GEOLOGICA CARPATHICA, 52, 5, BRATISLAVA, OCTOBER 2001
287 — 299
THE STRUCTURAL SETTING OF LOWER TRIASSIC FORMATIONS
IN THE AGGTELEK—RUDABÁNYA MOUNTAINS (NORTHEASTERN
HUNGARY) AS REVEALED BY GEOLOGICAL MAPPING
KINGA HIPS
Geological Research Group of the Hungarian Academy of Sciences, Múzeum krt. 4/a, 1088 Budapest, Hungary; hips@ludens.elte.hu
(Manuscript received December 8, 2000; accepted in revised form June 13, 2001)
Abstract: Lower Triassic formations in the Aggtelek—Rudabánya Mountains (NE Hungary) were mapped in the main
part of the Silica Nappe, and the results are presented in a new map at the scale of 1:50,000. The aim of this paper is to
present the structural observations collected during mapping and to interpret the field data and map-scale structures, and
by this means to demonstrate the structural setting of Lower Triassic formations in a new light. The mapped area is
located south of the Jósvafő—Bódvaszilas reverse fault-zone and divided into two parts by the NE—SW sinistral strike-
slip faults of the Darnó Zone. Beside these two major fault-zones, systems of E—W dextral strike-slip and NE—SW-
trending reverse faults were recognized. Three groups of folds were identified: one set of folds with NE—SW axes is
predominant and widely distributed in the entire mapped area, whereas the other sets of folds with E—W and NW—SE
axes appear only locally. Their timing is uncertain. Characteristic associations of structural elements were recognized in
three structural segments. The predominant one consists of E—W trending strike-slip and the connecting NE—SW reverse
faults with a series of folds with NE—SW axes, suggesting NW—SE shortening and NE—SW elongation (according to
recent co-ordinates). Map-scale anticlines and synclines were also formed in this system (e.g. the Dobódél and Keskeny-
völgy Anticlines and the Varbóc Syncline). The map-scale structures reveal that the formerly proposed anticline with E—
W axis running all along the Jósva-völgy does not exist; only the E—W-trending Jósvafő Anticline is proved near Jósvafő.
Strike-slip duplexes and push-up fragments, consisting of mismatching blocks, are also very characteristic in the area of
investigation, pointing to major lateral shear zones.
Key words: Silica Nappe, Aggtelek—Rudabánya Mountains, Lower Triassic formations, 1:50,000 scale map, structural
setting, map-scale structures.
Introduction
At the beginning of the 20
th
century, Lower Triassic deposits
were subdivided into two parts, namely ‘Seis Beds’ and
‘Campil Beds’ by Vitális (1909) in accordance with the subdi-
vision in the Alpine—Carpathian—Dinaridic facies area. In the
1940’s, maps and cross-sections by Balogh (1948a,b, 1950,
1953a,b), and Balogh & Pantó (1952) provided new data on
sedimentary rocks. They recognized characteristic horizons
within the sequence, but keeping the previous names they did
not indicate them on their maps. The geological mapping pro-
gram of the Geological Institute of Hungary carried out be-
tween 1979 and 1985 (maps of Less et al. 1988 and Less
1998a,b) resulted in a detailed Triassic lithostratigraphic clas-
sification (Kovács et al. 1989) and structural evaluation of the
Aggtelek—Rudabánya Mountains (Grill 1989; Less 2000).
As a result of recent studies, the Lower Triassic lithostrati-
graphic units defined by Kovács et al. (1989) can be divided
into several subunits (Hips 1996), which were successfully
distinguished and mapped in the field. The area between Jós-
vafő and Bódvaszilas was suitable for detailed stratigraphic
studies. The Lower Triassic formations in the strongly tecton-
ized zones (i.e. Ménes-völgy, near the Slovak border) and in
the metasomatized field in the southern Rudabánya Moun-
tains (Rudabánya ore mine) (cf. Less et al. 1988) were not in-
vestigated.
The objectives of this paper are (1) to present the spatial dis-
tribution of structural elements and evaluate the structural set-
ting of Lower Triassic formations in the Aggtelek—Rudabánya
Mountains on a map on the scale of 1:50,000 (Appendix 1);
and (2) to describe and analyse the map-scale geologic struc-
tures. The stratigraphy of Lower Triassic rocks was discussed
and interpreted in the context of sedimentary facies in earlier
papers (Hips 1996, 1998). For the purpose of this paper, the ba-
sic evaluations of stratigraphic units are summarized in table
format and only a brief discussion of the formations is provided.
The map (Appendix 1) presents new results only from Lower
Triassic formations, other data are compiled with a few slight
modifications from Less et al. (1988) and Less (1998a,b).
Location
The Aggtelek—Rudabánya Mountains rise on the northeast-
ern border of Hungary, close to Slovakia (Fig. 1). They consti-
tute the southernmost, Hungarian part of the Mesozoic range
of the South Gemer area in the Inner Western Carpathians. The
mountains are made up of three tectonic units: the uppermost
Silica Nappe, the Meliata Series and the lowermost Torna Se-
ries (Kovács et al. 1989; Less 2000). These structural units ex-
tend across the Hungarian-Slovak border through the Slovak
Karst to the southern boundary of the Gemer Paleozoic. On the
288 HIPS
Hungarian side, the Lower Triassic formations are found only
in the Silica Nappe.
Outcrops of Lower Triassic formations
The investigated area is composed of two main territories,
where Lower Triassic formations crop out at the surface.
Fig. 1. A) Schematic terrane map of the Circum-Pannonian Region (after Kovács et al. 1996—97) with Hungarian national borders, and loca-
tion of South Gemer area with the Aggtelek—Rudabánya Mountains presented in B; 1 – Flysch Belt, 2 – Klippen Belt, 3 – Northern Cal-
careous Alps, 4 – Early Alpine units related to the European continental margin, 5 – Early Alpine shelf sequences related to the Apulian
(Southern Alps and Outer Dinarides) continental margin, 6 – ophiolites of the Penninic Ocean, 7 – ophiolites of the Vardar Ocean, 8 –
major strike-slip zones. B) Geological map of the South Gemer area (after Mello et al. 1996; Kovács 1997, and Less 1998b). Location of the
map of Lower Triassic formations in the central part of the mountains (presented in Appendix 1) is in darker colour.
These are (1) the hills surrounding the Bódva- and Jósva-völgy
and the Galyaság hills (outlined by the villages of Jósvafő,
Teresztenye, Szőlősardó, Perkupa, Bódvaszilas, Szögliget,
Szin, and Szinpetri), and (2) the northern segment of the Ruda-
bánya Mountains (outlined by the villages of Bódvarákó, Mar-
tonyi, and Dobódél) (Fig. 2). These areas presented on the map
(Appendix 1) will be discussed in detail below.
THE STRUCTURAL SETTING OF LOWER TRIASSIC FORMATIONS 289
Moreover, Scythian formations of small spatial distribution
are known in Ménes-völgy to the north, in a narrow zone ex-
tending from the Hungarian-Slovak border eastward as far as
Bódvaszilas village. Further small outcrops appear in the sur-
roundings of Égerszög as well as in the Telekes-völgy and
north of Alsótelekes, and in the metasomatized series in the
ore mine in the southern Rudabánya Mountains (Fig. 2).
Good outcrops for stratigraphic investigations with quasi-
continuous exposure of Lower Triassic formations can be
studied in two segments. The lower part of the sequence is ex-
posed west—northwest of Perkupa (from the Bódvaszilas
Sandstone to Szinpetri Limestone Member (s.str.) (Fig. 3).
The upper part of the sequence crops out along the road be-
tween Szinpetri and Jósvafő, and north and south of Róna-
Bükk-völgy (Dobódél) (from the uppermost part of the Szin
Marl to the uppermost Szinpetri Limestone) (Fig. 3).
The Silica Nappe was detached from its original basement.
The Upper Permian—lowermost Lower Triassic Perkupa
Evaporite Formation (Fig. 3) served as the sole-thrust. How-
ever, the blocks of conglomerate—sandstone series in the
northern neighbourhood of Bódvaszilas is presumed to be a
fragment of the underlying continental red beds (Vozárová &
Fig. 2. Distribution of the Lower Triassic formations in the Aggtelek—Rudabánya Mountains (only schematically illustrated in the strongly
tectonized zones). The details in the mid-part of the area are shown in Appendix 1.
Vozár, pers. commun.). From the Scythian Jósvafő Limestone
Member to the Anisian Gutenstein Formation a continuous
stratigraphic sequence is observed in the neighbourhood of
Jósvafő and southeast of Dobódél village. In other cases, the
contact with the younger formations is tectonic, except in the
southern part of the area where an Oligocene—Miocene cover
was deposited transgressively with a gap. Along the rivers,
Quaternary terrace deposits cover the Triassic formations in
many places.
Stratigraphy
The Silica Nappe in Hungary can be divided into two dis-
tinct Mesozoic facies units displaced later by the Darnó faults.
As a consequence, at present they are separated by sinistral
strike-slip deformation zone. These are the Aggtelek and the
Bódva Facies (Kovács 1984; Kovács et al. 1989; Kovács &
Hips 1998). They are defined by coeval syn-rift deposits sepa-
rated in the course of rifting. Platform carbonates in the Agg-
telek Facies and slope and basinal deposits in the Bódva Fa-
cies, characterize the formations from Upper Anisian to
290 HIPS
Carnian in age. The pre-rift Lower Triassic and Lower Anisian
formations, except for small facies differences, are uniformly
developed in both facies units.
The Upper Permian—Lower Triassic sequence is represented
by evaporitic, siliciclastic, mixed siliciclastic—carbonate, and
carbonate sedimentary rocks. These can be subdivided into
four formations: the Perkupa Evaporite, Bódvaszilas Sand-
stone, Szin Marl, and Szinpetri Limestone (Kovács et al.
1989), and several subunits (Hips 1996) (Fig. 3). The thick-
ness of the sequence is about 800 m, not counting the mostly
Upper Permian Perkupa Evaporite. The reader is referred to
Hips (1998) for detailed discussion of sedimentary facies and
ramp sedimentation during the Early Triassic.
In many settings of the western Tethyan depositional area,
within the Lower Triassic, the boundary between the Induan
and Olenekian stages cannot be determined due to the simple,
low-diversity fauna. According to the recently valid stage-sub-
division of the Triassic, the Scythian formations in the Agg-
telek—Rudabánya Mountains could not be age-subdivided at
all. A more detailed subdivision of the formations can be made
only on the basis of the alternative three-fold division.
The Perkupa Evaporite Formation consists predominantly of
anhydrites and subordinately of gypsums, dolomites, siltstones
and shales (Fig. 4) deposited in a sabkha and connecting shal-
low marine environments. It is very poor in fossils, but it can
be presumed that the age of the formation is upper Permian
and lowermost Scythian and, thus, the Permian-Triassic
boundary is located within its upper part. In the course of the
overthrusting of the Silica Nappe, its own evaporitic base as a
sole-thrust was strongly deformed and larger slabs of obducted
Middle Triassic ophiolites were imbricated inside the evapor-
ite series (Réti 1985).
The Bódvaszilas Sandstone Formation, previously known as
‘Seis Beds’, consists of an alternation of purplish red, subordi-
nately greenish grey sandstones, siltstones and shales (Figs. 5—
6). In its uppermost part, red oolite limestones appear forming
a characteristic horizon. Index fossils, such as Claraia clarai
(Emmr.), C. aurita (Hauer) and Eumorphotis hinnitidea (Bitt-
ner), indicate its Induan—lower Olenekian (upper Griesba-
chian—Nammalian) age. The thickness of the formation is ap-
proximately 200—250 m. It is underlain by the Perkupa
Evaporite and overlain by the Szin Marl. In both cases the
boundary of the formations is conformable; however, changes
in lithology and colour are rather sharp.
The Szin Marl Formation is made up predominantly by al-
ternations of brownish-grey, finely crystalline or crinoidal
limestones and beige marlstones. In addition, grey, reddish-
brown, or varicoloured oolites, grey coarse crinoidal lime-
stones, clayey marlstones and siliciclastic layers, as fine sand-
stones, siltstones and shales are also characteristic (Figs. 7—9).
The formation corresponds to the lower half of the former
‘Campil Beds’. Seven ‘lithofacies’ units can be distinguished
(A—G) within the formation (Hips 1996). They represent char-
acteristic facies (or facies successions) which are arranged in
Fig. 3. Stratigraphic subdivision of the Lower Triassic sedimentary rocks in the Aggtelek—Rudabánya Mountains, after Hips 1996 (verti-
cal subdivision is thickness proportional). (M.T. – Middle Triassic, Anis – Anisian, LST – Limestone, SST – Sandstone.)
THE STRUCTURAL SETTING OF LOWER TRIASSIC FORMATIONS 291
stratigraphic sequence. They are indicated by their predomi-
nant rocks (App. 1 and Fig. 3). Two of them were already de-
fined by Kovács et al. (1989), and although the original defini-
tions had to be corrected, the names were kept. Upper
Olenekian (Spathian) age is proved by the occurrence of Tiro-
lites cassianus (Quens.) and T. gr. carniolicus Mojs. The total
thickness of the formation is about 350 m. It is overlain by the
Szinpetri Limestone Formation.
The Szinpetri Limestone Formation is composed predomi-
nantly of typical dark grey nodular, so-called ‘vermicular’
limestones. Its lower half, where marlstone and clayey marl-
stone intercalations or flasers occur, was named the Szinpetri
Limestone Member (s.str.) (Fig. 10), whereas its upper half,
where the mottled, bioturbated limestones alternate with lami-
nated ones, was named Jósvafő Limestone Member (Fig. 11)
(Kovács et al. 1989). It corresponds to the former uppermost
‘Campil Beds’. On the basis of occurrences of Stacheites sp.,
Dinarites dalmatinus (Hauer) and Costatoria costata (Zenk.),
its age is uppermost Olenekian (upper Spathian) and it is also
possible that the upper part of the formation may extend into
the lowermost Anisian. The thickness of the formation in the
Aggtelek Facies is about 150—200 m, whereas in the Bódva
Facies the development of the formation is reduced.
Earlier it was accepted that the lithostratigraphic boundary
between the Szinpetri Limestone and the overlying Gutenstein
Formation coincides with the Scythian/Anisian boundary.
However, it appears more realistic that the lithostratigraphic
boundary is not synchronous in the Aggtelek and Bódva Fa-
cies. Because of poor faunal assemblage, which tolerated re-
stricted environmental conditions, this prediction cannot be
confirmed in the present stage of knowledge.
Structural evaluation
In this section, the structural interpretation based on field
data collected during mapping of Lower Triassic formations is
described and presented in the uncovered geological map at
1:50,000 scale (App. 1). The paper provides additional data on
the geological setting of the central part of the mountains. A
more detailed study dealing with the deformation history of
the mountains was recently published by Less (2000).
Lower Triassic formations are also known from drilling
cores, and some of them are important from a structural point
of view. The local data of cores significantly improved the
structural interpretations based on mapping. Short summaries
of the borehole data are presented for the relevant structural
descriptions.
Major fault-zones and fault systems
The Darnó Zone is a significant NE—SW-trending sinistral
strike-slip fault-zone (Telegdi Roth 1937, 1951; Szentpétery
1997; Less 2000) which divides the Rudabánya Mountains
into segments. The western faults of the Darnó Zone (‘line 1’
according to Less 2000) separate the Aggtelek and the Ruda-
bánya Mountains. The Silica Nappe is represented by the Agg-
telek Facies on the western side of ‘line 1’ and by the Bódva
Facies on the eastern side. The shear zone itself is composed
of blocks in a complicated structural position, especially to the
south of Perkupa (Less 1998b). To the northeast of Perkupa
the zone widens and strike-slip duplexes line the tectonic
boundary between the evaporites and Triassic formations
along two major faults. Such small blocks are composed of
Fig. 6. Characteristic ball-and-pillow structures in red sandstones
formed by water escape in the course of diagenesis, Bódvaszilas
Sandstone Formation, near Perkupa. Scale in cm.
Fig. 5. Hummocky cross-stratified red sandstones and shales from
the upper half of the Bódvaszilas Sandstone Formation, near Perku-
pa. Coin (2.5 cm diameter) for scale.
Fig. 4. Alternating layers of silty—clayey anhydrite (e.g. at the
head of the hammer) and laminated anhydrite within diapiric
folds, Perkupa Evaporite Formation, Alsótelekes quarry. Hammer
for scale. Photo courtesy of Csaba Péró.
292 HIPS
Lower, Middle and Upper Triassic formations to the south—
southwest of Dobódél (on the left side of the Bódva River). On
the right side of the river two strike-slip duplex blocks are also
directly related to the other major fault. One of these blocks is
composed of Szin Marl that is pinched between the Perkupa
Evaporite and Bódvaszilas Sandstone. Strongly folded strata
with steep dip values (70—90°) confirm the strong strain in the
outcrops to the south of Bódvaszilas and in the core cut in well
Bódvaszilas—9. Another strongly tectonized block of marls is
situated southwest of the previous one (cf. Fig. 12: 4—4’). The
Fig. 7. Cross-bedded coarse crinoidal limestones within shales,
Szin Marl Formation unit B, between Perkupa and Varbóc. Scale is
19 cm long.
Fig. 8. One of the most characteristic lithologies of the Szin Marl
Formation is red oolite limestones with blackened bivalve coquinas,
Miklóshegy Limestone (unit C), Perkupa vineyard. Pen (on top left)
for scale.
Fig. 9. Characteristic microfacies of the Szin Marl. A – Distal tempestite layer with graded debris of crinoidal fragments (C) and foraminifers (ar-
rows) covered by clear muds; note the stylolitic boundary to the next tempestite layer at the top of the photo, unit B, near Perkupa. Scale bar is 2
mm. B – Oolite grainstone with Meandrospira pusilla (Ho) in the nucleus of an ooid (middle), unit C, Perkupa vineyard. Scale bar is 0.5 mm.
deformation along this sinistral lateral displacement zone took
place in the Oligocene—Lower Miocene on the basis of facies
distribution according to Szentpétery (1997).
Another characteristic deformation zone is the ENE—WSW-
oriented Jósvafő—Bódvaszilas Fault Zone, which continues to-
wards Kečovo (cf. Mello et al. 1996). Blocks of Middle Trias-
sic formations are thrust over older Middle—Lower Triassic
formations with southeastern vergency (Balogh 1948b, 1953a)
(Fig. 12). This is a type of young-on-older thrust. Balogh
(1948b) and Less (2000) observed as a general situation that
THE STRUCTURAL SETTING OF LOWER TRIASSIC FORMATIONS 293
Fig. 10. Nodular dark grey limestones from the Szinpetri Lime-
stone Member (s.str.), Szinpetri type locality. Hammer for scale.
Fig. 11. Slump structures in laminated dark grey limestone, Jós-
vafő Limestone Member, Jósvafő type locality. Scale in cm.
south of the axis of the Horný vrch the main reverse fault
zones verge southward (cf. Mello et al. 1996). Part of the Jós-
vafő—Bódvaszilas reverse fault-zone is measurable in the field
north of Jósvafő (Fig. 13). Slickenside lineation on the fault
plane indicates thrust with SE vergency, supposedly in an ear-
lier phase which was probably followed by normal displace-
ment afterward (Csontos pers. commun.).
The Jósvafő—Bódvaszilas deformation zone is most proba-
bly composed of additional E—W-directed lateral segments.
Small-dimension, isolated lenses of mismatching rocks made
up of Scythian formations older than the enclosing ones occur
within this fault zone. These blocks are interpreted as push-up
structures in a left-stepping dextral strike-slip system formed
by compression in the transfer zone of tectonic motion (cf.
Woodcock & Fisher 1986). Such strike-slip duplexes occur at
bends of the main shear zone. In this manner small blocks of
the Szinpetri Limestone Member (s.str.) and unit F of Szin
Marl are pinched between the Szinpetri Limestone and Middle
Triassic formations north—northwest of Szinpetri (Fig. 12: 2—
2’). In the western neighbourhood of Szögliget, larger blocks
of the Middle Triassic and Szin Marl formations are imbricat-
ed along the belt. Moreover, thick brecciated zones delineate
blocks within the Szin Marl between Szögliget and Bódvaszi-
las (Fig. 12: 4—4’).
Evaporites and the related red sandstones—shales (northeast
of Jósvafő and west of Szin, cf. Balogh 1953a) most probably
injected up along small opening (pull-apart) segments of the
Jósvafő—Bódvaszilas Fault Zone in a later phase, supposedly
at the same time as the normal displacement of the upper, Mid-
dle Triassic blocks.
A further characteristic element of the fault-system of the
area is represented by E—W dextral strike-slip faults and the
connecting NE—SW reverse faults, as revealed by compilation
of the map. The dextral strike-slip faults are well marked by
split marker horizons of the Szin Marl and formation bound-
aries, in the region between Perkupa, Szin and Szinpetri.
These faults can barely be traced in the Szinpetri Limestone
because of its monotonous development. The displacements
along these strike-slip faults are between 50 and 250 m.
A system of NW—SE faults was also recognized near Jós-
vafő (Less et al. 1988). They cut and offset the Jósvafő—Bód-
vaszilas zone.
Folding
Folds are characteristic and dominant structural elements of
the area (cf. Grill 1989). Their orientations (Figs. 14—15) sug-
gest the following subdivision; however, no evidence could be
observed to interpret their relative order.
Folds with NE—SW axes are predominant in the investigated
area. These metre-sized, open to tight, mostly asymmetrical
folds (e.g. Fig. 16) are widely distributed. On the basis of mea-
sured dip directions, map-scale anticline and syncline struc-
tures with similar orientation are recognized. These are the fol-
lowing: (1) the Varbóc Syncline northeast of Varbóc, which
can be traced to the northwest of Perkupa; (2) another small
syncline southeast of Szin; (3) an assumed anticline in
Keskeny-völgy with an overthrust northwestern limb; and (4)
a succession of small-scale anticlines and synclines south of
Jósvafő. In the Bódva Facies (5) a similar pair of syncline and
anticline (Dobódél Anticline by Balogh 1952) is formed
southeast of Dobódél. The Varbóc Syncline can hardly be rec-
ognized to the SW because of poor exposure of the monoto-
nous Szinpetri Limestone. There is a possible continuation in
294 HIPS
Fig. 12. Cross-sections of the central part
of the Aggtelek Mountains (lines indicat-
ed on the map, App. 1). Legend: letters
are same as those used on the map. (Not
all geographical names are indicated on
the map.)
Fig. 13. Young-on-older thrust fault (arrows) of the Jósvafő—Bód-
vaszilas Zone exposed in a quarry north of Jósvafő (N—S cross-sec-
tion). Wetterstein Limestone with brecciated base is overthrust on
Gutenstein Formation. Hammer (for scale, in middle) is at the con-
tact of the breccia and the Gutenstein Formation.
the Middle Triassic formation in the Teresztenye-plateau ac-
cording to Less (1998b). (For more discussion on the combi-
nation of anticline—syncline structures with other structural el-
ements see the sections below.)
One set of folds with approx. E—W axes is also very charac-
teristic and widely distributed in Lower Triassic formations
and the Gutenstein Formation (cf. Grill 1989). They are half
metre to a couple of metre-size open or close folds. Smaller-
scale anticline and syncline structures can be recognized in the
eastern neighbourhood of Jósvafő on the hillside of
Cseresznyés-kút north of the Szinpetri—Jósvafő road. The
Gutenstein Formation (from Kecső-völgy) and Jósvafő Lime-
stone (to Almás-völgy) are folded into a bigger anticline struc-
ture indicated by dip directions. This Jósvafő Anticline was
recognized by Schréter (1935) and confirmed by Jaskó (1935)
west and south of Jósvafő.
A set of folds with NW—SE (and N—S) axes is observed only
locally. They are 20—50 cm to 1 m in size, predominantly
closed, sometimes open, either asymmetrical or symmetrical
THE STRUCTURAL SETTING OF LOWER TRIASSIC FORMATIONS 295
Fig. 15. Location sketch map of observed folds in Lower Triassic formations.
Fig. 14. Density diagram of the directly measured (stars) and con-
structed (dots) fold axes.
N—S direction. He dated their formation prior to Late Creta-
ceous. The second phase occurred in connection with the sinis-
tral strike-slip motion along the Darnó Zone (Late Oligocene—
Early Miocene) and created folds with E—W axes. Anticlines
in the Jósva valley and near Dobódél originated as a result of
the second phase. The directions of the measured fold hinges
published by Grill (1989) are closely comparable to those pre-
sented in this study in Figs. 14 and 15. Nevertheless, there is
no clear distinction between the two sets of folds on his map.
NNW—SSE-trending folds can be found as interpreted ele-
ments of the second phase, and WSW—ENE-trending folds
formed in the first phase. There are local folded areas where
the axes of first and second phase-folds are almost parallel.
Distribution of dips, which is presented on the
π-diagram
(Grill 1989), shows good correlation with the map in this
study. Sets of anticlines and synclines published by Mello
(1971) from the Slovak part of the Silica Nappe trend in simi-
lar directions as in the Lower Triassic of the investigated area.
Less (2000) interpreted one/main folding phase of the
mountains prior to the Late Cretaceous. He discussed the ex-
planation by Balogh (1948b) on the folding phase followed by
continuous compression, which displaced the syncline cores
(composed of rigid platform limestones) onto the top of the
neighbouring anticlines with southern vergency along reverse
faults (e.g. the Ménesvölgy Zone between Silická Brezová and
Bódvaszilas, the Jósvafő—Bódvaszilas Zone, and several slices
in the Rudabánya Mountains).
To summarize, further extended investigation on folding and
connecting structural elements is needed to characterize the
ductile deformation in the mountains.
folds. A set of smaller-scale anticlines and synclines is recog-
nized north of Henc-völgy (Szőlősardó), east of Varbóc, and
near Szinpetri. The large areal distribution of Szinpetri Lime-
stone between Varbóc and Teresztenye also suggests one (or
more smaller scale) syncline(s) of NW—SE strike, parallel to
the set of anticlines—synclines north of Henc-völgy. A similar
situation is presumed north of Szinpetri and Szin.
Grill (1989) in an earlier study distinguished two folding
phases. The regional folding direction of the first phase is NE,
and axes of this set of folds deviate with ca. 20—30° around a
296 HIPS
Evaporite diapirs
One feature, which cannot be disregarded, is the presence of
a thick evaporite series at the base of the Silica Nappe. Thus,
diapiric processes could be very important mainly in the weak-
ened shear-zones (Grill & Szentpétery 1988). However, evi-
dence in the surface outcrops in the investigated area is spo-
radic. The evaporite series was supposedly pushed up in more
different times, but in a similar manner along the opening seg-
ments of strike-slip faults.
Fault-related mismatching rocks serve as a very good exam-
ple for evaporite tectonics. Red sandstones—shales are ob-
served in very restricted surface distributions along the Jós-
vafő—Bódvaszilas Fault Zone (northeast of Jósvafő and west
of Szin, cf. Balogh 1953a), and along a brecciated zone (in the
Jósvafő Limestone) east of Jósvafő in the Jósva valley (Fig.
12: 1—1’) (cf. Balogh 1953a; Less et al. 1988). One of these
small blocks was penetrated by Jósvafő-2 well (Less et al.
1988), red siliciclastics of the Bódvaszilas Sandstone (0.0—26.0
m), anhydrites and green siliciclastics of the Perkupa Evaporite
(26.2—76.4 m), and dark grey limestones (probably Jósvafő
Limestone) (76.4—84.9 m) occur. According to the borehole data
the evaporite series is relatively close to the surface.
Appearances of red sandstones—shales at the surface along
fault-zones may indicate upward movement of evaporites.
Older rocks were most probably pushed up by underlying gyp-
sum—anhydrite series along locally opened pull-apart portions
of the fault zones.
Discussion of the principal structures
The progressive decrease in age of the Scythian formations
westward resulted from general westerly tilting. This uni-
form younging trend is disturbed by several tectonic zones.
The map-scale structures are described and analysed in this
section.
Predominant structures
On the basis of the deformation style in the Lower Triassic
formations, three E—W-trending segments can be distinguished
in the Aggtelek Mountains. In the northernmost, between Bód-
vaszilas and Szin, a generally ‘intact’ stratigraphic position of
the Lower Triassic formations can be found. Moreover, several
push-up duplexes are accommodated along the front of the
Jósvafő—Bódvaszilas reverse fault zone. The Middle Triassic
formations are overthrust far on top of the Lower Triassic
units. Thus the uppermost part of the Scythian sequence is
missing at the surface.
In the middle belt, between Szin and Szinpetri—Perkupa, the
E—W-trending dextral strike-slip and connecting NE—SW re-
verse faults are the most characteristic elements. The front of
the Jósvafő—Bódvaszilas Fault Zone is lined by small-dimen-
sion duplex lenses. On the other hand, in the southernmost
segment, south of Jósvafő—Szinpetri—Perkupa, combinations
of anticlines and synclines with thrusts are the dominant map-
scale structures in the Lower Triassic formations. In this seg-
ment, the Jósvafő—Bódvaszilas thrust fault is observed within
the Middle Triassic formations north of Jósvafő.
In the Rudabánya Mountains a NE—SW striking pair of anti-
clines and synclines is the main structural feature in the Lower
Triassic formations.
Groups of structural elements
Elements of four structural phases (Fig. 17) were recognized
in the Lower Triassic formations. Their timing is uncertain.
The description is given in the supposed relative order.
First phase. Elements of the first group are the folds and an-
ticlines—synclines with E—W axes observed mainly in the
neighbourhood of Jósvafő (Fig. 12: 1—1’). Their formation
suggests a N(NE)—S(SW) shortening (according to recent co-
ordinates), which occurred prior to the Late Cretaceous (cf.
Less 2000).
Second phase. Elements of the second phase predominate in
the distribution area of the Lower Triassic formation: NE—SW-
striking synclines and anticlines, young-on-older thrust com-
bined with E—W lateral segments (Jósvafő-Bódvaszilas Zone),
push-up duplexes, E—W dextral lateral zones, NE—SW thrust
faults, and evaporite injections. They are connected in special
combinations and they are the most impressive map-scale
structures of the area. Their formations suggest a NW—SE
shortening and NE—SW elongation (according to recent co-or-
dinates).
A complex combination of structural elements was observed
in the southernmost Lower Triassic structural segment. A
map-scale interference structure of two anticlines (one of that
was formed in the first phase and the other refolded it in the
second phase) is interpreted southwest of Szinpetri village, be-
tween the Almás- and Keskeny-völgy. The half-dome struc-
ture is defined by outcropping Szin Marl and pinched between
E—W strike-slip faults from the north and south and a reverse
fault from the southeast. The axes of the anticlines are more or
less at a 120° angle to each other. The first anticline with
WNW—ESE-striking axis forms the continuation of the Jós-
vafő Anticline. This anticline was most probably later folded
Fig. 16. Closed, SE-verging asymmetrical folds with NE—SW axes
plunging SW in red sandstones of Szin Marl unit D, along the cart
road in the Perkupa vineyard (NW—SE cross-section). Hammer for
scale.
THE STRUCTURAL SETTING OF LOWER TRIASSIC FORMATIONS 297
along the NE—SW-trending axis indicated in the Keskeny-
völgy (Fig. 15). Thereafter, the northwestern limb of the sec-
ond anticline was overthrust with southeastern vergency onto
its southeastern limb, supposedly parallel to its axial surface.
As a consequence the younger part of the Szin Marl (units D—
F) crops out from beneath the Szinpetri Limestone along the
Keskeny-völgy and dips to the northwest, north and west (Fig.
12: 2—2’). Older Szin Marl units (B—D) are exposed at the sur-
Fig. 17. Groups of structural elements observed in Lower Triassic
formations (recent co-ordinates).
face along the southern lateral faults at the head of the Almás-
völgy.
Another very characteristic map-scale structure of the south-
ern segment is the combination of the Varbóc Syncline and a
major strike-slip fault zone. The E—W fault extends north of
Perkupa and can be traced to the west. This fault-zone has a
right lateral offset, combined with north—northwest-directed
thrust. The northern limb of the Varbóc Syncline was thrust
and displaced along this fault (Fig. 12: 3—3’). Most of the later-
al motion along its western termination was probably trans-
formed into a NE—SW-striking reverse fault that can be traced
in the Szövetény-völgy. The overthrust process results in sur-
face outcrops of Szin Marl units (upwards from unit D, and
unit B in a separate block) from beneath the Szinpetri Lime-
stone in the Szövetény-völgy. This pattern of folding, reverse
fault, and lateral strike-slip is very similar to the situation in
the Keskeny-völgy described above.
The outcrop of unit B in the Szövetény-völgy was drilled by
the Tornakápolna-3 well. The drilling penetrates from unit B
of Szin Marl (7.0—51.5 m) through the Bódvaszilas Sandstone
(51.5—131.9 m) down into the evaporites, dolomites, radiolar-
ites and basalt (131.9—600.0 m). This block could be interpret-
ed as the southeastern termination of the hinge region of the
WNW—ESE-trending Jósvafő Anticline, which would explain
the relatively elevated position of the block.
Third phase. Small-scale NNW—SSE striking synclines and
anticlines making up minor elements of the area were suppos-
edly formed in the NE—SW shortening phase (based on recent
co-ordinates). Furthermore, smaller-dimension blocks of
Gutenstein Formation, Jósvafő Limestone and Szin Marl can
probably be explained as a frontal thrust at the junction of
strike-slip faults at the head of the Keskeny-völgy. These
smaller-dimension structures are considered to belong to the
third phase.
Fourth phase. Strike-slip duplexes also involving Lower
Triassic formations along the Darnó Zone were already de-
scribed in detail above. Structural elements formed in connec-
tion with sinistral lateral motion along the Darnó faults are
part of the fourth phase (N—S shortening and E—W elongation,
according to recent co-ordinates) (see details in Szentpétery
1997 and Less 2000).
It must be mentioned that Less (1998b, 2000) regards the re-
verse fault in the Szövetény-völgy and the lateral fault extend-
ing from Jósvafő to Perkupa (and one to north, and two other
E—W trending lateral faults to south) to be part of the Darnó
system.
Existence of Jósvafő Anticline
The concepts on the ‘Jósva-völgy’ anticline, formerly pre-
sented by Balogh (1948a,b, 1952, 1953a), Less et al. (1988),
Grill (1989), and Less (1998b, 2000) need to be modified in
the light of new mapping and the above mentioned observa-
tions. A major anticline with E—W axis running all along the
Jósva valley is only an apparent one. The principal evidence is
the dips of the Lower Triassic units (cf. Grill 1989, Fig. 3a).
The general NNE—SSW strike of the Lower Triassic units
along the Bódva valley cannot support the existence of an anti-
cline structure in the eastern part of the Jósva valley.
298 HIPS
Other evidence is the following. In the neighbourhood of
Jósvafő, NW—SE and E—W trending faults cut and displaced
the northern and southern limbs of an anticline with a WNW—
ESE axis. This anticline was observed west and south of Jós-
vafő by Schréter (1935) and Jaskó (1935) and named the Jós-
vafő Anticline. Its southeastern continuation can be
recognized in the Almás- and Keskeny-völgy interference
half-dome structure. A possible updoming structure outcrop-
ping in Szövetény-völgy is interpreted as its southeastern ter-
mination. However, there is no evidence for a direct continua-
tion of any anticline of E—W axis from Szinpetri to the east
along the Jósva-völgy. The measured fold axes are E—W east
of Jósvafő and NE—SW south of Jósvafő. Furthermore, along
the Jósva valley, several folds and local anticline—syncline
structures of NE—SW axes are present, e.g. in the Keskeny-
völgy, in the surroundings of Szin, and north and west of Perku-
pa. Additionally some of them are combined with overthrusts
or strike-slip faults. Thus, the major-scale anticline with E—W
axis is only apparent. The structural situation instead indicates
three independent folding phases interfering with each other.
Conclusions
The mapped area in the Hungarian part of the Silica Nappe
is located to the south of the Jósvafő—Bódvaszilas reverse fault
zone and divided into two parts by the NE—SW sinistral strike-
slip faults of the Darnó Zone. The Upper Permian—Lower Tri-
assic sequence can be subdivided into four lithostratigraphic
units: the Perkupa Evaporite, the Bódvaszilas Sandstone, the
Szin Marl, and the Szinpetri Limestone Formations. Several
subunits were recognized (Hips 1996), successfully separated
and mapped. Formation boundaries, characteristic members of
the Szin Marl, especially red sandstones—shales and oolite
limestones, and biostratigraphic results from the Bódvaszilas
Sandstone, help delineate tectonic structures of the investigat-
ed area.
The Jósvafő—Bódvaszilas tectonic zone was probably active
in sections and/or in several phases. The younger formations
were displaced along dextral strike-slip faults and were over-
thrust to the southeast over the older formations after a folding
phase. This is a type of young-on-older thrust. Small blocks
were pushed up along the E—W lateral segments, which are ac-
commodated along the front of the fault zone. Along the main
faults of the Darnó Zone, small blocks of mismatching rocks
involving Lower Triassic formations are interpreted as strike-
slip duplexes.
Folds are characteristic structural elements in the Lower Tri-
assic formations. Three groups were identified. One set of
folds with NE—SW axes is predominant and widely distributed
in the entire mapped area. Map-scale anticlines and synclines
were also formed in this system (e.g. the Varbóc Syncline, the
assumed Keskeny-völgy anticlines, and an anticline and syn-
cline near Dobódél). Other sets of folds with E—W and NW—
SE axes appear only locally but several anticlines and syn-
clines are also recognized. The map-scale structures reveal
that the formerly proposed anticline with E—W axis running all
along the Jósva-völgy does not exist. The E—W Jósvafő Anti-
cline is proved near Jósvafő but there is no evidence for its
continuation eastward of Szinpetri.
Evidence for evaporite tectonics is sporadic in the surface
outcrops. Fault-related mismatching rocks are observed in the
neighbourhood of Jósvafő. Older rocks were supposedly
pushed up by upward-moving, underlying gypsum—anhydrite
series along opening segments of lateral faults.
On the basis of the deformation style in the Lower Triassic
formations three E—W trending segments can be distinguished
in the Aggtelek Mountains. Characteristic elements of four
structural phases were recognized; however, their timing is un-
certain. The first phase consists of folds and anticlines—syn-
clines with E—W axes observed mainly in the neighbourhood
of Jósvafő. Elements of the second phase predominate in the
distribution area of the Lower Triassic formation: NE—SW
striking synclines and anticlines, young-on-older thrust com-
bined with E—W lateral segments (Jósvafő-Bódvaszilas Zone),
push-up duplexes, E—W dextral lateral zones, and NE—SW
thrust faults. They form special combinations and are the most
impressive map-scale structures of the area. Elements of the
third phase, which are the small-scale NNW—SSE-striking
synclines and anticlines and frontal thrusts at junctions of
strike-slip faults, are in a minority. Strike-slip duplexes involv-
ing Lower Triassic formations were recognized as parts of the
Darnó Zone-related structures (fourth phase).
Acknowledgments: The map presented in this paper is a re-
sult of my PhD research. The inspiration, help and support of
my supervisor, Sándor Kovács, is gratefully acknowledged. I
am very grateful to László Csontos, László Fodor, and Balázs
Koroknai, for discussions on the structural observations and
their contributions to the interpretation. Their constructive re-
views of the manuscript are highly appreciated. The paper
benefited from critical comments of the GC reviewers, György
Less and Jozef Michalík. I thank Csaba Péró for processing
the photos. The fieldwork was partly sponsored by the Hun-
garian Scientific Research Fund (OTKA) No. F029790 and
T019431, and publication was supported by No. P33540.
Dictionary of Hungarian words used on the map
hegy – hill; kút – spring; patak – creek; völgy – valley.
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