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?
, MÁRTON FORIÁN-SZABÓ
, ANIKÓ BÉRCZI-MAKK,
and SÁNDOR JÓZSA
Department of Geology, Eötvös Loránd University of Sciences, Pázmány P. sétány 1/C, H-1117 Budapest, Hungary;
Geological Institute of Hungary, Stefánia út 14, H-1143 Budapest, Hungary; firstname.lastname@example.org
Department of Petrology and Geochemistry, Eötvös Loránd University of Sciences, Pázmány P. sétány 1/C, H-1117 Budapest, Hungary;
(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,
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
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
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.
190 VELLEDITS et al.
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
Stratigraphy of the Kisfennsík Nappe
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 (
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
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
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.
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
5 6 7 8 9 10 11 Tot.
Physoporella heraki BYSTRICKÝ
Poikiloporella duplicata (PIA)
Teutloporella herculea STOPPANI
Thaumatoporella parvovesiculifera RAINERI
Aulotortus sinuosus WEYNSCHENK
Diplotremina astrofimbriata (KRISTAN-TOLLMANN)
Endothyra brassica (TRIFONOVA)
Endothyranella tricamerata SALAJ
Gsollbergella spiroloculiformis (ORAVECZ-SCHEFFER)
Nodosinella libera TRIFONOVA
Ophthalmidium tori ZANINETTI et BRÖNNIMANN
Trochammina almtalensis KOEHN-ZANINETTI
Trochammina alpina KRISTAN-TOLLMANN
Variostoma acutoangulata KRISTAN-TOLLMANN
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
STRATIGRAPHY AND ORIGIN OF THE KISFENNSÍK NAPPE 193
Fig. 4. Microfossils and facies of the Kisfennsík Limestone. Fossil site numbers (see Fig. 2 for location and Table 1) are in brackets. Pho-
tos a), c), f), g), i), k), l), m) and o) are from Velledits et al. (1999). a) Aulotortus sinuosus Weynschenk (2); b) Endothyra brassica (Tri-
fonova) (2); c) Gsollbergella spiroloculiformis (Oravecz-Scheffer) (2); d) Ophthalmidium tori Zaninetti et Brönnimann (2); e) Variosto-
ma acutoangulata Kristan-Tollmann (3); f) Diplotremina astrofimbriata (Kristan-Tollmann) (2); g) Trochammina alpina
Kristan-Tollmann (3); h) Nodosinella libera Trifonova (2); i) Physoporella heraki Bystrický (2); j) Poikiloporella duplicata (Pia) (6); k)
Gastropod section in micritic-pelmicritic matrix (3); l) Enlarged part of the dissolved gastropod shell of Fig. 4k: the ostracod-bearing
lime mud infiltrated into the moldic pore was recrystallized later on (3); m) Wackestone with different types of gastropods: some of them
include geopetal structure (2); n) Grainstone with peloids and with Glomospirella sp. (1); o) Griphoporella sp. (3); p) Macroscopic view
of the Kisfennsík Limestone rich in megalodontids (1).
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-
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-
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
Depositional environment: s
ubtidal lagoon, the coral frag-
ments show that there was a reef, or a patch reef in the neigh-
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
weathered surface, and in thin sections.
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.
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.
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:
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
STRATIGRAPHY AND ORIGIN OF THE KISFENNSÍK NAPPE 195
Fig. 5. Macro- (c and f) and microscopic view of metavolcanites from the Kis-fennsík area. Location numbers in brackets refer to Fig. 2.
a) Metabasalt with amygdales filled with calcite, 1N (1); b) Opacitized metabasalt lithoclast with well oriented, thin albite laths in basal-
tic pyroclastite, 1N (3); c) Basaltic pyroclastite with interfingering, recrystallized limestone lenses. From Pa-60 borehole, at 12.0 m (2);
d) Plagioclase and glauconitized-chloritized pyroxene phenocrysts in cumuloporphyric metaandesite, 1N (8); e) Pseudomorphic pyrox-
ene in andesitic pyroclastite, 1N (7); f) Foliated mixture of crystalline Kisfennsík Limestone and andesitic metavolcanite (photo of Cs.
Péró) (7); g) Tabular plagioclase crystal and opacitized basic metavolcanite clast in andesitic pyroclastite 1N (8); h) Deformed, wavy,
opacitized lithoclast in andesitic pyroclastite 1N (8); i) Opacitized biotite crystalloclast in andesitic pyroclastite 1N (8).
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.
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,
STRATIGRAPHY AND ORIGIN OF THE KISFENNSÍK NAPPE 197
Fig. 6. Structural units in NE Hungary (after Haas & Kovács 2001; Lexa et al. (Eds) 2000; Csontos 2000; Forián-Szabó & Csontos 2002).
but the intensive subsequent shortening, and the position of
Paleogene formations with different facies fitting well in to
the exhumation history of the Bükkium suggests, that
thrusting can probably be related to the most intensive and
considerably ductile, Cretaceous tectogenetic period of the
Bükk Unit (Forián-Szabó & Csontos 2002). K-Ar and zircon
fission track measurements on mylonites from the Eastern
Bükk Mts showed that the age of the last ductile deformation
is around 80 Ma (Árkai et al. 1995). There is clear structural-
sedimentological evidence for the sinistral strike-slip move-
ment along the Darnó Zone during the Miocene (Márton &
Fodor 1995; Sztanó & Józsa 1996). However, this belt is also
supposed to function as a left lateral shear zone during the
Cretaceous (Csontos 1999). Unfortunately, we do not know,
whether the Kisfennsík Nappe was already emplaced at the
time of the northward shift of the Bükk Unit in the Creta-
ceous. Anyway, considering the post-Senonian structural con-
vergence (that is the Miocene sinistral strike-slip movement
along the Darnó Zone), in comparison with the present-day
position (Fig. 6), the even longer distance between Bükkium
and Silicicum at the time of the possible nappe emplacement
makes the Silicic origin of the Kisfennsík Nappe less proba-
ble. One can speculate that they represent outliers of an out-
of-sequence nappe transported from an extra-Bükkian root
zone and emplaced onto metamorphosed, partly eroded Bük-
kian substratum. Such a supposed (Silicic) cover nappe is ex-
pected to be non-metamorphosed (Csontos 1988), like the for-
mations of the Silicic nappes and also their pebbles in the
Upper Cretaceous Nekézseny
lomerate (Gosau sedi-
ments; Brezsnyánszky & Haas 1984). In fact, rocks belonging
to the Kisfennsík Nappe often have an anchimetamorphic
character (Fig. 5f). The Kisfennsík Nappe is partly thrust upon
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.
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.).
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