Climatic controls on sedimentary environments in the Triassic of the Transdanubian Range (Western Hungary)

Palaeogeography, Palaeoclimatology, Palaeoecology 353–355 (2012) 31–44

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Climatic controls on sedimentary environments in the Triassic of the Transdanubian Range (Western Hungary) János Haas a, Tamás Budai b, c, Béla Raucsik c,⁎ a b c

Geological, Geophysical and Space Science Research Group of the Hungarian Academy of Sciences, Eötvös Loránd University, H–1117 Budapest, Pázmány P. sétány 1/c, Hungary Geological and Geophysical Institute of Hungary, H–1143 Budapest, Stefánia u. 14, Hungary Department of Geology, University of Pécs, H–7624 Pécs, Ifjúság útja 6, Hungary

a r t i c l e

i n f o

Article history: Received 1 February 2012 Received in revised form 12 June 2012 Accepted 28 June 2012 Available online 10 July 2012 Keywords: Transdanubian Range Triassic Palaeoclimate Dolomites Clay minerals

a b s t r a c t During the Triassic the Transdanubian Range was a segment of the western Neotethys margin where the climate was mostly determined by a strong global monsoonal system. As a consequence of the global climatic conditions and its geographic setting, warm to hot temperature prevailed in this area. However, there were significant changes in the precipitation pattern from dry to wet conditions in connection with the intensity of the monsoon system and the actual setting of this area within the monsoon system. The aim of our research was to interpret the palaeoclimatic conditions and their changes for the Triassic succession of the Transdanubian Range on the base of geochemical, mineralogical, sedimentological and palaeontological data, with special regard to the climate indicator facies (e.g. different types of dolomites; clay mineral assemblages). Nine evolutionary stages were distinguished. During the Early Triassic mixed siliciclastic–carbonate ramp sedimentation took place under arid climate that was interrupted by a humid pulse (Campil Pluvial Event). In the early Anisian a shallow carbonate ramp was developed under arid to semi-arid climate. The predominatly dry conditions prolonged during the middle Anisian,. The latest Anisian and the Ladinian carbonate platforms were developed under mostly semi-arid climate. The semi-humid climate of the earliest Carnian was followed by a definitely wet interval (Carnian Pluvial Event) that was characterised by an intense terrigenous input into the Julian intraplatform basins. Arid and humid conditions alternated during the final stage of basin upfilling from the latest Julian to early Tuvalian. Then a marked climatic change took place in the latest Carnian when the humid climate was changed to semi-arid conditions. From the middle to late Norian a gradual increase of humidity may have taken place that resulted in a decreasing intensity of the early dolomitisation of the carbonate sediments of the broad internal platform. At the very end of the Norian there was a marked climate change leading to enhanced humidity but with a definite seasonality. Humid climatic conditions prevailed during the Rhaetian (Kössen Event). Evaluation of the similarities and differences of the palaeoclimatic conditions for the Transdanubian Range and some selected areas in the western Neotethys (Dolomites, Northern Calcareous Alps, Mecsek), and the Peri-Tethyan Germanic Basin is also presented. © 2012 Elsevier B.V. All rights reserved.

1. Introduction The Transdanubian Range (TR) is a NE–SW trending chain of moderately elevated mountains and hills, extending in a length of about 200 km (Fig. 1). It is made up predominantly of Triassic formations representing a large segment of the Neotethys passive margin that was located between the South Alpine and Upper Austroalpine realms (Haas et al., 1995; Gawlick, 2000; Mandl, 2000). The total thickness of the Triassic formations is 3–4 km. As a result of detailed studies of outcrops, quarries and drill cores commenced more than 150 years ago, the lithostratigraphic units and their relationships

⁎ Corresponding author. Tel.: +36 72 503 600; fax: +36 72 501 531. E-mail address: [email protected] (B. Raucsik). 0031-0182/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.palaeo.2012.06.031

are well known, and there are a great number of data on the facies characteristics and age of the units (Fig. 2). According to the present-day concepts derived mostly from geophysical constrains (Tari and Horváth, 2010), the Transdanubian Range Unit is an Upper Austroalpine-type nappe which was not affected by Alpine metamorphism and although it was subject to multi-stage deformation, no significant displacements took place within the unit. Therefore the facies relationships reflect the original palaeogeographic setting and providing a good potential for the analysis of the controlling factors of the facies development. Setting and basic characteristics of the facies are controlled by tectonic, eustatic and climatic factors. Effects of the tectonic events and sea level changes were comprehensively evaluated in several papers (e.g. Broglio Loriga et al., 1990; Haas and Budai, 1995, 1999; Budai and Haas, 1997). Interpretation of the climatic conditions was also

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Fig. 1. Simplified map of the Transdanubian Range showing the surface extension of the Triassic formations and the exposures (outcrops and cores) referred in the text (after Haas and Budai, 1999). Bak: Balatonakali core; Cs: Csopak; Csk: Csákánykő; Drt‐1: Dörgicse core; Kk‐9: Köveskál core; Po‐89: Porva core; Rzt‐1: Rezi core; Szk: Szentkirályszabadja. Late Triassic basins: CsB: Csővár Basin; HB: Hármashatárhegy Basin; ZsB: Zsámbék Basin.

Fig. 2. Chronostratigraphic chart of the Triassic formations of the Transdanubian Range (after Haas and Budai, 1999). Abbreviations: P: Permian; J: Jurassic; OLENEK: Olenekian; DF: Dachstein Fm; IF: Inota Fm; MF: Mátyáshegy Fm; RD: Rezi Dolomite; SH: Sándorhegy Fm; SQ: third-order cycles (depositional sequences).

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attempted for some parts of the Triassic succession (e.g. Balog et al.., 1999; Rostási et al.., 2011) but no comprehensive analysis has been carried out for the time being. Accordingly, the aim of the present paper is the interpretation of the climatic conditions and their changes for the whole Triassic succession of the Transdanubian Range on the basis of evaluation of those lithological features and biofacies characteristics, which may apply as climate indicators. In the last couple of years a series of palaeoclimate investigations were performed for the area of the Southern Alps (e.g. Breda et al., 2009; Berra et al., 2010; Kustatscher et al., 2010; Preto et al., 2010; Stefani et al., 2010) which had a close palaeogeographic relation with the TR, and also for other regions of the western Neotethys realm and the Germanic Basin, respectively (e.g. Szulc, 2000; Feist-Burkhardt et al., 2008; Hagdorn and Nitsch, 2009; Kozur and Bachmann, 2010). Another goal of this paper is to compare the data of the different areas of the western Neotethys and to evaluate the cause of the similarities and differences of the palaeoclimatic conditions. 2. Methods For interpretation of the climatic conditions an integrated approach was applied; results of geochemical, mineralogical, sedimentological, and palaeontological studies were evaluated with special regard to the climate-indicator facies (e.g. evaporites, various paleosols, carbonate crusts). Two aspects of the evaluation are discussed below in a greater detail, the climate indicator potential of the dolomites and the clay minerals, respectively. Both dolomites and argillaceous rocks play important role in the upbuilding of the Triassic of the Transdanubian Range, therefore palaeoclimate evaluation of this rock types needs careful analysis of the available data. 2.1. Dolomites as palaeoclimate indicators There are various models for the formation of dolomites that may occur on the surface or in near-surface to shallow, intermediate, and deep burial settings (Machel, 2004). From among the family of dolostones only those which were formed via near-surface and in some cases shallow burial dolmitization processes have relevance in the palaeoclimate evaluation. Penecontemporaneous dolomites commonly form on arid tidal flats or below it via reflux and evaporative pumping and in evaporative lagoons via reflux and most probably with mediation of microbes (McKenzie et al., 1980; McKenzie and Vasconcelos, 2009). Consequently, recognition of these genetic types of dolomites provides evidence for hot and dry climate. However, dolomites formed on the surface and near to the surface and/or from evaporitic brines tend to recrystallise during burial masking the original textural properties (Machel, 2004). Seawater dolomitisation in shallow burial setting may also be informative but in this case for deciphering of the model and history of dolomitisation application of wide range of petrographic and geochemical methods are needed. 2.2. Clay minerals as palaeoclimate indicators The clay minerals of sediments and sedimentary rocks reflect changes in the source area, and/or intensity of continental hydrolysis, and/or depositional conditions (Chamley, 1989; Weaver, 1989; Adatte et al., 2002; Deconinck et al., 2003, 2005; Dera et al., 2009; Brański, 2010). Clay minerals are usually produced via hydrolitic chemical weathering processes (Chamley, 1989; Weaver, 1989). The composition of the clay mineral assemblages (mineralogical composition of the ‘clay fraction’, i.e. generally of the b2 μm grain size fraction) is climatically controlled, although it is significantly influenced by the length of hydrolysis, the water–rock ratio, and water chemistry (Weaver, 1989; Nesbitt et al., 1997; Fürsich et al., 2005). Therefore, the clay mineralogy is widely regarded to be a powerful tool for interpreting weathering conditions (Chamley, 1989; Weaver, 1989; Ruffell et al.,

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2002; Sheldon and Tabor, 2009), and the clay minerals may provide reliable information on climatic effects (Thiry, 2000). In general, illite and chlorite are generated during initial stages of chemical weathering via transformation of micas and ferromagnesian minerals, respectively (Nesbitt and Young, 1989; Weaver, 1989; Liu et al., 2005). Their predominance in a given sample may indicate the prevalence of physical erosion and/or rapid denudation of the source area (Fürsich et al., 2005) and, consequently, also coeval dry and/or cold climate. Since illite and chlorite are almost insensitive to the continental hydrolysis they may serve as ‘internal standards’. That is why various clay mineral ratios are usually applied for the characterization of sedimentary successions (e.g., Ruffell et al., 2002; Liu et al., 2005). Enhanced chemical weathering leads to formation of smectite and kaolinite (Chamley, 1989; Nesbitt and Young, 1989; Weaver, 1989; Liu et al., 2005). Smectite generation is usually related to climatic conditions of alternating wet and dry seasons and low water–rock ratio and/or diminished relief (Weaver, 1989; Ruffell et al., 2002; Fürsich et al., 2005). This corresponds generally to poorly drained environments and monsoonal climate characterised by strongly seasonal precipitation. Smectite-dominated weathering crusts and soils are commonly associated with hematite and calcite (Sheldon and Tabor, 2009). Kaolinite-dominated weathering crusts typically occurs on well-drained slopes at high water–rock ratio; the abundance of kaolinite is a good indicator of hot and humid (subtropical to tropical) climate (Chamley, 1989; Ruffell et al., 2002; Fürsich et al., 2005; Liu et al., 2005; Sheldon and Tabor, 2009). Kaolinite-dominated pedologic profiles are generally associated with oxide and oxyhydroxide minerals such as hematite, gibbsite and goethite (Viczián, 2007; Sheldon and Tabor, 2009). It is noteworthy that the dominance of smectite and kaolinite may indicate slow erosion rates or erosion of weathering profiles formed previously during a long time-range (Fürsich et al., 2005). The eventual clay mineral content of a sedimentary rock sample is controlled by the lithology of the provenance, weathering regime, depositional environment (e.g., sorting), and diagenesis. For the palaeoclimate analysis we must keep in mind that the climate affects only one of the above mentioned controlling factors i.e. the weathering conditions prevailed both in the sedimentary basin and mainly in the provenance (Singer, 1980). 3. Evolutionary stages and major climatic events 3.1. Early Triassic 3.1.1. Siliciclastic–carbonate mixed shelf sedimentation—arid climate with a humid pulse Sea level rise at the Permian/Triassic boundary led to a significant (probably more than 100 km wide) coastal onlap in the area of the TR (Haas et al., 1988; Haas and Budai, 1995). The Late Permian alluvial plain and the evaporitic lagoonal to coastal sabkha deposits became covered by earliest Triassic shallow carbonate ramp and fine siliciclastic ramp facies that was southwestward surrounded by a lagoonal dolomitic facies with some evaporites locally (Köveskál Dolomite Formation, Fig. 2). It means that after the definitely arid Late Permian, the earliest Triassic should have been still rather dry, probably semi-arid. In the early Olenekian this type of sedimentation was changed by an intense siliciclastic input (“Campil event”, Broglio Loriga et al., 1990) widespread along the shelf of the western Tethys. This is manifested itself in the sequence of the TR by the appearance of red sandstone and siltstone (Zánka Member, Fig. 3). This event is generally interpreted as a remarkable climatic change from dry to wet and, coevally, that resulted in enhanced denudation of the uplifted provenance (Broglio Loriga et al., 1990; Budai and Haas, 1997). Shallow lagoonal to peritidal dolomite, locally with anhydrite or gypsum characterises the Smithian/Spathian boundary interval (Hidegkút Dolomite, Fig. 1; Haas et al., 1988) suggesting recurrence of the arid–semi-arid climatic conditions during the middle Olenekian.

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successions is problematic if resedimentation of formerly developed continental weathering crusts cannot be equivocally excluded. Once formed, kaolinite remains stable for a geologically long time-range and, consequently, if the climate turns into less humid or even arid, the kaolinite remains stable and unaltered in the provenance (Thiry, 2000). Inherited origin of the kaolinite in the studied Lower Triassic sedimentary rocks was first suggested by Viczián (1987). His opinion is in accordance with observation of Bidló (1980) on poorly crystalline kaolinite as dominant mineral in red clay beds of the Upper Permian Balatonfelvidék Sandstone. The Upper Permian kaolinite occurrences seem to be rather confusing, since coeval evaporitic lagoonal and coastal sabkha deposits, indicating arid conditions, are known in the NE part of the Transdanubian Range. However, there was a long-lasting subaerial exposure period prior to the Permian sediment accumulation that may provide reasonable explanation. An extensive kaolinitic continental weathering crust could be developed during the Carboniferous– Early Permian continental sedimentation; this kaolinite-rich material may have been redeposited during the Late Permian and Early Triassic under already more arid climatic conditions. A completely different origin can be assumed for explanation of polymineralogical clay mineral assemblage of the siliciclastic Zánka Member (Figs. 2 and 3, Table 1). The predominance of the kaolinite over the relatively high amount of illite and chlorite suggests enhanced weathering and intensive erosion in the continental background. It seems to be very probable that a rapid climatic shift to the more humid conditions is recorded by the marked changes in the lithological properties. The Olenekian silty marl (Csopak Formation, Fig. 2) with carbonate tempestite interlayers was formed in middle to outer ramp setting. The clay mineral assemblage is dominated by illite (1Md illite polytype) and IS with subordinate amount of kaolinite and, in some levels, with minor chlorite (Table 1). This assemblage indicates weak continental hydrolysis suggesting relatively dry conditions in the distal continental source area. Fig. 3. Shallow marine sandstone and bioturbated siltstone layers in the Zánka Formation (lower Olenekian). Core Balatonakali, Balaton Highland.

3.2. Middle Triassic

Concerning the clay mineralogical composition of the Lower Triassic formations, a predominance of mixed-layer illite/smectite (IS) and illite is reported. Significant amount of chlorite was detected in the Alcsútdoboz Formation (Fig. 2, Table 1). High concentration of kaolinite (±chlorite) was pointed out in the Köveskál Formation and also in the Zánka Member (Fig. 2, Table 1; Haas et al., 1988). Moreover, prevalence of kaolinite over the illite–IS assemblage has been described from sections representing the deepest part of the Arács Formation (Fig. 2, Table 1). Because of moderate degree of thermal maturity and diagenetic overprint of the whole Triassic sequence (Viczián, 1987; Viczián and Kovács-Pálffy, 1997; Budai et al., 1999) the high abundance of illitic material in the Lower Triassic rocks can be regarded partly as a manifestation of early diagenetic K-fixation and related illitization process during the semi-arid periods (Weaver, 1989). The high bottom water salinity and ionic strength in the porewater could generate favourable conditions for K-uptake of different expandable minerals, mainly of smectite and/or highly expandable IS (Bailey, 1988; Hutcheon et al., 1998). As a consequence, 1Md IS with a composition close to the pure illite was formed (Viczián, 1987). The well crystalline 2M illite found in each investigated Lower Triassic formations suggests moderate degree of continental hydrolysis and rapid, enhanced physical erosion in the provenance (Weaver, 1989; Fürsich et al., 2005). The occurrence of kaolinite in the dolomitic and evaporate-bearing Köveskál Formation and in the lowermost, dolomite-rich part of the Arács Formation (both Induan in age; Fig. 2, Table 1) seems to be contradicting with the suggested semi-arid climatic scenario. However, the palaeoclimatic interpretation of the kaolinite-rich sedimentary

3.2.1. Early Anisian shallow marine carbonate ramp—arid to semi-arid climate At the beginning of the Anisian a significant change took place in the sedimentation pattern due to the decrease of the terrigenous input. The mixed siliciclastic-carbonate ramp transformed into a shallow marine carbonate ramp during the early Anisian; it is represented by the restricted ramp–lagoon facies of the Aszófő Dolomite (Fig. 2). Due to dissolution of evaporites, it is typified by cellular structure. Bird's-eye and teepee structures, desiccation cracks, and common occurrence of pseudomorphs after gypsum (Fig. 4) indicate dry (arid–semi-arid) climatic conditions (Haas et al., 1988; Budai et al., 1993). In the middle part of the lower Anisian the Aszófő Dolomite passes gradually upward into dark grey limestones, rich in organic material (Iszkahegy Limestone, Fig. 2). In the lower part of the formation, characterised by a laminitic structure, a monospecific ostracode assemblage (Lutkevichinella lata) occurs that indicates hypersaline, oxygen-depleted bottom water (Monostori M., pers. comm., 2004). The laminitic layers progress upward into bioturbated beds with epibenthic biota (Meandrospira dinarica, Costatoria costata, Natiria sp.) suggesting decreasing restriction of the lagoon. The Iszkahegy Formation is overlain by bedded bituminous dolomites of the Megyehegy Formation (Fig. 2) formed in restricted ramp setting probably under dry climatic conditions, as well. The Aszófő and Iszkahegy Formations (Fig. 2) are characterised by a rather uniform clay mineralogical composition with the predominance of illite and IS (Table 1). Occurrence of kaolinite has not been reported yet from these formations. Based on the kaolinite-free clay mineralogical composition and the abundance of 1Md illite polytype (Viczián, 1987; Table 1), possibly aggraded during the early diagenesis (Bailey,

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Table 1 Summary of the published clay mineralogical data of the Triassic sedimentary rocks from the Transdanubian Range (TR). Abbreviations: mm: montmorillonite; ill: illite; IS: mixed-layer illite/smectite; kao: kaolinite; chl: chlorite; sm: smectite. Author

Area

Lithostratigraphy age

Clay mineralogical composition

Notes

Viczián (1987), Haas et al. (1988) Haas et al. (1988)

Vértes S foreland Balaton Highland

ill, IS ≫chl ill, IS >kao

Both 2M and 1Md illite polytypes

Viczián (1987), Haas et al. (1988)

Balaton Highland

kao > ill, IS

Abundant 2M ill polytype

Viczián (1987), Haas et al. (1988)

ill, IS, kao, chl

Well crystalline chl and 2M ill polytype

ill, IS ≫kao, chl

Both 2M and 1Md illite polytypes

ill, IS

Both 2M and 1Md illite polytypes

Viczián (1987)

Balaton Highland, Bakony Balaton Highland, Bakony Balaton Highland, Bakony Bakony

ill, IS

Both 2M and 1Md illite polytypes

Viczián (1987)

Bakony

ill, IS

Both 2M and 1Md illite polytypes

Viczián (1987)

Balaton Highland, Bakony Balaton Highland

Alcsútdoboz Fm Induan Köveskál Fm Induan Arács Fm Induan Zánka Mb Early Olenekian Csopak Fm Late Olenekian Aszófő Fm Lower Anisian Iszkahegy Fm Lower Anisian Megyehegy Fm Lower Anisian Felsőörs Fm Middle Anisian Tagyon Fm Middle Anisian Vászoly Fm Upper Anisian Buchenstein Fm Anisian/Ladinian Füred Fm Early Julian Veszprém Fm Julian Veszprém Fm Julian Carnian basin facies Veszprém Fm Julian Veszprém Fm Julian

ill, IS >chl

Both 2M and 1Md illite polytypes

kao, ill

From a red palaeosol layer

ill, IS

Neoformed illite and very expandable IS, both volcanogenic in origin Presence of glaucony

Viczián (1987), Haas et al. (1988) Viczián (1987), Haas et al. (1988)

Viczián et al. (1996) Viczián (1987) Viczián (1987)

Balaton Highland, Bakony Bakony

Rostási et al. (2011)

Balaton Highland

Rostási et al. (2011)

Balaton Highland

Rostási et al. (2011)

Zsámbék Basin

Viczián (1987, 1995) Földvári in Góczán et al. (1991)

Bakony Bakony

Budai et al. (2005)

Vértes

Viczián (1987)

Keszthely Mts

Korpás (1980), Viczián (1987)

Bakony, Zala Basin Gerecse, Buda Mts

Nemecz and Varjú (1967), Korpás (1980)

Hauptdolomit Fm Tuvalian/Norian Kössen Fm Rhaetian Dachstein Fm Norian/Rhaetian

ill > sm ill, IS ill, IS, chl, kao mm, ill, IS > kao

Marls are enriched in ill, limestones are enriched in IS chl is absent

ill, IS >kao, chl mm, ill > kao, chl

Both 2M and 1Md illite polytypes

ill > kao and mixed-layer clays (illite/vermiculite, chlorite/smectite, chlorite/vermiculite) kao, ill > IS

Mainly terrigenous in origin, the mixed-layer phases likely derive from alteration of volcanogenic material

ill, IS, sm ≫ kao, chl

Böhmite and gibbsite in a single kao-rich sample

sm ≫ kao

Poorly crystalline sm; böhmite and gibbsite in a single kao-rich sample

1988; Hutcheon et al., 1998), the clay mineral assemblage confirms the assumption of a relatively long dry period prevailed during the whole early Anisian. 3.2.2. Middle Anisian isolated platforms and basins—dry conditions with a short humid episode As a consequence of the middle Anisian extensional tectonics the former carbonate ramps were dissected along normal faults during

Fig. 4. Dolomicrite with calcite pseudomorphs after clusters of gypsum crystals in the Aszófő Dolomite (Lower Anisian). Core Köveskál Kk‐9, Balaton Highland.

the Pelsonian. Asymmetric hemipelagic basins came into existence above the downfaulted blocks, whereas isolated carbonate platforms evolved on the uplifted ones (Budai and Vörös, 1992, 1993, 2006; Vörös et al., 2003). The basin succession (Felsőörs Formation, Fig. 2) consists of bituminous laminites and flaser bedded cherty limestones with rich ammonite and bivalve assemblage (Vörös et al., 2003). On the coeval isolated carbonate platforms (Tagyon Formation, Fig. 2) cyclic successions made up of alternation of shallow subtidal dasycladacean (Physoporella) limestones/dolomites and peritidal beds with laminar and pisolitic calcretes/dolocretes were formed (Figs. 5 and 6) (Budai et al., 1993; Budai and Haas, 1997; Vörös et al., 2003) suggesting semi-arid to arid climate (Wright, 2007). However, a red argillaceous layer containing more than 50% kaolinite (Viczián et al., 1996) was encountered in the upper part of the succession that can be interpreted as a clayey paleosol horizon. This may imply a short humid episode within the Pelsonian. Sea level rise in the late Illyrian led to drowning of the platforms and deposition of pelagic carbonates after a cc. 2 Ma long gap (Budai and Haas, 1997). 3.2.3. Latest Anisian and Ladinian platforms and basins—dry conditions with a volcanism-related wetter episode Detailed palaeontological studies of ammonite (Vörös, 1998, 2002) and ostracode assemblages (Monostori M. pers. comm., 2004) prove that the basins of the Balaton Highland area became deeper and deeper from the Illyrian to the late Ladinian (Budai et al., 2001;

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(Budai and Vörös, 2006). In the cyclic internal platform succession of the Budaörs Dolomite the Diplopora-bearing subtidal beds are usually capped by stromatolites with desiccation features (Fig. 7) and supratidal calcretes/dolocretes. The carbonate paleosols and the pervasive tidal-flat dolomitisation suggest semi-arid climate during the Ladinian. 3.3. Late Triassic

Fig. 5. Pisolitic dolocrete with root-related pores in the Tagyon Formation (Pelsonian). Core Dörgicse Drt‐1, Balaton Highland.

Budai and Vörös, 2006). Due to the late Illyrian volcanic activity the pelagic carbonate sedimentation was accompanied with deposition of rhyolitic and andesitic volcanic tuffs (Vászoly Formation, Fig. 2). In a small area, NE to the Balaton Highland, sandstone and conglomerate, derived from erosion of basic and intermediate volcanites occur (Inota Formation, Fig. 2) that is rich in plant fragments. These beds may have been deposited under relatively humid conditions that were probably related to the intense volcanic activity. According to observation of Viczián (1987), the clay mineralogical composition of the Vászoly Formation is dominated by illite and highly expandable IS. XRD character of the illite is very similar to that of the so-called ‘Füzérradvány-type’ illite which was described from volcanoclastic beds (Nemecz and Varjú, 1970). The Ladinian basin succession is made up by bedded nodular limestones (Buchenstein Formation, Fig. 2) showing lateral transition to the NE with the platform carbonates (Budaörs Dolomite, Fig. 2)

3.3.1. Julian basins and isolated platforms—a humid period At the Ladinian/Carnian boundary a characteristic pelagic limestone sequence developed (Füred Limestone, Fig. 2) which is interpreted as a product of a highstand progradation episode of the Budaörs Platform (Budai and Haas, 1997; Budai and Vörös, 2006). The upper part of the earliest Julian Füred Limestone is composed of alternating limestone and thin marl beds in many sections which indicates an increase in fine siliciclastic input. However, based on restricted clay mineralogical data, these marl layers contain abundant illite and IS but kaolinite is missing (Rostási et al., 2011). Since kaolinite is usually considered as a mineralogical indicator of enhanced continental hydrolysis, this clay mineral assemblage cannot be regarded as an evidence for increased humidity. Upsection, in the higher part of the Julian a drastic change in the dominant lithology can be observed; the previously mentioned pelagic limestone–marl alternation is overlain by a thick (up to 800 m) succession composed of fine-grained, mixed carbonate–siliciclastic sediments (Veszprém Marl, Fig. 2). The formation is subdivided into two marl-dominated members. They are separated by a pelagic nodular limestone horizon that is progresses into a coarser-grained lithoclastic and bioclastic facies towards the neighbouring platforms; it is a highstand wedge of late Julian age (Budai and Haas, 1997; Haas and Budai, 1999). According to Rostási et al. (2011) the marls of the Veszprém Formation are characterised by a polymineralogical clay mineral suite; large amounts of illite, chlorite and IS, associated with kaolinite indicate intense weathering and strong erosion of probably high-relief areas due to the humid climatic conditions. The IS may have been formed by burial illitization from a smectitic material that possibly derived partially from altered volcanic material and transported from a distal source. Rostási et al. (2011) also observed that the limestone intervals of the Veszprém Formation are enriched while the marls are poor in IS, suggesting a relation between the fine siliciclastic input and the sea level changes. 3.3.2. Final stage of basin filling in the early Tuvalian—alternating arid and humid conditions In the area of the Balaton Highland the Veszprém Marl is overlain by the approximately 100 m thick Sándorhegy Formation (Fig. 2) that

Fig. 6. Millimetre-sized vadose pisolits (lower part) and laminites with a small tepee structure (upper part) in the Tagyon Dolomite (Pelsonian). Szentkirályszabadja, Balaton Highland.

Fig. 7. Stromatolite with fenestral pores (desiccation pores) in the peritidal facies of the Budaörs Dolomite (Ladinian). Budaörs, Buda Mts.

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is made up of alternation of limestone and marl intervals. This formation represents the final stage of the infilling of the Carnian basins; it is unconformably overlain by the Hauptdolomit. There is a continuous transition from the Veszprém Marl to the lower member of the Sándorhegy Formation. The ostracode fauna of this calcareous marl interval indicate normal salinity shallow-marine conditions with predominance of Bairdia (Monostori, 1994). The transitional beds are followed by black bituminous laminites with dolomite interbeds (Fig. 8). Imprints of millimetre to centimetresized gypsum crystals were encountered on the surface of some laminae (Fig. 9); the vugs in the dolomite beds are probably formed via dissolution of evaporites (Nagy, 1999). Very limited clay mineralogical data were obtained from this facies. According to Rostási (2011) the predominance of illitic material with minor kaolinite and IS is characteristic. The ostracode fauna is of low-diversity. In some layers the species Simeonella brotzenorum nostorica is dominant or even monospecific indicating hypersaline environment (Monostori, 1994). Appearance of the bituminous laminite succession above the Veszprém Marl was interpreted as a consequence of a sea level drop which resulted in the restriction of the previously open circulation of the relatively shallow basin (Nagy, 1999). However, intense evaporation was also needed for the establishment of the hypersaline bottom water that implies a definite climatic change from warm and humid to hot and arid in the late Julian. The next, approx. 20 m thick marl interval contains a normal salinity-ostracode assemblage (Monostori, 1994). It is overlain by shallow-marine peloidal, bioclastic, oolitic-oncoidal limestone with sublitoral foraminifera and ostracode fauna and Megalodonts, early Tuvalian in age (Monostori, 1994; Góczán and Oravecz-Scheffer, 1996; Nagy, 1999). Amber grains were encountered in the basal part of this member (Budai et al., 1999; Csillag and Földvári, 2005). Then there is another cc. 10 m thick marl horizon which is followed by thickbedded limestone with crinoids, and brachiopods. The upper boundary of the formation is an uneven erosion surface which is covered by a red argillaceous bed with scattered lithoclasts. It is probably indicates a sea level drop and subaerial exposure prior to the onset of the Dachstein platform evolution (Budai and Haas, 1997). These parts of the Sándorhegy Formation were deposited under normal-salinity shallow-marine conditions. Enhanced terrigenous input led to deposition of the marl intervals which probably indicate more humid climatic episodes. Amber droplets can be considered as indicators of the humid climate, as well (Gianolla et al., 1998b; Roghi et al., 2006). 3.3.3. Platfom evolution with pervasive dolomitisation in the late Tuvalian to early Norian—seasonally arid climate By the late Tuvalian the Carnian basin of the Balaton Highland was filled up by the Veszprém and Sándorhegy Formations. Upfilling of

Fig. 8. Bituminous laminite of the lower member of the Sándorhegy Formation (uppermost Julian). Pencil as scale is 12 cm in length. Csopak, Balaton Highland.

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the Zsámbék Basin in the foreland of Gerecse Mts (Fig. 2) has been completed also by the latest Carnian. In contrast other intraplatform basins, i.e. the Hármashatárhegy Basin in the Buda Mts. and the Csővár Basin in the area east to the Danube, which came into existence also in the early Carnian, survived for a long time; the Csővár Basin remained open in the earliest Jurassic (Haas, 2002). As a result of the upfilling of the larger basins and coeval extension of the platforms an extremely levelled topography established over a predominant part of the area of the TR giving rise to the development of the huge Dachstein platform. In the wide internal platform belt the lower part of the platform carbonates (uppermost Carnian to lower Norian) was subjected to pervasive dolomitisation. This unit was defined as Haupdolomite (Fig. 2) that is made up of metre-scale cycles (Lofer cycles). The typically megalodont- and foraminifera-bearing subtidal beds are overlain by stromatolites and/or dolocretes (Fig. 10a,b). The dolomitisation occurred in the interior of the platform, in tidal-flat setting during the subaerial exposure episodes of the high-frequency cycles. The dolomitised subtidal beds are low in Fe2+ and Mn2+ and have the heaviest δ 18O. This indicates evaporative, oxidative brines sourced from supratidal flats as dolomitising fluid (Balog et al., 1999). The intense and laterally extended dolomitisation indicates a semi-arid, hot subtropical seasonal setting that may reflect megamonsoonal climate (Balog et al., 1999). Lack of dolomitisation in the most external parts of the platform can be explained by the practically continuous subtidal setting of this belt.

3.3.4. Reduction of the early dolomitisation in the middle to late Norian—gradually increasing humidity During the middle to late Norian the general sedimentation pattern of the platform development did not changed significantly but the extension and intensity of dolomitisation decreased. The pervasive dolomitisation ended earlier in the northeastern part of the TR which was located closer to the offshore margin of the platform-system (Fig. 2). Moreover, a several hundred metre thick transitional unit occurs between the completely dolomitised and the undolomitised parts of the platform that is characterised by partial and selective dolomitisation and alternation of dolomitised and undolomitised beds or bedsets. The transitional interval is also characterised by the appearance of reddish or greenish calcareous-argillaceous (usually reworked) paleosol and overlying stromatolite layer at the base of the Lofer cycles (Haas, 2004). In the partially dolomitised successions the lower and the uppermost part of the cycles were affected by dolomitisation, as a rule. The dolomitisation probably occurred during the subaerial exposure periods in the few metre thick loose carbonate mud which was deposited during the previous cycle. At the surface decimetre-thick dolocrete crust was formed via percolation of evaporating seawater whereas partial dolomitisation of the basal part of the cycles may have been caused by reflux dolomitisation of the unconsolidated lime mud (Haas and Demény, 2002). The difference in the intensity and processes of dolomitisation of the Hauptdolomit and the transitional unit may be attributed to a shift in the climate from semi-arid to semi-humid during the middle to late Norian. However, enlargement of the permanently inundated external platform belt may have also contributed to the decreasing extension of dolomitisation. By the late Norian the pervasive dolomitisation was restricted to the SW segment of the TR. In the wide central segment undolomitised cyclic platform limestones were formed (Dachstein Limestone, Fig. 2), whereas the NE sector was still characterised by the accretions of the predominantly subtidal oncoidal limestone facies. Cessation of the early dolomitisation over a predominant part of the TR together with appearance of microkarstic features at the base of the Lofer cycles and common occurrence of the calcareous–clayey paleosol horizons (Figs. 11 and 12) suggest the continuation of the trend of increasing humidity (Haas, 2004).

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Fig. 9. Vugs after dissolved gypsum crystals in the lower member of the Sándorhegy Formation. Csopak, Balaton Highland.

3.3.5. Fine terrigenous sedimentation in the Kössen Basin in the latest Norian to Rhaetian—humid period At the end of the middle Norian, probably in connection with the incipient opening of the Penninic Ocean, a new extensional basin began forming in the SW part of the TR (Haas, 2002). It is reflected in the appearance of platy, locally cherty dolomite of subtidal restricted basin facies (Rezi Dolomite, Fig. 1) above the peritidal– lagoonal Hauptdolomit. In the uppermost Norian a significant change is visible in the lithofacies, the dolomite is overlain by dark grey to black clayey marl (Fig. 13) with organic-rich (alginite) deposits in the basal part of the section (Kössen Formation, Fig. 1). Mollusc coquina beds, intrabreccia horizons, and slump structure characterise the basal transitional interval. Interfingering of the basin facies (Kössen Formation) and the coeval

platform facies (Dachstein Limestone) was also pointed out (Haas, 2002). The abrupt change in the lithology probably reflects the onset of a humid phase which resulted in increased runoff, enhanced erosion, terrigenous influx, and increased nutrient supply. The clay mineralogical composition of the Kössen Formation shows a rather complex pattern: most of the examined borehole samples taken from the Zala Basin and the Bakony Mts., respectively (Fig. 1) contain abundant illite, IS and smectite with minor chlorite and kaolinite (Viczián, 1987) (Table 1). The illite and IS-dominated clay mineral assemblage imply at least periodically dry climate on the provenance. Massive accumulation of the freshwater planktonic green algae Botryococcus in several horizons in the Kössen Formation (Venkatachala and Góczán, 1964) appears to confirm the interpretation of the enhanced humidity; a stratified water column with fresh- to brackish-water upper layer and anoxic bottom conditions can be supposed.

Fig. 10. (a) Domal stromatolite in the Hauptdolomit (lower Norian); (b) the fenestral pores are filled by calcite and/or anhydrite. Csákánykő, Vértes Mts.

Fig. 11. Karstic pocket, filled with reddish paleosol at the base of a Lofer cycle within the Dachstein Limestone (upper Norian). Core Porva Po–89, Northern Bakony Mts.

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Fig. 12. Reworked paleosol clast consists of tiny globular grains in the supratidal facies of a Lofer cycle. Scale is 0.5 cm in length. Core Porva Po–89, 149.6 m.

Prasinophytes, brackish to freshwater green algae were detected in the uppermost Norian to Rhaetian calcareous marl and limestone basin facies (Mátyáshegy Formation) in the Buda Hills (Haas et al., 2000). Prasinophytes of the genera of Tasmanites, Cymatiosphaera and Pterospermella were also encountered in the Rhaetian (inclusively the T–J boundary interval) cherty limestone of distal slope and basin facies (Csővár Formation) in Csővár (Góczán, 1997; Götz et al., 2009; Haas et al., 2010). Occurrence of these fossils suggests stratified water

Fig. 13. Laminated claymarl in the Kössen Formation (lower Rhaetian). Core Rezi Rzt–1, Keszthely Mts.

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column and, accordingly, increased runoff probably from ambient islands into these basins. On the other hand, abundant Corollina meyeriana pollen found in the Kössen Formation (Venkatachala and Góczán., 1964) and also in the lowermost Rhaetian part of the Csővár Formation (Góczán, 1997) indicates warm and dry (semi-arid) climatic conditions on the continental source areas (Vakhrameev, 1981; Bonis et al., 2010). This interpretation appears to be in harmony with that based on the clay minerals and it can be explained by the alternation of dry and wet seasons under the influence of the mega-monsoon climate. As a consequence of the establishment of the Kössen Basin the peri-continental Dachstein platform became an isolated platform (Mandl, 2000; Haas, 2002). However, the platform evolution continued during the Rhaetian. As to the basic characteristics there is no significant difference between the Norian and the Rhaetian Lofer cycles, although the peritidal members are usually thinner and the cycles are commonly truncated in the Rhaetian successions (Haas, 2004). According to detailed studies of an upper Rhaetian Dachstein Limestone succession in the Gerecse Mts., the cycles are bounded by microkarstic disconformity surfaces which are covered by clayey paleosol, calcrete, clayey calcrete or composite calcrete consisting of alternation of clayey and calcareous horizons. Interpretation of these paleosol layers is not straightforward. The predominance of calcretes suggest semi-arid climate; the fluctuating clay contents can be interpreted as the result of rainy periods led to episodic deposition of airborne dust (Mindszenty and Deák, 1999). The sporadic data from the Dachstein Limestone report kaolinite-rich clay mineralogical composition with abundant poorly crystalline smectite, böhmite and gibbsite (Korpás, 1980). This assemblage suggests humid climatic conditions that must have prevailed at least episodically. 4. Discussion In the Triassic the area of Central Europe was located between 20 and 35° North (Fig. 14). Accordingly subtropical trade winds may have dominated the air-mass circulation that should have resulted in low precipitation (Feist-Burkhardt et al., 2008). However, the sedimentary records indicate more humid conditions in certain periods

Fig. 14. Palaeogeograhic map of the western Neotethys during the Late Triassic (modified after Szulc, in Feist-Burkhardt et al., 2008). Abbreviations: CABM: Central, Armorican, Brabant and London Massif; D (SA): Dolomites (Southern Alps); FL: Fennoscandian Land; GB: Germanic Basin; IC: Inner Carpathians; M: Mecsek; NCA: Northern Calcareous Alps; NT: Neotethys; PT: Palaeotethys; RH: Rhodopes; TC: Transcaucasus; TR: Transdanubian Range; VB: Vindelician–Bohemian Massif.

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that can be attributed to the influence of a strong global monsoonal system developed due to accretion of the Pangea supercontinent and the equatorial setting of the Tethys realm. By the Triassic all continents united in the Pangea that was surrounded by the Panthalassa Ocean. Contemporaneously behind the subducting Palaeotethys, a new ocean branch, the Neotethys began opening from east to west. Accordingly the deep oceanic Panthalassa embayment, i.e. the Tethys realm survived in the equatorial zone and it was surrounded from three sides by the Pangea supercontinent. This peculiar setting resulted in the creation of a very intense monsoon circulation (“mega-monsoon circulation”— Parrish and Curtis, 1982; Parrish, 1993; Kutzbach, 1994). It was manifested itself in abundant but seasonal rainfall, concentrated during the summer in the northern hemisphere in western part of Pangea (North America) and relatively dry equatorial belt in its eastern part facing the western Tethys (Parrish, 1993). In the Jurassic further widening of the Tethys and onset of the opening of the Atlantic Ocean led to disintegration of Pangea and cessation of the monsoon system. In the Triassic the TR was a segment of the western Tethys margin that became the passive margin of the newly formed Neotethys from the Middle Triassic. It was located in the subtropical convergence zone between the South Alpine and the Upper Austroalpine domains (Haas et al., 1995). The area of the Mecsek Zone that is the most external belt of the later Tisza Microplate was situated in the proximity of the Variscan range of the European plate facing to the Tethys (Török, 1998; Szulc, 2000) whereas the Germanic Basin was an intracontinental basin system characterised by terrestrial and shallow marine deposition (Feist-Burkhardt et al., 2008). Interpretations on the Triassic climate of these regions are compared to that of the TR in this paragraph. The palaeogeographic setting of the domains compared is shown on Fig. 14. The chart on Fig. 15 presents the main

climatic stages of these domains. Since the prominent climatic changes are mostly expressed in the succession of the wet and dry periods, these climate components are displayed on the chart.

4.1. Early Triassic The Early Triassic succession of the Germanic Basin is characterised by fluvial deposits (Lower and Middle Buntsandstein) suggesting a well-developed braided river network and scarcity of evaporites (Feist-Burkhardt et al., 2008). Similar fluvial deposits occur in the Mecsek and Villány–Bihor Zone in the Tisza Megaunit and the Bavaric Unit of the Northern Calcareous Alps (NCA) representing the European Tethys margin (Bleahu et al., 1994; Haas et al., 1995; Mandl, 2000). These sedimentological characteristics indicate substantial rainfall during winter seasons probably as a result of the monsoon circulation (Kutzbach and Gallimore, 1989). It means a significant climate change after the arid Late Permian conditions in the Germanic Basin (Zechstein) and in the area of the Bavaric Untit (Haselgebirge) as well; however, no substantial change occurred in the area of the Tisza Megaunit. More varied climatic conditions can be reconstructed for the domain of the TR and the Dolomites. According to detailed comparative studies (Broglio Loriga et al., 1990) the highly similar coeval facies pattern reflects roughly synchronous sea level fluctuations and climatic changes. The arid Late Permian was followed by probably semi-arid climate in the Induan. There was a marked humid period in the early Olenekian in both areas which was manifested itself in strong terrigenous input (“Campil event”). The semi-arid conditions resumed in the middle part of the Olenekian.

Fig. 15. Chronostratigraphic chart of the Triassic showing the main climatic stages of the compared areas. Abbreviations: P: Permian; J: Jurassic; OLENEK.: Olenekian; a: arid; sa: semi-arid; sh: semi-humid; h: humid.

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4.2. Early Anisian In the fluvial sandstone succession of the Upper Buntsandtein in the Germanic Basin calcretes are replaced by aridisols in the Rötton Formation. Similar facies characterise the lower Anisian of the Mecsek Mts. Cellular dolomites with evaporites are widespread in the area of the NCA (Reichenhall beds), in Lombardy (Carniola di Bovegno), in the Dolomites (Lower Serla Formation) (Gianolla and Jacquin, 1998; Gianolla et al., 1998a) and in the TR (Aszófő Dolomite), as well. It means that the semi-arid conditions were changed by arid climate in the earliest Anisian not only in the epicontinental European basins but all around the western Tethys, too. This phenomenon was attributed to the decrease of monsoonal effect (Feist-Burkhardt et al., 2008). In the TR there is no evidence for a Bithynian humid episode that caused karstification on the Mt. Rite platform in the Dolomites (De Zanche et al., 1993; Stefani et al., 2010). 4.3. Middle Anisian–Ladinian In the Germanic Basin, and also on the Mecsek ramp, the Pelsonian (Lower Muschelkalk) is typified by shallow marine carbonates under influence of heavy subtropical storms (Aigner, 1985; Török, 1993; Jaglarz and Szulc, 2003). A Bithynian–Pelsonian humid pulse was identified in the Dolomites (Kustatscher et al., 2010; Stefani et al., 2010). Abundance of plant remnants typifies this interval in the Dont Formation of basin facies in the Dolomite. Plant remnants are also common in the corresponding Felsőörs Formation in the TR. However, calcrete layers in the Pelsonian platform carbonates of the Balaton Highland suggest semi-arid climate in this region. Arid to semi-arid conditions prevailed in the Germanic Basin in the Illyrian (Middle Muschelkalk) when evaporites (sulphates and halite) were formed. After a brief humid episode in the early Ladinian (Lower Keuper) in the younger part of the Ladinian and in the earliest Carnian arid conditions prevailed (Lower Gipskeuper) (Hagdorn and Nitsch, 2009). The Mecsek area was probably much less dry (semi-arid to semi-humid) during the middle Anisian to early Ladinian (Török, 1993: Viczián, 1995) although rauhwacke horizons in Illyrian dolomites may indicate an arid episode; the upper Ladinan is missing here. In the Dolomites the supratidal facies of the carbonate platform successions are characterised by carbonate paleosols and dolomite crusts implying semi-arid conditions. Along with calcisols large tepee structures occur in the uppermost Anisian–lowermost Ladinian platform succession of the Latemar (Stefani et al., 2010). Calcretes are also common in the supratidal facies in early Illyrian platform carbonates (Tagyon Formation) in the TR (Budai and Vörös, 2006). Common occurrence of calcretes and pervasive tidal flat dolomitisation of the Ladinian to lowermost Carnian Budaörs Dolomite suggest semi-arid conditions for this interval. 4.4. Carnian In the Germanic Basin the evaporite formation (Gipskeuper) was interrupted by deposition of coarse-grained fluvial sediments in the middle part of the Carnian (Schilfsandstein, Arden Sandstone) suggesting a striking change in the climate from arid to definitely humid (Schröder, 1977; Simms et al., 1994; Kozur and Bachmann, 2010). A similar trend is visible in the Mecsek area, that is manifested itself in the appearance of brackish, lacustrine and fluvial deposits. Intense terrigenous input characterises the mid-Carnian also in the NCA (Raibl beds, Lunz Formation) and in the Dolomites (Cassian Formation) as well, where it caused demise of the rimmed carbonate platforms in many places. This phenomenon is generally interpreted as a fingerprint of a rapid climatic shift from arid to humid conditions (“Carnian Pluvial Event”) (Simms and Ruffell, 1989; Gianolla et al., 1998a, 1998b; Keim et al., 2001; Ruffell et al., 2002; Rigo et al., 2007). In the basins of the TR a significant lithological change is visible in the lowermost Carnian. Due to the enhanced terrigenous influx

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the pelagic carbonates (Füred Limestone) progressed into clayey rocks (Veszprém Marl) in the early part of the Julian, indicating the onset of a wet period that may correspond with the “Carnian Pluvial Event”. However, this change took place earlier than that in the Dolomites (Gianolla et al., 1998a, 1998b; Roghi et al., 2010; Rostási et al., 2011) and it was interrupted by a dry episode in the latest Julian. 4.5. Latest Carnian to late Norian In the Germanic Basin the late Carnian is represented by evaporitic playa facies in the central part of the basin and mostly alluvial sandstones in marginal settings (Hagdorn and Nitsch, 2009), implying arid to semi-arid climate. In the Norian fluvial sandstone and playa mudstone facies alternate (Lövenstein Formation); the cyclic alternation may reflect periodical changes of semi-humid and semi-arid conditions (Hornung, 1999). In the Mecsek unit the Upper Triassic is represented by fluvial siliciclastic deposits. The Carnian and the Rhaetian are proved by sporomorphs but there is no evidence for any Norian record; it is probably missing. In the realm of the Neotethys margin a huge carbonate platform-system began forming in the latest Carnian in the area of the NCA, Southern Alps and also in the TR. The very wide internal platform was subjected to pervasive tidal flat dolomitisation during latest Carnian to early Norian interval indicating semi-arid climate (Iannace and Frisia, 1993; Balog et al., 1999; Haas, 2004). In the central part of the TR a gradual change took place in the dolomitisation pattern in the middle part of the Norian: the total dolomitisation was changed to partial and selective dolomitisation (Haas and Demény, 2002; Haas and Budai, 2011). Appearance of palaeokarstic features that was accompanied by humid paleosol horizons also suggests a gradual climatic change; a trend of increasing humidity. A similar trend was reported in the dolomitisation pattern for the NCA (Tirolicum) that is manifested in the gradually increasing extension of the Dachstein Limestone in the internal belt of the outer platform (Mandl, 2000). Thus a significant difference may have been existed in the timing of the cessation of pervasive dolomitisation in the internal platform in the previously mentioned units that can be explained by a shift in the climatic change related to the differences in the palaeogeographic setting of the different units. 4.6. Rhaetian In the Germanic Basin a marked change in the lithological feature occurs within the Rhaetian Stage. The topmost part of the Middle Keuper consists of red to purple claystones with dolocrete and calcrete nodules (Hagdorn and Nitsch, 2009). The playa facies indicates arid condition for the early Rhaetian. The Upper Keuper is represented by freshwater claystones, plant-rich and coal-bearing paralic sediments, brackish-water and marine claystones, and sandstones which imply humid climate during the late Rhaetian. Onset of the accumulation of a thick coal-bearing succession in the Rhaetian, constraints similar conditions for the area of the Mecsek Mts. In the area of the western Tethys a marked change, reflecting enhanced humidity, took place close to the Norian–Rhaetian boundary. In the basins the freshwater input is evidenced by the appearance of chlorococcale algae (Botryococcus) in the Kössen Formation of the Austroalpine units (Berra and Cirilli, 1997) and also in the TR (Venkatachala and Góczán, 1964) and the algae Pediastrum in the Riva di Solto Shale in the Southern Alps (Buratti et al., 2000). As far as the platforms are concerned, in the area of the NCA and in the TR, as the result of the gradually increased humidity, the pervasive tidal-flat dolomitisation came into an end by the late Norian in the internal platform. In contrast, in the Southern Alps cessation of the pervasive early dolomitization took place only as a result of the marked end-Norian climate change. It is reflected in the appearance of polycyclic paleosols in the Dolomites (Sella Massif) overlain by the shallow-marine Dachstein Limestone (Berra et al., 2010). Paleosols on the top of the Dolomia

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Principale suggest subtropical setting characterised by alternating dry and wet seasons (Retallack, 2001).

authors thank Finn Surlyk and two anonymous reviewers for their constructive comments.

5. Conclusions

References

1. Reconstructed Triassic climate evolution of the TR can be fitted well into that of the European–western Tethyan region. Along with the palaeogeographic setting of this realm it was mostly controlled by the mega-monsoon system related to the development of the Tethys Ocean. 2. As a consequence of the global climatic conditions and its geographic setting, warm to hot temperature prevailed in the area of the TR during the whole Triassic. However, there were significant changes in the precipitation pattern from dry to wet conditions in connection with the intensity of the monsoon effect and the actual setting of this area within the monsoon system. 3. In the TR and also in the palaeogeographically neighbouring South Alpine and Austoalpine domains the Late Permian arid climate was followed by a mostly semi-arid one in the Early Triassic that was briefly interrupted by the “Campil Pluvial Event”. In the Germanic Basin after the extremely arid Zechstein era, the increasing humidity was even more pronounced whereas in the Mecsek unit of the Tisza Megaunit where the Late Permian was rather wet no significant change occurred in the Early Triassic. 4. Akin to that in the South Alpine domain, the Middle Triassic was predominantly semi-arid in the TR, but the two humid episodes (Bithynian–Pelsonian; Ladinian–Carnian) pointed out in the Dolomites could not be unambiguously recognised in the TR. After an arid episode in the early Anisian the Anisian climate of the Mecsek area did not differed remarkably from that of the TR. The Germanic Basin was generally rather dry (arid to semi-arid) during the whole Middle Triassic. 5. For the Carnian a long wet interval interrupted by a short dry episode was interpreted in the TR. A humid episode was also recognised in the Dolomites (“Carnian Pluvial Event”) but it was probably shorter just like in the area of the NCA. Wet climate prevailed also in the Mecsek area probably from the earliest Carnian. In the Germanic basin the predominantly arid conditions were interrupted by a humid episode in the middle part of the Carnian. 6. A marked climatic change took place in the TR in the latest Carnian when the humid climate was changed to semi-arid conditions. Until the middle part of the Norian semi-arid conditions prevailed also in the South Alpine and Austroalpine domains. Then in the area of the TR and probably also in the NCA a gradual increase of humidity may have taken place during the middle to late Norian while the semi-arid conditions did not change in the South Alpine domain. Arid climate characterised the Germanic Basin during the whole Norian. 7. At the very end of the Norian there was a marked change in the TR that led to enhanced humidity but with a definite seasonality i.e. alternation of dry and wet seasons. In the Southern Alps a similar change took place but it was more drastic and abrupt because it was not preceded by an interval of the gradually increasing humidity. The Rhaetian was characterised by wet climate also in the Mecsek area whereas in the Germanic Basin the humid climate became prevailing only in the late Rhaetian. Acknowledgment This study was supported by the Hungarian Research Fund 68224 (T. Budai) and 81296 (J. Haas); by the Bolyai Research Scholarship of the Hungarian Academy of Sciences (B. Raucsik) and by the ‘Developing Competitiveness of Universities in the South Transdanubian Region (SROP-4.2.1.B-10/2/KONV-2010-0002)’ project (B. Raucsik). The

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