Davor Pavelić

Revised Middle Miocene datum for initial marine flooding of North Croatian Basins (Pannonian Basin System, Central Paratethys)The Pannonian Basin System (PBS) originated during the Early Miocene as a result of extensional processes between the Alpine-Carp

The Pannonian Basin System (PBS) originated during the Early Miocene as a result of extensional processes between the Alpine-Carpathian and the Dinaride Orogenic Belts. The Paratethys Sea flooded the new basins successively during the Karpatian (late Burdigalian, Early Miocene) and the Early Badenian (middle Langhian, Middle Miocene). The North Croatian Basins (NCB) occupied the south-western margin of the PBS and the Central Paratethys Sea. Their initial marine flooding has until now been dated as Karpatian in age. The transgression into the NCB invaded a lacustrine environment therein, representing the northern prolongation of the vast Dinaride Lake System extending southwards as far as the Adriatic Plate. We reinvestigate two sections from opposite margins of the NBS - from Mt. Medvednica on the west and from Mt. Požeska on the east - including corresponding lowermost marine Miocene deposits to critically examine the Karpatian datum. Our new biostratigraphic data – integrating calcareous nannoplankton, planktic and benthic foraminifera, diatom and mollusk records – have substantially revised the previous interpretation. The presence of a calcareous nannoplankton assemblage of the NN5 Zone and the planktic and benthic foraminifera of the regional Lower Lagenidae Zone now place the transgression into the main Early Badenian transgressive pulse of the Central Paratethys. Consequently, the initial marine transgression correlates accurately with the middle part of the Early Badenian, which is more than 2 m.y. younger than the previously inferred datum and at least 1 m.y. younger than the lower boundary of the Badenian and the Middle Miocene, respectively. Finally, the basal lacustrine infill of the NCB, previously dated as Ottnangian (middle Burdigalian, Early Miocene) and continuously grading into marine deposits, has to be reconsidered as Early Badenian as well.

Late Pleistocene climate history of the Baranja loess plateau – evidence from the Zmajevac loess-paleosol section (northeastern Croatia)

The Zmajevac loess-palaeosol succession (LPS) of the northeastern Baranja loess plateau is exposed along the southern slope of Bansko Brdo, on the western bank of the Danube River. The investigated 17.5-m-thick section shows 4 palaeosol, 1 loess-like and 6 loess horizons. Their integrative palaeoenvironmental analysis combines quantified dana from the mollusc record, magnetic susceptibility, grain-size, calcimetry and mineral abundances to reconstruct the pattern of regional palaeoclimate evolution. This result combined with infrared optically stimulated luminescence age est CLEAL imates by GALOVIC et al. (2009) enabled correlation of the depositional units to Middle to the Late Pleistocene Marine Isotope Stages (MIS) 6 to 2. Magnetic susceptibility measurements show strong peaks in the palaeosol horizons pointing to increased concentrations of pedogenic ferrimagnetic minerals. Sedimentological and mineralogical parameters are in good agreement with other Pannonian Basin LPS. Terrestrial gastropod palaeoecology based on 1705 specimens of 13 species counted from loess and loess-like horizons documents cyclic transitions between cryophilous to cold resistant and mesophilous to thermophilous assemblage types. Whereas Helicopsis striata, Arianta arbustorum and Chondrula tridens are common throughout the succession, the typical loess representatives Pupilla sp., Vallonia tenuilabris and Columella columella are abundant only in certain horizons. Nevertheless, species tolerating open and dry habitats are abundant throughout the succession. The faunal spectra for the samples prove the dominance of transitional palaeoecological assemblage types, whereas uniformly defined types are rare. One of these, the Columella columella assemblage from the base of the section proved to be indicative of the Penultimate Glacial Maximum.

Lower Miocene Alluvial Deposits of the Po¾e¹ka Mt. (Pannonian Basin, Northern Croatia): Cycles, Megacycles and Tectonic Implications

In the area of the present Po¾e¹ka Mt. braided alluvial fans were formed during the Early Miocene above the subsiding Cretaceous- Palaeogene basement. Due to autocyclic processes, i.e. lateral migration of flows due to vertical aggradation of longitudinal bars, or migration of the main trench, small-scale fining-upward cycles were formed. The complete succession of the alluvial deposits is composed of two fining-upward megacycles, which are the consequence of allocyclic influences, i.e. the pulsating character of synsedimentary tectonics. Megacycles were developed parallel to backstepping of the front of the fault scarp towards the mountain massif, caused by normal faulting along the active margin of an extensional basin. This kind of depositional style indicates that the Sava fault operated as a normal fault at the beginning of its life during the Early Miocene, probably the Ottnangian.

Early Miocene European loess: A new record of aridity in southern Europe

The intercalation of silty units and coarse-grained units represented by conglomerates and breccia characterizes a Lower Miocene terrestrial sedimentary sequence in the North Croatian Basin, a part of the southwestern Pannonian Basin system. These sediments were previously interpreted as alluvial sediments, where the silty units would reflect deposition on a floodplain. However, in this study, we show new results that support a different interpretation of the genesis of the silty units. The units, which vary in thickness between 6 and 180 cm, are mostly composed of structureless loose silt. They are brownish yellow to yellowish brown in color and do not contain fossils. Scanning electron microscopy indicated that quartz grains show fracture faces, conchoidal fractures, V-shaped percussion marks, linear steps, and conchoidal crushing features. Such microtextures together with the macroscopic characteristics of the silt units indicate that they were deposited by wind. Therefore, this study reports the first occurrence of Miocene loess outside of China. Silt-sized particles were probably produced by salt-weathering processes on salina-type lake flats during long arid periods. Alluvial deposition was controlled by a more humid climate, so the intercalation of eolian silty units with alluvial conglomerates and breccias reflects alternation of arid and more humid periods in the early Miocene. This agrees with regional paleoclimate studies that show cyclicity in the climate, with a dry cycle and orbital-scale climate variability controlling paleoenvironmental and sedimentary changes in the area during the early Miocene.

Stratigraphy and Palaeogeography of Miocene Deposits from the Marginal Area of Žumberak Mt. and the Samoborsko Gorje Mts. (Northwestern Croatia)

Miocene sediments rimming the Palaeozoic–Mesozoic–Palaeogene rocks, form Žumberak Mt. and the Samoborsko Gorje Mts. Spatial analysis of the setting and development of the surface Miocene stratigraphy, at the marginal areas of the Žumberak and Samoborsko Gorje Mts., allows four palaeogeographic areas to be distinguished: Žumberak, Plesivica–Sveta Jana, Samobor–Sveta Nedelja and Grdanjci. In the Miocene deposits (totaling 350 m), within the area of Žumberak, coarse-grained clastics from deltaic deposits of Pannonian age prevail. Here only, 50 m of sediments of Pliocene–Pleistocene age overlie the Miocene deposits whereas Mesozoic carbonates represent the basement. The Plesivica–Sveta Jana area is characterized by a 600 m sequence of Miocene deposits, mainly overlying Triassic dolomites, where finely-grained layers of marls and silts prevail. In this area, Miocene successions from the Badenian to the Pontian are characterized by a continuity of sedimentation with an inherited depositional environment. In the area of Samobor–Sveta Nedelja, the basement is diverse: Triassic dolomites, volcanogenic–sedimentary complex of Cretaceous age and a clastic–carbonate complex of Palaeogene age. The Miocene succession shows a regressive trend from the Badenian to the Pontian and the total thickness is estimated at 400 m. The area of Grdanjci differs considerably from the other Miocene palaeorelief. An approximately 50 m-thick series of coarsegrained clastics with coal is distinguished, of unclear stratigraphic age (Ottnangian?). Miocene sediments of the Grdanjci area are represented by both a transgressive type of conglomerates and shallow water limestones of Badenian age, with a total thickness of about 100 m. The development of the Miocene stratigraphy of the Žumberak and Samoborsko Gorje Mts. is generally correlative with that in the other parts of the Pannonian area, though it does exhibit local variations. Comparison of the Miocene palaeorelief of Žumberak Mt. with the Samoborsko Gorje Mts., together with neighbouring areas, enabled wider correlation with other parts of northern Croatia, and the more distant Western and Central Paratethys.

Magmatic provenance and diagenesis of Miocene tuffs from the Dinaride Lake System (the Sinj Basin, Croatia)

This study presents new insights on the provenance, genesis, and post-depositional history of the Miocene pyroclastic tuffaceous layers (~18 and ~15 Ma) preserved in argillaceous sediments and interbedded within the lacustrine sedimentary succession of the Sinj Basin in central Dalmatia (Dinaride Lake System, Croatia). Analysed tuffs are classified as smectitic tuffs composed of three main lithotypes: (a) vitriclastic tuffs, (b) altered vitriclastic tuff, and (c) tuffaceous clays. The high field strength element (HFSE) contents of the tuffs, as well as the major- element chemistry of the vitric glass, suggests that parental magmas were high-K calc-alkaline trachyandesites. This is consistent with the distinctive heavy-mineral assemblages including clinopyroxene, zircon and apatite, identified in less evolved parental magmas, and biotite in more evolved ones. The regional geological data imply the placement of the parent volcano(es) outside the Dinaric Alps region, most probably in an area corresponding to the present-day southern margin of the Pannonian Basin where volcanic rock suites of analogous age and geochemistry are reported. Minor compaction and high permeability of coarse ash-sized pyroclastic material allowed for extensive in situ diagenetic clay mineral formation dominated by smectite. Following discrete smectite formation, the illite-smectite mixed-layering took place as a result of mica/illite alteration or surface illitization processes. On the basis of the very-low grade alteration of volcanic materials, it is suggested that diagenesis operated in an open hydrologic system of a lacustrine environment.

Topography controlling the wind regime on the karstic coast: late Pleistocene coastal calcareous sands of eastern mid-Adriatic, Croatia

Aeolian dunes controlled by regional climate have been formed in many coastal areas of the Mediterranean Sea during the Quaternary. Generally, they are formed under a landward-blowing wind, and comprise numerous reworked penecontemporaneous shallow-marine carbonate grains. Along the eastern mid-Adriatic Sea, late Pleistocene aeolian and alluvial sands occur as isolated patches in karstic depressions on several islands and the Pelješac Peninsula. At most localities, the sands consist of a mixture of mostly carbonate rock fragments and siliciclastic material. A higher proportion of shallow-marine bioclasts was found only at one locality. The terrestrial material was transported to the coastal area by at least two rivers: paleo-Cetina and paleo-Neretva River, and was subsequently reworked and transported by wind, resulting in aeolian deposition. Sandy units of various thicknesses exhibiting sharp erosional bedding planes and cross-bedding are interpreted as representing aeolian dunes and sand sheets controlled by a complex wind regime. The mineralogical composition at almost all localities indicates near-river flood plains as the main sand source. Although the area was affected by strong winds blowing landward and parallel to the coast, they significantly deviated due to the local topography produced by the tectonically deformed and karstified carbonate basement. In this way, the late Pleistocene aeolian deposits on the mid-Adriatic islands differ from deposits from most Quaternary Mediterranean coastal aeolian belts, as they contain very small quantities of penecontemporaneous shallow-marine carbonate grains and were deposited by winds blowing in varying directions instead of prevailing landward-blowing winds.

Magnetic fabric of Late Miocene clay-rich sediments from the southern Pannonian basin

The magnetic fabric of Late Miocene sediments from the southern Pannonian basin was studied on oriented samples collected from 19 geographically distributed localities. All of them are characterized by near-horizontal magnetic foliation plane after tilt correction, indicating weak deformation. Well-developed lineations were observed for 16 localities, which are interpreted as due to compressional/transpressional deformation, except from three localities, where the fabric must have been formed in an extensional setting. Comparison between the orientation of the map-scale folds and faults and magnetic lineation directions shows that magnetic lineation is either related to NNE-SSW directed compression, leading to the formation of folds or it can be connected to NW–SE or NNE-SSW trending dextral faults.

The Sedimentological Significance and Stratigraphic Position of Coarse-Grained Red Beds (?Oligocene) of the Northwestern Margin of Mt. Pozeska Gora (North Croatia)

Coarse-grained clastic sediments of rhyolitic-granitic composition which are associated with the magmatic complex of Mt. Pozeska Gora were previously designated as granites. They are deposited in a continental environment or, more precisely, in an alluvial fan or proximal parts of a braided river system, or in rapid mountain streams during a strong rainfalls. According to their spatial relationship with respect to surrounding Upper Cretaceous granites and rhyolites and Ottnangian sediments; and considering the facies characteristics, we assume that these sediments belong to the Oligocene.