Mineralia Slovaca, Web ISSN 1338-3523, ISSN 0369-2086 51 (2019), 31 – 60, © Authors 2019. CC BY 4.0

Outline of the geology of (W. Carpathians)

JOZEF HÓK1, ONDREJ PELECH2, FRANTIŠEK TEŤÁK2, ZOLTÁN NÉMETH2 and ALEXANDER NAGY2

1Comenius University in Bratislava, Department of Geology and Paleontology, Faculty of Natural Sciences, Ilkovičova 6, SK-842 15 Bratislava, Slovakia; [email protected] 2 State Geological Institute of Dionýz Štúr, Mlynská dolina 1, SK-817 04 Bratislava, Slovakia

Abstract: The paper provides an overview of the main Alpine and earlier Hercynian (Variscan) tectonic units, as well as superimposed “post- stacking” formations. Simplified localization maps of mentioned tectonic units, lithostratigraphic tables with emphasis on typical lithostratigraphic members and models of the assumed paleogeographical positions are included. References have been selected with an intention to provide more detailed information on a particular issue, resp. tectonic unit. Paper follows dual division of principal tecto- nic zones into the External (EWECA) and Internal Western Carpathians (IWECA), which reflects different rock composition as well as different time and mechanisms of their structuralization. Key words: Western Carpathians, tectonics, lithostratigraphy, thrust belt

• Dual division into External (EWECA) and Internal Western Carpatians (IWECA) is followed after ear- lier works • The main Alpine tectonic units in Slovakia are descri- bed in the order: EWECA - Outer Group of (Krosno and Magura nappe systems and Oravicum), IWECA - Lower Group of Nappes (Vahicum and Tat- ricum), Middle Group of Nappes (Veporicum, Fatri-

Highlights cum and Hronicum), Upper Group of Nappes (Ge- mericum, Turnaicum, Meliaticum and Silicicum), as Graphical abstract well as the Zemplinicum with an exceptional status. • The Upper Cretaceous‒Cenozoic sequences are un- conformably and transgressively overlying the nappe structures.

Introduction Principal tectonic units of the Western Carpathians – former division based on tectonic belts Information about the geology of Slovakia was published by various authors (e.g. Andrusov, 1968; The territory of Slovakia is formed by the Western Maheľ & Buday, 1968; Maheľ, 1974, 1986; Mišík, 1997a; Carpathians. Only southern regions of Slovakia represent Plašienka et al., 1997; Kováč et al., 2003; Janočko et al., a part of the system, which extends here 2006; McCann, 2008; Bezák et al., 2011; Plašienka, 2018). from the area of . The present day geological Existing geological maps (Biely et al., 1996a, b; Lexa et structure of the W. Carpathians is generally a result of the al., 2000; Bezák et al., 2004, 2008, 2009; Geologická Alpine orogenic stage, having preserved also remnants of mapa Slovenska 1 : 50 000, 2013) mostly lack the relevant earlier Hercynian (Variscan) evolution. description of the geological structure of Slovak territory. A tectonic unit is here considered as the three-dimen- This contribution provides concise information about sional rock body with defined borders, its own (unique) tectonics and lithostratigraphy of the principal Alpine lithostratigraphic, metamorphic and structural content and tectonic units of Slovakia in a comprehensible form to defined tectonic evolution (Fig. 1). Since the second half a foreign reader. of 20th century (Andrusov, 1973), the suffix -icum is used

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Fig. 1. Position of principal Alpine tectonic units and post-nappe formations in the territory of Slovakia (based on Hók et al., 2014). for the names of the Western Carpathian Alpine tectonic in relics, which either were not reworked by the Alpine units. deformation, or the degree of their Alpine overprint still Tectonic units in the frame of the W. Carpathians are allows to decipher older tectonic events. The Hercynian arranged in imbricated structures one above the other, structural arrangement suggests the displacement of rock generally thrust from the south to the north (i.e. having complexes generally from the north to south (or NNW to northern vergency; Fig. 2). The reason is that the Alpine SSE; i.e. south-vergent). It means that Hercynian orogeny orogenetic processes produced the horizontal crustal had generally opposite vergency than that of Alpine one shortening and closed existing sedimentary basins. From (Bezák, 1994; Jacko et al., 1997; Németh, 2002). The main the view of recent W. Carpathians it started in the southern lithotectonic units of the Hercynian (Variscan) tectonic - internal regions and proceeded generally to northern – setting were formed due to the Meso-Hercynian lithospheric external zones of W. Carpathian belt (Plašienka, 2018). collision, which was accompanied with a thickening of the According to timing and deformation mechanisms, crust (380–340 Ma) and intrusion of granitic rocks. Later the orogenic zone of W. Carpathians is divided into Ex- in the Neo-Hercynian stage (340–260 Ma) the compression ternal Western Carpathians (EWECA), containing the was replaced by the extension (probably a post-orogenic Neo-Alpine () nappes and the Internal Western relaxation), representing the second period of intrusions Carpathians (IWECA) with Paleo-Alpine (Cretaceous) of granitic bodies (Broska et al., 2013; Uher et al., 2014). nappe stacking (Fig. 2). The boundary between them is The oldest tectonic events, which for now can be reliably represented by the Klippen Belt zone (Oravicum). attributed to the Hercynian orogeny, took place during In the Alpine structure of the W. Carpathians, products the Early (Mississippian; 360–330 Ma). of the Hercynian (Variscan) orogenic phase are preserved On the contrary, the sediments of Late Carboniferous

32 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians)

Fig. 2. Schematic cross-section showing the main tectonic units of the Western Carpathians in the territory of Slovakia with marked emplacement timing of particular group of nappes and the age of their tectonic individualization (based on Hók et al., 2014). age (Pennsylvanian) represent the termination of the The Flysch Belt of EWECA represents massive accre- Hercynian orogeny in the territory of W. Carpathians. tionary wedge, a nappe stack composed of the Cretaceous The degree of metamorphic transformation during the and mainly the formations in typical “flysch” Hercynian orogeny can be generally considered to be development, with alternating clayey shales and sand- higher (amphibolite-granulite facies) than during the stones, deposited in the deep-water environment by the Alpine tectono-metamorphic processes. gravity flows, mostly of the turbidity currents. The Alpine nappe emplacement in the external zones The (or the Klippen Belt, Oravi- of the W. Carpathians (EWECA) culminated during the cum) represents a narrow and intensively deformed belt. Neo-Alpine phase in , resp. the Miocene. The Name “Klippen Belt” is derived from their characteris- EWECA include the Flysch Belt, consisting of the Kros- tic morphotectonic features – the steep cliffs – so-called no and Magura nappe systems (displaced Cretaceous and klippen, towering above the surrounding soft relief. The Paleogene sediments) as well as the independent Oravic “klippen” are composed of Jurassic and Early Cretaceous (or Klippen Belt) tectonic units, built of sedi- limestones that are more resistant to erosion than the sur- ments (Fig. 3). rounding Upper Cretaceous and Paleogene marlstones and The Carpathian foredeep is situated outside the ter- clayey sediments. ritory of Slovakia (Fig. 3). It consists of autochthonous The principal Paleo-Alpine tectonic units, internally predominantly sandy and clayey sediments of the Neo- (i.e. south) of the tectonic unit of Oravicum, are as follows: gene age, lying on their original basement - the European the Vahicum, Tatricum, Fatricum, Veporicum, Hronicum, Platform (in their northern part) and Gemericum, Bôrka Nappe, Meliaticum, Turnaicum and (northwestern part). Assignment of the external Carpathi- Silicicum. These tectonic units, forming IWECA, are tra- an foredeep sediments into the W. Carpathian structure is ditionally arranged in the higher order zones termed as disputable, because they represent autochthonous sedi- “belts” (the Core mountains Belt, Vepor Belt and Gemer mentary cover of neighbouring basement units. Belt, Fig. 3).

33 Mineralia Slovaca, 51 (2019)

Fig. 3. Division of the Western Carpathians into separate sub-zones and belts (modified after Hók et al., 2001).

The Core mountains Belt represents northernmost units participating in the structure of the Vepor Belt are and the most external tectonic unit of IWECA (Fig. 3). represented by the Hronicum and Silicicum. The Vepor This belt is separated from the south located Vepor Belt by Belt is separated by the Čertovica thrust from the belt of the Čertovica thrust on its southern (internal) margin. The Core mountains, located northwest, and the Margecany- Čertovica thrust is a product of Lower Cretaceous thrusting Lubeník thrust divides it from the Gemer Belt, thrust of Veporicum on Tatricum. The term Core mountains above the Vepor Belt from the south (Fig. 3). (originally Uhlig’s (1903) Kerngebirge) is derived from The Vepor Belt covers large areas of Central Slova- the typical morphotectonic phenomenon, where the kia (Fig. 5) - generally the Veporské vrchy Mts., Stolické central part of the mountain range (core) is formed by vrchy Mts. and the Revúcka vrchovina Highland, eastern the crystalline basement rocks (granites and crystalline part of the Nízke Tatry Mts. (so-called Kráľovoholské Ta- schists) and these are overlain by the Late and try), northeastern part of the Tribeč Mts. (so-called Rázdiel mainly the Mesozoic sedimentary (cover) sequences, and Part), Kozie chrbty Mts., Branisko and Čierna hora Mts. often also directly by the Cenozoic sediments (e.g. in the Malé Karpaty Mts.). Besides Tatricum, tectonic units of Apart from the aforementioned regions, the Vepor Belt, or the Vahicum, Fatricum and Hronicum are involved in the Veporicum, crops out from below the Neogene vol- the geological structure of the Core mountains. The Core canites (traditionally named neovolcanites) in the form mountains belt encompasses the Malé Karpaty Mts., of so-called “islands” or horsts. The largest horsts are the Považský Inovec Mts., Žiar Mts., Strážovské vrchy Mts., Sklené Teplice Horst between the towns of Sklené Tep- Malá Fatra Mts., Veľká Fatra Mts., Tatry Mts., western lice and Vyhne, the Pliešovce Horst exposed directly in part of the Nízke Tatry Mts. (so-called Ďumbierske Tatry the Pliešovce and the Lieskovec Horst east of the Zvolen Mts.) and the western part of the Tribeč Mts. (so-called town. Zobor part; Mazúr & Lukniš, 1986). The Gemer Belt represents the most internal and struc- The largest part of the Vepor Belt is represented by turally highest belt in the Alpine nappe structure of the W. the tectonic unit of Veporicum. Similarly as Tatricum, Carpathians (Fig. 3). It is located in the Volovské vrchy also the Veporicum is composed of Early Paleozoic Mts. and the Slovenský kras Mts. and includes tectonic crystalline basement and Late Paleozoic–Mesozoic units of Gemericum, Bôrka Nappe, Meliaticum, Turnai- sedimentary cover. Besides the Veporicum, other tectonic cum and Silicicum.

34 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians)

New tectonic division of the Western Carpathians – The IWECA Middle group of nappes was combination of tectonic belts and groups of nappes structuralized during the (Cenomanian– ) and is formed by the tectonic units of It is obvious that division of W. Carpathians to External Veporicum, Fatricum and Hronicum. (EWECA) and Internal (IWECA) does not encounter The Veporicum is predominantly composed of crys- any contradiction, because the tectonic individualization talline basement (granitoids, gneisses and mica schists). of External W. Carpathians (EWECA) took place Based on lithostratigraphy of autochthonous Late Paleo- during the Neo-Alpine phase in Neogene, i.e. later zoic and Mesozoic sediments, the Veporicum is divided than that of IWECA (Paleo-Alpine phase; Cretaceous). into Northern and Southern Veporicum, separated by the EWECA includes Krosno and Magura nappe system and Pohorelá thrust (Fig. 2). Oravicum. These units are built of Mesozoic to Paleogene The Fatricum is a tectonic unit of nappe character, sediments, and particularly the Krosno and Magura nappe transferred from the former position on the contact of systems are represented by the “flysch” character deep- the present Veporicum and Tatricum. Synonymously water sediments deposited by the gravity flows (turbidity it is often referred as the Krížna Nappe. It occurs in currents). Aforementioned units represent the Outer allochthonous position in the Core mountains Belt and group of nappes, which is present only in External W. Carpathians (EWECA) (Fig. 2). overlies the Tatricum. Stratigraphic range is very variable, The situation is however more complex internally especially in lower members. It is a result of closing of (south) of the Klippen Belt (Oravicum), where the its former sedimentary basin and related decollement with individualization of IWECA took place earlier - in movement of the Fatricum thrust sheet on its stratigraphic Cretaceous. The vertical division, however, raises members with suitable rheology. Sedimentary sequence the question how to lead the boundary between the usually terminates with the earliest Upper Cretaceous particular belts in a way not split the same tectonic unit (Cenomanian) “flysch”-like sediments (Poruba Fm.). being encompassed in several belts (cf. Andrusov et al., The Hronicum represents, similarly as the Fatricum, 1973; Maheľ, 1983; Mišík et al., 1985; Plašienka, 1999). a stack of partial nappe bodies structuralized during Late The tectonic division based on tectonic stacking of the Cretaceous from the facially subdivided sedimentary main elements of the nappe structure, being separated basin. Synonymously it is designated as the Choč Nappe. (individualized) at different times on subhorizontal It occurs in the Core mountains Belt as well as in the Vepor (usually overthrust) contacts, allows to allocate four main Belt and overlies the Fatricum and Veporicum. Unlike groups of nappes (Outer, Lower, Middle and Upper) with the Fatricum, the original root area of the nappe is not different mutual structural superposition and the age of known, although it is evident that it comes from southerly tectonic individualization (Hók et al., 2014; Fig. 1). The (more internal) paleogeographic zones than the Fatricum. subhorizontal division in this case is dominating over the The Hronicum sedimentary basin was formerly assumed vertical division into belts. between the Vepor Belt and Gemer Belt. Stratigraphic The Lower group of nappes of Internal W. Car- range of Hronicum is from Carboniferous to the Early pathians (IWECA) is represented by the tectonic unit of Cretaceous. The complete sedimentary sequence is Tatricum, composed of crystalline basement rocks and however nowhere preserved. The most typical sequences Late Paleozoic/Mesozoic sedimentary cover, as well as of Hronicum are composed mainly of Triassic carbonates tectonic unit of Vahicum. The Lower group of nappes was (limestones and dolomites). Carboniferous and Permian structuralized in the late Cretaceous to Paleogene (Figs. 1 volcanites and sediments represent very characteristic and 2). lithostratigraphic members of Hronicum, forming thick The Tatricum is generally regarded as the lowermost rock sequence of the Ipoltica Group. and sub-autochthonous unit of the IWECA. In tectonic superposition above Tatricum there are present several The IWECA Upper group of nappes is located allochthonous tectonic units: the lower unit, or nappe, is southernmost or most internal, representing tectonically called Fatricum, the structurally higher unit is represented the highest group of nappes of IWECA. It is composed by Hronicum. Both tectonic units, Fatricum and Hroni- of Paleozoic rock sequences of Gemericum and mostly cum are ranging here from to the Middle group of nappes, Mesozoic complexes of the Bôrka Nappe, Meliaticum, where they belong together with Veporicum. Turnaicum and Silicicum as the Early Cretaceous nappe The Vahicum is hypothetical tectonic and paleogeo- structures (Fig. 2). graphic unit (Maheľ, 1981). The Belice Unit (Plašienka The Gemericum is exposed in a largescale anticlinal et al., 1994) in the Považský Inovec Mts. was considered dome – anticlinorium, which forms the region of Volovské as the main representative of the Vahicum in the present vrchy Mts. (the Spišsko-gemerské rudohorie Mts., resp. surface occurrences. Structural position of the Belice Unit Spiš-Gemer Ore Mts.). It substantially differs from the is, however, in contradiction with previous interpretations other basic W. Carpathian tectonic units by different rock (Pelech et al., 2016). composition, age and metamorphism. Unlike the Tatricum

35 Mineralia Slovaca, 51 (2019) and Veporicum it is composed mainly of the low-grade the north since Early Cretaceous (in Gemer Belt) to the metamorphic rocks with dominating Paleozoic age – the Late Cretaceous (in the Core mountains Belt). Early Paleozoic basement and its mostly Late Paleozoic The Turnaicum represents another nappe unit, cropping sedimentary cover. out from below the Silicicum (Fig. 2) and occurring in the The Bôrka Nappe contains rock sequences of Per- southern part of the Gemer Belt, mainly in the Slovenský mian to Middle Jurassic age. They are characterized by kras Karst plateau. Its Late Carboniferous to Late Triassic higher-grade metamorphic overprint, reaching in Meso- rock sequence bears characteristic metamorphic overprint. zoic members the subduction related high-pressure and It differs from the Silicicum by the occurrence ofthe low-temperature (HP-LT) blueschists facies. The paral- Triassic pelagic carbonate facies, by this way forming the lelization of the protolith of metamorphites with the cover transitional member between Meliaticum and Silicicum sequences of southern Gemericum indicates that they are during the basin evolution. most probably derived from the zone between the Gemeri- The Silicicum, often referred as the Silica nappe, cum and Meliaticum (e.g. Németh, 1996, Fig. 4 ibid.). is structurally the highest tectonic unit of the IWECA The Meliaticum is a tectonic unit of nappe character, Alpine nappe structure. It occurs as a relatively flat known in present day surface only in relics, cropping out lying nappe body in the region of Slovenský kras Mts., from below the nappes of Turnaicum and Silicicum (Fig. Slovenský raj Mts., Galmus Mts. and Muránska planina 2). It represents a tectonic melange of Triassic carbonates, Mts. (Fig. 2). The sedimentary sequence of the Silicicum radiolarites and volcanites, occurring as blocks in the dark ranges from the latest Permian–Early Triassic to the Late and black Jurassic shales and radiolarites. Sedimentary Jurassic (Callovian to Oxfordian). A substantial part of sequences indicate that it represents former zone of oceanic the Silicicum is built by the Middle and Upper Triassic character. During the convergence, the Bôrka Nappe rocks shallow water limestones (e.g. Wetterstein limestones), were subducted and exhumed. Subduction of oceanic often containing abundant fossil remains. crust and the gradual closure of the Meliaticum basin caused the displacement of rock complexes originally Description of the principal tectonic units deposited at the southern margin of this basin (in today’s geographical coordinates) and forming the tectonic units of The External Western Carpathians (EWECA) en- Turnaicum and Silicicum. Decollement and emplacement compass the Flysch Belt and Klippen Belt (Fig. 4). The of the Meliaticum, Turnaicum and Silicicum nappe units sediments of the Carpathian Foredeep represent au- represent the beginning of the shortening of the Internal W. tochthonous Miocene–Pliocene sedimentary cover of the Carpathians. Related thrusting and nappe displacements European Platform as well as Bohemian massif and are maintained its polarity from the south (internal areas) to generally situated below the Krosno nappe system. Re-

Fig. 4. Map of the External Western Carpathian nappes. 36 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians) garding its position, the Carpathian foredeep should not to The Skole Nappe is situated NE in the foreland of be assigned to the Carpathian system. Sub-Silesian Nappe on Polish territory, not reaching the territory of Slovakia. The Sub-Silesian Nappe crops out as Flysch Belt – Krosno and Magura nappe system a thin body on the border of Skole and Silesian nappes. The EWECA are mostly formed by the Cretaceous to Silesian Nappe is found in a limited extent in the northern Paleogene deep-sea “flysch” deposits. Original flysch Kysuce region (Potfaj et al., 2002, 2003), where only basins were bordered by continental crust ridges, which the Godula succession is present. Sandstone-rich Istebna provided a clastic material to the basins. The Flysch Belt Fm., Sub-Menilite Fm. with spherically disintegrating is one of the few zones being continuous across the whole Ciężkowice sandstones, Menilite Fm. and Krosno Fm. are Carpathian arc. typical. EWECA represents a system of rootless nappes am- The Dukla Nappe reaches the NE edge of Slovakia. putated from their former basement and transported to the Its sedimentation area was initially associated with the foreland represented by the European platform and the Magura Basin. Younger deposits have affinity rather with sediments of Carpathian foredeep. the Silesian Nappe. To the west, Dukla Nappe passes into Flysch Belt consists of several nappe systems arranged thin bodies of Grybów and Fore-Magura nappes, which in imbricated style - the internal units are thrust over the underlie the Magura Nappe and crop out in the Smilno external ones. Mostly the Magura nappe system occurs tectonic window. in Slovakia, and represents the southernmost part of the The most characteristic for the Krosno nappe system Flysch Belt. The underlying Krosno nappe system includes are the menilite shales or Menilite Formation, composed the Dukla, Silesian, Skole and other smaller nappes (see of brown claystones with bodies of sandstones and black Fig. 4). The lithostratigraphic units within nappe systems cherts which were formed from diatoms tests during the are shown in Fig. 5. The Krosno nappe system is generally late Eocene to early . Another very characteris- characterized by variegated claystones, the Magura nappe tic lithostratigraphic unit is the Sub-Menilite Formation of system by prevailing sandstones. Eocene age, being composed of variegated (red, green and The sedimentary basins were situated in the area grey) claystones and sandstones. The menilite shales are between the IWECA block and the European Platform. known as the main oil-bearing horizon across the EWE- Similarly, as the area of the Carpathian foredeep, also the CA. Magura Basin was connected to the west with the flysch Magura nappe system foreland of the Eastern (Rhenodanubian Flysch) The Magura nappe system is the largest tectonic unit of and similarly to the north and east to the flysch nappes in the EWECA, and represents the main part of the EWECA present and Ukraine (in the Eastern Carpathians). on the Slovak territory (Cieszkowski, 1992; Lexa et al., The oldest preserved EWECA sediments are represented 2000; Oszczypko et al., 2015; Kaczmarek et al., 2016). by the Upper Jurassic limestones, marls and carbonate The Magura nappe system is divided into the partial tec- flysch. However, it can be assumed that the formation tono-lithofacial units. In ordering from the north (external of future Flysch Belt basins is related to the regional extension period in the area of the W. Carpathians, which units) to south (internal ones) these are the Siary, Rača, took place in the Middle Jurassic (Plašienka, 2018). The Bystrica, Krynica and Biele Karpaty units. Together with former sedimentary area of the EWECA was gradually the Biele Karpaty Unit, which occurs only in the western closed since the end of middle Eocene (the Biele Karpaty part of the zone and has a special status, the Magura nappe Unit) up to the early Miocene (the Krosno nappe system). system forms tectonically the highest part of EWECA. The youngest sediments are represented by the locally Moreover, the Krynica Unit was as well backthrust south- preserved Miocene deposits (Karpatian). ward over the Klippen Belt (Oravicum) in the Orava re- Marginal nappe system gion (Pešková et al., 2012). The outermost (most external) EWECA unit is The rocks of the Magura nappe system have deposited Pouzdřany-Ždánice-Waschberg Nappe, not reaching the in a few hundred kilometers wide Magura Basin having territory of Slovakia (Fig. 4) and representing the 2,000 to 4,000 meters depth. The time, when the Magura allochthonous body (nappe) over the Bohemian Massif Basin started to open, has not been reliably confirmed margin. yet, because the nappe is completely detached from its Krosno nappe system substratum. There is assumed the Upper Jurassic time of its Several tectono-lithofacial nappes (or units) north of opening (Pícha et al., 2006; Hrouda et al., 2009; Golonka the Magura nappe system form the Krosno nappe system. et al., 2013; Oszczypko et al., 2015). Pelagic claystones They are arranged from outer to inner as follows: Skole, and thin-bedded “flysch” deposits (Ropianka Fm. and Sub-Silesian, Silesian and Dukla (Grybów, Fore-Magura) Beloveža Fm.) deposited in the deep-sea environment nappes. Only Silesian and Dukla (Grybów) nappes reach on the bottom formed probably by oceanic or distal the territory of Slovakia (Lexa et al., 2000). continental crust. Along with thin-bedded deposits the red

37 Mineralia Slovaca, 51 (2019) and green (variegated) claystones, mudstones or marls position of the sandstones reflects the nature of the source have deposited especially during the Upper Cretaceous and area (ridges/cordilleras). Its sedimentary structures are lower Eocene (Cebula Fm., Ondrášovec Mb. and Lower determined by the nature of the current transport, global Beloveža Mb.). Sandy fans and lobes penetrated into the temperature and sea-level changes. The Malcov Fm. basin and partly also on the slopes of the basin. Clastic represents the fill of smaller piggy-back sub-basins. The north-vergent thrusting by the end of Oligocene and in turbidity sedimentation dominated since Maastrichtian. early Miocene until Badenian caused the spatial reduction Each fan deposited hundreds of meters of sandstones (less and the origin of the fold and thrust setting. The boundary conglomerates). of the Krosno and Magura nappe systems in the According to petrographic and sedimentological is characterized by the occurrence of Jurassic limestones properties, we can distinguish several major types of (olistoliths, formerly known as the so-called External sandstones in the Magura nappe system: Soláň (Mutne), Klippen Belt). Dozens of lithostratigraphic units have been Szczawina, quartz-carbonate, Riečky, Skawce, glauconitic determined by the combination of mentioned lithotypes and Magura type sandstones. The petrographic com- and lithofacies (Fig. 5).

Fig. 5. Simplified lithostratigraphic scheme of the Flysch Belt in the Slovak territory (modified after Potfaj, 1993; Lexa et al., 2000; Teťák et al., 2016).

38 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians)

Fig. 6. Supposed paleogeographic position of the Oravic and Klippen Belt sensu lato successions during Jurassic period.

Klippen Belt – Oravicum The Czorsztyn succession is characterized by The Klippen Belt represents narrow (max. 15 km wide) generally shallow water sediments. The most typical and more than 600 km long morphotectonic structure on member is represented by the Czorstyn Limestones the boundary between the Internal and External W. Car- (Middle to Late Jurassic) - the red nodular limestones with pathians (Figs. 1 and 4). The Klippen Belt contains the abundant fossils, especially ammonites. Another typical Oravic rock successions as well as successions derived member is a sandy-crinoidal limestone (Middle Jurassic). from the IWECA (Fig. 5). The Czorsztyn sequence occurs in the outer – northern The exceptional tectonic complexity and numerous margin of the Oravicum/Klippen Belt and represents most identified rock successions (Mišík, 1997b) and formations externally located sequence among the Klippen Belt units. (e.g. Birkenmajer, 1977) of the Klippen Belt are related The Kysuca succession is typical by Jurassic to the fact that it suffered multiphase deformation: for the deep-water sediments - the Allgäu Formation, green and first time together with the Internal Western Carpathians red radiolarites and Pieniny Limestone. and for the second time after the Paleogene with the The Czorsztyn and Kysuca successions are typical with Flysch Belt. Structure was additionally complicated by variegated (red, green and grey) marlstones (or calcareous the strike-slip faults longitudinally segmenting its units. claystones) and marly limestones mostly of the Late Creta- The essential segmentation of sedimentary basins of the ceous age. They are known under various local names (e.g. future Klippen Belt, similarly as in the case of other W. Púchov Marls) and often collectively they are referred as Carpathian tectonic units, occurred in the Jurassic. the “Couches Rouges”. The Oravic units were during the Jurrasic situated in The Klape Unit is present in the Považie (Middle Váh the paleogeographical position surrounding the hypotheti- Valley) and Orava regions in the frame of Klippen Belt. cal continental ribbon known as the Czorsztyn ridge (Fig. The most typical is the flysch formation predominantly of 6). The Czorstyn ridge was separated from the European the Late Cretaceous age, containing several characteristic platform by the oceanic domain of the Northern Pennini- members with exotic material (Orlové Sandstone, Sphe- cum or the Magura ocean in the north, and from the Inter- rosiderite Beds, Upohlav Conglomerates). The Klape nal Western Carpathian block by the oceanic domain of the Southern Pennicum or the Vahicum (Plašienka, 2012; sequence is folded together with Klippen Belt main Plašienka & Soták, 2015). According to its different facial sequences (Czorstyn and Kysuca) and in the majority of character, resulting from differing paleogeographic areas, occurrences the strata are in an overturned position. several sedimentary successions were distinguished, incl. The Manín Unit, known only in the Middle Váh the Czorsztyn and Kysuca, as well as the Niedzica/Pruské Valley (name is derived from the Manínska tiesňava and Czertezik successions termed as the Oravicum. Gorge), is most internal sequence of the Klippen Belt. The The most widespread are the Czorsztyn and Kysuca paleogeographic position of the former sedimentary basin (also Kysuca-Pieniny) successions. They are tectonically is problematic and placed on the northern margin of the amputated and displaced from their former substratum, Tatricum, as well as on the northern margin of the Fatricum therefore their sedimentary sequence starts with Lower (i.e. southern edge of Tatricum). The most characteristic Jurassic rocks. part of this Early Jurassic to Middle Cretaceous sequence is

39 Mineralia Slovaca, 51 (2019) the Urgonian Limestone (Manín Fm.) - the organodetritic 6) and considered as an equivalent of the Alpine Pennini- limestone with abundant macrofossils (algae, corals, cum (Maheľ, 1981). Supposed oceanic crust of the Vahi- rudists). With the Manín Unit in the eastern part of the cum is unknown from the surface presence. Some authors Klippen Belt the Haligovce Unit is correlated (Mišík, parallelize Vahicum with occurrences of Upper Cretaceous 1997b). Horné Belice Group (Belice Unit) in the Považský Inovec The Drietoma Unit is a structural element derived Mts. (Plašienka et al., 1994). Substantial part of the Horné from the Fatric nappe system incorporated into the western Belice Group is represented by the Late Cretaceous (Turo- segment of the Klippen Belt. Typical lithostratigraphic nian–Maastrichtian) turbidites (“flysch”), with occurrences members of the Upper Triassic (Norian) ‒ Lower Cretace- of olistoliths of crystalline basement, and Early Triassic ous (Berriasian) Drietoma Unit are the Carpathian Keuper to Upper Cretaceous sediments (Rakús in Ivanička et al., and Allgäu Fm. 2011; Pelech et al., 2016). Similar formations also occur The Internal Western Carpathians (IWECA) in the borehole SBM-1 Soblahov east of Trenčín (Maheľ, encompass following tectonic units, individualized in the 1985), as well as above Tatric sedimentary cover east of Cretaceous: Vahicum, Tatricum, Fatricum, Hronicum, Piešťany (Pelech et al., 2017). The sediments of the Horné Veporicum, Gemericum, Bôrka Nappe, Meliaticum, Belice Group in the Považský Inovec Mts. are therefore of Turnaicum and Silicicum. These units are present in the unclear tectonic affiliation and probably represent a rem- Core mountains Belt, Vepor Belt as well as the Gemer nant of larger sedimentary wedge-top basin adjacent to the Belt (Figs. 1 and 3). In the subhorizontal division of W. IWECA area (Pelech et al., 2016). Carpathians into the separate Alpine groups of nappes, Tatricum the Vahicum and Tatricum represent the Lower Group of Tectonic unit of Tatricum contains Hercynian crystal- Nappes, the Fatricum, Hronicum and Veporicum represent line basement rocks (granitoids, gneisses and mica schists), the Middle Group of Nappes and the Gemericum, Bôrka covered by the Late Paleozoic (rarely Carboniferous, more Nappe, Meliaticum, Turnaicum and Silicicum represent often Permian) and Mesozoic rocks, deposited directly on the Upper Group of Nappes (Fig. 1). the basement. The Lower Group of Nappes The crystalline basement rocks of the Tatricum The rock complexes of the Lower Group of Nappes were formed by the Hercynian magmatic and (Vahicum and Tatricum), crop out mainly in the Core tectono-metamorphic processes. Concerning the Hercynian mountains Belt (Figs. 2 and 7). structure, it is not possible to distinguish between the Vahicum Tatricum and Veporicum crystalline basements, forming The Vahicum is a hypothetical tectonic unit paleogeo- during Hercynian orogeny the uniform stabilized unit, later graphicaly situated in the frontal part of the IWECA (Fig. overlapped by cover sequences. The Hercynian tectonics

Fig. 7. Position of rock complexes of tectonic units of Vahicum and Tatricum of the Lower Group of Nappes (based on Hók et al., 2014).

40 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians) had the opposite polarity (south-vergent) than the Alpine northern slopes of the Ďumbierske Tatry Mts), or they are one – so being thrust generally from the north to south, affected by the contact metamorphism of nearby granitoids the high grade metamorphic rocks were structurally the (i.e. being metamorphosed by the heat rising from the highest and their relics are today found in the northernmost granite magma, e.g. Harmónia Series or Pezinok Group (most external) part of this unit and vice versa – the low in the Malé Karpaty Mts). Other occurrences encompass grade metamorphic rocks are the lowest and their relics are the metasediments in the Bukovecká dolina Valley on preserved in the south (Bezák, 1994). The Alpine north- the southern slopes of the Ďumbierske Tatry Mts. and vergent nappes overprinted the pre-existing structure, occurrences in the Veporicum crystalline basement – making the reconstruction of the original position of the the Jánov grúň Complex, Predná hoľa Complex and the Hercynian tectonic units rather complicated (Hrouda et Krakľová Fm. al., 2002). Based on the present state of knowledge, it is Middle Lithotectonic Unit possible to reconstruct the Hercynian structure into the The Middle Lithotectonic Unit is known mainly from following three units (Bezák, 1994): the Veporicum (Putiš et al., 1997), however occurs also Upper Lithotectonic Unit (ULU) – composed of in several Core mountains as the Malé Karpaty Mts., Po- high-grade metamorphic rocks (gneisses, migmatites, važský Inovec Mts. and Tribeč Mts. MLU is built of mica granitoids and amphibolites) it is present predominantly in schist to gneiss complexes with amphibolites, locally or- the Core mountains; thogneisses and minor metaquartzites, graphitic gneisses Middle Lithotectonic Unit (MLU) – forms the sub- and metamorphosed sedimentary Fe-ores. Several com- stantial part of the Veporicum crystalline basement and plexes of the MLU are described from the Northern Vepo- consists of gneisses, mica schists and relicts of low-grade ricum (Hron, Čierny Balog and Kráľova hoľa complexes). metamorphic rocks; Lower Lithotectonic Unit Lower Lithotectonic Unit (LLU) – is present in The low-grade metamorphic complexes with variegated southernmost zones of the Veporicum and consists of low lithology, assigned to the LLU, occur in the Southern grade metamorphic crystalline schists. Veporicum (e.g. Ostrá, Klenovec and Sinec complexes), as Lithological composition of the aforementioned units well as within the Pezinok-Pernek Series (Pernek Group) is even more complicated in detail. Lower-grade metamor- in the Malé Karpaty Mts. phic sequences occur within each lithotectonic unit and The vast majority of the Tatricum granitoid rocks paragneisses are intruded by granitoid rocks of different are Carboniferous in age. The youngest granitoid rocks ages (Bezák et al., 2004). The Upper Lithotectonic Unit are known in the area of Rochovce (Rochovce granite). is overlain by a separate complex with characteristic low- They are however known only in the sub-surface position, grade metamorphic rocks known as the Upper Epizonal originally due to their contact metamorphism of the Complex (e.g. the Pernek Group in the Malé Karpaty surrounding rocks. The 80 Ma age of intrusion was based Mts.). on radiometric dating (Hraško et al., 1999). Upper Lithotectonic Unit Tatricum sedimentary cover sequences Protolith of the ULU metamorphites was represented The crystalline basement was deeply eroded after mainly by greywackes with smaller proportion of sand- the end of the Hercynian tectogenesis and the evolving stones and basic volcanic rocks. These complexes were depressions were gradually filled with the Late Paleozoic partly intruded by granitoids, later transformed to or- continental sediments. Carboniferous sediments are known thogneisses. only in the northern Považský Inovec Mts. (Novianska The reconstruction of the tectonic relationships in- dolina Fm.). The Permian sediments occur in a limited dicates that these complexes in the highest position are extent in the Malé Karpaty Mts. (Devín Fm.), Považský usually overlying the medium-grade metamorphic rocks. Inovec Mts. (Kálnica Group), Tribeč Mts. (Skýcov Fm. It is best seen in the Západné Tatry Mts. (Janák, 1994) and and Slopňa Fm.), Malá Fatra Mts. (Stráňanský potok Fm.), in the eastern Nízke Tatry Mts. The ULU occurs mainly Tatry Mts. (Meďodoly Fm.) and Ďumbier part of the Nízke in the Core mountains Belt (Tatry, Nízke Tatry, Branisko Tatry Mts. (Vážna Fm.). They consist of greywackes, a Čierna hora, Malá Fatra, Strážovské vrchy and Považský arkoses, sandstones and shales of generally variegated Inovec Mts.). colours (red, purple, green). The composition of the The ULU contains also probably Early Paleozoic sediments and their weak sorting reflects the proximity low-grade metamorphic complexes (greenschist facies; of the source area (consisting of granites and crystalline so-called upper epizonal complexes) occurring in isolated schists clasts) and generally short transport (Vozárová & occurrences within the higher metamorphic crystalline Vozár, 1988). basement rocks of the Tatricum and Veporicum, having The Mesozoic sedimentary sequence starts in the local names according their regional distribution. Locally Early Triassic and continues with several gaps up to the they overlie the older granites (Klinisko Phyllites on the Late Cretaceous (Cenomanian) with exception of the

41 Mineralia Slovaca, 51 (2019)

Považský Inovec Mts. (Campanian), Tatry and Veľká Fatra Carpathian Keuper. The latest Triassic (Rhaetian) in the Mts., where the sedimentary record ends in the middle Tatricum region is characterized by a discontinuity in Turonian (Pelech et al., 2017 and references herein). The sedimentation. The continental sediments of the Late Lower Triassic rocks in the whole Tatricum region are Triassic are preserved in the Tichá dolina Valley in the characterized by the quartzites and shales (Lúžna Fm.), Tatry Mts. (Tomanová Fm.), where the footprints of which are discordantly overlying the Permian rocks or dinosaur were found (see Niedźwiedzki, 2011). Non- more often directly the crystalline basement. The quarzites deposition and often a significant erosion occurred in the represent the continental sedimentation, being in the Middle Early Jurassic due to major paleogeographyc changes Triassic replaced by the marine carbonate sedimentation (Gutenstein Limestone and Ramsau Dolomite). During in the Tethyan region (Plašienka, 2018). In the Middle the Late Triassic the sedimentation continued in shallower Jurassic the sedimentation in the Tatricum was divided lagoonar and continental (terrestrial) conditions. into two contrasting facies - the deep-water type facies Succession of versicolour sediments (red, violet, yellow (Fatra type or synonymously Šiprúň type), containing a sandstones, shales and dolomites) is referred to as the Middle Jurassic radiolarites, radiolarian limestones and

Fig. 8. Simplified lithostratigraphic column of the Tatric sedi- mentary cover sequence (modified after Biely et al., 1996a).

42 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians)

Fig. 9. Position of the tectonic units of Middle Group of Nappes (based on Hók et al., 2014). Dark-red colour indicates position of Veporicum, depicted in Fig. 10 below.

Fig. 10. Tectonic scheme of essential portion of the Veporicum, present in the Veporské vrchy Mts., Stolické vrchy Mts. and Revúcka vrchovina Mts. (modified after Hók et al., 2001).

43 Mineralia Slovaca, 51 (2019) spotted marly limestones and shales (“Fleckenmergel” ‒ Čierťaž granite, etc.) and various grade metamorphic Allgäu Fm.), and the shallow water facies (Tatra type), rocks (migmatites, gneisses, mica schists and phyllites), characterized by the crinoid and sandy limestones (Hierlatz which similarly as granites, are designated by local names Limestone). (Muráň orthogneiss, Klenovec gneiss, Brezina mica The Fatra type of the sedimentary cover sequences schist, etc.). The Veporicum crystalline basement contains occurs in the Veľká Fatra Mts., Malá Fatra Mts., Považský relatively well-preserved relics of Hercynian structure. The Inovec Mts. and Strážovské vrchy Mts. The Tatra type prevailing part of the crystalline basement is composed of occurs in the Tatry, Nízke Tatry Mts. and Tribeč Mts. the Middle lithotectonic unit and, contrary to the Tatricum, Beside the aforementioned basic facial types a number also the Lower lithotectonic unit with the lower grade of specific successions occurs in the particular Core metamorphic rocks is present. The geological and tectonic mountains. Typical example represent the cover sequences structure of the crystalline basement is very complicated. in the Malé Karpaty Mts., among which the Borinka It is mainly due to the considerable share of Hercynian succession exhibits a contrasting difference from all other tectonics and its subsequent significant Alpine overprint. sedimentary cover sequences (Plašienka, 2012). This fact has led in the past to various interpretations of the The Tatricum was considered structurally as the geological setting, reflecting different levels of knowledge lowermost tectonic unit in the frame of Alpine setting and geological information about the region. Differing of Internal Western Carpathians, which is overridden by interpretations are still widely used today. other tectonic units, forming large-scale nappe structures. Vertical division of the Veporicum was based upon the The internal structure of the Tatricum itself is however differing proportion of the individual types of the crys- considerably complicated with a wide range of partial talline rocks and sedimentary cover sequences (Zoubek, thrusts, duplexes in the sedimentary cover sequences, 1957). According to this principle the Veporicum was as well as crystalline basement, e.g. fold of Giewont divided (from the south to the north) to the Kohút Zone, and Červené vrchy in the Tatry Mts., fold of Tlstá in Kráľova hoľa Zone, Kraklová Zone and Ľubietová Zone the Nízke Tatry Mts., Žibrica duplex in the Tribeč Mts. (Fig. 10). The individual zones were thrust above each oth- The allochthonity (nappe position) of the granitoid rocks er or separated by the subvertical faults (e.g. Muráň-Divín forming the Bratislava and Modra bodies was documented Fault, Pohorelá Line). Later on (Klinec, 1966, 1971), re- in the Malé Karpaty Mts. The granitoid bodies are thrust vealing the Alpine nappe position of the crystalline com- over the Borinka cover succession. The Borinka sequence plexes, a horizontal division into the Kráľova hoľa and is due to its facial difference and the allochthonous position Hron complexes became predominant. The Kráľová hoľa of granitoids considered to be even lower tectonic element composed predominantly of granitic rocks and than Tatricum (i.e. Infratatricum; Plašienka et al., 1997). Complex, high-grade metamorphic rocks (migmatites, gneisses and Middle Group of Nappes amphibolites) is lying in the nappe position above the The Middle Group of Nappes is represented by Ve- Hron Complex, consisting of lower grade metamorphic poricum (crystalline basement and sedimentary cover rocks (mica schists, phyllites). sequences), which occurs in the Vepor Belt (Fig. 9) and Veporicum sedimentary cover sequences thin-skinned nappes of Fatricum and Hronicum that over- It is possible to divide the sedimentary sequences of lie tectonic units of Tatricum and Veporicum in the Core Veporicum into two distinct successions: the Southern mountains Belt and the Vepor Belt (Fig. 1). Veporicum sedimentary cover unit (Federáta Unit) and Veporicum the Northern Veporicum sedimentary cover unit (Veľký Veporicum covers significant part of Central Slovakia (Figs. 1, 9 and 10). The Vepor Belt is divided from the bok Unit). The Federáta Unit is present in the Kohút and Core mountains Belt (Tatricum) by the Čertovica Kráľova hoľa zones. It covers the southeastern margin of thrust and from the Gemer Belt (Gemericum) by the the Veporicum and dips under the Gemericum along the Margecany-Lubeník thrust. The Gemer Belt is thrust Lubeník thrust and at the same time it forms the substratum over the Vepor Belt. The largest part of the Vepor Belt is of the Muráň Nappe (Silicicum) in the Muránska planina built by the Veporicum. Other tectonic units involved in Plateau. The contact zone with corresponding kinematics the geological structure of the Vepor Belt are represented (thrusting and subsequent unroofing) was proved also in the by the Silicicum and Hronicum. As in the case of the eastern margin of the Gemer Belt – along the Margecany Tatricum, the Veporicum is composed of a crystalline part of the Lubeník-Margecany thrust zone, forming the basement and sedimentary cover sequences of the late mutual contact of the Spiš-Gemer Ore Mts. and Čierna Paleozoic to Mesozoic age. hora Mts. (cf. Németh et al., 2012). The Veľký Bok Unit is Veporicum crystalline basement present mainly in the Kráľovohoľské Tatry (eastern part of The crystalline basement of Veporicum is the Nízke Tatry Mts.). predominantly composed of specific types of granitic The Federáta Unit represents complicated system of rocks (e.g. Vepor type, Sihla type, Hrončok granite, thrust slices affected by the low-grade metamorphic over-

44 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians) print. The Mesozoic sedimentary sequence ranges from During Alpine tectogenesis it was displaced, together with the Lower to Upper Triassic. However, also the Upper the underlying Veporic crystalline basement above the Carboniferous and Permian rocks (Revúca Group) are its Tatricum. Its autochthonous position above the north- integral part, often representing tectonically independent ern zones of Veporicum (as the sedimentary cover) was thrust slice. The dolomites of the Late Triassic age (No- preserved. The Veľký bok Unit is exposed in the zone of rian) represent the youngest lithostratigraphic member, direct contact of Tatricum and Veporicum (so-called root substituting the rocks of Carpathian Keuper, which rep- zones of the Krížna Nappe), for example in the Nízke Ta- resents the most significant difference with regard to the try Mts. (the Veľký bok sequence), Branisko Mts., Čierna sedimentary sequence of the Northern Veporicum. hora Mts. and Tribeč Mts. (Veľké Pole sequence). The Veľký bok Unit is characterized by close linkage Fatricum to the crystalline basement, lithostratigraphic and tectonic The Fatricum (other names: Krížna Nappe, Krížna affinity to the Fatricum and sedimentary sequence ranging sequence/series) is an (allochthonous) nappe unit present from Permian to the earliest Lower Cretaceous (). in the Core mountains Belt above the Tatricum and below Tectonic position of the Veľký bok Unit, confined to the the Hronicum nappe. The Fatricum, unlike other thin- Fatricum, similarly as paleogeographic location relates to skinned nappes, is well identifiable from its root zones to southern margin of former sedimentary basin of Fatricum. its foreland. The westernmost surface occurrences of the

Fig. 11. Simplified lithostratigraphic column of the Fatricum (modified after Biely et al., 1996a).

45 Mineralia Slovaca, 51 (2019)

Fatricum are known from the northern part of the Malé that of the Tatricum cover (Figs. 8 and 11). Therefore, Karpaty Mts., the easternmost ones are known from the characteristic phenomenon with repeating sedimentary Humenské vrchy Mts. Hinterland (internal or southern) successions arises in the Core mountains Belt. The zones of the nappe are exposed in the Kráľovohoľské Fatricum is however characterized by the presence of Tatry (eastern part of the Nízke Tatry Mts.), Starohorské thicker sequences of the Jurassic and Cretaceous age, vrchy and Tribeč Mts. In this context, often an obsolete which are not so well developed in the Tatricum and term “Sub-Tatric” nappes for the Krížna and Choč Nap- Hronicum. Another typical sign represents the locally pes is also still in use (e.g. Jurewicz, 2005; Wolska et al., up to 500 m thick formation of Albian–Cenomanian 2016). flysch known as the Poruba Formation, which forms the The former sedimentary basin of Fatricum was situated uppermost and at the same time the youngest member of south (internally) of the Tatricum approximately in the the Fatricum sedimentary sequence. It is usually overlied area of present tectonically compressed boundary between by the Hronicum. the Veporicum and Tatricum. Recently, e.g. the Veľký bok The Fatricum is usually tectonically divided into two Unit is situated in this area. units, distinguished mainly by the lithofacial character of The rock complexes of Fatricum are composed almost the Jurassic part of the sedimentary sequence. exclusively of sedimentary rocks because the crystalline The Zliechov Unit, sometimes referred to as the Kríž- basement was separated during the nappe emplacement, na Unit s.s. represents deep-water sequence. It is charac- except the Veľký bok Unit in the Nízke Tatry Mts., Veľké terized by the presence of the Jurassic spotted limestones pole Unit in the Tribeč Mts. and tectonic slices of the Fa- and marlstones (Allgäu Formation) and radiolarites (Ždiar tricum in the Starohorské vrchy Mts. Fm.). It represents the spatially dominant part of the Fatri- Stratigraphic range of Fatricum is from the cum, usually located above the Vysoká Unit. Lower Triassic to earliest Upper Cretaceous (Albian– The Vysoká Unit and its equivalents (Beckov, Belá, Cenomanian). The older Permian rocks are known only Ďurčiná and Iľanovo units) represent shallow-water se- from few locations close to the root zone of the nappe. quence characterized by the presence of Jurassic crinoi- Lithostratigraphy of the Fatricum is entirely similar to dal and sandy-crinoidal limestones (Hierlatz Formation).

Fig. 12. Schematic cross-section showing position of the Triassic sediments arranged in partial nappes system across the sedimentary basin of the Hronicum (according to Havrila, 2011, simplified).

46 J. Hók et al.: Outline of the geology of Slovakia (W. Carpathians)

Fig. 13. Simplified lithostra- tigraphic column of the Hronicum (modified after Biely et al., 1996a).

Fatricum shallow-water units are spatially less significant tectonically imbricated into the system of partial nappes than in the Zliechov Unit and are usually located in its (Fig. 12). footwall. Hronicum rock complexes stratigraphically range from Hronicum Late Carboniferous to Early Cretaceous. Jurassic and Cre- The Hronicum (syn. Choč nappe, formerly Upper taceous sediments are, however, eroded and occur only Sub-Tatric nappe) represents structurally the highest nappe in the Brezovské Karpaty and Čachtické Karpaty Mts., in the Middle Group of Nappes located above the Fatri- Strážovské vrchy Mts. and on the northern slopes of the Nízke Tatry Mts. cum and Veporicum. Occurrences of the Hronicum are Characteristic feature of the Hronicum is the presence limited to the Core mountains and Vepor belts. It crops out of Late Carboniferous and Permian volcano-sedimenta- in the Malé Karpaty Mts., Považský Inovec Mts., Tribeč ry formations included in the Ipoltica Group, formerly Mts., Strážovské vrchy Mts., Žiar Mts., Malá Fatra Mts., known also as the Melaphyre Series (Vozárová & Vozár, Chočské vrchy Mts., Veľká Fatra Mts., Vysoké Tatry Mts., 1979). It forms basal part of the nappe that is present pre- Nízke Tatry Mts., Branisko Mts. and Čierna hora Mts. dominantly across the more internal (southern) zones of Presence of the Hronicum was proven in deep boreholes the Hronicum occurrence. In the north, the Hronicum se- of the northeastern part of the Slovak sector of the Vienna quence usually starts with the Triassic carbonates. Basin under the sediments of the Neogene age. In several Another characteristic feature is the alteration of areas of the internal Western Carpathians, the Hronicum is shallow water and deep water lithofacies during the Middle

47 Mineralia Slovaca, 51 (2019)

Fig. 14. Position of the Upper Group of Nappes (based on Hók et al., 2014). Triassic (Fig. 12). The shallow water, reefal and lagoonal and Slovenský raj Mts.) and eastern part of the Revúcka facies are represented by Wetterstein limestones and vrchovina Mts. The Upper Group of Nappes is tectonically dolomites, which build Mojtín-Harmanec and Čierny Váh superimposed above the Middle Group of Nappes, in par- carbonate platforms. The deep-water facies are represented ticularly over the Veporicum unit. It represents the highest by Z