GEOLOGICA CARPATHICA, DECEMBER 2007, 58, 6, 531 540

GEOLOGICA CARPATHICA, DECEMBER 2007, 58, 6, 531 540 Paleomagnetic properties of the ignimbrites from the famous fossil footprints site, Ipolytarnóc (close to the Hungarian-Slovak frontier) and their age assignment EMŐ MÁRTON 1, DIONÝZ VASS 2, IGOR TÚNYI 3, PÉTER MÁRTON 4 and TIBOR ZELENKA 5 1 Eötvös Loránd Geophysical Institute of Hungary, Palaeomagnetic Laboratory, Columbus ut. 17 23, H-1145 Budapest, Hungary; paleo@elgi.hu 2 Geological Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, 840 05 Bratislava 45, Slovak Republic Present address: Matičná 5, 831 03 Bratislava, Slovak Republic; dionyz.vass@zoznam.sk 3 Geophysical Institute of the Slovak Academy of Sciences, Dúbravská cesta 9, 845 28 Bratislava, Slovak Republic; geoftuny@savba.sk 4 Eötvös Loránd University, Geophysics Department, Pázmány Péter sétány 1/c, H-1117 Budapest, Hungary; martonp@ludens.elte.hu 5 University of Miskolc, Department of Geology, Egyetemváros, H-3515 Miskolc, Hungary; zelenka.tibor@freemail.hu (Manuscript received September 10, 2006; accepted in revised form June 13, 2007) Abstract: On geological grounds, the ignimbrites/tuffs of the Ipolytarnóc area were regarded as belonging to the oldest of the three Miocene tuff complexes of the Pannonian Basin. From the paleomagnetic point of view, the three complexes are significantly different in the area which comprises North Hungary and South Slovakia, since the oldest is characterized by about 80º, the middle by about 30º counterclockwise, while the youngest about 10º clockwise rotation with respect to the present North. The significant differences in declinations are attributed to block rotations, which affected the area in the time intervals of 18.5 17.5 Ma and 16 14.5 Ma. Earlier, a pilot study on three ignimbrite sites from Ipolytarnóc indicated only 30º of counterclockwise rotation, which suggested that the volcanism was younger than assumed, while the underlying Eggenburgian sediments showed the expected large rotation. Following up indications, we carried out a detailed paleomagnetic study at this locality on a large number of samples from the terrestrial sequence which covers the Eggenburgian sandstone. These were the footprint sandstone and the overlying unaltered, ignimbrites which represent three volcanic cycles separated by clastic sediments. Ignimbrites from the surrounding area were also tested. The results obtained are of high quality, statistically well defined on the site level and are highly consistent on the between-site level. The polarity is normal for the first two cycles and reversed for the youngest. The rotation angle indicated is about 30º. Thus, we conclude that the ignimbrites at the Ipolytarnóc area are indeed younger than 17.5 Ma, so they belong to the Middle Tuff Complex of the Pannonian Basin. Key words: Miocene, Northern Pannonian Basin, Ipolytarnóc, correlation, paleomagnetic marker horizon, ignimbrites. Introduction Ipolytarnóc, the famous site of fossil footprints of mammals, birds and of subtropical-tropical plants is situated in the Cserhát Upland which is dominated by elongated hills and ridges built of Oligocene and Miocene sediments and volcanics, and are topped by Pliocene-Pleistocene basalts. The uplands belong geologically to the Buda (Hungarian) Paleogene Basin, the Fi akovo-pétervására Basin and the Nógrád-Novohrad Basin. In those basins Miocene ignimbrites and tuffs are widespread. Most of the ignimbrites and tuffs, including those of the Ipolytarnóc area, are considered to represent the oldest Miocene Tuff Complex of the Pannonian Basin. In the Pannonian Basin three Tuff Complexes of Miocene age are distinguished (Hámor 1973; Póka et al. 1998): a Lower Tuff Complex, a Middle Tuff Complex and an Upper Tuff Complex (Póka et al. 1998). All three were paleomagnetically studied in northern Hungary (Márton & Márton 1996; Márton & Pécskay 1998; Karátson et al. 2000; Póka et al. 2004) and in southern Slovakia (Márton et al. 1996). It was shown that they differ from each other significantly in declinations. The oldest exhibits about 80º, the middle about 30º counterclockwise rotation and the youngest about 10º clockwise rotation with respect to the present North suggesting important tectonic rotation events between the complexes. These events provide paleomagnetic marker horizons. The ages of the rotations are known from K/Ar isotope data obtained for the ignimbrites of the Bükk Foreland (Márton & Pécskay 1998) to be 18.5 17.5 Ma and 16 14.5 Ma, respectively. From the Nógrád-Novohrad Basin a number of ignimbritic sites belonging to the Gyulakeszi Tuff Formation and related sedimentary localities were studied earlier and most of them exhibited about 80º counterclockwise rotation (Márton & Márton 1996). However, three sites from Ipolytarnóc yielded only about 30º westerly declinations (Márton & Márton 1996). It seemed that the ignimbrites of Ipolytarnóc formed after the first Miocene rotation, but this suggestion was met by the scepticism of several geologists who thought that the paleomagnetic results for the Ipolytarnóc ignimbrites were anomalies due to local tectonics or to an excursion of the geomagnetic field. In order to decide if the Ipolytarnóc ignimbrites were really younger www.geologicacarpathica.sk

PALEOMAGNETIC PROPERTIES OF THE IGNIMBRITES FROM THE IPOLYTARNÓC 533 sediments indicate either warm and humid or arid climate. A famous example of the first is the post-lower Eggenburgian sequence of Ipolytarnóc protected area where the sandstone deposited by rivers is famous for fossil animal footprints and contains rich subtropical-tropical flora of rain forest (Jablonszky 1914; Hably 1985). Although the continental deposits at Ipolytarnóc are considered to be equivalent to the Zagyvapálfalva Formation (Bartkó 1985), the sandstone with foot prints was distinguished as a member Ipolytarnóc Beds (Bartkó 1985, recte Ipolytarnóc Member), and the overlying felsic ignimbrite/ tuff bodies and the tuffs were considered as equivalent of the Gyulakeszi Rhyolite Tuff Formation (Bartkó l.c.). In contrast to the Ipolytarnóc type deposits, the mottled clay (free of fossil macroflora) deposited by rivers indicates an arid climate. The continental sediments of the Nógrád-Novohrad Basin are covered by lake deposits with marine intercalations (Salgótarján Formation). The lower part of the Salgótarján Formation is coal-bearing, the upper part consists of claystone with tuffaceous intercalations, or tuff layers with marine pelitic intercalations containing nannoflora NN3 NN4 Zones pointing to the Ottnangian age of the Salgótarján Formation (Lehotayová 1982; Vass 2002). The Salgótarján Formation is followed by marine deposits which are subdivided into two formations and in northern Hungary: the lower Egyházasgerge Sandstone Formation and the upper Garáb Schlier Formation (calcareous siltstone, Hámor 1973). In southern Slovakia the equivalent of the two formations is the Modrý Kameň Formation (Vass (Ed.) 1983; Vass & Elečko (Eds.) 1992). Badenian rocks are either intrusive bodies of andesite (Karancs, Šiator, Halič Castle Hill) or andesite volcaniclastics, lahars, tuffs, andesite epiclastic conglomerates and sandstones. Inside the volcaniclastic sequence there are lithotamnium limestone and calcareous mudstone rich in marine fossils (Vinica and Lysec Formations). The elongated hills and ridges of the Cerová vrchovina Upland and of the Northern Cserhát Upland are topped by basalts of the Cerová Formation (Vass & Kraus 1985) and/ or Salgó Basalt Formation (Jámbor in Gyalog 1996). The basalt lava flows are underlain by gravels of Pliocene- Pleistocene river channel lag. plagioclase was clearly visible, sanidine identifiable, the mafic minerals were fresh, the pumice glassy. Microscopic analysis also revealed that there were differences in mineral composition between the ignimbrites of the different cycles. The most important are summarized as follows. The first cycle (thickness is about 15 m) starts with finegrained material deposited in water (biotite is the mafic mineral) and continues with poorly welded ignimbrite (biotite and green hornblende are the mafic minerals). The volcaniclastics of the second cycle (about 25 m thick) are biotite and pyroxene-bearing, and are obviously the products of a violent explosion (indicated by the presence of glass shards). Glass shards are missing from the third cycle (ignimbrite is about 40 m thick), and the mafic mineral is exclusively biotite. This ignimbrite contains lithoclasts of andesitic and rhyolitic composition. Paleomagnetic sampling was concentrated on the above described fresh volcaniclastics in the natural conservation area (Fig. 2) but similar ignimbrites were also collected from several sites around the main section, both in Hungary and Slovakia. Some of the satellite sites, are correlated geologically to the second cycle of the main section (Fig. 2), but a few are too distant for reliable geological correlation, yet useful for checking the lateral extent of Paleomagnetic sampling NE of Ipolytarnóc village, in the natural conservation area belonging to the Bükk National Park of Hungary, there are excellent outcrops exposing Eggenburgian marine sandstone, which is covered discordantly by a sequence of subhorizontal sandstone with animal footprints and plant remnants followed by three cycles of the ignimbritic volcanism, separated by coarse-grained clastic deposits of non-volcanic material (Korpás 2003). The paleomagnetic samples for the present study were drilled from the products of the ignimbritic volcanism, which were also studied microscopically. Under the microscope, the ignimbrites and tuffs were unaltered, since the zonation in the Fig. 2. Sedimentary ignimbritic sequence at Ipolytarnóc Natural Conservation Area (after Korpás 2003) with the numbered paleomagnetic localities and sites from the section by Korpás (2003) on the right side, and paleomagnetic sites related to the 2nd cycle based on geological and paleomagnetic considerations, on the left side.

534 E. MÁRTON, VASS, TÚNYI, P. MÁRTON and ZELENKA the Ipolytarnóc type of ignimbritic volcanism (sites 24, 25, 30, 31). Laboratory measurements and results The drill cores, oriented in the field with a magnetic compass were cut into standard-size specimens in the laboratory. Samples from two sites however, which were collected as oriented hand samples, were drilled in the laboratory (sites 5 and 25), before cutting. The measurements and demagnetizations were carried out in two laboratories, in the Paleomagnetic Laboratory of the Eötvös Loránd Geophysical Institute of Hungary and in the Paleomagnetic Laboratory of the Geophysical Institute of Slovak Academy of Sciences. In the first, JR-5A and JR-4 magnetometers, KLY-2 Kappabridge, Schoenstedt AF and thermal demagnetizers and an AF demagnetizer built at the Technical University, Budapest, in the second, MAVACS thermal demagnetization system, KLY-2 and JR-5 were used. After measuring the natural remanent magnetization (NRM) and susceptibility in the natural state, the samples were subjected to either alternating field (AF), or less often, thermal demagnetization in increments. As Fig. 3 documents, the volcanic samples behaved on demagnetization in a most regular manner, while the sediments exhibited somewhat noisy behaviour. Demagnetization curves were analysed for linear segments and locality/site mean paleomagnetic directions were calculated from components defined by these segments (Table 1). Mean paleomagnetic directions are characterized by excellent or good statistical parameters, especially in the ignimbrites deposited on land (Table 1). The footprint sandstone and sites belonging to the first and second ignimbritic cycles and those not correlated to the master section of Fig. 2 have normal polarity. Some of the latter (Lipovany, Mucin, Botos árok) are quite distant (a few km) from the master section, thus, they are important for demonstrating the consistency in space of the paleomagnetic directions. The two sites representing the third cycle have reversed polarity. The average declination calculated from all sites of Table 1 is around 330º (sites with reversed polarity are entered in the calculation as normal polarity sites). All paleomagnetic site-mean directions, except two (sites 17 and 33 drilled from blocks which were probably not perfectly in situ) cluster so tightly that graphical representation on a stereonet is not practicable. Discussion and conclusions The large number of good quality and consistent paleomagnetic data available now from the Ipolytarnóc area (Table 1) represent three cycles of the ignimbritic volcan- Fig. 3. Ipolytarnóc Natural Conservation Area. Typical demagnetization behaviour of the natural remanent magnetization for footprint sandstone and volcanic material deposited in water and on dry land. Key: in Zijderveld diagrams, full/open circles: projection of the NRM in the horizontal/vertical plane; in the others, dots: NRM intensity, circles: susceptibility. R0 initial susceptibility.

PALEOMAGNETIC PROPERTIES OF THE IGNIMBRITES FROM THE IPOLYTARNÓC 535 Table 1: Ipolytarnóc, footprint sandstone and overlaying ignimbrites (3 cycles) plus ignimbrites from outside of the protected area. Paleomagnetic site-mean directions based on the results of principal component analysis (Kirschvink 1980). Key: n/no number of used/collected samples; Dº, Iº declination, inclination before tilt correction; D C º, I C º declination, inclination after tilt correction; k and 95 º statistical parameters (Fisher 1953). ism. They all show about 30º counterclockwise declination deviation from the present North, with normal polarity for the first two and reversed polarity for the third cycle. The Ipolytarnóc master section sits on top of the earlier studied glauconitic sandstone of Eggenburgian age which yielded the expected rotation angle (Table 2, locality 2). Thus, a difference of about 60º in declination is observed within the same section between the stratigraphically well-dated marine glauconitic sandstone and the subhorizontal terrestrial sequence which follows it discordantly. The difference in declination between them suggests that the terrestrial sequence postdates the first Miocene rotation event, so that it must be younger than 17.5 Ma. Other explanations for the difference in declinations, like local tectonics or anomalous behaviour of the magnetic field can safely be excluded, as the first would have also involved the glauconitic sandstone, the second, because of the fairly long duration of the volcanism indicated by differences in composition, in mode of explosion between the cycles, for the time necessary for the deposition of sediments separating the cycles and for the complete reversal of the Earth s magnetic field. The above reasoning is valid if we regard the magnetization of the footprint sandstone at the base of the terres- Fig. 4. Comparison of overall-mean paleomagnetic directions between Eggenburgian lower Ottnangian sediments and ignimbrites of the Nógrád-Novohrad Basin (A), lower ignimbrites of the Bükk Foreland (B, all reversed polarities), upper ignimbrites of the Bükk Foreland (C, all reversed polarities), and ignimbrites (and footprint sandstone) from Ipolytarnóc and related area (D). For data refer to Table 3.

536 E. MÁRTON, VASS, TÚNYI, P. MÁRTON and ZELENKA Table 2: Paleomagnetic site-mean directions from the Nógrád-Novohrad Basin, outside of the Ipolytarnóc area. Key: as for Table 1. Table 3: Miocene overall-mean paleomagnetic directions from N. Hungary and S. Slovakia. Key: as for Table 1. * inclination shallowing due to compaction. ** slightly worse statistics after tilt correction of sediments. trial sequence as primary. However, the possibility cannot be excluded that it was remagnetized by the directly overlaying ignimbrite body (1st cycle of the Ipolytarnóc ignimbrites) while it was hot. If so, the footprint sandstone may belong to the Zagyvapálfalva Formation of late Eggenburgian age. As Tables 1 and 2 show, there are now a fairly large number of Miocene paleomagnetic results from the Nógrád-Novohrad Basin. Based on their declinations, they are divided into a group predating, and another group, postdating the first Miocene counterclockwise rotation of the area. Further subdivision can be made by tying the sites/localities to the standard polarity time scale (Gradstein et al. 2004), using polarity information in combination with available geological constraints/considerations and isotope ages. The result is shown in Figs. 5 and 6. Concerning Fig. 5, there are two localities (15 and 16) which are problematic, since they belong to the Salgótar-

PALEOMAGNETIC PROPERTIES OF THE IGNIMBRITES FROM THE IPOLYTARNÓC 537 Fig. 5. Nógrád-Novohrad Basin, ignimbrites and sediments with paleomagnetic results tabulated in Table 2. The sampling sites/localities are tied to the standard polarity time scale (after Gradstein et al. 2004) which is correlated with chronostratigraphy and biostratigraphy (Strauss et al. 2006). CHZ paleomagnetic chronozone, E paleomagnetic event, numbers encircled-paleomagnetic site/locality, corresponding to the numbers shown in Fig. 1, in the Tables and throughout the text, A, first, B second paleomagnetic marker horizons. Explanation of lithology: 1 conglomerate, 2 sandstone, 3 calcareous siltstone/claystone, 4 coal seam, 5 clay/claystone (Bukovinka/Zagyvapálfalva Formations), 6 rhyolite/rhyodacite tuff and ignimbrite, 6a redeposited tuff and tuffaceous sandstone.

538 E. MÁRTON, VASS, TÚNYI, P. MÁRTON and ZELENKA Fig. 6. Ipolytarnóc Natural Conservation Area and surroundings. Ignimbrites and sediments with paleomagnetic results tabulated in Table 1. The sampling sites/localities are tied to the standard polarity time scale (after Gradstein et al. 2004) which is correlated with chronostratigraphy and biostratigraphy (Laurent et al. 2004). Key as for Fig. 5. Fig. 7. Geological interpretation of Ipolytarnóc Natural Conservation Area section considering the paleomagnetic properties of footprints sandstones as thermally remagnetized. The sampling sites/localities are tied to the standard polarity time scale (after Gradstein et al. 2004) which is correlated with chronostratigraphy and biostratigraphy (Laurent et al. 2004). Key as for Fig. 5.

PALEOMAGNETIC PROPERTIES OF THE IGNIMBRITES FROM THE IPOLYTARNÓC 539 ján Formation, yet exhibit much larger rotation than 30º. Therefore, we cannot exclude the possibility that the boundary of the Zagyvapálfalva/Bukovinka and the Salgótarján Formations is older than suggested by Fig. 5. In the Ipolytarnóc area, the ignimbrites/tuffs belonging to the first two cycles are of normal polarity (Table 1). Thus, in Fig. 6 the normal polarity sites at Ipolytarnóc and surroundings (Table 1) are placed in the time span of 17.2 17.5 Ma (Fig. 6). The third cycle with reversed polarity is placed in the following reversed polarity interval, thus correlated with the Middle Tuff Complex of the Bükk Foreland (Fig. 4). The age of the sandstone with footprints is not really constrained paleomagnetically. On the assumption that its remanence is primary, the position indicated in Fig. 6 is valid. In the opposite case, the stratigraphic column of Fig. 7 can be constructed, which has the advantage of maintaining the co-evality of the flora assemblage from the site NE of Lipovany and from the site of Ipolytarnóc, both indicating subtropical tropical rain forest climatic conditions (Němejc 1967; Němejc & Knobloch 1973; Hably 1985). The age assignment suggested by Fig. 6, has consequences for the degree of continuity of deposition as well as for the paleoclimate. Concerning the first, we have to calculate with a considerable hiatus (missing Bukovinka/Zagyvapálfalva and Salgótarján Formations) in the Ipolytarnóc area (Fig. 6). This is surprising, because the mentioned formations do occur in the vicinity, on the Slovak side at Lipovany and at Čakanovce villages. The paleoclimatic implication is that the rain forest vegetation is of Ottnangian age and is most probably younger than the Salgótarján Formation characterized by luxurious swamp vegetation indicative of a cooler, but still humid climate. Finally, it has to be mentioned that a recently published paper of Pálfy et al. (2007), which was accessible on-line a few days after the revised version of this paper was submitted, contains new radiometric data concerning the numerical age of the ignimbrite formation at Ipolytarnóc, which is 17.42± 0.04 Ma (crystal zircon U-Pb age). Thus, the results of two independent methods the paleomagnetic and the radiometric are in perfect agreement, both suggesting that the Ipolytarnóc felsic ignimbrites are of late Ottnangian age. Acknowledgment: We thank Imre Szarvas for field guidance, Doc. M. Bielik, Dr. M. Jelenska and M. Lantos for revising the manuscript. Our special thanks are due to József Duska (director of the Bükk National Park), and Imre Szarvas, who is in charge of the Ipolytarnóc area, for permission to drill in the protected area and for accommodation on the spot. The work was financially supported by the Hungarian Scientific Research Fund (OTKA) Project No. T043773, by Grant Agency VEGA Project Nos. 4042, Agency for Science and Research, Project No. 51-011305, APVT-51002804 and 6045/26 and a joint project of the Academies of Sciences of Slovakia and Hungary. References Báldi T. 1983: Oligocene and Lower Miocene formations of Hungary. Akadémia Kiadó, Budapest, 1 293 (in Hungarian). Báldi T. 1986: Mid-Tertiary stratigraphy and paleogeographic evolution of Hungary. Akadémia Kiadó, Budapest, 1 196. Bartkó L. 1985: Geology of Ipolytarnóc. Geol. Hung., Ser. Paleont. 44, 49 71. Fisher R. 1953: Dispersion on a sphere. Proc. Roy. Soc. London, Ser. A. 217, 295 305. Gyalog L. 1996: Key to the geological maps and short description of the stratigraphic units. MÁFI Alkalmi kiadványa 187, 1 171 (in Hungarian). Gradstein F.M., Ogg J.G. & Smith A.G. 2004: A geological time scale 2004. Cambridge University Press, 1 500. Hably L. 1985: Early Miocene plant fossils from Ipolytarnóc, Northern Hungary. Geol. Hung., Ser. Paleont. 44 46, 75 255. Hámor G. 1973: Relationship between the type of sedimentation and tectonization in epirogenic areas. Földt. Közl. 103, 245 240 (in Hungarian). Jablonszky J. 1914: Flora Mediterranean in age at Tarnóc. Földt. Int. Évkönyve. 22, 4, 227 274 (in Hungarian). Karátson D., Márton E., Harangi Sz., Józsa S., Balogh K., Pécskay Z., Kovácsvölgyi S., Szakmány Gy. & Dulai A. 2000: Volcanic evolution and stratigraphy of the Miocene Börzsöny Mountains, Hungary: An integrated study. Geol. Carpathica 51, 325 343. Kirschvink J.L. 1980: The least-squares line and plane and the analysis of paleomagnetic data. Geophys. J. Roy. Astron. Soc. 62, 699 718. Korpás L. 2003: New sedimentological model of the Ipolytarnóc sandstone. Chronology of the volcanic event and reconstruction of the eruption centre. Magyar Karszt és Barlangkutató Társulat, 1 42 (in Hungarian). Laurent L., Hilgen F., Shackleton N.J., Laskar J. & Wilson D. 2004: The Neogene period. In: Gradstein F.M., Ogg J.G. & Smith A.B. (Eds.): A geologic time scale. Cambridge University Press, Cambridge, 409 440. Lehotayová R. 1982: Miocene nannoplankton zones in West Carpathians. Západ. Karpaty, Ser. Paleont. 8, 91 110. Lexa J., Bezák V., Elečko M., Mello J., Polák M., Potfaj M. & Vozár J. (Eds.) 2000: Geological map of Western Carpathians and adjacent areas 1:500,000. Geol. Surv. Slovak Rep., Bratislava. Márton E. & Márton P. 1996: Large scale rotations in North Hungary during the Neogene as indicated by palaeomagnetic data. In: Morris A. & Tarling D.H. (Eds.): Palaeomagnetism and tectonics of the Mediterranean Region. Geol. Soc. London, Spec. Publ. 105, 153 173. Márton E. & Pécskay Z. 1998: Correlation and dating of the Miocene ignimbritic volcanics in the Bükk foreland, Hungary: complex evaluation of paleomagnetic and K/Ar isotope data. Acta Geol. Hung. 41, 467 476. Márton E., Vass D. & Túnyi I. 1996: Rotation of the South Slovak Paleogene and Lower Miocene rocks indicated by paleomagnetic data. Geol. Carpathica 47, 31 41. Nemějc F. 1967: Paleofloristical studies in the Neogene of Slovakia. Sborník Národního muzea 23, 1 32 (in Czech). Nemějc F. & Knobloch E. 1973: Die Makroflora der Salgótajáner Schichten Grupp (Die Flora aus Lipovany). In: Papp A., Rögl F. & Seneš J. (Eds.): Chronostratigraphie und Neostratotypen. Miocän der Zentralen Paratethys. Bd. III: M 2 -Ottnangien. Vydavate stvo Slov. Akadémie vied, Bratislava, 694 759. Pálfy J., Mundil R., Renne P.R., Bernor R.L., Kordos L. & Gasparik M. 2007: U Pb and 40 Ar/ 39 Ar dating of the Miocene fossil

540 E. MÁRTON, VASS, TÚNYI, P. MÁRTON and ZELENKA track site at Ipolytarnóc (Hungary) and its implication. Earth Planet. Sci. Lett. 258, 160 174. Póka T., Zelenka T., Szakács A., Seghedi I., Nagy G. & Simonits A. 1998: Petrology and geochemistry of the Miocene acidic explosive volcanism of the Bükk Foreland, Pannonian Basin, Hungary. Acta Geol. Hung. 41, 437 466. Póka T., Zelenka T., Seghedi I., Pécskay Z. & Márton E. 2004: Miocene volcanism of the Cserhát Mts. (N. Hungary): Integrated volcano-tectonic, geochronologic and pertochemical study. Acta Geol. Hung. 47, 221 246. Seneš J. 1965: Paleogene of Little Danubian Lowland and Southern Slovakia (Buda Development). In: Andrusov D. 1965 (Ed.): Geologie der Tschechoslowakischen Karpathen. Vol. 3. Vydavate stvo Slov. Akadémie vied, Bratislava, 298 322 (in Slovak). Vass D. (Ed.) 1983: Explanations to the geological map of Ipe ská kotlina Depression and Krupinská planina Plain, 1: 50,000. GÚDŠ, Bratislava, 1 126 (in Slovak). Vass D. 2002: Lithostratigraphy of Western Carpathians: Neogene and Buda Paleogene. ŠGÚDŠ, Bratislava, 1 202. Vass D. & Elečko M. (Eds.) 1992: Explanations to the geological map of Lučenská kotlina Depression and Cerová vrchovina Upland, 1: 50,000. GÚDŠ, Bratislava, 1 196 (in Slovak). Vass D. & Kraus I. 1985: Double age of basalts in the Southern Slovakia and their relation to Poltár beds. Miner. Slovaca 17, 435 440 (in Slovak).