EGU Stephan Mueller Special Publication Series, 3, 79–94, 2002 c European Geosciences Union 2002

Towards a new time scale for the Upper continental series of the Pannonian basin (Central )

M. Sacchi1 and F. Horvath´ 2 1Istituto per l’Ambiente Marino Costiero (IAMC), Consiglio Nazionale delle Ricerche (CNR), Calata Porta di Massa, Porto di Napoli, 80100 – Napoli, Italy 2Eotv¨ os¨ University, Department of Geophysics, Pazm´ any´ Peter´ set´ any´ 1/C – 1117 – Budapest, Hungary Received: 2 May 2000 – Accepted: 29 May 2002

Abstract. In this study we assert that most of the “Pontian” jor relics of this ancient aquatic realm, called Paratethys stratigraphic succession of western Hungary is much older (Laskarev, 1924), are represented by the present-day Black than Pontian stage (older than 7 Ma). In fact, these strata Sea, the Caspian Sea and the Aral Sea (Fig. 1). It is generally form a clearly distinct chronostratigraphic unit between the accepted that open to restricted marine conditions prevailed Pontian strata (as they are defined in the type area of the in the Pannonian basin throughout the syn-rift phase (Lower Black Sea basin) and the Pannonian strata (as they are de- Miocene to early Mid Miocene). However, since the early fined in the type area of the Vienna basin). To denote such a post-rift phase (late Mid Miocene) the basin became an iso- problematic chronostratigraphic interval we propose the in- lated brackish-water lake that was progressively filled up by troduction of a new stage (or substage) named Transdanubian large prograding delta systems. between the Pannonian sensu stricto (s.s.) and Pontian s.s. Establishing a reliable chronostratigraphic framework for stages of the Upper Miocene series of the Central Paratethys the non-marine sedimentary fill of the Pannonian System (ca. 9.0–7.4 Ma in the chronology adopted in this basin and understanding the variation in space and time of study). facies associations at basin scale have been long-debated The Transdanubian stage has been defined in terms of problems. Paratethys stages were based mainly on mol- biostratigraphy, lithostratigraphy, magnetostratigraphy and lusk assemblages. Correlation among marine episodes in the allostratigraphy. The location of a suitable stratotype has also Paratethys was obtained by marine planktonic microfossils, been proposed. As a first approach, we tried to avoid the in- while correlation of regional stages of the Paratethys with the troduction of new terms in the already complex chronostrati- standard marine stages still remains somewhat obscure, be- graphic nomenclature of the Pannonian basin. However, we ing practically impossible in terms of biostratigraphy only arrived to the conclusion that the introduction of the Trans- (Magyar and Hably, 1994; Sacchi et al., 1997, 1999a, b). danubian as a new stage (or substage) is a necessary break- Nowadays consensus seems to be emerging around the need through, to avoid further confusion and circular reasoning in- of a multidisciplinary approach to integrate the classic bios- volving facies associations versus chronostratigraphic units. tratigraphic analysis and geologic mapping on a lithostrati- Transdanubian strata represent a distinct anticipation of graphic base (Sacchi, 2001). the Pontian facies within the intra-Carpathian area. The fact According to the regional chronostratigraphy adopted for that these strata have been reported for decades as “Pontian” the nonmarine strata of the intra-Carpathian area (Central Pa- in the literature has been the source of much terminological ratethys) the Upper Miocene- sequence of the Pan- confusion and chronostratigraphic miscorrelation. nonian basin (Pannonian stage sensu (s.) Lorenthey,˝ 1900, or “Pannonian sensu lato” (s.l.), is subdivided into Pannon- ian sensu Stevanovic,´ 1951, or “Pannonian sensu stricto” 1 Introduction (s.s.) and Pontian (s. Andrussov, 1887) stages. An infor- mal twofold subdivision into “Lower Pannonian” and “Upper During the Oligocene-Neogene the Pannonian basin was part Pannonian” is also used in Hungary, particularly in the prac- of a vast epi-continental basin system that developed as a tice of seismic-stratigraphic interpretation. In this case the series of brackish seaways, lakes and wetlands within the term “Lower Pannonian” is often assumed to correspond to interiors of central Eastern Europe and western Asia. Ma- the Pannonian stage s.s. and the term “Upper Pannonian” to the Pontian stage, respectively. It is beyond the scope of this Correspondence to: M. Sacchi paper to review the historical development of the Pannon- ([email protected]) ian s.l. non-marine stratigraphy of the Central Paratethys. 80 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series

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Fig. 1. Outline of the Paratethys-Mediterranean region during Late Miocene (after Muller¨ et al., 1999).

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Fig. 2. Historical development of the Pannonian stage of the Central Paratethys and correlation with the standard Neogene time scale. Note that a three-fold subdivision of Pannonian s.l. strata (s. Lorenthey,˝ 1900) similar to the one discussed in this study had been already introduced, early last century, by Hornes¨ (1901) and Halavats´ (1903).

The reader is referred to the detailed reviews of Korpas-´ (Muller¨ and Magyar, 1992; Magyar and Hably, 1994; Gya- Hodi´ (1983), Papp et al. (1985), Steininger et al. (1990), Ste- log, 1996; Sacchi et al., 1997, 1999a, b; Horvath´ and Tari, vanovic´ et al. (1990), Rogl¨ (1996, 1998), Sacchi et al. (1997, 1999). Particularly it has become clear that none of the stage 1999b), Magyar et al. (1999a, b), Muller¨ et al. (1999), Sacchi names currently used in the literature adequately represent (2001) (Fig. 2). the middle part of the Pannonian s. Lorenthey˝ (1900) (ca. 9.0–7.4 Ma, in the chronology adopted in this study). The In the last few years several authors have pointed out reason for the inadequacy of the official Paratethys stage sys- that the Late Miocene chronostratigraphy of the Paratethys tem in offering a reliable chronostratigraphic picture of the is affected by terminological and conceptual inconsistencies M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series 81

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Shift the boundary between Pannonian s. str. and Pontian s. Stevanoviæ (1951) up to the base of the 1 Pontian as it is defined in its type section of the Eastern Paratethys. 2 Maintain the Pontian s. Stevanoviæ (1951) only for the Central Paratethys and use the term Pontian with two different meanings.

3 Introduce a new stage (Transdanubian) in order to fill the “chronostratigraphic gap” between the Pannonian s. str. and Pontian s. str. . 4 Delete the stage name "Pontian" from the Western-Central Paratethys stage system and reintroduce the use of the term “Pannonian” s. Lõrenthey (1900).

Fig. 3. Correlation between the Late Neogene (a) Mediterranean and (b) Central Paratethys stages. Column (c) illustrates four possible redrawings of the Late Miocene chrono-stratigraphic framework of the Pannonian basin (Central Paratethys) (from Sacchi et al., 1997, slightly modified) (see text for discussion).

Pannonian s.l. stage is multifold. Among the important fac- In this study we propose a new chronostratigraphic frame- tors hindering time-stratigraphic correlation there are: work of the Upper Miocene continental record of the Pan- nonian basin, in the stratigraphic interval corresponding 1) the general diachronous trends of the lithostratigraphic to the -lowermost of the standard ma- patterns in the Paratethys continental realm (younging rine time scale (ca. 9.0–7.0 Ma in the chronology adopted from West to East); in this study). The opportunity to introduce the concept of Regional Stratotype Sections and Points (RSSPs) for 2) documented radiations and migrations of endemic mol- large (intra)continental bioprovinces as regional standards lusk faunas from central to eastern Paratethys during for marine-continental correlations is also discussed. Late Miocene-Pliocene;

3) the remarkable facies dependence of faunas which makes it difficult to recognize the First and Last Oc- currence of index fossils (Sacchi, 2001). 82 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series

CENTRAL EASTERN STANDARD EPOCH PARATETHYS PARATETHYS STAGES STAGES STAGES 0 QUARTER- HOLOCENE HOLOCENE HOLOCENE NARY PLEISTOCENE PLEISTOCENE PLEISTOCENE

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2 The need for a new time scale is very complex indeed, as the term “Pontian” has deep roots in the literature. It is widely used in the Mediterranean region Chronostratigraphic miscorrelation between the base of the by both Paratethyan and Mediterranean stratigraphers, and eastern Paratethys Pontian (Pontian s.str.) and the base of the certainly, it would not be easy to convince workers to substi- Central Paratethys Pontian (Pontian s. Stevanovic,´ 1951) due tute it with a new stage name “labeled” for Central Paratethys to diachronism of biofacies was first demonstrated in the Pan- use only. On the other hand, the correlation of the Eastern nonian basin by Muller¨ and Magyar (1992). This problem Paratethys Pontian with time-equivalent strata of the Central was largely a consequence of the correlation suggested by Paratethys is still obscure. Stevanovic´ (1951) who proposed the “extension” of the Pon- One might consider that an easy (conceptual, not practi- tian stage of the eastern Paratethys to the central Paratethys cal) solution to the problem would be to “stretch” the upper realm, based on the presumed coeval appearance of common boundary of the Pannonian s.str. stage (s. Stevanovic,´ 1951) mollusc species on both sides of the Carpathians. However, up to the lower boundary of the Pontian s.str. stage (e.g. the Pontian mollusc fauna of the Eastern Paratethys prac- Rogl,¨ 1996, 1998). This solution, unfortunately, would cause tically consists of Pannonian Lake (Central Paratethys) im- even more confusion in the terminology. In fact, the “short” migrants and their descendants, and hence is much younger Pannonian s.str. stage (Stevanovic,´ 1951) at least had the than its intra-Carpathian counterpart (Muller¨ et al., 1999). basic advantage of being correlative with the Lower Pannon- The fact that the base of the Pontian s.str. stage is nearly ian of the Hungarian literature (s. Lorenthey,˝ 1900; Halavats,´ 2 Ma younger than the top of the Pannonian s.str actually rep- 1903). This equivalence appears to be deeply rooted and sta- resents a major obstacle in the chronostratigraphic procedure ble in the Central Paratethys stratigraphic terminology of the within the Central Paratethys. This circumstance recalls the last decades. With the eventual upward shifting of the top attention on the practice of adopting a stage defined in the of the Pannonian s.str. stage this correlation would be lost, Eastern Paratethys (like the Pontian s.str.) for chronostrati- and much confusion would arise. Furthermore, the upper- graphic subdivision in the Central Paratethys. The problem most strata of a “stretched” Pannonian stage would include M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series 83 sedimentary deposits that display typical “Pontian facies” re- 3.1 Magnetostratigraphy semblance and have been referred to as Pontian for decades. Whatever the solution may be, the key question remains Iharosbereny-1´ is one among a series of continuously cored how to fill the “chronostratigraphic gap” between the Pan- exploratory wells drilled in the Hungarian part of the Pan- nonian s.str. and Pontian s.str. stages (Fig. 3). In the fol- nonian Basin that have been processed for detailed mag- lowing pages possible options to “fill” this “gap“ within the netostratigraphic study (Juhaz´ et al., 1994, 1999; Magyar Upper Miocene series of the Pannonian basin are presented et al., 1999). The sedimentary succession cored at Iharos- and discussed. Particularly we adopt the Transdanubian (ca. bereny-1´ displays no evidence for movement of connate or 9.0–7.4 Ma in the chronology discussed in this study) as ground water and the strata seem to have remained undis- an intermediate stage (or substage) between the Pannonian turbed and unexposed since burial. Therefore, the study s.str. (s. Stevanovic,´ 1951) and the Pontian s.str. (Andrussov, samples most likely display original magnetization (Magyar 1887) (Fig. 4). et al., 1999b); minor secondary magnetization disappeared at 10–30 mT (Elston et al., 1990, 1994; Lantos and Elston, 1995). Details of paleomagnetic studies have been published elsewhere (Elston et al., 1990, 1994; Kokay et al., 1991; Lan- tos et al., 1992; Lantos and Elston, 1995. 3 The regional stratigraphic framework of SW Pannon- The magnetic polarity zones of Iharosbereny-1´ well sec- ian Basin tion have been correlated to the Global Polarity Time Scale (GPTS) of Cande and Kent, 1995 (Fig. 6). The magnetic polarity zones detected within the Iharosbereny-1´ core sec- Several studies have been recently published on the sequence tion lie above the long normal polarity interval of Chron stratigraphy of the Upper Neogene fill of the Pannonian basin C5n (Juhaz´ et al., 1999; Magyar et al., 1999a). The first (Pogacs´ as´ et al., 1988; Elston et al., 1990; Csato,´ 1993; two normal polarity intervals in the lower part of the sec- Ujszaszi´ and Vakarcs, 1993; Vakarcs et al., 1994, Vakarcs, tion between ca. 1100 m and 1075 m and 990 m and 900 1997). The results we present in this paper are based on the may be namely correlated with chrons C4Ar.1n and C4An. recent recognition and correlation of unconformity-bounded Similarly, the major uppermost four normal polarity inter- stratigraphic units within the non-marine Upper Miocene vals at 180–240 m, 275–310 m, 380–410 m, 425–500 m can strata of the western Pannonian basin (Sacchi et al, 1999a). be namely correlated to Chrons C3Bn, C3Br.2n, C3Br.1n Based on methods and procedures of sequence stratigra- and C4n.2n. Less obvious is the calibration of the large and phy (Vail, 1987; Galloway, 1989), five 3rd-order (with 106 discontinuous normal polarity zone developing at depth of year periodicities) sequences at regional scale in the Upper 525 m to 850 m. Juhaz´ et al. (1999) and Magyar et al. (1999) Miocene succession of the western Pannonian basin have have proposed that the base of Chron C4n.1n can be located been recognized (Fig. 5). The sequence stratigraphic pro- at a depth of ca. 730 m. in the Iharosbereny-1´ section. cedure was applied not as a rigid model or template, but rather to promote an integrated stratigraphic approach. This 3.2 Sequence stratigraphy includes full combination of biostratigraphy, magnetostratig- raphy, radiometric age determination, sequence (or genetic) The Upper Miocene stratigraphic sequences of the SW Pan- stratigraphy and classic field study (Sacchi et al., 1999a). nonian basin have been designated from bottom to top, A detailed lithostratigraphic and paleontologic description as Sarmatian-1 (SAR-1) and Pannonian-1 (PAN-1) through along with geophysical logs of Iharosbereny-I´ well were used Pannonian-4 (PAN-4). The stacking pattern of stratigraphic in this study. Available magnetostratigraphic data included sequences gives a general picture of the evolutionary stages magnetic polarity logs from a number of wells in the Hungar- of the prograding delta systems in the SW Pannonian basin. ian part of the Pannonian basin (Lantos et al., 1992, Juhasz,´ Maximum thickness of the whole sequence stack is in the 1994; Lantos and Elston, 1995; Magyar et al, 1999b; Sac- order of 3 km. The major unconformity at the base of the chi et al., 1999a). Iharosbereny-I´ well log has been cor- post-rift sequence of the western Pannonian basin in South- related with the global magnetic polarity scale (Kande and ern Transdanubia is often associated with a significant strati- Kent, 1995, Berggren et al., 1995) and seismic reflectors in graphic gap whose amplitude increases from WSW (Drava the Southern Transdanubia. The obtained sequence strati- basin) to ENE (Somogy). This may cause amalgamation of graphic framework was tied to a regional biostratigraphic and more sequence boundaries (Fig. 5). magnetostratigraphic framework recently developed for the Calibration of seismic profiles with borehole data shows Upper Miocene succession of the Pannonian basin (Juhasz´ et that maximum flooding surface mfs-2 marks the peak of a al., 1999; Magyar et al., 1999a, b; Muller¨ et al., 1999). Ra- major flooding event associated with large scale transgres- diometric data on volcanic rocks interbedded within the Up- sion of Congeria czjzeki lacustrine beds (Szak´ Fm.) onto per Miocene continental strata of western Hungary were also the Pannonian basin margins. Mfs-2 correlates with the base used to constrain chronostratigraphic interpretation (Balogh of magnetic polarity zone C4An and hence can be dated at et al., 1986; Balogh, 1995; Pecskay´ et al., 1995). 9.03 Ma. It represents a quasi-isochronous surface at basin 84 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series modified). 5. Fig. Post-rift tectono-stratigraphic Two-way travel time (s) 2 1 0 2 1 . . . framework . . 5 5 5 0 0 0 etncadsqec tairpi rmwr fPnoinsl taabsdo h nepeaino a 70k fsimcscin coswsenHnay(rmSch,2001, Sacchi, (from Hungary western across sections seismic of km 1700 ca. of interpretation the on based strata s.l. Pannonian of framework stratigraphic sequence and Tectonic B N a N P W k L

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( u c M r e MIOCENE PLIOCENE EPOCH f a a Time (Ma) ) 1 1 1 1 c 9 8 7 6 5 4 3 2 1 0 1 e 3 2 0 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series 85

TIME (Ma) Y T

I IHAROSBERÉNY-1 5 R

CHRONS 9 A L K O C Depth

P (m) C3r 0 5.894 6 6.137 100 C3An 6.269

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) 7.650 500 a C4n M (

8 8.072 600 E 8.225 M 8.257

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1100 10

1200 C5n Fig. 6. Correlation of Iharosbereny-1´ well polarity zones with the Global Po- larity Time Scales (GPTS) of Cande 1300 and Kent (1995) (CK95) (after Juhasz´ et al., 1994, 1999; Magyar et al., 1999b; 1377 Sacchi, 2001).

scale and correlates with the top of Pannonian s.str. stage characterized by the development of open lake strata. Sub- (Lower Pannonian s. Lorenthey,˝ 1900) (Figs. 5–8). surface data show maximum flooding surface mfs-3 may be Sequence boundary Pan-2 correlates with the base of zone correlated to offshore lacustrine marl with Congeria rhom- C4r (ca. 8.7 Ma). It is associated with a significant drop boidea. This surface represents another useful quasi time- of base level of erosion within the Pannonian basin, which line at basin scale that may be regarded as a good proxy in was accompanied by extensive subaerial exposure of the lake western Hungary for the base of Pontian as it is defined in margins. This is documented in the so-called marginal facies the stratotype area of the Black Sea basin. Consequently, the of Transdanubia (Sacchi, 2001). stratigraphic unit bounded by maximum flooding surfaces mfs-2 and mfs-3 can be correlated with the lower part Pon- Maximum flooding mfs-3 is within the lower part of zone tian s. Stevanovic´ (1951). This unit can be seen as an “antic- C3Br (ca. 7.4 Ma). It represents the final stage of a second ipation“ of the Pontian s.str. facies in Hungary. According to important flooding event within the basin, which is again 86 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series N Iharosberény-I SECTION NA-41 / So-1 S N Iharosberény-I SECTION NA-41 / So-1 S 0 0 0 0

0.43 s mfs-3 (7.43 Ma) T )

0.5 PAN-3 0.5 w s 0.43 s mfs-3 (7.43 Ma) ( T o

)

Pan-2 SB (ca 8.70 Ma) w 0.5 0.62 s PAN-3 0.5 - e s w ( o mfs-2 (9.03 Ma) m Pan-2 SB (ca 8.70 Ma) a - i 0.62 s

e 0.75 s t w y

l mfs-2 (9.03 Ma)

m a i t

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a v l

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syn-rift strata ( T 1.5 Pre-Sarmatian 1.5 PAN-2 3rd-order stratigraphic sequence s w and psreyn-r-ifrtif tb satrsaetma ent ) T 1.5 1.5 PAN-2 3rd-order stratigraphic sequence and pre-rift basement mfs-2 3rd-order maximum flooding surface

Panm-f3s-2 3rd3-rod-rodredre sre mquaexinmcuem b ofluonoddainryg surface Pan-3 3rd-order sequence boundary 0 5 km 2.0 9.03 Magnetostratigraphic calibration (Ma) 2.0 0 5 km 2.0 9.03 Magnetostratigraphic calibration (Ma) 2.0

ny ko y Ba n ko ton a ala B B n ke to La ala B ke La Somogy Somogy Fig. 7. Magnetostratigraphic cali- Iharosberény-I bration of Pannonian s.l. strata at IhDarosberény-I r Iharosbereny-I´ well site with the GPTS Dá rva sek of Cande and Kent, 1995 (CK 95) (af- áv b Mec k a as cse ter Magyar et al., 1999b; Sacchi et al., bain Me sin 1999a; Sacchi 2001). Maximum flood- ing surfaces mfs-2 (9.03 Ma) and mfs- 0 50 km 3 (7.43 Ma) represent two quasi time- 0 50 km lines at basin scale.

this interpretation it is concluded that Pontian s.str. (younger ian basin into two main tectono-stratigraphic units namely than 7 Ma) strata are practically missing in outcrop in central- Late Miocene and Pliocene in age (Fig. 5). western Hungary. Sequence boundary Pan-4 (ca. 5.0 Ma) is likely to be as- sociated with a stratigraphic gap (Juhasz´ et al., 1999) and 4 Definition of Transdanubian stage (or substage) significant tectonic overprint as suggested by the general tectono-stratigraphic patterns within the Neogene basin fill. Based on the integrated stratigraphy of the Upper Miocene The higher rank unit bounded by Pan-1 SB and Pan-4 SB ap- succession of SW Pannonian basin discussed in this study, proximately correlates with the Tortonian-Messinian strata of we propose the introduction of the Transdanubian stage in the the standard time scale. The major unconformity developing regional chronostratigraphic scale of the Central Paratethys at Pan-4 SB subdivides the post-rift strata of western Pannon- (Fig. 9). The Transdanubian is intended to substitute the M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series 87 y t 5 S e d i m e n t a r y i r 9 textures and structures IHAROSBERÉNY-1 WELL ) a l K y o m g e n Chrono- s C ( s Carbonates Depositional setting r c t p

o u e

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v t n p d n s i n r

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t

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fp = flood plain b/s = bay/shoreface sl = shallow lacustrine ol = open lacustrine

Stratigraphic gap Pan - 2 3rd-order sequence boundary mfs - 2 Maximum flooding surface fs Minor flooding surface

Fig. 8. Interpretation of the Pannonian s.l. (Upper Miocene) succession cored at Iharosbereny-1´ well site, western Pannonian basin, Hungary. Chronostratigraphic subdivision of Pannonian s.l. strata is after Sacchi et al. (1999a, b). Magnetic polarity zones have been calibrated to the GPTS of Cande and Kent (1995) (CK95). lower part of the “Pontian” s. Stevanovic´ (1951) which re- ate stage between “Lower Pannonian” (Pannonian s.str.) and vealed to be significantly older than Pontian age s.str. “Upper Pannonian” (Pontian s.str.) is not new. In fact since the earliest stratigraphic studies on Pannonian strata, Hornes¨ In terms of the informal chronostratigraphy often used in (1901) had defined a “Middle Pontian” interval (Mittlere Hungary, the Transdanubian may be introduced as the third Congerienschichten) and Halavats´ (1903) “Middle Pannon- middle subdivision of the Pannonian s.l. stage (s. Lorenthey,˝ ian” strata (Congeria ungulacaprae and Congeria balatonica 1900). It is worth noting that the concept of an intermedi- 88 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series nt atrSch,2001). Sacchi, (after units 9. Fig. 10 12 11 7 9 6 8 5 TIME (Ma) isrtgahcdfiiino h rndnba tg,o usae(aeMoeeo h eta aaehs)adcreainwt antsrtgahcadsqec stratigraphic sequence and magnetostratigraphic with correlation and ) Paratethys Central the of Miocene (Late substage or stage, Transdanubian the of definition Biostratigraphic INTEGRA GRAPHY STRA MAGNETO-

C

Polarity an ( de 19 & 95 K TI- ) C3Br C3Ar C3Bn C5r C4r C3An C3r C5Ar C5n C4Ar C4An C4n C3n C5An en

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TORTONIAN MESSINIAN ZANCL. Age a TIGRAPHY VALLIAN l . Local (Hungarian) SARMATIAN Sacchi (2001) Paratethys Central P A N N O N I A N S. L. THIS STUDY

EARLY MID LATE TIGRAPHY OF THE P

Pannonian s.str. TransdanubianP ontian s.str. Dacian Regional S. b. pannonicus Mecsekia ultima bentorii oblungus flagellates pec Po Spiniferites Spiniferites Spiniferites paradoxus Galeacysta Dino- sva validus etrusca ntia rad din ens ium is

deep water

digitifera banatica "Paludina beds" (freshwater) Magyar et al. (1999a, b) Congeria Congeria (restricted marine) Sarmatian fauna BIOSTRA ANNONIAN S.L. SEQUENCE OF SW HUNGARY Mollusc zones C. praerhomboidea L. praeponticum

Congeria czjzeki sublittoral Lymnocardium Lymnocardium rhomboidea schedelianum Congeria soproniense TIGRAPHY

Lymnocardium Lymnocardium Lymnocardium Prosodacnomya P. carbonifera C. o L. serbicum

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Balaton Tihany highland peninsula

Lake Balaton

Fig. 10. Alternating shallow lacustrine and terrestrial strata cropping out at Tihany- Feherpart,´ Lake Balaton. The section is currently regardedFig. 10. as Pontian Alternating faciostratotype shallow in Hungarylacustrine (M uller¨and andterrestrial Szonoky,´ strata 1990). cropping Our study out showed, at Tihany-Fehérpart, however, that these strata Lake are Balaton. much older thanThe the section Pontian stage. is currently We suggest regarded this section as Pontian may be selected faciostratotype as Transdanubian in Hungary stratotype (Müller (ca. 9.0 and to 7.4 Szónoky, Ma). 1990). Our study showed, however, that these strata are much older than the Pontian stage. We suggest this section may be beds).selected Both as these stratotype stratigraphic Transdanubian units substantially (ca. 9.0 to coincide 7.4 Ma ). northern shore of Lake Balaton, western Hungary (Fig. 10). with the Transdanubian stage defined and discussed in this Selection of a boundary stratotype – The lower bound- study. ary of Transdanubian stratotype section is not exposed at The Transdanubian time interval is actually not repre- Tihany-Feherp´ art,´ but has been cored in the near subsur- sented in any proposed stratotype of the Miocene Series of face (55.4 m beneath the topographic surface at Lake Bala- the Central Paratethys. ton shore, Tihany-62 well). This stratigraphic level crops out Name – The name “Transdanubian” is proposed after the in the northern Transdanubia (Bakony, Vertes,´ Gerecse Mts.) name of the inner Carpathian region west of the Danube river, and more research work should be to be done to select an ap- to denote the stratigraphic interval in study. It is the region propriate Transdanubian boundary stratotype in this area. A of Hungary where the best outcrops of these rocks can be possible candidate in scope may be preliminarily selected in found. the clay pit sections exposed at Tatabanya´ area at the bound- Rank of the Chronostratigraphic Unit – The Transdanu- ary between the open lacustrine strata (Szak´ Fm.) and the bian has a duration of ca. 1.6 Ma. It could be ascribed to the base of the overlying silty layers of Somlo´ Fm (top of the rank of stage or substage, depending on the reorganization of Congeria czjzeki bearing beds). the general chronostratigraphic framework. Biostratigraphic definition – In terms of molluscan bio- Location of the stratotype – A suitable stratotype for the zonation (Magyar et al, 1999b) the Transdanubian stage cor- Transdanubian stage is represented by the Tihany-Feherp´ art´ responds to the littoral Congeria balatonica-Lymnocardium section which is presently used as faciostratotype for local (decorum–serbicum) zone and the Congeria ungulacaprae- (Hungarian) reference to the Pontian facies of the Black Sea Prosodacnomya (carbonifera–dainelli) zone (see Middle (Muller¨ and Szonoky,´ 1990). This section is exposed at the Pannonian of Halavats,´ 1903). Its lower part correlates 90 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series ersnsteTasauinsaedsusdi hsstudy. this in discussed stage Transdanubian the represents 11. Fig. N 3.0 Depth 1.5 (km) 0 N kthscinars h etr anna ai,bsdo einlsimcpols h tairpi ntbtenmxmmfloigsrae f- n f- c.9074Ma) 9.0-7.4 (ca. mfs-3 and mfs-2 surfaces flooding maximum between unit stratigraphic The profiles. seismic regional on based basin, Pannonian western the across Sketch-section W m f

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Chronostratigraphic framework of the upper Miocene stratotype sections of the Paratethys stage system (from Sacchi, 2001, modified). ) a M ( E M I T 2 1 5 8 0 6 9 7 1 1 1 Fig. 12. 92 M. Sacchi and F. Horvath:´ Towards a new time scale for the Upper Miocene continental series to the sublittoral Congeria praerhomboidea zone and the troduction, still far from satisfactory. Apart from the obvious Spiniferites validus microplankton zone, though it may out- difficulties in correlating non-marine stages of the Paratethys reach their rather uncertain upper boundaries. The lower and standard marine stages, the Paratethys Stage System is boundary of the Transdanubian correlates with the base of clearly affected by severe internal inconsistency. Particularly, Chron C4An and displays an age of 9.03 Ma, while the up- the boundaries and the internal subdivision of the broad time per boundary is within the lower part of zone C3Br (7.43 Ma) interval between the Sarmatian (Mid-Late ) and (Fig. 9). the Pleistocene have not been unambiguously defined at in- Allostratigraphic definition – From the perspective of al- terregional scale. lostratigraphy (Salvador, 1994) the Transdanubian stage may In the last decades, the use of different names or even dif- be defined as a genetic stratigraphic unit (s. Galloway, ferent meanings for the same names has proliferated to such 1989) bounded by two consecutive third-order maximum an extent that, possibly, the only unequivocal chronostrati- flooding surfaces, namely, mfs-2 and mfs-3 of this study graphic term one could use to indicate rocks of that time in- (Fig. 11). Transdanubian strata correspond to a regressive- terval is “Pannonian” (s. l.) as it was originally introduced transgressive cycle that can be regarded as an “anticipation” by Roth (1879) more than a century ago. of the Pontian facies of the Black Sea in Hungary. One “mission” of stratigraphy is trying to find the largest Recognition of Transdanubian boundaries in the outcrop international consensus around the definition and conve- and subsurface – As they correspond to maximum flooding nience in the practical use of Stages. In fact, modern trends surfaces, both boundaries of the Transdanubian stage are eas- in chronostratigraphy include the concept of Global Stra- ily recognized in the outcrop (sharp facies contrast between totype Section and Points (GSSPs). Of course one can- the underlying open lacustrine beds and the overlying regres- not approach the chronostratigraphic study of the Paratethys sive fluviatile-terrestrial strata) as well as in deep seismics bioprovince (although it is a huge bioprovince) in terms of (high-amplitude and high-lateral continuity of reflectors at “global” stages. Nevertheless, we believe it might be worth- the top of transgressive systems tract typically overlain by while to agree upon regionally valid, useful, and accepted downlapping strata of the highstand systems tract deposits). definition of stages. The wider the region where a certain Completeness of the boundary stratotype section – Re- stage can be successfully tested and used, the higher is its gional stratigraphic correlation indicates that the critical intrinsic value. Therefore, an international cooperation and interval for defining the base of the Transdanubian stage effort would be required in order to work out “Regional is remarkably complete in the whole northern Transdanu- (i.e. Paratethyan) Stratotype Section and Points” (RSSPs) bian area. Sequence stratigraphy predicts that condensation (Fig. 12). This would probably be a necessary step towards and/or minor non-depositional hiatus may occur at maximum the process of abandoning excessive fragmentation and pro- flooding surfaces. However if hiatuses occur, their duration liferation of local chronostratigraphic subdivisions within the is likely to be below the resolution provided by biostratigra- continental realm of Paratethys. phy. Magnetostratigraphic definition – Based on correlation with calibrated magnetostratigraphy of Iharosbereny-I´ well, 6 Conclusions the lower boundary of the Transdanubian stage can be placed at the base of chron C4An of the global magnetic polar- We propose the introduction of the Transdanubian as an in- ity scale (Cande and Kent, 1992, 1995; Berggren, 1995) termediate stage (or substage) between the Pannonian s.str. (Figs. 7–9). and Pontian s.str stages of the Upper Miocene series of the Geochronology – According to the revised calibration of Central Paratethys System (ca. 9.0–7.4 Ma in the chronology global magnetic polarity scale of Cande and Kent (1995), the adopted in this study) (Figs. 2, 4 and 9). lower boundary of the Transdanubian stage displays a mag- The reason for introducing a new stage in the already com- netostratigraphic age of 9.025 Ma (Figs. 7–9). plex chronostratigraphic framework of the Paratethys stage Potential correlation with Eastern Paratethys stages – system is twofold. The Transdanubian stage is a rock unit Based on its integrated stratigraphic definition the Trans- likely to be recognizable at regional scale and it may sig- danubian stage as a first approach, might be tentatively cor- nificantly enhance stratigraphic correlation in the Central related with the Maeotian stage of the Eastern Paratethys Paratethys. On the other hand, we consider its introduction as (Pevzner, 1987). a necessary breakthrough, to avoid further confusion and cir- cular reasoning involving facies associations versus chronos- tratigraphic units. 5 Discussion Transdanubian strata correspond to a regressive-transgres- sive cycle that can be regarded as an “anticipation” of the If the Late Miocene chronostratigraphy of the Mediter- Pontian facies of the Black Sea in Hungary (Fig. 12). The ranean can be regarded as one of the best known time in- introduction of the Transdanubian stage may help to unravel tervals of the stratigraphic column, on the other end the the long-lasted debate on Late Neogene chronostratigraphy Late Miocene chronostratigraphy of Central-Eastern Europe of the central Paratethys. A major impact of the new strati- (Central Paratethys) appears to be, some decades after its in- graphic correlation we present in this study is the significant M. Sacchi and F. 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