Marijan Kovačić

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.

Palaeomagnetic Results from the Sarmatian/Pannonian Boundary in North-Eastern Croatia (Vranovi? Section, Našice Quarry)

The Sarmatian/Pannonian boundary in the Central Paratethys basin is marked by a major regressive event, which isolated the basin from the open sea and resulted in a palaeoenvironmental change from restricted marine to brackish water ecosystems. The exact age of this environmental change is still ambiguous since direct age control on the boundary interval is lacking, mainly due to the scarcity of suitable sections. The Vranovi? section in the Nasice Quarry in Croatia, however, is relatively long and continuously exposed. A detailed sedimentological and biostratigraphic study indicates that it contains the Sarmatian/Pannonian boundary and that it reflects the same palaeoenvironmental trend as other Paratethyan sequences. Here, we present palaeomagnetic and rock magnetic results from the Vranovi? section, based on 183 sampled levels distributed along 55 m of cyclically bedded limestones and marls. Rock magnetic data indicate the presence of maghemite or haematite in the Sarmatian deposits and low contents of magnetite in the Pannonian rocks. Thermal demagnetization results indicate dominantly normal polarities, and the mean direction closely coincides with the present-day field direction at Nasice. We conclude that magnetostratigraphic age control cannot be derived for the Vranovi? section because of a dominant secondary (post-tilt) magnetization. Consequently, a firm numerical age based on magnetostratigraphy cannot be assigned to Sarmatian/Pannonian boundary events from this section.

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.

Composition and provenance of Neogene sedimentary rocks of Dilj gora Mt. (south Pannonian Basin, Croatia)

The petrographic composition and transport direction of medium and coarse-grained clastic material of Dilj gora Mt. which is located in the south Pannonian basin, show that this area experienced several changes in provenance of arriving detritus through the Neogene. Detritus for the oldest Lower Miocene (Ravan unit) was transported generally from the south and most probably derived from clastic and carbonate sediments and metamorphic rocks of the Internal Dinarides. Detritus of the Lower Miocene–Middle Miocene (Tuk unit) was originated by weathering of acid magmatic and metamorphic rocks with significant input of materials from local sources, primarily from the Internal Dinarides and from Požeska gora and Dilj gora Mts. During the entire Middle Miocene (Zdenci, Dubovik and Glogovica units) and through the older part of the Late Miocene (Croatica and Pavlovci unit) the deposition of siliciclastic gravel and sandy detritus was less significant. Only the Middle Miocene deposits (Kasonja unit) contain clastic detritus derived from granitoids, metamorphic and sedimentary rocks of the hinterland. The source area of this detritus was most probably in the Slavonian Mts. (Papuk, Psunj, Požeska gora Mt.) or the mountains of northern Bosnia (Motajica Mt.). At the time of late Upper Miocene (Andrasevec and Nova Gradiska units) detritus derived from different metamorphic and older sedimentary rocks. The structural and mineralogical maturity of these sediments and their transport directions indicates an Alpine-Carpathian provenance of material. Most of the detritus of the Pliocene sediments (Cernik unit) also belong to an Alpine-Carpathian provenance, however a small part of it is of local origin and came from uplifted and mainly sedimentary rocks.Determinated various textural characteristics and diverse modal compositions and provenance of Neogene clastic material of Dilj gora Mt. can be attributed to differing source rock compositions and locations of source areas, but they are also the product of different controls on sedimentation such as different rates of subsidence and extension of Pannonian Basin interrupted by compressional events, basin water-level fluctuations connected with global sea-level changes and infilling of PB by delta progradation.

Diagenesis of Miocene pelitic sedimentary rocks in the Sava Depression (Croatia)

Abstract Miocene pelitic sedimentary rocks from six wells in the Sava Depression (sub-basin in the south-western part of the Pannonian Basin System) were investigated in order to determine the degrees of diagenetic alteration. Qualitative and semiquantitative mineral compositions of samples and the content of smectite in illite-smectite (I-S) were determined by X-ray powder diffraction (XRD). Vitrinite reflectance and thermal alteration index (TAI) were measured in order to estimate the palaeotemperatures. Carbonate minerals, clay minerals and quartz are the main constituents of the pelitic sediments. Feldspars (albite), pyrite, opal-CT and hematite are present as minor constituents in some rocks. The mineral composition of the rocks, apart from previously known differences caused by various depositional environments and clastic material provenance, is dependent on the degree of diagenetic processes. At elevated temperatures and large burial depths the minerals formed by alteration processes or precipitated at the surface; smectite, kaolinite and calcite were gradually replaced by minerals formed by diagenetic processes, i.e. by illite-smectite, illite, chlorite, Ca-excess dolomite/ankerite and albite. Based on XRD data for smectite, I-S and illite, three stages of diagenetic development have been established. The early stage was characteristic of samples at depths <1.8 km containing smectite, I-S of the random R0 type and detrital illite. The middle stage begins with the appearance of the ordered R1 type of I-S at the depths >1.8 km and temperature above 80℃. At depths >4.6 km with corresponding temperatures >190℃, the late stage began, characterized by the presence of R>1 I-S with <10% smectite.

Evidence for Badenian local sea level changes in the proximal area of the North Croatian Basin

Quantitative analysis of palynomorphs, foraminifera and ostracods enabled the recognition of biotic events and the reconstruction of environmental change in the Badenian sediments from the Vrhovcak section of Mt. Samoborsko gorje (NW Croatia). During the Middle Miocene the investigated area of Mt. Samoborska gora was located at the south-western margin of the North Croatian Basin, which represents the south-western edge of the Pannonian Basin System and the Central Paratethys Basin. This marginal position within the basin controlled the specific evolution of the depositional area during the Badenian. The occurrence of coal bearing horizons and freshwater flora and fauna in the middle part of the Vrhovcak section provide new data for the reconstruction of Badenian palaeoenvironments. A fall in sea level and the probable isolation of this area in the Badenian seems to be responsible for the appearance of a new fauna and flora. The marine sediments from the base of the Vrhovcak section may be correlated to cycle TB 2.4 of the main Badenian transgression, which affected the entire Central Paratethys area. This was followed by a regression and lowstand (Ser2), which, correlated to the middle part of the section, with freshwater sediments and coal bearing horizons. The upper part of the Vrhovcak section with marine sediments represents the Late Badenian cycle TB 2.5.

Discriminant function analysis of Upper Miocene and Pliocene sands from the southwestern part of the Pannonian Basin System, Croatia

Multiple discriminant analysis (MDA) of Upper Miocene and Pliocene sands of SW portion of Pannonian Basin System is performed in order to find out optimum criteria of separating previously defined informal lithostratigraphic units - Ozalj, Andrasevec, Hum Zabocki, Cernik and Pluska. Heavy mineral association is employed as independent variables, or descriptors, in the process of discrimination and results of analysis established a clear and strong bond between characteristic heavy mineral assemblages in the Upper Miocene and Pliocene sands their affinity to particular lithostratigraphic units. In this respect, Pluska unit is especially highlighted, followed by Ozalj and Hum Zabocki units. Close heavy mineral/lithostratigraphic unit relationship was found very useful in unraveling the basic sedimentologic meaning hidden under specific discriminant functions in the mathematical model. The most prominent is DF1 accounting for almost three fourth of the total variance of the investigated sedimentary system. In accordance with its “key” mineral it is labeled kyanite function which indicates the (metamorphic) provenance of the siliciclastic mineral detritus. The second most important, DF2, is labeled garnet-zircon function and, being bipolar, it points at both provenance of siliciclastic material (older sedimentary rocks) and hydraulic conditions during the detritus transport and sedimentation. Finally, DF3 is of minor importance indicating stability of heavy mineral association in sandy sediments. Three lithostratigraphic units, namely Ozalj, Pluska and Hum Zabocki are clearly separated by the functions labeled after their distinctive (“key”) heavy minerals.