The South-Western Boundary of Central Paratethys

Paratethys was the intercontinental bioprovince, which began to evolve in the Oligocene due to the counterclockwise rotation of Africa that caused the closure of the Tethys Ocean. It extended from the western Molasse Basin in Switzerland and the Rhone Basin in France towards Lake Aral in Asia. Paratethys is subdivided into Western Paratethys, Central Paratethys and Eastern Paratethys. The Central Paratethys extended from Bavaria to the Carpathian mountain chain (LASKAREV, 1924; SENE©, 1979; STEININGER & RÖGL, 1979, 1984; RÖGL & STEININGER, 1983, 1984; RÖGL, 1998, 1999) (Fi g. 1). The nature of the evolution of Central Paratethys and the occurrences of an endemic fauna has necessitated the establishment of local Miocene stages (Fig. 2).


INTRODUCTION
Paratethys was the intercontinental bioprovince, which began to evolve in the Oligocene due to the counterclockwise rotation of Africa that caused the closure of the Tethys Ocean.It extended from the western Molasse Basin in Switzerland and the Rhone Basin in France towards Lake Aral in Asia.Paratethys is subdivided into Western Paratethys, Central Paratethys and Eastern Paratethys.The Central Paratethys extended from Bavaria to the Carpathian mountain chain (LAS-KAREV, 1924;SENE©, 1979;STEININGER & RÖ-GL, 1979, 1984;RÖGL & STEININGER, 1983, 1984;RÖGL, 1998RÖGL, , 1999) ) (Fi g. 1).The nature of the evolution of Central Paratethys and the occurrences of an endemic fauna has necessitated the establishment of local Miocene stages (Fig. 2).
In the geotectonical sense, the largest part of Central Paratethys is represented by the Pannonian Basin System, formed due to continental collision and subduction of the European plate under the African (Apulian) plate (HORVÁTH & ROYDEN, 1981;ROYDEN, 1988;TARI et al., 1992;HORVÁTH, 1995;KOVÁ» et al., The South-Western Boundary of Central Paratethys Davor PAVELI∆ 1998).The Pannonian Basin System is surrounded by the Alps and Carpathian mountains, and by the Dinarides which existed as land between the Mediterranean Sea and Pannonian Basin System during its evolution.The southwestern part of the Pannonian Basin System consists of the North Croatian Basin and the Northern Bosnia region (PAVELI∆, 2001).
The Dinarides represent a mountain complex, which formed during the Tertiary and Quaternary due to tectonic activity, which caused disintegration and uplift of the Mesozoic carbonate platform.In the Tertiary, compressive movements culminated with orogenesis of the Dinarides.Further neotectonic activity caused uplift and transpressive deformations of the older structure.These tectonics strongly controlled the formation of many small Neogene basins within the Dinarides which were characterized by fresh-water sedimentation and an endemic fauna.That tectonic activity has been strongest along the recent eastern Adriatic coast due to the continental collision of the Adriatic microplate and the Dinarides.This collision caused the compression and uplift of blocks which is represented by a mountain chain known as the High Karst Belt, the highest peaks of which reach from 1400-1913m (BAHUN, 1974;;PAPE©, 1985;HERAK, 1986HERAK, , 1991HERAK, , 1999;;ALJINO-VI∆ et al., 1987;BLA©KOVI∆, 1991, 1998, 1999;HE-RAK & TOMI∆, 1995;MARIN»I∆ et al., 1977;MA-TI»EC et al., 1997, 2001;PAMI∆ et al., 1998;DRA-GI»EVI∆ et al., 1999;KUK et al., 2000;DRAGI»E-VI∆, 2001).
Several papers deal with the palinspastic reconstruction of Central Paratethys, or some parts of it during it's evolution (STEININGER & RÖGL, 1979, 1984;RÖ-GL & STEININGER, 1983, 1984;MARINESCU, 1992;K O V A » et al., 1998, 2001;RÖGL, 1998RÖGL, , 1999;;MAGYAR et al., 1999;GULYÁS, 2000;PAVELI∆, 2001).In some of these articles the southwestern Central Paratethys boundary was constructed in the area of north Bosnia and central Croatia.However, these boundaries were not located in detail, and are, in part, incorrect due to a lack of data from this area, and a language problem.The locations of these boundaries also imply that the Neogene fresh-water basins within the Dinarides do not belong to Central Paratethys, neglecting the view of ANI∆ (1951ANI∆ ( -1953)), who suggested that these basins might be a part of that realm during Sarmatian time.The correlation of Neogene sediments and fauna of fresh-water basins within the Dinarides with the North Croatian Basin and Northern Bosnia region, and with the Adriatic region, supports the suggestion that these fresh-water basins may be considered as a part of Central Paratethys, although there was no marine sedimentation.

THE NORTH CROATIAN BASIN AND NORTHERN BOSNIA REGION
The evolution of the North Croatian Basin and Northern Bosnia region, as a part of the marginal zone of the Pannonian Basin System was generated by continental rifting processes.The main depressions in this area represent elongated half-grabens formed by tectonic subsidence along the listric faults and strike-slip faults (TARI & PAMI∆, 1998;LU»I∆ et al., 2001;PAVE-LI∆, 2001).Formation of the North Croatian Basin and Northern Bosnia region started in the Ottnangian, with fresh-water deposition.The first phase was characterized by accumulation of coarse-grained breccias and conglomerates, with subordinate sandstones and siltstones.Deposition took place in braided alluvial fans,  , 1979;PAVELI∆, 2001;PAVELI∆ et al., 2001), in which silts and sands with sporadic layers of gravel were deposited, together with peats along the lake margins.The lake had an endemic fauna of molluscs and ostracods, such as C o n g e r i a f u c h s i, U n i o sp., and H e t e r o c y p r i s sp.(Fig. 3).Lacustrine deposits contain remnants of mammalian species Prodeinotherium bavaricum , Gomphotherium angustid e n s and Brachypotherium brachypus (RADOV» I∆ et al., 1998).
During Karpatian time lacustrine conditions were replaced by marine environments due to a minor marine transgression caused either by the opening of a Paratethyan seaway to the Mediterranean as a consequence of the tectonic activity within the Dinarides (S T E I N I N-GER & RÖGL, 1979;HAMOR & SZENTGYÖRGYI, 1981;RÖGL & STEININGER, 1983, 1984; RÖGL, The Early Badenian was characterized by a sea-level rise well correlated with the global sea-level rise at the beginning of the Middle Miocene (RÖGL & STEI-NINGER, 1983;HAQ et al., 1987;STEININGER e t al., 1989;RÖGL, 1996RÖGL, , 1998;;KOVA» & HUDA»KO-VA, 1997;PAVELI∆ et al., 1998).Coarse-grained siliciclastic material was transported into shallow marine environments, and also to the relatively deeper marine environments, where marls and gravelly calcarenites were deposited (PAVELI∆ et al., 1998;VELI∆ et al., 2000).Favourable ecological conditions resulted in expansion of shallow-and deep-water benthic and planktonic species, such as Amphistegina sp., Lenticulina cultrata , Cibicidoides ungerianus , Uvigerina pygm o i d e s, Globigerina praebulloides , G l o b i g e r i n o i d e s trilobus a n d Preaorbulina glomerosa (Fig. 3).Intense volcanism produced sequences a few hundred metres thick in some places.During the Late Badenian, the last Miocene marine transgression flooded this area.It was connected with the broad re-opening of the Indo-pacific seaway (RÖGL & STEININGER, 1983, 1984; ST E I N- INGER et al., 1988;RÖGL, 1996RÖGL, , 1998)), and coincides with a temporary sea-level rise at 13.4 Ma (HAQ et al., 1987).Sedimentation was similar to that during the Early Badenian.The most important Late Badenian species are Bolivina dilatata , Pappina neudorfensis , Ammonia beccarii and Spirorutilus carinatus .
Due to the beginning of the isolation of the basin during the Sarmatian, brackish-water environments developed, resulting in deposition of shallow water gravel, biocalcarenites and limestones, and general dominance of fine-grained deposits in the deeper parts of the basin.Typical Sarmatian foraminiferal species are Elphidium macelum, Elphidium josephinum, A n o malinoides badenensis and Porosononion granosum .Ervilia dissita dissita , Musculus sarmaticus a n d C a r d ium vindobonense belong to the molluscan association.
In the Early Pannonian the environment became "caspi-brackish", locally even fresh, followed by expansion of endemic species of molluscs and ostracods, as a consequence of definite basin isolation (STE-ININGER et al., 1988).The Pannonian deposits consist of littoral lacustrine limestones, and deep water marls.The Pannonian fossil association contains Radix croatica, Congeria banatica , Clivunella sp. and Hemicytheria c r o a t i c a .In the Pontian a gradual shallowing took place, reflected by increased terrigenous material.The species are also endemic, including Paradacna okrugici , Paradacna abichi , Congeria croatica and C o n g e r i a rhomboidea.
Thicknesses of the Neogene deposits in fresh-water basins vary from a few hundred metres to 1900 m in the Livno-Duvno Basin and 2600 m in the Sarajevo-Zenica Basin (Fig. 4).Siliciclastics dominate but marls and limestones also occur.Some sediments are coal-bearing (Fig. 3).
Neogene basins in this area were of fresh-water.Some sediments are determined as alluvial, lacustrine, or marsh and swamp, but there have been no detailed sedimentological data.
The main geological problem of these basins is the dating of sediments.Basins did not have any connection with the sea during their evolution, and endemic species with no chronostratigraphic value developed.Therefore, the Neogene is subdivided on the basis of local mollusc and ostracod associations, superposition, lithostratigraphic correlation, flora, and occasional mammal occurrences (Fig. 3).However, these stratigraphic interpretations are almost highly speculative, sometimes very confusing, and partly incorrect, and are therefore of little use for detailed correlations with Central Paratethys and Mediterranean stages.
Neogene sediments overlie the pre-Neogene basement or Oligocene deposits, and are characterised by frequent lateral and vertical variations, and different sedimentary thicknesses as a result of the independent local basin evolution.Columns for the Sarajevo-Zenica and Livno-Duvno Basin are shown in Fig. 3.
The oldest Neogene sediments are dated as the upper part of the Oligo-Miocene.Siliciclastics predominate, the most frequent include conglomerates, sandstones, marls and clays.Characaean limestones and coal beds occur sporadically.A mollusc association c o n t a i n s Helix rugulosa, Helix geniculata, L y m n a e a s o c i a l i s, Lymnaea dilatata , P l a n o r b i s sp. and P i s i d i u m sp.
Lower Miocene sediments are more widespread than Oligo-Miocene ones.They consist of clays, limestones, marls, sandstones, conglomerates and coal intercalations.Tuff is found in some basins.Dacite-andesite tuff beds in the Sinj Basin are interpreted as a consequence of volcanic activity in Bosnia (©U©NJARA & ©∆AVNI»AR, 1974) (Fig. 4

and C e r a t o p h y llum sinjanum. Mammalian species, such as D y n o t h e r ium bavaricum, occur.
The Middle Miocene sediments show a low degree of diagenesis.During the Middle Miocene marls, limestones, sandstones, clays and conglomerates were deposited.Coal beds occur in some places, pyroclastics too.The most frequent molluscs belong to the genus Conger i a : Congeria pernaeformis , Congeria jadrovi , C o n g eria dalmatica , Congeria drvarensis , Congeria bosnia c a , Congeria bihacensis etc. Gastropods include O r ygoceras bifrons , Planorbis cornu , Clivunella katzeri, Fossarulus tricarinatus , Prososthenia schwartzi , M e l anopsis geniculata , Melanopsis inconstans, M e l a n o p s i s lanzae, Melanopsis euristoma, Melanopsis kispatici and Melanopsis pilari.»I» I∆ & MILOJEVI∆ (1977) mention mammals found in Bosnia and Herzegovina, such a s Mastodon angustidens, Mastodon longirostris , D ynotherium bavaricum and Rinoceras sansaniensis , but it is now clear that some of these species are of a different Neogene age.In the Sinj Basin (Fig. 4), M a s t o d o n a n g u s t i d e n s sp. and A c e r a t h e r i u m sp.aff.i n c i s i v u m were determined (OLUJI∆, 1999).
The Upper Miocene and Pliocene deposits are characterized by marls, clays, siltstones, sandstones, conglomerates, limestones and coal beds.A molluscan association consists of Congeria dalmatica , C o n g e r i a z o i s i, Orygoceras dentaliforme , Orygoceras cornucopia e, H y d r o b i a sp., V a l v a t a sp., L y m n a e a sp., P i s i d i u m o v u l u m, Melanopsis acanthica , Melanopsis defensa, Prososthenia tournoueri etc.Some ostracods have been found, such as Paralimnocythere rostrata , P o t a m o c yp r i s sp. and C a n d o n a sp..The youngest Pliocene to Pleistocene newly determined molluscan species are Odontohydrobia croatica and Limnidia likana ( J U R I- ©I∆-POL©AK et al., 1997).The Upper Miocene and Pliocene sediments are overlain by Quaternary deposits.

THE ADRIATIC REGION
In a region of the Adriatic, as a part of the Mediterranean, marine deposition was almost continuous from the Paleogene into the Neogene, although transgressive contacts have been registered at some localities.Sediments of Neogene age are almost of marine origin and the occurence of fresh-water sediments which include endemic species, such as on Pag Island ( KOCHAN-SKY-DEVIDÉ & SLI©KOVI∆, 1978), are very rare.The unconformities between sediments observed in several places belong to different stages, and are consequences of emergence due to local tectonics (TURK, 1971;JENKO & BISTRI»I∆, 1978;KALAC & BAJ-RAKTAREVI∆, 1989;MILETI∆ et al., 1995).The emergence was particularly long-lasting during the Oligocene and Early Miocene, and resulted in the formation of a land corridor for mammalian migration from the Dinarides to Apulia (DE GIULI et al., 1987; J. RADOV»I∆, pers.comm.) Generally, carbonates and fine-grained sediments prevail, and the thickness of the Neogene deposits reaches eight hundreds metres (D.MILETI∆, pers.comm.) which is much less than in the Dinarides, North Croatian Basin and Northern Bosnia region, suggesting minor tectonic controls (Fig. 3).The stratigraphy of the Neogene deposits in the Croatian part of the Adriatic region is based on foraminiferal associations (JENKO & BISTRI »I∆, 1978;KALAC & BAJRAKTAREVI∆, 1989;MILETI∆, 1994;MILETI∆ & BAJRAKTARE-VI∆, 1995;MILETI∆ et al., 1995).A geological column of the Koraljka-I well, which was located in the central Adriatic, is presented in Figs. 3 and 4.
Early Miocene sedimentation is characterized by a dominance of carbonates, i.e. limestones and marls (Fig. 3 During the Middle Miocene marl sedimentation dominated, but limestones and sandy limestones were also deposited (Fig. 3).In a foraminiferal association Praeorbulina glomerosa , Orbulina suturalis , A n o m a l inoides pompilioides, Lenticulina vortex, S p i r o p l e c t i n e lla carinata , Globoquadrina langhiana , Orbulina universa, Globorotalia praemenardii , Globorotalia mayeri and Globorotalia menardi prevail.This association suggests open marine deposition.
In the Late Miocene, sedimentation was similar to that of the Middle Miocene.However, at the end of the Late Miocene evaporites were deposited in shallow lagoons.These deposits may be a result of a sea level fall due to the tectonic generated closure of the Atlantic-Mediterranean gateway.This event is known as the Messinian salinity crisis (RÖGL & STEININGER, 1983).From the foraminiferal association, G l o b i g e r i n a n e p e n t h e s, Lenticulina costata , Uvigerina rutila , E l p h idium crispum, Elphidium complanatum, G l o b i g e r i n oides extremus, Globorotalia conomiozea , G l o b i g e r i n oides bollii and Ammonia beccarii dominate.
Marls, siltstones and sandstones characterize Pliocene sedimentation.Conglomerates are very rare and only occur sporadically.Deposition was open marine.The cause of the sea level rise in the Pliocene was a reopening of the Atlantic-Mediterranean gateway in the beginning of the Pliocene (RÖGL & STEININGER, 1983).The most important Pliocene foraminiferal species are Globorotalia margaritae , Uvigerina rutila , Globorotalia puncticulata , Anomalina helicina, G l o b orotalia aemiliana , Globorotalia crassaformis , Globorotalia inflata and Epistomina elegans.

DISCUSSION AND CONCLUSION
The faunal characteristics of species which occur in sediments in the Neogene fresh-water basins within the Dinarides is almost endemic and can not be correlated with a marine fauna in the Adriatic region.However, they show many similarities to endemic species found in deposits of the North Croatian Basin and Northern Bosnia region, i.e.Central Paratethys.The most frequent endemic species which occur both in the North Croatian Basin and Northern Bosnia region, belong to the molluscan genera Congeria , Unio, Lymnaea, Pisidiu m, M e l a n o p s i s, P l a n o r b i s , Valvata and Clivunella, and the ostracod genus Candona .
Sedimentation in the North Croatian Basin and Northern Bosnia region, and in the Dinaridic freshwater basins also show similarities.Frequent changes of different types of sediments, including siliciclastics, coarse-grained deposits, coal-bearing beds, pyroclastics, emersions as well as mammalian occurrences are characteristic of both areas.The thickness of sediments in the Dinaridic fresh-water basins is also more comparable to the North Croatian Basin and Northern Bosnia region than to the Adriatic region.The strong tectonic control on sedimentation is also similar.
Similarities between the North Croatian Basin and Northern Bosnia region with Dinaridic Neogene basins suggest that these small basins show many faunal and depositional characteristics of Central Paratethys, and may be considered as a part of this realm.This means that the south-western boundary of the Central Paratethys may be constructed within the High Karst Belt, the mountain chain which separated the Mediterranean from Central Paratethys (Fig. 4), similar to ANI∆'s (1951ANI∆'s ( -1953) ) idea.In this sense, the boundary located in the northern Bosnia and central Croatia represents only the south-western shoreline of the sea or large lake which occupied the largest part of the Central Paratethys (Fig. 4).
which were strongly influenced by synsedimentary tectonics (PAVELI∆ & KOVA»I∆, 1999).In the central part of Mt.Papuk a salina-type lake developed (©∆AV-NI»AR et al., 1983).During the second sedimentation phase a hydrologically open fresh-water lake was formed in this area (K O C H A N S K Y -D E V I D É

Fig. 4
Fig. 4 Approximate locations of the south-western shoreline of the Paratethyan Sea, and the south-western boundary of Central Paratethys.