GeolCarp_Vol54_No3_189

STRATIGRAPHY AND ORIGIN OF THE KISFENNSÍK NAPPE 189

STRATIGRAPHY AND ORIGIN OF THE KISFENNSÍK NAPPE

(BÜKK MOUNTAINS, NE HUNGARY).

IS THE SILICA UNIT REALLY PRESENT IN THE BÜKK MOUNTAINS?

FELICITÁSZ VELLEDITS

, MÁRTON FORIÁN-SZABÓ

, ANIKÓ BÉRCZI-MAKK,

OLGA PIROS

and SÁNDOR JÓZSA

Department of Geology, Eötvös Loránd University of Sciences, Pázmány P. sétány 1/C, H-1117 Budapest, Hungary;

fvelledits@freemail.hu; foka@ludens.elte.hu

Geological Institute of Hungary, Stefánia út 14, H-1143 Budapest, Hungary; library@mafi.hu

Department of Petrology and Geochemistry, Eötvös Loránd University of Sciences, Pázmány P. sétány 1/C, H-1117 Budapest, Hungary;

jozsa@iris.geology.elte.hu

(Manuscript received April 10, 2002; accepted in revised form December 12, 2002)

Abstract: The Kisfennsík Nappe is the uppermost tectonic unit of the Bükk Mountains (NE Hungary). The nappe

consists of slightly metamorphosed platform limestones with dolomites at the base, and intercalating metavolcanites. On

the basis of lithological character and macrofossils (Megalodontidae and Gastropoda) of uncertain age, the Kisfennsík

Limestone was considered to be LadinianCarnian or Norian. The earlier and the here published results of microfacies

investigations and Foraminifera and Dasycladaceae assemblage prove a Carnian lagoonal depositional environment, for

the greater part of the Kisfennsík Limestone. In an eastern site (Galya-tetõ) reef facies was determined. Metavolcanites

show different petrographic characters: acidic pyroclastics, andesitic lavas and basic tuffs, amygdaloidal basalts are

present. Acidic-transitional metavolcanites appear at different stratigraphic horizons, below and above the basic ones.

Based on stratigraphic position and petrographic features, the basic ones can be correlated with the Carnian extensional

magmatism of the Bükk area (Szinva Metabasalt Formation). Considering the lithological features (presence of Triassic

volcanites) of the Kisfennsík Nappe, and the structural pattern of the larger area, its W-Carpathian Silicic Unit origin can

be excluded. The above mentioned features support an intra-Bükkian origin.

Key words: Carnian, Western Carpathians, Silicic Nappe, Bükk Mts, Kisfennsík Limestone, Bükkian-type succession,

microfossils, metavolcanite.

Introduction

The Kis-fennsík (Little High Plateau) is situated in the north-

ern part of the Bükk Mts (N Hungary), W of Miskolc, and N

of Garadna Valley (Fig. 1). This areal of ca. 25 km

is partly

covered with successions of debated origin. New investiga-

tions during the previous decades confirmed the nappe origin

of the upper unit (Kisfennsík Nappe, Less 1986). But the ex-

tra- versus intra-Bükkian origin of the nappe still remained un-

In his monograph, based on macrofossils (Margarosmilia con-

fluens Volz, Naticopsis cf. hoernesi Blaschke) Balogh (1964)

established a LadinianLate Triassic age. Dolomites and

metaandesites found in the NW sector of the Kis-fennsík area

were correlated with the Bükkian Anisian dolomites and with

the older volcanic horizon in its cover (Balogh 1964). The de-

tailed mapping of Gy. Less confirmed the nappe position of

the Kisfennsík Limestone, which, together with the above

mentioned dolomites and volcanites, are grouped into an up-

GEOLOGICA CARPATHICA, 54, 3, BRATISLAVA, JUNE 2003

189198

Fig. 1. Location map. The frame refers to the geological map of Fig. 2.

certain (Csontos 1988; Plaienka 1997). The

aim of this paper is to present new stratigraphic

data from the Kisfennsík Nappe, which, to-

gether with re-evaluated tectonic conditions,

allows us to consider the origin of the succes-

sion. We would like to answer the long-stand-

ing question: Is the Silicic Unit really present

in the Bükk Mts?

The light, massive limestone bodies (Kis-

fennsík Limestone) identified by Schréter

(1916), were regarded as MiddleUpper Trias-

sic. These are thrust over older sequences

(Schréter 1943). Jámbor (1959) mapped a dia-

base tuff horizon, dividing the Kisfennsík

Limestone into a lower (Ladinian) and an up-

per (Upper Triassic) part with megalodontids.

STRATIGRAPHY AND ORIGIN OF THE KISFENNSÍK NAPPE 191

permost Bükkian nappe (Kisfennsík Nappe Less 1986,

1988; Less et al. 2002). On the basis of megalodontid determi-

nation by E. Végh-Neubrandt (pers. comm.), Csontos (1988)

supposed a probably Silicic-type nappe fragment, comprising

non-metamorphic Dachstein-type (Kisfennsík) limestone. To-

gether with the recent investigations (comprising microfacies

analysis and detailed structural mapping) of the authors, the

following structural model can be outlined. (The structural

features of the Kis-fennsík area, including the stratigraphy of

the lower tectonic units and the structural evolution of the NE-

Bükk Mts, are discussed in Forián-Szabó & Csontos (2002).)

The nappe outliers of the Kisfennsík Nappe are superimposed

onto nappes and slivers overthrust onto the North Bükk Anti-

cline (Bükk Parautochthonous, Fig. 2). In the SW nappe outli-

ers can be found directly upon the Paleozoic to Lower Triassic

formations of the North Bükk Anticline, while in the N and

NW the Kisfennsík Nappe is thrust upon younger shales form-

ing the Harica Nappe (Mónosbél Formation, Fig. 2). The Ju-

rassic age of the shale is proven by radiolarian finds (Kozur

1984) and by Jurassic foraminifers found in neptunian dykes

of an olistolith in the shale (Büdös-kút olistolith, Fig. 2;

Velledits 1998). In the central and western part of the area the

tectonic underlayer of the Kisfennsík Nappe is mainly an Up-

per Triassic, anchimetamorphic cherty limestone belonging to

a sliver of the North Bükk Anticline (Fig. 2). The structural

mapping of the investigated area and the geometry of the in-

tercalated volcanite bodies indicated, that the sole thrust of the

Kisfennsík Nappe cuts off even younger formations towards the

SE (Fig. 3; Forián-Szabó & Csontos 2002). The original sedi-

mentary cover of the Kisfennsík Limestone is unknown; at the

southern nappe margin the Oligocene Csókás Formation lies

transgressively on its eroded surface (Fig. 23; Less 1991).

In the followings we give the descriptions of different for-

mations belonging to the Kisfennsík Nappe, including new

stratigraphic results.

Stratigraphy of the Kisfennsík Nappe

Kis-fennsík dolomite

In the NW part of the investigated area, the NE-SW striking

belt of Szalasznya (Fig. 2) is mainly composed of grey-co-

loured, often brecciated dolomites. Scattered occurrences of

dark-grey limestones and some cherty limestone are also asso-

ciated with this dolomite. Unexposed contacts with the white

Kisfennsík-type limestone and with metavolcanites, and the

lack of any biostratigraphic data from this belt allow different

interpretations (Fig. 3). Previous mappers identified it with the

Anisian Hámor Dolomite (Balogh 1964). The mapping result

of Less 1986 established a Hámor Dolomite, Szentistvánhegy

Metaandesite (Anisian-Ladinian), Fehérkõ (Kisfennsík) Lime-

stone succession for this thrust fragment. Considering the Car-

nian age of the Kisfennsík Limestone at the central part of the

area (see below), and the NW dipping ramp-model of the Kis-

fennsík Nappe (Fig. 3 and Forián-Szabó & Csontos 2002), the

above mentioned grey dolomite and limestone could be the

underlayer of the Kisfennsík Limestone. According to P. Pe-

likán (pers. comm.) siliciclastics in the upper part of the bore-

hole Tardona-116 (Fig. 2) are attributed to the Scythian under-

layer of the Hámor Dolomite. If it is so, the below described

andesitic metavolcanites can be the products of the Anisian-

Ladinian volcanic event (

Szentistvánhegy Metaandesite

Less 1986). Because of the already mentioned stratigraphic

uncertainities (regarding the metavolcanites as well) it is also

possible to evaluate sediments in the NW as a lower part of the

Wetterstein-type Kisfennsík platform, which contains scat-

tered or continuous dolomitized segments. The lack of fossils

and the deficient stratigraphic data do not allow certain identi-

fication of the Kis-fennsík dolomites with any of the de-

scribed dolomite formations; therefore we do not assign it to

any formation.

Kisfennsík Limestone Formation

This is the most voluminous rock type of the nappe, its larg-

er and smaller blocks and fragments are widespread in the Kis-

fennsík area (Fig. 2). The colour of the Kisfennsík Limestone

is white, white-grey, pale red, or yellowish. It is a massive,

platform limestone, deposited partly in a lagoonal, partly in a

reef environment. In the lagoonal environment the different

members of the Lofer cycle are present. In several samples

outlines of reef building organisms (corals, sphinctozoans)

can be observed, representing the reef environment. Microfos-

sils: Dasycladaceae (Fig. 4ij and o) and Foraminifera (Fig.

4ah and n) of the Kisfennsík Limestone identified from thin

Fig. 3. Stratigraphic scheme of the Kisfennsík Nappe, and its correlation possibilities (continuous and broken stripes) with the Bükkian Tri-

assic. See text for explanation. The simplified stratigraphic column of the Bükkian Triassic is compiled after Pelikán et al. (1993) and

Velledits (1998).

192 VELLEDITS et al.

sections are listed in Table 1. The fossil sites are shown on

Fig. 2. At first sight the Kisfennsík Limestone appears to have

mainly non-metamorphic character, containing well preserved

algal mats, green algae, gastropods, and megalodonts, which

are observable also with naked eyes (Pelikán et al. 1993; Fig.

4p). However, most of the mapped limestone bodies contain

more or less recrystallized or brecciated zones. The spatial

distribution of recrystallization is very complex, it seems very

hard to limit. Around the contacts with the intercalating

metavolcanites (Válint-kereszt, Pa-60 borehole; Fig. 2) a

stronger recrystallization can be observed due to the heat

transmission. In other areas without volcanites the degree of

the recrystallization can vary from metre to metre.

According to Velledits et al. (1999) and the new results, the

types of microfacies are the following:

I. Lagoonal facies

I.1 Oncoidal wac

kestone: in micritic matrix oncoids with

0.52 cm diameter, foraminifers, peloids, and recrystallized

mollusc shells, gastropods can be seen. The coatings of the

oncoids are thick consisting more layers. Polygonal mud

cracks, some centimetres in diameter and smaller birdseyes

(fenestral fabrics) filled with brown-grey ostracod micrite are

very frequent in this microfacies type. In a thin section in the

dissolved place of a gastropod shell (moldic porosity) a huge

number of ostracod shells can be observed (Fig. 4kl). The

depositional environment is the shallow subtidal part of a la-

goon. During diagenesis the deposited carbonate mud with

oncoids and foraminifers got to an emerged position, where

polygonal desiccations cracks were generated. Due to the in-

fluence of freshwater the aragonitic shells of the gastropods

were also dissolved. An ostracod lime mud was infiltrated

into the moldic pores, which has been recrystallized later on.

The ostracod bearing lime mud is a characteristic sediment for

the ponds on the tidal flat.

I.2

Mudstone with desiccation cracks: the micritic, pelmi-

critic matrix is rich in foraminifers, porostromata algae frag-

ments, oncoids, and coated lithoclasts. Birdseyes can be found

in the entire rock: their lower part is filled with ostracodal mi-

Table 1: Microfossils and microfacies types of the Kisfennsík Limestone Formation fossil sites. Microfossils of locality 2, 3 and partly of

1 are from Velledits et al. (1999). The microfacies codes refer to the classification found in the text. The fossil sites are shown on Fig. 2.

Number of pieces by localities

Fossil

group

Fossil

5 6 7 8 9 10 11 Tot.

Griphoporella sp.

Gyroporella sp.

Physoporella heraki BYSTRICKÝ

Poikiloporella duplicata (PIA)

1 11

Teutloporella herculea STOPPANI

dac

eae

Thaumatoporella parvovesiculifera RAINERI

Agathammina sp.

Ammobaculites sp.

Ammodiscus sp.

Aulotortus sinuosus WEYNSCHENK

2 1

Aulotortus sp.

Diplotremina astrofimbriata (KRISTAN-TOLLMANN)

Diplotremina sp.

Earlandinita sp.

3 4

Endothyra sp.

1 6

Endothyra brassica (TRIFONOVA)

Endothyranella sp.

Endothyranella tricamerata SALAJ

Gaudryina? sp.

Gaudryinella sp.

Glomospirella sp.

4 1

Gsollbergella sp.

Gsollbergella spiroloculiformis (ORAVECZ-SCHEFFER)

Nodosaria sp.

Nodosinella libera TRIFONOVA

Oberhaueserellidae sp.

Ophthalmidium tori ZANINETTI et BRÖNNIMANN

Spirillina sp.

Textularia sp.

Trochammina almtalensis KOEHN-ZANINETTI

Trochammina alpina KRISTAN-TOLLMANN

Trochammina sp.

Variostoma acutoangulata KRISTAN-TOLLMANN

1 2

Variostoma sp.

ini

?Reophax sp.

II.

Characteristic microfacies types

(see text for classification)

3,4,5 1,3,6,7 1-4

6-8 1,2 7,3 3,4 7 3 3 1,2 6,3

194 VELLEDITS et al.

crite, while the upper part is filled with sparite. The carbonate

mud was deposited in the subtidal lagoon environment. Due

to subsequent desiccation and dissolution of freshwater cavi-

ties, desiccation and entgassing pores originated, which were

partly filled with ostracod mud.

I.3 Grainstone with peloids, and with bio- and lithoclasts

(Fig. 4n): this mic

rofacies type develops from the previous

type. In some thin sections it can be observed, that the dense

and extensive net of the mud cracks isolates the peloids. If

these sediments are affected by agitated water, then the pe-

loids will be rounded, and the bioclasts coated. In some thin

sections two generations of cements can be observed. The

grains are covered with rim cement, and the space between the

grains is filled with sparite. Sometimes the entire space be-

tween the rim cement is filled with calcisilt. Depositional en-

vironment: the high-energy part of the platform, and the win-

nowed platform edge sands. Diagenesis: in some thin sections

the grainstone and the mudstone textures occur together. The

transition between these two types is continuous. We can con-

clude, that the sediment deposited in the subtidal environment

(wackestone), after that it was desiccated and cracked in the

supratidal zone. Later this sediment was redeposited (grain-

sto

ne).

I.4 Algal mat: some mm thick laminae with birdseyes. The

cavities are 3

15 mm, and follow the layering, their inner

parts are filled with two generations of sparite. The material of

the algal lamina is pelmicrite, which represents the sediments

captured by blue-green algae. Some foraminifers occur as

well. Depositional environment: intertidal lagoon.

I.5 Limestone beds with megalodontids: medium grey,

thick bedded limestone layers, densely packed with double

megalodontids: they measure 510 cm (Fig. 4p). Depositional

environment: subtidal lagoon.

I.6 Wackestone with gastropods: gastropods (5 %), ostra-

cods (1 %), and some foraminifers in micritic matrix. The dif-

ferent types of gastropod sections can be even 12 mm in di-

ameter. Geopetal structures are also observable (Fig. 4m).

Depositional environment: subtidal environment of the la-

goon.

I.7 Wacke-packestone with dasycladacean algae:

The preservation of this material is very bad. Longitudinal

and cross-sections of green algae: Poikiloporella duplicata

(Pia) (Fig. 4j), Physoporella heraki Bystrický (Fig. 4i), Teut-

loporella herculea Stoppani, Gyroporella sp., Griphoporella

sp. (Fig. 4o) can be seen in micritic matrix. In the matrix po-

lygonal cavities were generated, which are filled with brown

grey ostracodal micrite. The ostracodal micrite can fill the

cavity entirely, or it fills only the lower part of the cavity (li-

bella structure). Depositional environment: dasycladacean al-

gae prefer the tropical, subtropical lagoonal seawater. They

live in the subtidal environment, generally at depths of 35 m

(Flügel 1982). Later, in the tidal flat in the desiccated lime

mud polygonal mud cracks were formed, which were enlarged

by dissolution of freshwater. These cavities were filled with

the typical deposits of intertidal ostracodal mud.

I.8 Wackestone with coral fragments: In micritic matrix re-

crystallized fragments: foraminifers, echinoderms, ostracods,

radiolarians?, and corals. Ostracod cavity filling can also be

observed.

Depositional environment: s

ubtidal lagoon, the coral frag-

ments show that there was a reef, or a patch reef in the neigh-

bourhood.

II. Reef

This environment can be identified in slightly metamor-

phosed limestones, where the inner structure of the fossils dis-

appeared. Only the outlines of the fossils can be observed on

the

weathered surface, and in thin sections.

II.1 Rudstone:

The rock is dark grey. It contains 13 cm big lithoclasts, the

space between them is filled with sparite. The lithoclasts are

not (or only slightly) rounded. If the space between the litho-

clasts is bigger, it is filled with sparite with more generations.

The lithoclasts are composed of recrystallized material, in

which some recrystallized biogenic components: corals, bryo-

zoans, and echinoderms can be observed.

II.2 Bafflestone:

The rock is light grey. In micritic matrix outlines of fossils

can be obser

ved: corals, bryozoans, sphinctozoans?. The inner

structure and the incrustation of these primary reef builders

cannot be observed. Both microfacies types are characteristic

of the reef environment. In the Bükk Mountains these occur in

the reef facies of Hór Valley (Flügel et al. 1992) and Mész

Valley (Velledits & Péró 1987), too. The bafflestone microfa-

cies represents the autochthon reef, the rudstone is typical for

the detritus belt around the reef, and the reef slope.

Age of the Kisfennsík Limestone: The dasycladacean Phys-

oporella heraki Bystrický (Fig. 4i) lived only during the Car-

nian. Among the forams Gsollbergella spiroloculiformis

(Oravecz-Scheffer) (Fig. 4c), Ophthalmidium tori Zaninetti et

Brönnimann (Fig. 4d ) and Nodosinella libera Trifonova (Fig.

4h) indicate Carnian.

Metavolcanites

Macro- and microscopic petrography allows us to distin-

guish two main types of metavolcanites: a basaltic (1) and an

acidic-transitional type (2). Type (1) seems to occur in a cer-

tain, ca. 1030 m thick stratigraphic horizon within the Kis-

fennsík Limestone (Jámbor 1959) of Carnian age, along and

above a flat section of the sole thrust of the Kisfennsík Nappe

(Forián-Szabó & Csontos 2002 and Fig. 2, 3). Volcanites be-

longing to type (2) occur at different stratigraphic levels. In

the surroundings of the Válint-kereszt they appear in the Kis-

fennsík Limestone over the metabasalts, while metaandesites

to the NW are considered to occupy a stratigraphic horizon

below the metabasalts (Fig. 3). Petrologic characters of the

two main types are as follows:

Metabasalt

Petrographically similar metabasalts were described from

the Carnian of the Bükk Mts (Szinva Metabasalt, Pelikán et al.

1993; Szoldán 1990), therefore we assign the Kis-fennsík me-

tabasalts to the above mentioned formation (Fig. 3). It is inter-

calated with the Kisfennsík Limestone. Toward the massive

platform limestone small angular limestone clasts and lenses

196 VELLEDITS et al.

appear first, then even thicker bands of recrystallized lime-

stones are interlayered in the metabasalt (Fig. 5c). In thin sec-

tion at the margins of the limestone clasts subsequently crys-

tallized, thick albite laths are observable. Macroscopically the

metabasalt is dark-green coloured, with a weakly developed

cleavage. Frequent alteration changes its colour into brown-

ish. In thin sections closely packed, irregular, elongated basal-

tic clasts occur in some fine matrix with flow texture. The

very fine-grained matrix is mainly composed of chlorite, and

possibly also of pumpellyite (appearing in some samples as fi-

brous patches with radial structure). Basaltic clasts are strong-

ly chloritized, opacitized and calcitized, and they are often

amygdaloidal (Fig. 5a). Amygdales are filled with calcite,

chlorite and albite. Several basaltic clasts contain well-orient-

ed, thin albite laths (Fig. 5b). Crystalloclasts are rare: they are

represented by apatites, large plagioclase tables and also large

(up to 2 mm) magnetites, titanomagnetites and spinels.

Acidic-transitional metavolcanites

Rocks of this type occur at Válint-kereszt above the me-

tabasalts, and are also intercalated with the Carnian Kis-

fennsík Limestone (Fig. 2), while metavolcanites to the NW

are deposited most probably below the basaltic horizon, close

to the dolomitic underlayer of the Kisfennsík Limestone (see

Chapter Kis-fennsík dolomite). Acidic-transitional metavol-

canites are present as badly outcropping, scattered, small bod-

ies. At Válint-kereszt the transition between the metavolcanite

and the Carnian limestone has similar texture to that observed

between the metabasalts and the same limestone (Fig. 5f).

Macroscopically the volcanites are reddish, sometimes grey-

or brown-coloured, fine-grained, mostly altered and often fo-

liated. In thin section pyroclastics and extrusives can be dis-

tinguished. The matrix of the pyroclastics is often wavy and

pumiceous (Fig. 5i). It contains a large quantity of fine-

grained opaque minerals (magnetite, hematite and limonite).

The former glass is totally altered to sericite and chlorite. Li-

thoclasts are partly represented by acidic volcanites. Subtypes

of acidic volcanoclasts are: pumiceous, sometimes with flow

and/or felsitic texture, the material of which is totally recrys-

tallized to chlorite, sericite and quartz (1) and extrusives with

microholocrystalline groundmass (2). The above described

acidic volcanoclast types contain porphyric altered plagio-

clase and biotite, and irregular shaped amygdales. More basic

lithoclasts similar to the metabasalts described in Chapter

Metabasalt are also present in pyroclasts: they contain thin

albite laths and in some cases amygdales in mostly opacitized,

fine-grained matrix (Fig. 5g). There are the following crystal-

loclasts of pyroclastics: feldspar, few quartz, biotite (Fig. 5h)

and opaque minerals. Some spinel crystalloclasts of unclear

origin were found in acidic pyroclastics near Válint-kereszt

(Location 7, Fig. 2). Extrusives (locality No. 5, 7, 8, 9 on Fig.

2) are represented mainly by metaandesites with cumulopor-

phyric texture (Fig. 5d). The microholocrystalline to glassy

groundmass contains large plagioclases and chlorite-glauco-

nite pseudomorphs after euhedral pyroxenes (Fig. 5e). Both in

matrix and porphyric minerals fine-grained pumpellyite oc-

curs. Despite the upper stratigraphic position, the above de-

scribed acidic pyroclastics and metaandesites and the Ani-

sianLadinian Szentistvánhegy Metaandesite (Szoldán 1990)

have similar petrographic features.

Consequently, based on observations described in Chapter

Stratigraphy of the Kisfennsík Nappe, the examined slice

of the Kisfennsík Nappe fits to the Bükkian sequence (Fig. 3).

The origin of the Kisfennsík Nappe

On the basis of the frequent occurrences of large-sized mega-

lodontids in the Kisfennsík Limestone (Fig. 4p) not found

elsewhere in the Bükk Mts, Csontos (1988) considered it to be

a Norian Dachstein-type limestone. In the surrounding area

this formation can be found in the Silicicum, therefore he as-

sumed such an extra-Bükkian origin for the nappe. Referring

to Csontos (1988), in more recent publications (e.g. Plaienka

1997) the Kisfennsík Nappe is still assigned to the Silicic

nappes. However, the nappe rests upon the Bükk Parautochth-

onous and partly on a Szarvaskõ-type nappe (Harica Nappe),

the units of which are displaced fragments of the Internal Di-

naridic system (Haas & Kovács 2001). Do we have a Silicic

Nappe emplaced over these Dinaridic blocks?

The presence of volcanites has a crucial importance in con-

siderations of nappe origins. In the Bükkium a thick Triassic

volcanic sequence was preserved due to the intense polycy-

clic, calc-alkaline and basic-neutral extensional volcanism in

the AnisianCarnian period (Harangi et al. 1996; Fig. 3). Ac-

cording to Pelikán et al. (1993), the older, AnisianLadinian,

calc-alkaline volcanic period (Szentistvánhegy Metaandesite)

resulted in a thickness of up to ca. 500 m of volcanic material.

On the other hand, in the Silicicum the Bükkian-type intense

Triassic volcanism is almost completely missing: only thin

layers of green tuffs and tuffites can be found locally in the

basal part of the Wetterstein limestones, N of Silická Brezová

(Early Ladinian, Bystrický 1973). The stratigraphic content of

the Upper Triassic platform limestones and dolomites of the

Kisfennsík Nappe, including intercalated metavolcanites fits

well into the Bükkian evolution history. The frequent occur-

rences of megalodontids in Upper Triassic platform develop-

ments in the Bükk Mts are restricted to the Kis-fennsík area.

The difference in the abundance of megalodontids between

Kis-fennsík and other platform areas in the Bükk Mts can be a

consequence of either an original biofacies differentation, or

of an apparent lack of fossils due to the relatively higher meta-

morphic grade of the rocks outside the Kis-fennsík area. The

Carboniferous to Triassic sequence of the Bükkium was re-

cently compared and successfully correlated with successions

in the Dinarides (Protiæ et al. 2000). Both the Kisfennsík

Limestone of the Bükkium and the corresponding Upper Tri-

assic platform limestones of the Jadar and Sana-Una Units

(Serbia, Leliæ and Podvidaèa Formations) are rich in mega-

lodontids (Protiæ et al. 2000).

From a structural point of view the Kisfennsík Nappe is also

hardly explainable as an extra-Bükkian nappe. According to

the structural investigations of Forián-Szabó & Csontos

(2002), in the Kis-fennsík area the already emplaced Kis-

fennsík Nappe together with rocks of the lower structural

units suffered an intensive, large and mid-scale folding.

The emplacement of the Kisfennsík Nappe cannot be dated,

198 VELLEDITS et al.

the upper members of the North Bükk Anticline (Upper Trias-

sic cherty limestone), but its southern part is largely emplaced

onto Carboniferous slates, and Permian sediments (Forián-Sza-

bó & Csontos 2002). Some small-scale younger overthrusting

onto the Paleozoic sediments is very likely, but because of

the intensive subsequent shortening of both the nappes and

the Parautochthonous (they were re-folded together) a ma-

jor reactivation of the Kisfennsík sole thrust is not probable.

Overthrusting of the Kisfennsík Nappe onto Carboniferous

rocks of the Bükk Parautochthonous can be linked to an inter-

nal (intra-Bükkian) thrusting.

Conclusions

Microfacies investigations and biostratigraphy record a

Carnian platform development in the Kis-fennsík area. The

Kisfennsík Nappe is mainly composed of massive, platform

limestone, deposited partly in a lagoonal, partly in a reef envi-

ronment. At different levels in the Carnian limestone, interca-

lated anchimetamorphic metavolcanites of different petrologic

character were recognized (metabasalts and metaandesites).

The above described stratigraphic content of the Kisfennsík

Nappe can be interpreted as a Bükkian-type succession. In the

present structural position the nappe lies on different strati-

graphic members (Carboniferous to Jurassic) belonging to

Bükkian successions. All the units in the Bükk Mts are de-

formed by post-emplacement folding. Together with structur-

al considerations, but mainly based on stratigraphic results,

the Silicic origin of the Kisfennsík Nappe can be excluded.

Acknowledgments: Gy. Less is thanked for field guiding and

fruitful discussions. L. Csontos and S. Kovács are thanked for

improving the text with critical remarks. N. Németh helped

with field observations. Mrs. Pellérdy is thanked for photo

processing. The authors are grateful to the reviewers Gy. Less,

P. Pelikán and D. Plaienka for valuable suggestions to im-

prove the manuscript. This work was financially supported

partly by the National Research Fund (OTKA) of F. Velledits

(Project No. T.26634.).

References

Árkai P., Balogh K. & Dunkl I. 1995: Timing of low-temperature meta-

morphism and cooling of the Paleozoic and Mesozoic formations of

the Bükkium, innermost Western Carpathians, Hungary. Geol. Rd-

sch. 84, 334344.

Balogh K. 1964: Die geologischen Bildungen des Bükk-Gebirges. Ann.

Inst. Geol. Hung. 48, 2, 245719.

Brezsnyánszky K. & Haas J. 1984: The Nekézseny Conglomerate Forma-

tion of Senonian age: a sedimentological and tectonic study of the

stratotype section. Földt. Közl. 114, 1, 81100.

Bystrický J. 1973: Triassic of the West Carpathians Mts. Guide to Ex-

cursion D, Xth Congr. of Carpathian-Balkan Geol. Ass., Bratisla-

va, 1137.

Csontos L. 1988: Étude géologique dune portion des Carpathes internes:

la massif du Bükk (Nord-Est de la Hongrie). Thése de Doctorat,

Univ. de Lille, 1327.

Csontos L. 1999: Structural outline of the Bükk Mts. (N Hungary). Földt.

Közl. 129, 4, 611651.

Csontos L. 2000: Stratigraphic reevaluation of the Bükk Mts (N. Hunga-

ry). Földt. Közl. 130, 1, 95131.

Forián-Szabó M. & Csontos L. 2002: Tectonic structure of the Kis-

fennsík area (Bükk Mountains, NE Hungary). Geol. Carpathica 53,

4, 223234.

Flügel E. 1982: Microfacies analysis of limestones. Springer, Berlin

Heidelberg New York, 1633.

Flügel E., Velledits F., Senowbari-Daryan B. & Riedel P. 1992: Riffor-

ganismen aus Wettersteinkalken (karn?) des Bükk-Gebirges, Un-

garn. Geol. Paläont. Mitt., 18, 3562.

Haas J. & Kovács S. 2001: The Dinaridic-Alpine connection as seen

from Hungary. Acta Geol. Hung. 44, 23, 345362.

Harangi Sz., Szabó Cs., Józsa S., Szoldán Zs., Árva-Sós E., Balla M. &

Kubovics I. 1996: Mesozoic igneous suites in Hungary: Implica-

tions for genesis and tectonic setting in the northwestern part of

Tethys. International Geology Review 38, 336360.

Jámbor Á. 1959: Geological re-investigation of the Kisfennsík area (Bükk

Mts.). MÁFI Évi Jel. 195556, 103122.

Kozur H. 1984: New biostratigraphical data from the Bükk, Uppony and

Mecsek Mountains and their tectonic implications. Acta Geol.

Hung. 27, 34, 307319.

Less Gy. 1986: Geological map of the Mályinka Garadna-völgy area

(Bükk Mts.). Scale: 1:10,000. Manuscript, Arch. Hung. Geol. Inst.,

Budapest.

Less Gy. 1988: Geological map of the Eastern Kis-fennsík (Bükk Mts.).

Scale: 1:10,000. Manuscript, Arch. Hung. Geol. Inst. Budapest.

Less Gy. 1991: Upper Oligocene larger foraminifers of the Bükk Moun-

tains. MÁFI Évi Jel. 1989, 411465.

Less Gy., Gulácsi Z., Kovács S., Pelikán P., Pentelényi L., Rezessy A. &

Sásdi L. 2002: Geological map of the Bükk Mts., 1:50,000. Geolog-

ical Institute of Hungary, Budapest.

Lexa J., Bezák V., Eleèko M., Mello J., Polák M., Potfaj M. & Vozár J.

(Eds.) 2000: Geological Map of Western Carpathians and adjacent

areas. Scale: 1:500,000. Ministry of Environment of Slov. Rep.,

Geol. Survey of Slov. Rep., Bratislava.

Márton E. & Fodor L. 1995: Combination of palaeomagnetic and stress

data a case study from North Hungary. Tectonophysics, 242,

99114.

Pelikán P., Csontos L., Less Gy., Velledits F., Dosztály L., Szabó Cs.

& Szoldán Zs. 1993: Bükk Unit. In: Haas J. (Ed.): Litostrati-

graphic units of Hungary. Triassic. MÁFI, Budapest, 101153 (in

Hungarian).

Plaienka D. 1997: Cretaceous tectonochronology of the Central Western

Charpatians, Slovakia. Geol. Carpathica, 48, 2, 99111.

Protiæ Lj., Filipoviæ I., Pelikán P., Jovanoviæ D., Kovács S., Sudar M.,

Hips K., Less Gy. & Cvijiæ R. 2000: Correlation of the Carbonif-

erous, Permian and Triassic sequences of the Jadar Block, Sana-

Una and Bükkium Terranes. In: St. Karamata & Sl. Jankoviæ

(Eds.): Proc. of the Int. Symp. Geology and metallogeny of the

Dinarides and the Vardar Zone. The Acad. of Sci. and Arts of the

Rep. of Srpska, Coll. and Monogr. Vol. 1. Banja Luka, 6169.

Schréter Z. 1916: The Eastern part of the Bükk Mountains (Borsod-Hev-

es). Földt. Int. Évi Jel. 1915, 348363 (in Hungarian).

Schréter Z. 1943: Geology of the Bükk Mountains. Beszámoló a m. kir.

Földt. Int. Vitaül. Munk. 5,7, 378411 (in Hungarian).

Szoldán Zs. 1990: Middle Triassic magmatic sequences form different

tectonic settings in the Bükk Mts. (NE Hungary). Acta Mineral.

Petrogr. Szeged 31, 2542.

Sztanó O. & Józsa S. 1996: Interaction of basin-margin faults and tidal

currents on nearshore sedimentary architecture and composition: a

case study from the Early Miocene of northern Hungary. Tectono-

physics, 266, 319341.

Velledits F. & Péró Cs. 1987: The Southern Bükk (northern Hungary)

Triassic revisited: The Bervavölgy Limestone. Annales Univ. Sci.

Budapest., Sec. Geol. 27, 1764.

Velledits F. 1998: Stratigraphic correlation and evolutionary analysis of

the Middle and Upper Triassic in the Bükk Mts. PhD Thesis, Eötvös

Univ., Budapest, 1122 (in Hungarian).

Velledits F., Bérczi-Makk A. & Piros O. 1999: Facies and age of the Kis-

fennsík Limestone (Bükk Mts). Földt. Közl. 129, 4, 573592 (in

Hungarian).