pass into a siltose to spon-
gitic microsparite and, further up, parallel laminated marls
that form the upper part of the column (Fig. 3). The se-
quence contains bivalves, small gastropods, imprints of
leaves (Acer cf. pseudoplatanus L.) with other plant and
fish remains, foraminifers, ostracods, and calcareous nan-
nofossils (Bajraktarević 1981; Avanić et al. 1995).
Among the siliceous microfossils, most abundant are the
diatoms, of which several taxa are unknown from the
Paratethys (Table 2). Silicoflagellates are somewhat less
abundant, the most frequent being: Deflandryocha cymbi-
formis Jerković, Def. spathulata Jerković, Dictyocha fibu-
la fibula Ehrenberg, D. rhombica (Schulz) Deflandre,
Distephanopsis crux (Ehr.) Dumitrica, Dss. crux parvus
(Bachmann) Desikachary et Prema, Dss. schauinslandii
(Lemmermann) Desik. et Prema, Dss. slavnicii (Jerković)
Desik. et Prema, Dss. stradneri (Jerković) Desik. et Prema,
Dss. soljani (Jerković) Desik. et Prema, Mesocena elliptica
(Ehr.) Ehrenberg, Paramesocena apiculata (Lemmermann)
Locker et Martini and P. circulus (Ehr.) Locker et Martini
(Plate 1). Rarer are species of the genus Archaeomonas (A.
angulosa Deflandre*, A. inconspicua Deflandre*, A. cf.
mangini Deflandre) and the ebriids Cardiuifolia gracilis
Hovasse*, Ebria triparita (Schumann) Lemmermann,
Ebriopsis valida Deflandre, Hovassebria ?bravispinosa
(Hovasse) Deflandre*, which were recorded for the first
time from this region. These are accompanied by the dino-
phycean Actiniscus stella Ehrenberg and sponge spicules.
Reworking of Mesozoic, Paleogene, Lower Miocene,
and Badenian deposits has also been observed. In the Sar-
matian deposits of the Podsused locality, 75 diatom spe-
cies have been recorded that were up to now unknown in
the investigated area; among those, 25 species have been
recorded for the first time for the Central Paratethys region
(marked by an asterisk). Above, we have listed only those
diatom species that were not previously mentioned by Ju-
rilj (1957), Table 2.
SARMATIAN BIOSTRATIGRAPHY OF THE MOUNTAIN MEDVEDNICA (NORTH CROATIA)
Fig. 2. 1 – Deflandryocha spatula Jerković (800
; 2 – Def. naviculoidea Jerković (800
; 3 – Def. cymbiformis Jerković (800
4 – Distephanopsis soljanii (Jerković) Prema et Desik. (800
; 5 – Dss. slavnicii (Jerković) Prema et Desik. (1100
; 6 – Dss. longispinus
(Schulz) Desik. et Prema (1100
; 7 – Dictyocha brevispina brevispina (Lemmermann) Bukry (750
; 8 – D. rhombica (Schulz) De-
; 9 – D. subclinata Bukry (750
. Scale bar = 10 m.
Kostanjek (Kst-I) locality
The geological column Kostanjek (Kst-I) is situated on
the southwestern slope of Mt Medvednica, within the ex-
ploitation grounds of the abandoned cement factory in
Podsused, near the Kostanjek village (Fig. 1). At the foot
of the deserted clay strip mine the top part of the Sarma-
tian deposits and the continuous transition into the Pan-
nonian beds is exposed. Only about 1.5 m of parallel
laminated marls of varved sediments, typical for the Sar-
matian, were sampled. They have a grey-greenish to brown
colour and are intercalated with white laminae, mostly
0.5—2 mm thick, reaching a maximum of 4 mm (Fig. 3).
Their fossil content includes fish remains, leaves, other
macro- (molluscs) and microfauna (ostracods, foramini-
fers), (Vrsaljko 1999), and calcareous nannofossils.
Diatoms are less abundant and less diverse than at Pod-
susedsko Dolje (Table 2). Rare species is Archaeomonas
colligera Hajós*, and even rarer are silicoflagellate frag-
ments and sponge spicules. Reworked phytoplankton of
GALOVIĆ and BAJRAKTAREVIĆ
Fig. 3. Geological columns.
SARMATIAN BIOSTRATIGRAPHY OF THE MOUNTAIN MEDVEDNICA (NORTH CROATIA)
Table 1: Correlation table of Sarmatian (eco) biozones according to different
Markuševec (Mar-I) locality
The geological column Markuševec (Mar-I)
is situated on the southwestern slope of Mt
Medvednica, in the bed of Mrzljak creek in
the village Markuševec (Fig. 1). In the bot-
tom part of the column, Sarmatian sediments
consist of coarse-grained clastic deposits
(conglomerates) and normally graded sands.
These are overlain by a 13 m thick alterna-
tion of light and dark, 3—5 cm thick, parallel
laminated marls of varved sediments. The
Sarmatian clastics unconformably overlie
Badenian biocalcarenites, whereas the transi-
tion to the Pannonian is continuous (Fig. 3).
They contain macro- (fish remains, molluscs)
and microfauna (foraminifers), and sporadi-
cally carbonized plant remains and calcare-
ous nannofossils (Galović et al. 2000).
The diatom assemblage is abundant and di-
verse (Table 2). Less abundant are the follow-
ing siliceous microfossils like sponge spicules
and silicoflagellates Dictyocha fibula ausonia
(Deflandre) Mc Cartney, Churchill et Woes-
tendiek, D. brevispina brevispina (Lemm.)
Bukry, D. pentagona (Schulz) Bukry et Fos-
ter*, D. rhombica (Schulz) Deflandre, D. sub-
clinata Bukry*, Distephanopsis crux (Ehr.)
Dumitrica, Dss. crux parvus (Bachmann) Desik.
et Prema, Dss. hannai (Bukry) Desik. et Pre-
ma*, Dss. longispinus (Schulz) Desik. et Prema,
Dss. schauinslandii (Lemm.) Desik. et Prema,
Dss. slavnićii (Jerković) Desik. et Prema, Dss.
staurodon (Ehr.) Desik. et Prema, Dss. stradneri
(Jerković) Desik. et Prema, Dss. šoljani (Jer-
ković) Desik. et Prema, Distephanus crux lock-
erii Amigo*, Ds. quinquengellus Bukry et
Foster, Ds. speculum speculum (Ehr.) Haeckel,
Ds. speculum elongatus Bukry, Mesocena el-
liptica (Ehr.) Ehrenberg, Paramesocena apicu-
lata (Lemm.) Locker et Martini, P. circulus
(Ehr.) Locker et Martini. More rare are ebriids
Ammodochium rectangulare (Schulz) Deflan-
dre, Cardiufolia gracilis Hovasse, Ebria tri-
parita (Schum.) Lemmermann, Ebriopsis
valida Deflandre, Hermesinum adriaticum Za-
charias*, Parathranium clathratum (Ehr.) De-
flandre, dinoflagellate endoskeletons Actiniscus
pentasterias Ehrenberg, A. stella Ehrenberg,
Planifolia tribrachiata Ernissee, archaeo-
monadaceas Archaeomonas angulosa Deflan-
dre, A. colligera Hajós, A. mangini Deflandre,
A. pseudocompressa Hajós*, A. sphaerica De-
flandre, A. spinosa Hajós*, and radiolarians.
micro- to nanno-scale belongs to the Paleogene, Lower
Miocene, and Badenian. In the investigated area, the dia-
tom Cymbella cf. ventricosa Kützing was recorded for the
first time, and Nitzschia sinuata var. tabellaria (Grunow)
Grunow* for the entire Paratethys area.
Fifty-six Sarmatian diatom species have been registered
for the first time in this region and 18 of them have not
been recorded so far from the Paratethys realm (marked by
an asterisk). The above mentioned assemblage contains
taxa that were not mentioned by Jurilj (1957). Reworked
GALOVIĆ and BAJRAKTAREVIĆ
Paleogene, Lower Miocene and Badenian have also been
A more detailed biostratigraphic and paleontological re-
search of the region was done in the second half of the
century, with the works of Kochansky-Devidé (1957,
1973), Sokač (1965, 1967, 1972, 1985), Šikić (1966,
1967, 1968, 1975), Bajraktarević (1976), Kochansky-Dev-
idé & Bajraktarević (1981), Polšak et al. (1986), Basch
(1990a,b), Basch et al. (1992), Šikić (1995) and Vrsaljko
(1999). The stratigraphy of the siliceous phytoplankton
was particularly researched by Jurilj (1957), Jerković
(1965, 1969, 1974), Bajraktarević (1983a,b,
1984) and Galović (2001).
In the Mt Medvednica environments the
transition from the marine Badenian into
the Sarmatian basin is presented. The later
was characterized by reduced salinity and
starvation of sediment supply (Avanić et al.
2003). This corresponds to the uppermost
part of the calcareous nannoplankton NN6
Zone (Martini 1971). The southwestern
slopes of Mt Medvednica are well known
for diatomaceous laminated marls with dia-
toms, sponge spicules, silicoflagellates,
ebriids, radiolarians and archaeomona-
daceans (Jurilj 1957; Jerković 1969; Ba-
jraktarević 1983a,b; Galović 2001). The
Paratethyan silicoflagellate cenozone Dic-
tyocha soljani has been established in the
laminated marls of “Dolje type” by Bajrak-
tarević (1984). Also, on the basis of a rare
occurrence of Dictyocha rhombica the as-
semblage could belong to Dictyocha rhom-
bica Zone (Martini 1977) in a broader
geographical context, corresponding to the
NN7 Calcareous Nannoplankton Zone (Ta-
ble 1) (Bajraktarević 1984).
The first occurrence of the diatom spe-
cies Rhaphoneis diamantella in the Para-
thetys is reported from the Karpatian
(Hajós 1986). According to the diatom zo-
nation, Rhaphoneis diamantella is a char-
acteristic species of the namesake Partial
Range Zone (mid-Atlantic region), ranging
in age between 12.25—11.5 Ma (Andrews
1978). The diatom species Actinocyclus
karstenii was recorded for the first time in
the southern part of the Indian Ocean, in de-
posits of ~ 11.7 Ma (Harwood & Maruyama
1992). In the Markuševec locality it was re-
corded in deposits belonging to the Middle
Sarmatian (NN7 Calcareous Nannoplank-
ton Zone), accompanied by R. diamantella,
Grammatophora hungarica, and Denticu-
lopsis hustedtii, which are characteristic for
the lower middle Miocene of the Paratethys (Hajós 1986).
One reason for their occurrence in younger sediments is
perhaps due to reworking, tectonics (Dol-I) and/or eustat-
ics. The beginning of the first Sarmatian transgression in the
Paratethys was dated at about 12.5 Ma (Kováč et al.
2001). The maximum transgression of the next cycle
(Harzhauser & Piller 2004), at the Markuševec and Pod-
sused localities, occurs in the middle part of the Sarmatian
(NN7 and/or NN7/NN8 Calcareous Nannoplankton Zone,
respectively; Galović 2003). It is recorded in neritic-lit-
toral development. These sediments contain molluscs be-
longing to the Ervilia-Mactra beds and a foraminiferal
assemblage with Elphidium hauerinum and Po-
rosononion granosum (Fig. 3) (Galović et al. 2000). The
following diatom species are indicative for the Middle
Table 2: Distribution of diatom species in samples from diferent localities; * – not reg-
istrated in the Paratethys during the Sarmatian. Continued on the next page.
SARMATIAN BIOSTRATIGRAPHY OF THE MOUNTAIN MEDVEDNICA (NORTH CROATIA)
Sarmatian in the Paratethys: Coscinodiscus doljensis,
Odontella aurita, Achnanthes baldjikii, Caloneis liber
var. zagrebiensis, Cocconeis distans, C. scutellum var. in-
equlepunctata, C. scutellum var. pulchra, Cymatosira bi-
harensis, Dimidiata saccula, Grammatophora insignis,
Mastogloia pethoei, M. szontaghii, Rhopalodia giberula
and Thalassionema nitzschioides. This means, that the
conditions suitable for the development of the above men-
tioned assemblage could be well established, both in some
other parts of the Paratethys (partially from Balchik,
Bulgaria by Temniskova-Topalova 1982; Mecsek Mt,
Hungary by Hajós, 1986; Bremia, Romania by Pantocsek
1886—1905; and Dolje & Rožman, Croatia by
Jurilj 1957) and in the investigated area. Sili-
coflagellates gradually disappear and the
abundance of diatoms is drastically reduced
toward the end of the Middle Sarmatian (lower
part of the NN8 Zone which belongs to the
Volhynian, Mărun eanu 1999). The beginning
of the appearance of Upper Sarmatian diatoms
in the Mar-I and Kst-I columns (Cocconeis
pediculus, Cymatopleura solea, Cymbella cf.
ventricosa, Cy. cf. sinuata, Nitzschia frustulum
var. obtusa) characterized the boundary. The
changes from the Middle to Upper Sarmatian
Paratethyan diatom assemblages (Achnanthes
baldjikii, Cocconeis distans, Thalassionema
nitzschioides) also could confirm the Middle/
Upper Sarmatian boundary. Besides, the Mid-
dle/Upper Sarmatian boundary (lower/upper
part of the NN8 Zone corresponding to the
Volhynian/Early Bessarabian; Papp et al.
1974; Mărun eanu 1999) may be established,
on the basis of both the phytoplankton (sili-
coflagellate, diatom and coccolithophorid) as-
semblage and of volcanic particles. Vass (1999)
attempted to correlate different and heteroge-
neous data for the Sarmatian age in particular
Paratethys areas, derived from magnetostratigra-
phy, chronostratigraphy, biostratigraphy, and
radiometric dating, focusing particularly on the
age of NN8 Calcareous Nannoplankton Zone.
In this paper, this zone is correlated with Vass’s
first datings. This zone is detected in Papp’s
‘Impoverishment zone’ (or Sarmatimactra vi-
taliana Biozone) with rare foraminiferal (Po-
rosononion granosum) and ostracod (Aurila
notata) species (Galović et al. 2000).
The silicoflagellate (Distephanopsis (Dis-
tephanus) soljani—Distephanopsis (Distepha-
nus) slavnicii) and the diatom zonation
(Anaulus simplex—Coscinodiscus doljensis) have
been correlated with other established zona-
tions (Table 1).
The silicoflagellate Distephanopsis sol-
jani—Distephanopsis slavnicii Zone
acterized by first and last occurrence of these
species in the Paratethys. It consists of: Dicty-
ocha subclinata Bukry, Dictyocha brevispi-
na brevispina (Lemm.) Bukry, Dictyocha rhombica
(Shulz) Deflandre, Deflandryocha cymbiformis Jerković,
Def. spathulata Jerković, Distephanopsis crux (Ehr.)
Dumitrica, Dss. longispinus (Schulz) Desik. et Prema,
Dss. schauinslandii (Lemm.) Desik. et Prema, Dss. strad-
neri (Jerković) Desik. et Prema, Dss. crux parvus (Back-
mann) Desik. et Prema and Distephanus crux lockerii
The diatom Anaulus simplex—Coscinodiscus doljensis
was established by Řeháková (1975, 1977) for the
Czech part of Central Paratethys (Table 1). This zone is
distinguished by a great species diversity of the genera Act-
Table 2: Continued.
GALOVIĆ and BAJRAKTAREVIĆ
inocyclus, Chaetoceros, Coscinodiscus, Achnanthes, Am-
phora, Cocconeis, Diploneis, Grammatophora, Mastogloia,
Navicula and Nitzschia. It is characterized by the index spe-
cies of Anaulus simplex Hajós, Coscinodiscus doljensis
Pant., C. sarmaticus Pant., Dimidiata saccula Hajós, Masto-
gloia szontaghii Pantocsek, Cymatosira biharensis Pant.,
Achnanthes baldjikii (Brightwell) Grunow, Cocconeis
scutellum f. birhafidea Jurilj, Co. scutellum var. raena (Pan-
tocsek) Cleve, Grammatophora insignis var. doljensis
Grun., Nitzschia doljensis Pant., Rhaphoneis mertzi Hajós,
Rhopalodia giberula var. rosmanniensis Jurilj. Typical
forms in the assemblage are Actinoptychus splendes var.
zagrebiensis Jurilj, Coscinodiscus rugulosus Hajós, C. niti-
dus var. zagrebiensis Jurilj, Melosira distans var. imbuta
Jurilj, Triceratium laetum f. quadrata Hajós, Achnanthes
rara Jurilj, Ach. saeptata var. doljensis Jurilj, Ach. saeptata
var. sussedana Jurilj, Amphora crassa var. gemmata Jurilj,
Am. crassa var. punctata Grun., Am. domkeana Jurilj, Am.
proteus var. nodosa Jurilj, Am. intersecta var. sarmatica Ju-
rilj, Caloneis liber var. zagrebiensis Jurilj, Cocconeis
andesitica Jurilj, Co. canaliculata Jurilj, Co. evolvens Ju-
rilj, Co. ornata var. birhaphidea Jurilj, Co. scutellum var.
parva (Grun.) Cleve, Diploneis perforata Jurilj, Campylo-
discus kuetzingii Pant., Cymatosira miocaenica Hajós, Dic-
tyoneis lorkovicii Jurilj, Dimerogramma minor (Greg.)
Ralfs, Diploneis vetula f. minor Jurilj, Mastogloia baltsch-
kiana Grun., M. angulata var. sarmatica Jurilj, M. sarmati-
ca Jurilj, Navicula latissima var. cuneata Jurilj, Opephora
gemmata f. minor Jurilj, Plagiogramma boryanum Hajós, P.
biharense Pant., Rhopalodia giberula var. protracta Grun.
and Surirella subfastuosa Pant.
In the Middle Miocene of the equatorial Pacific Ocean,
silicoflagellate species Dictyocha subclinata makes a
horizon of the Dictyocha varia Interval Zone (Table 1),
(McCartney et al. 1995). Dictyocha subclinata was also
found in Middle Miocene deposits of the northern Atlan-
tic. Its first appearance is within the CN5 Nannoplankton
Zone (Okada & Bukry 1980), which would correspond to
the beginning of the Sarmatian in the Paratethys. The
first occurrence of D. subclinata is observed when Cor-
bisema triacantha disappears (extinction), which is at the
Badenian/Sarmatian boundary in the Central Paratethys,
corresponding to the nannoplankton Zone NN7 (Hajós
1986). The equivalent of the silicoflagellate zone Dis-
tephanus slavnicii (Fig. 2) is the diatom Zone Anaulus
simplex—Coscinodiscus doljensis (Hajós 1986). The
Anaulus simplex—Coscinodiscus doljensis Diatom Zone
of the Central Paratethys is contemporaneous with the
Cymatosira biharensis—Mastogloia szontaghii Zone in
the Eastern Paratethys (Olshtynska 2001) based on co-
occurrence of the species.
Paleoecology and paleogeography concerning
The above mentioned phytoplankton assemblages oc-
cur in the middle to upper part of the Sarmatian deposits.
Most first appearances of marine planktonic diatoms, with
negligible amount of some benthic organisms in the sedi-
ments, are characteristic for warm climatic regions. This is
also proved by very rare occurrences of the silicoflagellate
Dictyocha fibula, which, in the Adriatic Sea, almost disap-
pears during the warmer season (Jerković & Kovačić
1970). Following the gradual global cooling, accompa-
nied by temperature oscillations, marine varved sediments
have been deposited (Schrader et al. 1986; Vaniček et al.
2000), with taxa adapted to a more temperate environment
(Distephanopsis crux, Dss. longispinus, Dss. schauinslan-
di, and Dss. staurodon, together with mesocoenas and
paramesocoenas; Bukry 1981; Desikachary & Prema
1996; Amigo 1999). The morphology of the apical ring in
the silicoflagellates is indicative of the temperature condi-
tions in which they developed. The more strongly (mas-
sive) skeletons indicate lower temperatures. Below 3 °C,
however, the development of the skeletons is reduced (Bo-
haty & Harwood 1998). Silicoflagellates are sensitive to
temperature variations, which could be indicative on the
orientation of the skeleton (McCartney & Loper 1989)
that is not symmetrical in the assemblage and because of
that the broader temperature ranges have been inferred for
the Sarmatian. The temperature ranges were obtained also
based on the diatoms, giving average temperature ranges
of 4—16 °C for cooler and from 15—27 °C for warmer peri-
ods. In the varve-type sediment, ecologically tolerant
forms, regarding salinity, vary from marine to brackish-
freshwater, represented in the assemblage with mostly
planktonic diatoms. Most samples contain assemblages,
indicative for salinity from 20—40 (Hajós 1986), but dur-
ing warmer seasons a thermohaline assemblage was
formed, containing both mesohaline and oligohaline
forms, though their share in the whole assemblage is less
than 5 % in the Middle Sarmatian. The ebriid Hermesium
adriaticum, which occurs in stratified waters in the halo-
cline, i.e. in an intermediate brackish/marine environment,
indicates oxic to anoxic conditions with a well-developed
chemocline (Fig. 3) (Viličić et al. 1996—97). This species
belongs to heterotrophic organisms that feed on dissolved
and suspended organic material accumulated around the
thermohaline zone (Mantoura 1987). During warmer sea-
sons, rivers bring terrigenous particles and organic materi-
al, and due to differences in density and temperature
between surface and bottom waters, a pycnocline to ther-
mocline is formed. H. adriaticum migrates in winter from
the eastern Mediterranean into the Adriatic (Gržetić 1982)
and has also been found in the Black Sea in anoxic layers
rich in H
S (Bodeanu 1969), which also contain sili-
coflagellate skeletons (Cornell 1977). With time, disoxic
conditions develop below the thermocline (oxygen being
used up by respiration of organisms), whereas on the bot-
tom bacteria decompose the organic matter and also use
up oxygen, producing anoxic conditions too. Such condi-
tions allowed the (permanent) preservation of the siliceous
phytoplankton taxa (Puškarić et al. 1990) and develop-
ment of dark, millimeter-thick laminae rich in organic ma-
terial. In cooler seasons, the temperature below and above
the thermocline becomes equal, the thermocline disap-
pears and upwelling occurs, nutrient rich bottom water
SARMATIAN BIOSTRATIGRAPHY OF THE MOUNTAIN MEDVEDNICA (NORTH CROATIA)
mixes with the oxygen-rich surface water. The temperature
near the sea bottom is much lower than in the surface lay-
ers. The silicoflagellate and diatom skeletons may accumu-
late because of reduced dissolution in lower temperature
conditions (Fig. 4). The seasonality, sedimentation rates
and a strong oxygen minimum zone, results in the preserva-
tion of annually laminated sediments as in the varved sedi-
With time, due to diagenetic processes, the BiS (biogen-
ic silica) participate in the formation of varve sediments in
the area of Mt Medvednica (Polšak et al. 1986). Also the
skeletons may be encrusted by authigenic minerals (fer-
rous, magnesium and calcium alumosilicates), which addi-
tionally affects their preservation potential and may be
seen in thin sections of Mar-I and Kst-I (pyrite and/or oth-
er opaque minerals). In the Late Sarmatian, the predomi-
nance of benthic forms indicates stronger near-shore and
meso-oligohalin influence (Cocconeis pediculus, Cy-
matopleura solea, Cymbella cf. ventricosa, Cy. cf. sinuata,
Nitzschia frustulum var. obtusa). Carbonate content in the
sediment of Kst-I increases from 44 % to 55 % at the end
of the Sarmatian, because of shallowing and more pro-
nounced near-shore influence. Due to various stress factors
(temperature, salinity, water transparency and chemistry)
many new species, variations and forms are registrated
(Table 2) (Jurilj 1957 and Hajós 1986). Such conditions
are indicated in the marginal brackish Paratethys environ-
ments, or, locally, in isolated bays (Hajós 1986). The
planktonic/benthic diatom ratio varies from min. 0.22 to
max. 0.83 corresponding to paleodepth from about 25 to
120 m (Pushkar & Cherepanova 2001) reveals the sea level
oscillations during the Middle and Late Sarmatian, with
a general regressive trend towards the end of the Sarma-
tian. The silicoflagellate and diatom assemblages (Cha-
etoceros spp., Thalassionema nitzschiodes) point to a
marginal Paratethys area and upwelling zone such as
coastal regions or epicontinental seas (Puškarić et al.
1990; Trepke et al. 1996). Because of the upwelling, the
surface water became enriched with nutrients (nitrates,
nitrites, ammonium salts, phosphates, and silica) that
were used up by the phytoplankton community during
assimilation. A part of the dissolved H
oslilicate) was brought in by rivers (Fig. 4). Fresh water
input is also evident by diatom assemblage, brought by
streams into the sedimentary environment (Aulacoseira
islandica, Cocconeis placentula var. euglypta, Diplo-
neis ovalis, Gyrosigma distortum var. parkeri). There is
an indirect way to find out whether the nutrient concen-
tration was high or low. The complexity of the structure
of the skeleton increases with the nutrient concentration.
In contrast to that, simpler forms develop in the condi-
tions of low nutrient concentrations. The presence of par-
ticular genera and species are evidence of a connection
with the Mediterranean (Dictyocha brevispina, D. fibula
ausonia, D. rhombica, Distephanopsis crux, Dss. stauro-
don, Distephanus quinquangellus, Mesocena elliptica,
Paramesocena circulus, Achnanthes hauckiana var. elip-
tica, Actinoptychus senarius, Amphora costata, Biddul-
phia biddulphiana, Chaetoceros holsaticus, Chaetoceros
lorenzianus, Climacosphenia moniligera, Cocconeis cru-
ciata, C. distans, C. fluminensis, C. ornata var.
birhaphide, C. quarnerensis var. lanceolata, Cymatosira
Fig. 4. Schematic paleoecological reconstruction of investigated marginal Paratethys area during the Sarmatian.
GALOVIĆ and BAJRAKTAREVIĆ
lorenziana, Diploneis vetula f. minor, Fragilaria brevis-
triata var. fossilis, Grammatophora marina, Mastogloia
quinquecostata, Paralia debyi, Plagiogramma stauropho-
rum, Planothidium quarnerensis, Rhabdonema hamulifer-
um, Thalassionema nitzschoides) and the Indopacific
(Cannopilus hemisphaericus, Dictyocha fibula ausonia,
D. pentagona, D. subclinata, Distephanopsis crux, Dss.
hannai, Dss. longispinus, Distephanus speculum, Parame-
socena circulus, Actinocyclus karstenii; Bukry & Foster
1973; Harwood & Maruyama 1992; McCartney et al.
1995) during the Middle Sarmatian. In the Markuševec lo-
cality, the connection with other marine areas (Eastern
Paratethys, Mediterranean, and the Indopacific) can be in-
ferred to have existed only above the middle part of the
column in laminated marls, when favourable conditions
for the development and preservation of siliceous micro-
fossils have been established (Fig. 4). The first input of sil-
iceous microfossils can be seen with the beginning of the
deposition of the Middle Sarmatian deposits when the
connection with other marine areas was established. At the
end of the Middle Sarmatian (s.str.) connection is reduced,
oscillated, and interrupted (Dictyocha brevispina brevispi-
na, D. fibula ausonia, D. fibula fibula, D. rhombica, Dis-
tephanopsis crux, Dss. staurodon, Distephanus speculum,
Ds. quinquengellus, Mesocena elliptica elliptica, Parame-
socena circulus). However, aberrant silicoflagellate forms
that accompany these changes are also present, though
very rare. It is well known that silicoflagellates, under
stress conditions, loose their symmetry, such as their api-
cal ring, and develop simpler forms (Guex 1993). All this
speaks in favour of specific conditions characterized by a
semi-restricted marine environment, like in a bay or the
Black Sea. In addition to the upwelling and the connec-
tions with other marine areas, occurrence of volcanic glass
(Šimunić 1993, pers. com.) may have also contributed to
locally favourable conditions for the preservation of sili-
coflagellate skeletons (Mar-I, Kst-I). In the marine envi-
ronment, volcanic glass is unstable and subject to
hydrolysis, releasing silica that is used by siliceous phy-
toplankton for the construction of their tests (Zen 1959).
Beside the volcanic activity, the region was also affected
by tectonics, which is revealed, in addition to sedimento-
logic indicators (angular unconformity in Podsusedsko
Dolje, Fig. 3), by the presence of the dinoflagellate Acti-
niscus pentasterias, an indirect indicator of tectonically
turbulent regions (Orr & Conley 1976).
According to the presented results, the middle part of
the Sarmatian of the Central Paratethys begins with a
transgression. At the beginning of the Middle Sarmatian,
in the investigated area, conditions favourable for the de-
velopment and preservation of siliceous phytoplankton
have been established. A large concentration of biogenic
silica in the sediment is indicative of marginal marine
environments with pronounced continental upwelling
(diatom species of Chaetoceros, Coscinodiscus curvatu-
lus, Thalassionema nitzschoides and silicoflagellates).
The alternations of dark, organic rich, mm laminae and
light laminae rich in carbonate are probably a conse-
quence of sedimentation changes due to the seasonal
variations in more temperate climate. At Mt Medvednica,
such areas were suitable for the development of marine
varved sediments. The interconnectedness of marine
realms has also been established. The Sarmatian phy-
toplankton assemblages that developed in the Mediterra-
nean and Indopacific region have been found in the
investigated area, which proves connections between
these seas. They have been established during the Mid-
dle Sarmatian, when species migrated, by means of cur-
rents, into our regions and were deposited in the
upwelling areas. The proofs for that may be also found in
other parts of the Central Paratethys (Hungary, Slovakia),
where the connections with these marine areas have also
been established on the basis of diatoms. Towards the
end of the Middle Sarmatian, these connections were
gradually interrupted. At the end of the Sarmatian the ba-
sin was isolated. This could be shown by a sharp de-
crease of biodiversity (both on the genus and species
levels), complete disappearance of silicoflagellates, also
changed assemblages and predominance of benthic dia-
toms (Cocconeis pediculus, Cymatopleura solea, Cym-
bella cf. ventricosa, Cy. cf. sinuata, Nitzschia frustulum
var. obtusa), which indicate the conditions of reduced sa-
linity and more near shore influence.
This paper resulted from the work
done within the project “Neogene clastic-carbonate com-
plexes of Mt Medvednica”, under the leadership of Dr. I.
Hećimović. We thank him for his expert leadership. Spe-
cial thanks to Prof. Ivan Gušić for his useful suggestions.
We also thank our colleagues Dr. M. Kovačić and Al. Šimu-
nić for their results of sedimentary-petrographic analyses,
as well as M. Drušković for calcimetry, all in the Croatian
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