GEOLOGICA CARPATHICA
, APRIL 2017, 68, 2, 147 – 164
doi: 10.1515/geoca-2017-0012
www.geologicacarpathica.com
Constraints on the depositional age and
tectonometamorphic evolution of marbles from the Biharia
Nappe System (Apuseni Mountains, Romania)
MARTIN KASPAR REISER
1
, RALF SCHUSTER
2
, PETER TROPPER
3
and BERNHARD FÜGENSCHUH
1
1
Institut für Geologie, Universität Innsbruck, Innrain 52, Bruno Sander Haus, 6020 Innsbruck, Austria;
martin.reiser@uibk.ac.at; bernhard.fuegenschuh@uibk.ac.at
2
Geologische Bundesanstalt, Neulinggasse 38, 1030 Wien, Austria; ralf.schuster@geologie.ac.at
3
Institut für Mineralogie und Petrologie, Universität Innsbruck, Innrain 52, Bruno Sander Haus, 6020 Innsbruck, Austria; peter.tropper@uibk.ac.at
(Manuscript received January 23, 2016; accepted in revised form November 30, 2016)
Abstract: Basement rocks from the Biharia Nappe System in the Apuseni Mountains comprise several dolomite and
calcite marble sequences or lenses which experienced deformation and metamorphic overprint during the Alpine orogeny.
New Sr, O and Cisotope data in combination with considerations from the lithological sequences indicate Middle to Late
Triassic deposition of calcite marbles from the VultureseBelioara Series (Biharia Nappe s.str.). Ductile deformation and
largescale folding of the siliciclastic and carbonatic lithologies is attributed to NWdirected nappe stacking during late
Early Cretaceous times (D2). The studied marble sequences experienced a metamorphic overprint under lower
greenschistfacies conditions (316 –370 °C based on calcite – dolomite geothermometry) during this tectonic event.
Other marble sequences from the Biharia Nappe System (i.e. Vidolm and Baia de Arieș nappes) show similarities in
the stratigraphic sequence and their isotope signature, together with a comparable structural position close to nappe
contact. However, the dataset is not concise enough to allow for a definitive attribution of a Mesozoic origin to other
marble sequences than the VultureseBelioara Series.
Keywords: marble, Srisotope stratigraphy, calcite – dolomite geothermometry, VultureseBelioara, Biharia, Dacia,
Apuseni Mountains.
Introduction
The Permo–Mesozoic sediments of the CircumPannonian
region provide important data for palaeogeographic correla
tions between different Megaunits/Megaterranes in the
Alpine – Carpathian –Dinaridic orogenic system (cf. Schmid et
al. 2008; Vozár et al. 2010). Surface outcrops in the Apuseni
Mountains allow study of the interaction between the Tisza
MegaUnit and the Dacia MegaUnit, represented by the
Biharia Nappe System, during the Alpine evolution.
The Mesozoic sediments of the Tisza MegaUnit in the
Apuseni Mountains experienced no or only slight meta
morphic overprint and thus are well correlated with other
Permo–Mesozoic sequences in the region (e.g., Kutassy
1928a, b; Patrulius et al. 1971; Lupu 1972; Haas & Péró 2004;
Haas et al. 2010; Kovács et al. 2010; Vozárová et al. 2010).
The Biharia Nappe System also contains lenses of carbonate
and dolomite rocks at different structural levels and often
exhibits calcite and dolomite marbles at the contact between
the tectonic units (see Fig. 1; Mârza 1965; Lupu 1972).
However, due to intense deformation and a pervasive meta
morphic overprint during the Cretaceous, the age of these
marble sequences is not well constrained.
Thus, this study presents a characterization of the marble
sequences within the Biharia Nappe System based on
field evidence, Srisotope stratigraphy, calcite – dolomite
geo thermo metry as well as analyses of carbon and oxygen
isotopy, to allow for their attribution to a Palaeozoic or
Mesozoic origin.
Geological background
Until the Early Jurassic, the Alcapa, Tisza and Dacia Mega
units were located in neighbouring positions, forming the
northwestern and northeastern Neotethys margin (e.g.,
Sǎndulescu 1984; Vörös 1993; Csontos & Vörös 2004; Haas
& Péró 2004; Schmid et al. 2008; Haas et al. 2010; Kovács et
al. 2010). The Middle/Late Jurassic eastward propagating
opening of the Alpine Tethys starts the separation of the
Alcapa, Tisza and Dacia Megaunits from Europe. Vörös
(1993) clearly shows a Mid to Upper Jurassic change from
a European to a Mediterranean faunal assemblage through
brachiopod taxa (e.g., Nucleata, Calvirhynchia contraversa)
for both units, namely Tisza and Dacia. It is an ongoing
discussion whether the Tisza and Dacia Megaunits were sepa
rated by an oceanic branch (e.g., Sǎndulescu 1984; Schmid et
al. 2008; Kounov & Schmid 2013), or whether the two units
formed part of the same microplate, which moved and rotated
away from the European margin in the Late Jurassic (Csontos &
Vörös 2004). Recent results indicate a comparable evolution
in both, Tisza and Dacia Megaunits from Early Cretaceous
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Fig. 1. a — Overview of the study area, a black square shows the position of the study area in the Alpine – Carpathian – Dinaride orogenic
system. Modified from Kounov & Schmid (2013). b — Simplified overview map of the Apuseni Mountains. Sample locations and abbrevia
tions of the units described in the text are given; a black frame marks the position of Fig. 2.
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times onwards and thus support a neighbouring position
throughout their Alpine evolution (Reiser et al. 2016).
Following the Late Jurassic emplacement of the South
Apuseni Ophiolites, Early Cretaceous deformation (D1) is
shown through structural and thermochronological data (Ar–Ar
muscovite and Ar–Ar hornblende; Dallmeyer et al. 1999;
Reiser et al. 2016). Subsequent NWdirected thrusting of the
Biharia Nappe System on top of the Bihor and Codru Nappe
during D2 caused greenschistfacies metamorphic overprint in
structurally lower parts of the nappe pile, namely the Bihor
Nappe, Codru Nappe, Baia de Arieș Nappe and Biharia Nappe
s.str. (cf. Ianovici et al. 1976; Balintoni & Vlad 1996; Kounov
& Schmid 2013). This late Early Cretaceous–early Late Creta
ceous phase is well constrained through structural and thermo
chronological data and responsible for the presentday nappe
stack of the Apuseni Mountains (Sǎndulescu 1984; Balintoni
1994b; Schuller 2004; Schuller & Frisch 2006; Schuller et al.
2009; Merten et al. 2011; Kounov & Schmid 2013).
Late Cretaceous extension/exhumation (D3; Reiser et al.
2016) is associated with syntectonic hanging wall sedimenta
tion of “Gosautype” sediments which seal the nappe contacts
of previous tectonic events (Schuller 2004; Schuller & Frisch
2006). Compressional deformation during the late Maastrich
tian–middle Eocene (“Laramian Phase”; D4) caused brittle
reactivation of previous structures (Balintoni 1994b; Merten et
al. 2011). TopNW to N and subordinate topESE highangle
thrusts along nappe contacts, N–S striking folds, as well as
uplift and erosion of basement and posttectonic sediments are
attributed to this E–W compression (Balintoni 1994b; Krézsek
& Bally 2006; Schuller & Frisch 2006; Merten et al. 2011).
The Biharia Nappe System of the Apuseni Mountains com
prises preVariscan, polyphase metamorphic crystalline base
ment (Balintoni et al. 2010), Palaeozoic granitoid intrusions,
a late Palaeozoic cover, Mesozoic sequences of variable thick
ness, and Jurassic ophiolites (e.g., Ianovici et al. 1976; Bleahu
et al. 1981; Sǎndulescu 1984; Pană 1998; Balintoni et al. 2009;
and detail map in Fig. 1). Syn to posttectonic deposits of
Early and Late Cretaceous age unconformably overlie the
nappe contacts between the Vidolm, the Baia de Arieș and
Biharia s.str. nappes (e.g., Bleahu et al. 1981; Csontos &
Vörös 2004; Schuller et al. 2009; Kounov & Schmid 2013).
Based on the fact that the Transylvanian Ophiolitic unit (which
includes the South Apuseni Ophiolites; Hoeck et al. 2009;
Ionescu et al. 2009, 2010) overlies the Bucovinian Nappe
System and the Biharia Nappe System (cf. Sǎndulescu 1984;
Krézsek & Bally 2006), Schmid et al. (2008) attributed the
Biharia Nappe System to the Dacia MegaUnit, while other
authors (e.g., Panǎ 1998; Csontos & Vörös 2004; Haas & Péró
2004) previously considered it to be an integral part of Tisza.
The VultureseBelioara Series (VBS) of the Biharia Nappe
s.str. (cf. Mârza 1965, 1969; Ianovici et al. 1976; Balintoni et
al. 1987) and the Sohodol Marbles of the Baia de Arieș Nappe
(Ianovici et al. 1976; Bordea et al. 1988) are examples of such
sequences thought to represent the Mesozoic cover of their
respective tectonic units (pers. comm. by Trümpy in Balintoni
1994a). A comparable succession consisting of siliciclastic
sediments, calcite marbles and dolomites is also present in the
structurally highest Vidolm Nappe, just below the South
Apuseni Ophiolites. Kounov & Schmid (2013) tentatively
attributed a Mesozoic age to this succession. Due to their
lower erodability, these calcite and dolomite marbles form
cliffs within the surrounding basement lithologies.
Marble sequences of the Biharia Nappe System
Vulturese-Belioara Series (VBS) and marbles of the Biharia
Nappe s.str.
The greenschistfacies metasedimentary succession of the
VultureseBelioara Series crops out at the contact between the
Biharia Nappe s.str. and the Baia de Arieș Nappe in the south
eastern part of the Apuseni Mountains (cf. Figs. 2, 3a and
Mârza 1965, 1969; Ianovici et al. 1976; Balintoni et al. 1987).
This sequence of quartzites, dolomites and marbles was tradi
tionally interpreted as the lowgrade metamorphosed middle
Palaeozoic cover of the mediumgrade metamorphic base
ment, but field observations by Trümpy (pers. comm. reported
in Balintoni 1994a) and Sasaran E. (pers. comm.) point
towards a deposition during the Triassic. Based on the strati
graphy of the VultureseBelioara Series, a correlation with the
FöderataStruženik Series of the Western Carpathians was sug
gested (Dimitrescu in Ianovici et al. 1976). The Vulturese
Belioara Series comprises the following lithologies: basal
quartzitic conglomerates with white and purple quartzcompo
nents (Fig. 3b) and sericitic schists; ~100 m of well bedded
(0.5–2 m) black graphitic dolomites with remnants of crinoids
(pers. comm. by Sasaran E.) passing into ~ 350 m thick, mas
sive reddish to yellowish dolomites, followed by 0.5–5 m of
thinbedded (0.5–10 cm), red weathered, sericitic and platy
marbles (see Fig. 3c) and finally ~ 350 m thickbedded light
grey, beige and white, partially dolomitic marbles (Fig. 3d, e)
at the top. Basal quartzitic conglomerates, dolomites and mar
bles dip to the SE and are folded around a NE–SW oriented
fold axis (Mârza 1965, 1969; Solomon et al. 1981; Ianovici et
al. 1976). The fold hinge is not exposed, but the relationship
between bedding and axial plane foliation indicates a synform.
Two large NNE–SSW trending faults dissect the Vulturese
Belioara Series causing the presentday geometry of three
ridges: the VultureseBelioara ridge in the NE, the Scariţa
Belioara ridge in the centre and the Leurda ridge in the SE
(Fig. 4). The bedding planes show a trend towards steeper
inclinations towards the SW and their strike changes from
NE–SW in the Belioara ridge to ENE–WSW in the Scariţa
Belioara ridge (Figs. 2, 3a, 4). A set of roughly N–S to NW–SE
trending vertical joints commonly exhibits hematitelimonite
ore mineralization. The mineralized joints provide evidence
for hydrothermal activity in the VultureseBelioara Series,
although its age cannot be constrained (Ianovici et al. 1976).
The Ocoliș and Poșaga valley cross the VultureseBelioara
Series and allow for comparison along two sections (Fig. 5).
In the Ocoliș profile only the lower limb of the fold is exposed
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and the calcite marbles and dolomites show a greater thickness
compared to the Poșaga profile. At the top of the succession,
a thin layer of mylonitized marbles (see Fig. 3e) cut off by
a brittle fault associated with fault breccias mark the nappe
contact to the overlying Baia de Arieș Nappe. Several NE–SW
trending faults, filled with brecciated fragments in a red matrix
cut (Fig. 3f) through the marbles towards the top of the succes
sion. The Poșaga Profile exhibits a complete section through
the fold: the calcite marbles are located in the core of the fold
and the dolomites and quartzitic conglomerate as thin layers
on both limbs. The dip of the bedding planes is slightly steeper
than in the Ocoliș profile (Fig. 5).
Several dolomite lenses crop out within the crystalline base
ment rocks in the eastern part of the Biharia Nappe s.str.
(Fig. 3g and h). The dolomite is yellowish brown in colour and
shows intense cross cutting by quartz veins. Lenses of pinkish
white quartzite are often associated with the dolomite.
The pattern of these lenses reflects the fold structure of the
Biharia Nappe s.str. and seemingly adhere to a continuous
structural level (cf. Fig. 2).
Sohodol Marbles and marbles of the Baia de Arieș Nappe
In the western part of the Apuseni Mountains, a sedimentary
sequence known as Sohodol Marbles (SOH in Fig. 1) overlies
the Baia de Arieș Nappe with a discordant contact (Ianovici et
al. 1976; Bordea et al. 1988). Basal black quartzites and gra
phitic schists are overlain by white to darkgrey, well bedded
(10 cm) marbles with strongly folded quartz lenses. These
white marbles are intercalated by thin reddish layers. The tran
sition from quartzites to marbles is marked by breccias and
cataclasites. The age of this marble succession is not well con
strained yet, but according to Ianovici et al. (1976) crinoid
stems were described in the Sohodol Marbles by Lupu (1972),
indicating a Mesozoic age of the Sohodol Marbles.
In the eastern part of the Baia de Arieș Nappe, near the town
of Baia de Arieș, several large marble lenses crop out in the
vicinity of Neogene intrusive bodies (VIN in Fig. 1). The age
of these coarse grained, white to yellowish marbles is not
known, but Kounov & Schmid (2013) tentatively attribute
a Mesozoic age in their map of the study area.
Fig. 2. Geological map of the VultureseBelioara Series. Sample locations and profile traces of Fig. 5 are given on the map.
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Fig. 3. Field observations, locations are marked in Fig. 2: a — the ScariţaBelioara ridge and isolated marble blocks along the fault, picture was
taken towards the north; b — polished section of the basal quartz conglomerate with red components; c — the red condensed marbles separa
ting the dolomites and calcite marbles; d — the contact between dolomites and calcite marbles in the field, picture taken towards the NE;
e — image of outcrop with typical layered calcite mylonites from which sample MR51 was taken; f — faultbreccia with red matrix;
g, h — isolated quartzite lenses, associated with strongly veined dolomite lenses.
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Marbles of the Vidolm Nappe
Similarly to the Baia de Arieș Nappe, the Vidolm Nappe
comprises several occurrences of calcite and dolomite marbles
(Fig. 1). Marble lenses are located within basement rocks
(e.g., sample MR83) and a sequence of calcite and dolomite
marbles is present below the tectonic contact with the over
lying South Apuseni Ophiolites (VID in Fig. 1). The marbles
at the top of the Vidolm Nappe exhibit basal quartzitic con
glomerates (“MetaPsephites”; Balintoni et al. 1987) and
black quartzitic schists (Ianovici et al. 1976). The calcite mar
bles are grey, metrescale to cmscale bedded with phyllitic
and quartzitic intercalations, while the overlying dolomite
marbles are yellowishwhite and massive. At the top of the
sequence, light grey marbles are present. The Vidolm Marbles
are directly overlain by the South Apuseni ophiolites and their
Late Jurassic to Early Cretaceous sedimentary cover, repre
sented by non/ lowmetamorphosed shallowwater limestones
(Ilie 1936; Sasaran 2005). The marbles exhibit isoclinal folds
and increa sing deformation towards the contact with the over
lying ophiolites. Several dikes with ferruginous crusts cross
cut the marbles and vertical joints exhibit ore mineralization.
Savu (2007) reports burialrelated metamorphism at tempera
tures from 200–400 °C for marbles in the uppermost part of
the Vidolm Nappe. Based on their position on top of the base
ment rocks, Kounov & Schmid (2013) assume a Mesozoic age
of these marbles, but other than that no information on their
age is given in published literature.
Methods
Mechanical sample preparation, Xray fluorescence spec
trometry (using a SpectroXepos Xray spectrometer) and O – C
isotope analyses were performed at the University of
Innsbruck, while the chemical sample preparation for
Srisotopic analyses was performed at the Geological Survey
of Austria in Vienna. Weathered surfaces were removed from
the samples before crushing and milling.
δ
18
O and δ
13
C isotopy
Stable isotope ratios from carbonates potentially yield infor
mation about their origin, for example, allowing reconstruc
tions on the isotopic composition of the ocean during their
deposition. However, processes such as deformation, volatili
zation, mineral reactions and metasomatism can affect and
alter the isotope ratio of the samples. Thus, the source sets an
isotopic baseline which can subsequently be shifted by isoto
pic fractionation. This study provides a general overview of
the δ
18
O and δ
13
C isotopy of the marbles, which is used for
comparative purposes. Oxygen and carbon isotope values of
several marbles from the Apuseni Mountains were measured
to distinguish between altered and original isotopic
compositions.
Subsamples for stable carbon and oxygen isotope analyses
were obtained using a handheld drill bit after removing the
weathered surfaces. Analyses were carried out at the Institute
of Geology at the University of Innsbruck, using a Thermo
finnigan GasBench II equipped with a CTC CombiPal
autosampler linked to a DeltaPlusXL mass spectrometer.
The analytical precision (1 sigma) is typically 0.08 % for δ
18
O
and 0.06 % for δ
13
C (Spötl & Vennemann 2003). The reaction
time is 82 minutes per sample. Carbon stable isotope ratios are
reported relative to the VPDB (ViennaPee Dee Belemnite).
The oxygen stable isotope ratios are given relative to the
VPDB and as well in VSMOW (ViennaStandard Mean Ocean
Water).
Calcite – dolomite geothermometry
Calcite – dolomite geothermometry is based on the tempera
turedependent miscibility between calcite and dolomite.
Increasing temperatures cause X
mg
in calcite to increase along
the calcitedolomite miscibility gap (Letargo et al. 1995). The
following equation by Anovitz and Essene (1987) describes
the compositiontemperature relation in calcite:
T(°K) = A(X
mg
) + B/(X
mg
)
2
+ D(X
mg
)
0.5
+ E
A, B, C, D and E are coefficients with the values –2360,
–0.01345, 2620, 2608 and 334. X
mg
represents the concentra
tion of mg in calcite (mg/(mg+ca)) in atoms per formula unit.
The formula above does not account for the molar concentra
tion of FeCO
3
in calcite. However, due to the low Fecontent
of the analysed limestones it is of no concern for the result.
The commonly occurring decomposition of dolomite from
calcite during cooling makes this geothermometer suitable for
lowgrade rocks. Due to the high reequilibrationrate during
retrograde conditions, the temperature estimates represent the
last thermal overprint and have to be considered as minimum
temperatures (Essene 1983).
Fig. 4. Piplot of bedding planes for the VultureseBelioara Series
showing a general dip towards the SE. A subset of steeply SSE dipping
bedding planes from the ScariţaBelioara ridge is marked with
×
symbols.
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Sr-isotope stratigraphy
The
86
Sr/
87
Sr ratio of dissolved Sr in the world’s oceans
changes over time and thus allows correlation and dating of
sediments using their
86
Sr/
87
Sr isotopic ratio (McArthur 1994;
Veizer et al. 1997, 1999; McArthur et al. 2012). McArthur et
al. (2001, 2004) present a standard curve of
86
Sr/
87
Sr variation
over the last 509 Ma. The curve represents the bestfit on
measurements of
86
Sr/
87
Sr in samples dated by biostratigraphy,
magnetostratigraphy and astrochronology enabling the user to
do a rapid conversion of
86
Sr/
87
Sr to age and vice versa
(McArthur et al. 2001). The reliability of Srisotope strati
graphy depends on the potential of the tested rocks to preserve
depositional isotopic values, but even marbles that have expe
rienced multiphase metamorphism (up to amphibolitefacies
conditions) and deformation may retain their depositional
Fig. 5. Profiles through the VultureseBelioara Series: OcolișSection (above) and PoșagaSection (below). For profile trace see Fig. 2.
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carbonisotope values and preserve nearprimary
87
Sr/
86
Sr
ratios (Frank et al. 1990; Melezhik 2001, 2013; SatishKumar
et al. 2008; Murra et al. 2011).
For Srisotope analyses, only pure white marble samples
from the centre of at least some decimetres wide layers were
chosen. The carbonate fractions of most samples were ana ly
sed for Mn, Mg, Sr and Ca by Xray spectroscopy to evaluate
the degree of postsedimentary alteration and to check for Rb
contamination (geochemical screening; e.g., Brand & Veizer
1980) according to the criteria of Melezhik et al. 2001. About
70 mg of WRpowder were dissolved in 0.1n CH
3
COOH
and the undissolved part of the sample was extracted by
a centrifuge immediately after dissolution of the carbonate.
The chemical preparation follows the procedure described by
Sölva et al. (2005).
Srratios were analysed on a Triton TI TIMS from Re double
filaments. Due to the fact that measurements have been per
formed over three years, changes in the hardware of the
machine caused different values for the NBS987 standard for
the individual periods of measurements:
2010
86
Sr/
87
Sr = 0.710252 ± 6 2σ
m
(n = 8)
2011
86
Sr/
87
Sr = 0.710246 ± 4 2σ
m
(n = 10)
2012
86
Sr/
87
Sr = 0.710278 ± 3 2σ
m
(n = 9)
The measured values were corrected for a standard value of
0.710248.
Results
Thin sections
Thin sections of the marbles were investigated under the
microscope to study geometrical relationships between the
mineral constituents with particular reference to calcite.
Homeoblastic and heteroblastic textures were discriminated
and the maximum grain size of calcite (MGS) was measured
to characterize the marbles. Deformation twins were discrimi
nated to qualitatively determine the degree of metamorphic
overprinting. The thin sections are discussed for each nappe
within the Biharia Nappe System (Vidolm, Baia de Arieș and
Biharia s.str.). In each section the thin sections are discussed
from bottom to top: the description starts with marble lenses
from the crystalline basement before the marbles at the top of
the nappes are discussed. Deformation twins in calcite are
used to provide an estimate of the thermal overprint recorded
in the calcite marbles (e.g., Jamison & Spang 1976; Ferrill
1991; Burkhard 1993; Ferrill et al. 2004).
Vidolm Nappe
Sample MR83 (Fig. 6a) was taken from a marble lens
containing retrogressed eclogite bodies (personal comm.
Balintoni I.; Fig. 6b) within the crystalline basement of the
Vidolm Nappe. A coarse grained homeoblastic texture indi
cates a high thermal overprint (amphibolite facies; cf. Pană
1998) with only little retrogressive overprint. However, seri
citic rims around mica flakes indicate a polymetamorphic evo
lution. The thin sections from the top of the Vidolm Nappe
exhibit decreasing grain sizes and increasing amounts of
dynamically recrystallized grains towards the hanging wall
contact with the South Apuseni ophiolites (samples MR101,
MR100, MR99 and MR89). Serrated grain boundaries in sam
ple MR101 (Fig. 6c) indicate grain boundary migration recrys
tallization under thermal conditions of 250–350 °C. Angular
feldspars showing undulose extinction support this conclusion
(Passchier & Trouw 1996). In combination with the presence
of thick and patchy type IV twins which are cross cut by
type II and type I twins (sample MR101; Fig. 6c) a polyphase
deformation can be inferred (cf. Ferrill et al. 2004).
Baia de Arieș Nappe
Mica flakes in sample MR23 (Fig. 6d) from a dynamically
recrystallized dolomite marble lens within the crystalline
basement are beginning to form a weak foliation. The predomi
nantly coarse grained samples from the Sohodol Marbles
(e.g., sample MR67; Fig. 6e) show grain boundary migration
recrystallization and are interpreted to have formed under
high anchizonal to lower greenschist facies temperatures
(250–350° C). The calcite twins range from patchy type IV
twins, bent and serrated thick twins (type III) to thin twins
(type I) crosscutting the former (Passchier & Trouw 1996).
Thus, a polyphase deformation is inferred. The very coarse
grains (2.5 mm) from sample MR163 (Vinţamarbles) proba
bly relate to a thermal overprint during the intrusion of
Neogene magmatics in the vicinity.
Biharia Nappe s.str.
Sample MR51 (Fig. 6f) represents a fine grained, dynami
cally recrystallized calcite mylonite at the contact between the
Fig. 6. Thin sections of marbles from different tectonic units. a — sample MR83 from the Vidolm Nappe, which exhibits tapered twinning
lamellae and coarse grained texture (crossed polarizers); b — garnet and amphibole minerals under crossed polarizers in a thin section of
a presumably retrogressed eclogite (personal comm. Balintoni, I.) associated with the marbles of sample MR83; c — thin twinning lamellae
overprinting thick and patchy twinning lamellae in sample MR101 from the Vidolm Nappe (crossed polarizers); d — heteroblastic texture of
sample MR23 from the Baia de Arieș Nappe. The large, dark grey grain in the centre exhibits patchy twins (crossed polarizers); e — sample
MR67 from the Sohodol marbles of the Baia de Arieș Nappe with coarse grain sizes and multiple generations of twins (crossed polarizers);
f — finegrained calcite mylonite of sample MR51 (VultureseBelioara Series; Biharia Nappe s.str.); g — sample MR27 (VultureseBelioara
Series; Biharia Nappe s.str.) exhibits triple junctions and patchy type IV twins, (crossed polarizers); h — sample MR41 (VultureseBelioara
Series; Biharia Nappe s.str.) exhibits a heteroblastic texture with small recrystallized grains and patchy type IV twins in larger grains (crossed
polarizers).
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VultureseBelioara Series and the overthrusted Baia de
Arieș Nappe. Most thin sections from samples of the
Vulturese Belioara Series (MR9, MR13, MR19, MR26,
MR27, MR41) exhibit a heteroblastic texture (e.g.,
Fig. 6g, h and Table 1). Intermediate grain sizes of
~1–1.5 mm show well developed triple junctions and
a se cond population of small recrystallized calcite grains
around the bigger ones. Larger grains (e.g., sample MR27;
Fig. 6g) exhibit patchy type IV twinning, overprinted by
recrystallization and cross cut by type II and III twins (cf.
scheme of Burkhard 1993). Sample MR41 from the red,
platy marbles shows very small, recrystallized grains and
larger ~1mmsized calcite grains with patchy type IV twins.
δ
18
O and δ
13
C isotopy
Analytical data from isotope analyses (Table 2) are sum
marized in Fig. 7 and compared with data from Pană
(1998; Table 3). Although only local names are given, the
dataset from Pană (1998) allows for a general comparison
with new data from this study. The studied samples cover
a broad range of δ
18
O values but cluster around 20–25 ‰
(SMOW), typical of diagenetically altered limestones
(Sharp 2007). Typical greenschistfacies limestones range
from –0.3 to +5.6 for carbon isotope values and from 18.1
to 28.1 for oxygen isotope values (Dunn & Valley 1985).
However, the isotopic values (Fig. 7) show an interesting
correlation: isolated marble lenses predominantly yield
δ
18
O
VSMOW
values ≤ 20 ‰ and a large spread in δ
13
C
VPDB
values, whereas samples from marble sequences located at
or close to nappe contacts cluster in a narrow range of
δ
13
C
VPDB
values and predominantly yield δ
18
O
VSMOW
values
of more than 20 ‰.
Due to Cretaceous metamorphism, all samples expe
rienced a thermal overprint and were possibly exposed to
alteration processes. However, the δ
18
O
VSMOW
values of
most analysed samples range within the limits of typical
unaltered marine limestones (between 22.6 and 30.9 ‰;
Veizer et al. 1999), suggesting that metamorphism did not
significantly alter the isotopic composition of the protolith.
According to Fölling & Frimmel (2002), samples with
δ
18
O
VSMOW
values between 20.6 and 16.4 (samples MR101,
MR67, MR161) experienced slight alteration and
δ
18
O
VSMOW
≤ 16.4 indicates considerable alte ration (sample
MR23). All samples from the Vulturese Belioara Series
yield δ
18
O
VSMOW
values between 28.1 and 30.1 ‰ and
a δ
13
C
VPDB
value between 2.1 and 2.6 ‰, which are typical
for unaltered marine limestones (Veizer et al. 1999). The
samples were taken from the white marbles and do not
cover the dolomites and the red layer between the dolomite
and marble successions. Sample MR19 from an isolated
marble block along the fault in the Belioara valley shows
slightly lower δ
18
O
VSMOW
and δ
13
C
VPDB
values, but still plots
within the range of the VultureseBelioara Series. The pre
sumably Mesozoic marbles from the Baia de Arieș Nappe
(Vinţa and Sohodol Marbles) yield slightly lower values
Sample
Geographic Position
Tectonic Unit
Lithostrat.
Unit
Macr
oscopic Characterisation
Mineral composition
Textur
e
Dominant
Twinning
Type
Max. grain size [mm]
Latitude
Longitude
MR89
46°24'12.544" N
23°30'23.466" E
V
idolm Nappe
VID
layered and folded mylonite
Cc, Dol, Qz, Fsp, Ms
heteroblastic
2
0.5
MR99
46°27'42.078" N
23°32'23.781" E
V
idolm Nappe
VID
fine grained yellowish white marble
Cc,
Ap, Ep, Ms
heteroblastic
2–3
0.5
MR101
46°28'03.425" N
23°32'28.572" E
V
idolm Nappe
VID
coarse grained yellowish white marble
Cc, Qz,
Ap
heteroblastic
3
2.0
MR102
46°30'04.664" N
23°35'23.136" E
V
idolm Nappe
VID
coarse grained yellowish white marble
Cc,
Ap, Mus, Py
heteroblastic
3
2.0
MR83
46°31'05.521" N
23°35'25.559" E
V
idolm Nappe
L
coarse grained white marble
Cc, Ms,
Ap
homeoblastic
3
2.0
MR22
46°21'30.267" N
23°01'1
1.868" E
Baia de
Aries N.
SOH
coarse grained light grey marble
Cc
heteroblastic
1
2.0
MR67
46°21'03.372" N
22°50'19.371" E
Baia de
Aries N.
SOH
coarse grained light grey marble
Cc
homeoblastic
2
2.0
MR163
46°21'45.709" N
23°15'54.1
11" E
Baia de
Aries N.
VIN
very coarse white marble
Cc
homeoblastic
4
2.5
MR23
46°24'19.178" N
23°13'04.455" E
Baia de
Aries N.
L
fine to medium grained, beige dolomite marble
Cc, Dol, Qz, Ms
heteroblastic
2
1.0
MR51
46°29'15.245" N
23°22'13.576" E
Biharia N. s.str
.
VBS
fine grained mylonite with dark layers
Cc, Qz, Py
homeoblastic
n.a.
0.05
MR26
46°30'23.343" N
23°26'33.964" E
Biharia N. s.str
.
VBS
medium grained layered marble
Cc, Ms, Qz
heteroblastic
2
1.2
MR27
46°30'27.1
14" N
23°26'30.332" E
Biharia N. s.str
.
VBS
medium grained layered marble
Cc, Ms, Qz
heteroblastic
2
1.2
MR9
46°29'46.972" N
23°25'53.775" E
Biharia N. s.str
.
VBS
medium grained white marble
Cc
heteroblastic
2
1.2
MR13
46°27'33.207" N
23°23'51.913" E
Biharia N. s.str
.
VBS
medium grained white marble
Cc,
Ap
heteroblastic
2
1.5
MR19
46°27'47.404" N
23°22'29.406" E
Biharia N. s.str
.
VBS
fine to medium grained white marble
Cc, Qz, Ser
, Py
heteroblastic
2
1.2
MR41
46°30'34.50" N
23°26'19.42" E
Biharia N. s.str
.
VBS
red weathered, platy marble
Cc
heteroblastic
n.a./ 4
1.0
MR161
46°31'49.002" N
23°34'31.059" E
Biharia N. s.str
.
L
yellowish dolomite breccia
Cc, Dol
heteroblastic
3
0.4
Table
1:
Important
sample
parameters
based
on
the
petrographic
analysis
of
the
thin
sections.
Abbreviations:
L = marble
lens
within
the
crystalline
basement;
VID = marble
sequence
from
the
upper
most part of the
V
idolm Nappe; SOH = Sohodol marbles from the Baia de
Arieș Nappe;
VIN = V
inţa marbles of the Baia de
Arieș Nappe;
VBS = V
ulturese Belioara Series (Biharia Nappe s.str
.).
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for δ
13
C
VPDB
(1.6–2.5 ‰) and considerably lower δ
18
O
VSMOW
values (20.1–23.8 ‰).
The δ
13
C
VPDB
values of the whole Vidolm Nappe dataset range
between 1.7 and 3.2 ‰ the values of δ
18
O
VSMOW
range between
20.4 and 27.5 ‰. The presumably Palaeozoic marble lens from
the crystalline basement of the Vidolm Nappe (sample MR83;
yellow triangle with red rim in Fig. 7) also yields stable isotope
values compatible with only slightly altered marbles.
Sample
Geographic position
Tectonic Unit
Lithostrat.
Unit
Type
C–isotopes
VPDB
O–isotopes
VSMOW
O–isotopes
VPDB
Latitude
Longitude
MR89
46°24'12.544" N
23°30'23.466" E
Vidolm Nappe
VID
C
2.23
27.53
–3.28
MR99
46°27'42.078" N
23°32'23.781" E
Vidolm Nappe
VID
C
3.19
26.45
–4.32
MR100
46°27'31.955" N
23°32'28.795" E
Vidolm Nappe
VID
D
2.33
25.70
–5.05
MR101
46°28'03.425" N
23°32'28.572" E
Vidolm Nappe
VID
C
1.73
20.37
–10.23
MR102
46°30'04.664" N
23°35'23.136" E
Vidolm Nappe
VID
C
2.10
22.99
–7.68
MR83
46°31'05.521" N
23°35'25.559" E
Vidolm Nappe
L
C
2.31
22.38
–8.27
MR22
46°21'30.267" N
23°01'11.868" E
Baia de Aries N.
SOH
C
2.48
23.85
–6.85
MR67
46°21'03.372" N
22°50'19.371" E
Baia de Aries N.
SOH
C
1.87
20.05
–10.53
MR163
46°21'45.709" N
23°15'54.111" E
Baia de Aries N.
VIN
C
1.62
22.67
–7.98
MR23
46°24'19.178" N
23°13'04.455" E
Baia de Aries N.
L
C
1.37
14.91
–15.52
MR14
46°27'33.207" N
23°23'51.913" E
Biharia N. s.str.
VBS
C
2.48
29.10
–1.75
MR51
46°29'15.245" N
23°22'13.576" E
Biharia N. s.str.
VBS
C
2.43
28.21
–2.62
MR26
46°30'23.343" N
23°26'33.964" E
Biharia N. s.str.
VBS
C
2.63
29.75
–1.13
MR27
46°30'27.114" N
23°26'30.332" E
Biharia N. s.str.
VBS
C
2.06
28.11
–2.72
MR9
46°29'46.972" N
23°25'53.775" E
Biharia N. s.str.
VBS
C
2.35
29.29
–1.57
MR13
46°27'33.207" N
23°23'51.913" E
Biharia N. s.str.
VBS
C
2.64
30.09
–0.8
MR19
46°27'47.404" N
23°22'29.406" E
Biharia N. s.str.
VBS
C
1.97
26.32
–4.46
MR161
46°31'49.002" N
23°34'31.059" E
Biharia N. s.str.
L
D
0.76
18.19
–12.34
Table 2: Overview of the results from δ
18
O and δ
13
C isotope analyses. Type refers to the lithology type: D for dolomite or C for calcite.
Abbreviations: L = marble lens within the crystalline basement; VID = marble sequence from the uppermost part of the Vidolm Nappe;
SOH = Sohodol marbles from the Baia de Arieș Nappe; VIN = Vinţa marbles of the Baia de Arieș Nappe; VBS = Vulturese Belioara Series
(Biharia Nappe s.str.).
Fig. 7. Plotted results of the data from δ
18
O and δ
13
C isotope analyses. Data from the present study and data from Pană (1998) are discriminated
by a red frame.
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Calcite – dolomite geothermometry
Equilibrium temperatures were calculated for four samples
from the Vidolm Nappe and the Biharia Nappe s.str. (see
Table 4; representative analyses are given in the Supplemen
tary data; Table S1). All temperature estimates plot within
greenschistfacies thermal conditions. Samples MR26 and
MR161, both from the Biharia Nappe s.str., yield slightly
higher temperatures than the Vidolm samples (~ 354 ± 54 °C
and 370 ± 45 °C versus ~ 316 ± 52 °C and 336 ± 37 °C; Table 4).
Samples MR100 and MR89 were both taken from the calcite
marble succession in the uppermost part of the Vidolm Nappe.
The thermal conditions indicate lowermost greenschistfacies
metamorphism and are in agreement with their relative struc
tural position in the Biharia Nappe System. A comparison with
data from Pană (1998) turned out to be difficult, because only
peak temperatures of the samples are given and not the tem
perature range as in the dataset of this study. A conversion
using the values given in figs. 5–10 in Pană (1998) seemed to
be unreliable, thus only the peak temperatures of Pană (1998)
are shown in Fig. 1.
Sr-isotope stratigraphy
A total number of seven samples were prepared and ana
lysed regarding their Srisotopy: four samples of fine grained
white marbles of the VultureseBelioara Series (MR9, MR13,
MR26, MR27), two samples from a presumably Mesozoic
marble succession of the Vidolm Nappe (MR99 and MR102)
and one coarse grained sample from a marble lens within the
crystalline basement of the Baia de Arieș Nappe (MR23b).
87
Sr/
86
Sr isotopic ratios are corrected for a NBS987 standard of
0.710248 and presented in Table 5 and Fig. 8. Geochemical
screening of Mn, Mg, Sr and Ca provides estimates on the
degree of alteration and allows discriminating samples which
are likely to yield a primary Srisotope composition (Table 5).
Additional data on the geochemical composition is shown in
the Supplementary data (Table S2). Values lower than 0.010
for Mg/Ca and lower than 0.10 for Mn/Sr are indicative for
a more or less primary isotopic signal with no or only insigni
ficant alteration (Melezhik et al. 2001; Murra et al. 2011).
With the exception of MR23b, all samples show no or only
slight alteration and plot within the range of possible values
for marine Srisotopy during the Phanerozoic (Howarth &
McArthur 1997). MR23b yields an isotopic ratio of 0.709541,
which is significantly higher than the rest of the samples. This
elevated value can be explained by the low Sr/Rb ratio (~ 50;
corresponding to a
87
Rb/
86
Sr ratio of ~ 0.06; see Table 5), and
the contribution of radiogenic
87
Sr due to the decay of
87
Rb.
Sr/Rb ratios of the other samples is >100 (corresponding to
87
Rb/
86
Sr ratios of about 0.02) and the
87
Sr/
86
Sr ratios range
between 0.708449 and 0.707655. Generally, the primary
Sample
Tectonic Unit
Lithostrat. Unit
Locality
Type
C-isotopes
VPDB
O-isotopes
VSMOW
O-isotopes
VPDB
13892
Biharia N. s.str.
L
Sagacea Valley
C
0.57
15.89
–14.57
13789
Biharia N. s.str.
L
Avram Iancu Village
D
–1.10
11.66
–18.67
13324
Biharia N. s.str.
L
Caselor Valley (Cimpeni)
D
1.51
16.45
–14.03
13324
Biharia N. s.str.
L
Caselor Valley (Cimpeni)
D
1.58
17.11
–13.39
11203
Biharia N. s.str.
L
Lupsei Valley S
D
–6.33
14.35
–16.06
13933
Biharia N. s.str.
L
Baisori Valley
C
–3.44
16.08
–14.39
13933
Biharia N. s.str.
L
Baisori Valley
D
–5.68
14.60
–15.80
13904
Biharia N. s.str.
L
Ocolis Valley
D
0.59
13.38
–17.00
13980
Vidolm Nappe
L or VID
Iara Valley (Surduc)
C
2.63
20.41
–10.19
9947
Vidolm Nappe
L or VID
Iara Valley (Surduc)
C
1.70
19.57
–11.00
9947
Vidolm Nappe
L or VID
Iara Valley (Surduc)
D
2.70
22.75
–7.92
11116
Baia de Aries N.
SOH
Sohodol Marble
C
1.96
23.28
–7.40
11119
Baia de Aries N.
VIN
Vinta
C
1.96
23.32
–7.36
13812
Baia de Aries N.
VIN
Cioara Valley
C
0.52
20.02
–10.56
13860
Biharia N. s.str.
VBS
Belioara Valley
C
2.33
26.01
–4.75
13863
Biharia N. s.str.
VBS
Posaga Valley
C
2.44
29.54
–1.33
13914
Biharia N. s.str.
VBS
Ocolis Valley
D
2.09
26.89
–3.90
Table 3: Overview of the results of δ
18
O and δ
13
C isotope analyses by Pană (1998). Type refers to the lithology type: D for dolomite or C for
calcite. Abbreviations: L = marble lens within the crystalline basement; VID = marble sequence from the uppermost part of the Vidolm Nappe;
SOH = Sohodol marbles from the Baia de Arieș Nappe; VIN = Vinţa marbles of the Baia de Arieș Nappe; VBS = Vulturese Belioara Series
(Biharia Nappe s.str.).
Sample
Tectonic Unit
Lithostrat.
Unit
Analysed
Cc-Dol pairs
T [in °C]
2σ
MR89
Vidolm Nappe
VID
5
336
37
MR100
Vidolm Nappe
VID
4
316
53
MR161
Biharia N. s.str.
L
4
370
45
MR26
Biharia N. s.str.
VBS
4
354
55
Table 4: Results of calcitedolomite geothermometry. Abbreviations:
L = marble lens within the crystalline basement; VID = marble
sequence from the uppermost part of the Vidolm Nappe;
VBS = Vulturese Belioara Series (Biharia Nappe s.str.).
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87
Sr/
86
Sr isotopic ratio of marine carbonate rocks situated
within the continental crust can only increase to higher values
due to postdepositional alteration during diagenesis and
metamorphism (Brand & Veizer 1980, 1981). Consequently,
the lowest
87
Sr/
86
Sr ratios of MR26 (0.707677) and MR13
(0.707655) have been accepted as the best proxy for the sea
water composition (Table 5 and Fig. 8) and allow narrowing
down of the range of possible sedimentation periods. While
the Mg/Ca ratio of sample MR26 (0.014) indicates little alte
ration, the ratio of MR13 (0.008) indicates a primary signal.
Low Mn/Sr ratios of 0.04 for sample MR26 and 0.05 for sam
ple MR13 also point to a primary signature with very little
alteration (e.g., Jacobsen & Kaufman 1999; Melezhik et al.
2001; Fölling & Frimmel 2002). Higher
87
Sr/
86
Sr ratios (see
other samples) yield a high number of intercepts with the marine
Srisotope curve and thus inhibit further interpretation.
Discussion
Biharia Nappe s.str.
Stratigraphic correlation of the Vulturese Belioara Series
The clastic metasediments (metasandstones, quartzitic
conglomerates and sericitic schists) at the base of the
VultureseBelioara series (Figs. 3b, 5) show similarities to other
Permian to Lower Triassic deposits of the Circum Pannonian
Sample Tectonic Unit Lithostr.
Unit
87
Sr/
86
Sr
measured ±1Sigma
87
Sr/
86
Sr
cor(0.710248)
± 2Sigma
cor(0.710248)
Rb
[ppm]
Sr
[ppm]
Ca
wt. %
Mg
wt. %
Mn
[ppm] Mg/Ca Mn/Sr Alteration
MR9 Biharia N. s.str.
VBS
0.707948 0.000004
0.707950
0.000008
1
163
39.0869 0.2774
7.7*
0.007
0.05
no
MR13 Biharia N. s.str.
VBS
0.707653 0.000005
0.707655
0.000009
1
167
39.0655 0.3076
7.7*
0.008
0.05
no
MR23 Biharia N. s.str.
L
0.709539 0.000004
0.709541
0.000008
2
99
20.5619 10.1803 69.7
0.500
0.70
–
MR26 Biharia N. s.str.
VBS
0.707681 0.000004
0.707677
0.000008
1
184
38.3008 0.5549
7.7*
0.014
0.04
little
MR27 Biharia N. s.str.
VBS
0.708038 0.000004
0.708034
0.000008
1
153
38.5080 0.3679
7.7*
0.010
0.05
little
MR99 Vidolm Nappe
VID
0.708326 0.000004
0.708296
0.000007
1
244
38.4437 0.2412
7.7*
0.006
0.03
no
MR102 Vidolm Nappe
VID
0.708479 0.000003
0.708449
0.000007
1
207
38.1578 0.2231 15.5
0.006
0.07
no
*at or below detection limit
Table 5: Results of Srisotope measurements corrected for a standard value of 0.710248 for the NBS987 (see text). Abbreviations: L = marble
lens within the crystalline basement; VID = marble sequence from the uppermost part of the Vidolm Nappe; VBS = Vulturese Belioara Series
(Biharia Nappe s.str.). Analyses marked with an asterisk (Mn values) are at or below the limit of detection. Alteration is estimated according to
the criteria of Melezhik et al. (2001).
Fig. 8. Plotted
86
Sr/
87
Sr ratios (horizontal lines) of samples MR13 and MR26 which intersected with the variation of
86
Sr/
87
Sr through the
Phanerozoic time modified from McArthur et al. (2004). Samples MR26 and MR13 from the VultureseBelioara Series were selected as they
provide a low Srratio which allows for a meaningful discrimination of depositional intervals. The Cretaceous interval is excluded due to
intense nappe stacking and metamorphic overprinting of the Biharia Nappe System.
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region (Burchfiel 1976; Vozárová et al. 2010; Kovács et al.
2010). Ianovici et al. 1976, correlate the red, laminated
metaconglomerates of the Biharia Nappe with Permian
deposits of the Codru Nappe System. Balintoni et al. (2002)
also discuss the occurrence of red, Permian metaconglomerates
in both, the Biharia and Codru nappe systems.
In the Anisian, dark grey dolomites are documented for the
Bucovinian, the Transilvanides, the Pădurea Craiului (Bihor
Unit) the Arieșeni Nappe (Biharia Nappe System) and several
nappes of the Codru Nappe System (e.g., FinișGîrda Nappe;
Patrulius et al. 1971; Burchfiel & Bleahu 1976; Vörös 2000;
Kovács et al. 2010). Together with the presence of crinoids
(pers. comm. Emanoil Sasaran and field observations by
Trümpy in Balintoni 1994a) we infer a Middle Triassic
(Anisian) depositional age for the black and grey dolomites.
Increasing thickness of the dolomites towards the NE, possi
bly relates to variations in the primary thickness of the dolo
mites or to tectonic omission (compare Fig. 2 and Fig. 5).
During the Triassic, the Tisza and Dacia Megaunits were
situated in neighbouring positions on the European continental
margin (e.g., Sǎndulescu 1984; Vörös 1993; Csontos & Vörös
2004; Haas & Péró 2004; Schmid et al. 2008) and thus allow
for a correlation between the Permo–Mesozoic sediments of
their nappe systems. Ianovici et al. (1976) already published
correlations between the Bucovinian Nappes, Transylvanian
Nappes and Codru Nappe System. Following the aforemen
tioned model and using the distribution of Lower Triassic–
Liassic facies zones, Kovács (1982) correlated the Arieșeni
Nappe (Biharia Nappe System; Balintoni et al. 2002, Balintoni
& Puște 2002) with the Finiș Nappe (Codru Nappe System).
However, due to intense facies differentiation from Anisian
times onwards, a correlation between the Triassic sediments of
the aforementioned units is difficult to undertake (c.f. Burchfiel
& Bleahu 1976; Vörös 2000). The thin layer (0.5–5 m; Fig. 3c)
of red, sericiterich, platy marbles which separates grey to
reddish dolomites and white marbles could correspond to red,
condensed limestones of Upper Triassic (possibly Carnian?)
age. All δ
18
O and δ
13
C values from the VultureseBelioara
Series plot within the field of unaltered marine marbles (accor
ding to Veizer et al. 1999). δ
18
O and δ
13
C isotopy also allows
for a clear distinction between the Vulturese Belioara Series
and calcite/ dolomite marble lenses from structurally lower
parts of the Biharia Nappe s.str. (Fig. 7). The studied samples
from the VBS show mostly homogeneous distributions of C,
O and Sr isotope ratios, which do not suggest obvious
postdepositional alte ration. This is supported by the high
δ
18
O values, which are commonly more sensitive to post
depositional resetting than the carbon isotope system. Inter
secting the results of Srisotope analyses with the marine
Srisotope curve (Table 5 and Fig. 8) allows for the discrimi
nation of several possible deposition intervals for the light
calcite marbles of the Vulturese Belioara Series.
Using the lowest
87
Sr /
86
Srvalues from MR13 and MR26,
the Silurian, Devonian and Carboniferous intervals can be
excluded and three intervals for deposition during the Permian,
Triassic and Jurassic/Cretaceous remain (Fig. 8). The Permian
interval can also be virtually excluded since no comparable
carbonate sequences (consisting of quartzite conglomerates,
dolomite and calcite marbles) are present in the Circum
Pannonian realm during this time span (cf. Seghedi et al. 2001;
Vozárová et al. 2010). Furthermore, the clastic meta sediments
at the base of the sequence are already interpreted as Permo–
Triassic deposits (see text above). It is possible to conclude
that the results of Srisotope analyses support the interpreta
tion of the Vulturese Belioara Series as Mesozoic cover of
the Biharia Nappe s.str. Possible age intervals for deposition
of the light grey calcite marbles are 231–220 Ma (Ladinian to
Carnian), and 195–72 Ma (Jurassic and Cretaceous). Given
that the Biharia Nappe System experienced Late Jurassic
emplacement of the South Apuseni Ophiolites (e.g., Csontos
et al. 2002; Schmid et al. 2008; Kounov & Schmid 2013;
Gallhofer et al. 2016), followed by deformation and metamor
phism during the Early Cretaceous, the Jurassic–Cretaceous
interval can be further restricted to 145–195 Ma. Assuming
a primary isotopic signal with no or only a little alteration
(Fig. 7 and Table 5) for the samples MR13 and MR26 a Mid
Triassic or Early Jurassic deposition of the light grey calcite
marbles is indicated. Thus, depending on the interpre tation of
the red, condensed marbles as possible Carnian deposits,
a Jurassic deposition of the overlying grey marbles has to be
favoured.
Thermotectonic evolution
Based on calcite – dolomite geothermometry, the thermal
overprint can be constrained to 354 ± 55 °C in the light grey
marbles of the VultureseBelioara Series (sample MR26;
Table 4). Marble lenses in the structurally lower parts of the
Biharia Nappe s.str. show slightly higher thermal conditions
(370 ± 45 °C see sample MR161 and data by Pană 1998). Late
Cretaceous zircon fission track ages (82–89 Ma; Kounov &
Schmid 2013) allow constraining of the thermal conditions
during the Late Cretaceous to ≤ 300 °C (cf. Reiser et al. 2016).
Whereas Ar–Ar muscovite data (113 Ma; Reiser et al. 2016)
from the basement in the footwall of the VultureseBelioara
Series indicate thermal conditions around 425° C (Harrison et
al. 2009) during Early Cretaceous times. Thus, the overprint of
the VultureseBelioara Series, as indicated by calcite – dolomite
geothermometry (~ 350 °C), can be constrained to late Early
Cretaceous or mid Cretaceous times (NWdirected nappe
stacking during D2; sensu Reiser et al. 2016). Recrystal
lization processes visible in the thin sections presumably relate
to this thermal imprint (see Fig. 6f). NE–SW trending fold
axes and SEdipping bedding planes from the Vulturese
Belioara Series also correlate with NWdirected thrusting
and nappe stacking during D2 (e.g., Ianovici et al. 1976;
Balintoni et al. 1996). Thin type I twins which form at
temperatures ≤ 200 °C (Burkhard 1993), together with brittle
deformation and apatite fission track data around 60 Ma
(Sanders 1998; Merten et al. 2011; Kounov & Schmid 2013)
constrain the late Maastrichtian–middle Eocene (D4) thermal
imprint.
161
MARBLES OF THE BIHARIA NAPPE SYSTEM, APUSENI MOUNTAINS, ROMANIA
GEOLOGICA CARPATHICA
, 2017, 68, 2, 147 – 164
Baia de Arieș Nappe
Although the quartzitic conglomerates and sericitic schists
at the base of the Sohodol marble sequence resemble typical
Permo–Early Triassic sequences, our dataset does not allow
for a meaningful interpretation as a Mesozoic sequence (as
proposed by Ianovici et al. 1976). However, the O and C
isotopic values which plot within the frame of greenschist
facies altered marbles do not inhibit this interpretation (Fig. 7).
The presence of several different types of twinning in the thin
sections allows us to infer a polyphase deformation of the
Sohodol Marbles with the last stage at low temperatures, less
than 200 °C (Passchier & Trouw 1996; Ferrill et al. 2004).
The presence of Late Cretaceous posttectonic sediments
(Schuller 2004; Schuller et al. 2009) overlying the marbles
indicate thermal conditions for the Sohodol Marbles of
≤ 200 °C during Late Cretaceous times.
Vidolm Nappe
The isotopic values of marble lenses within the Vidolm
basement are close to the values of the Mesozoic cover, the
structural position (Fig. 1) and the presence of eclogitic bodies
associated with the marbles indicate a Palaeozoic origin. Pană
(1998) reported thermal conditions of about 500 °C (Cc – Dol
thermometry) from the aforementioned marbles. It follows
that their isotopic composition did not significantly change,
even under highgrade conditions. Furthermore, the Srratios
of the marbles from the top of the Vidolm Nappe (Fig. 8)
turned out to be too high to allow for a meaningful distinction
between a Palaeozoic and Mesozoic deposition age and thus
are not considered for further interpretation. The attribution of
a depositional age to the other dolomite and calcite marbles is
difficult. However, the clastic sequence at the base of the mar
bles allows for a tentative correlation with the Vulturese
Belioara Series (Fig. 9). The results of calcite – dolomite
geothermometry provide evidence for a greenschist facies
overprint (reaching temperatures of ~ 320 °C; Fig. 4) of the
calcite and dolomite marbles at the top of the Vidolm Nappe.
Since samples from the Vidolm basement already cooled
below the zircon partial annealing zone (PAZ) at about 100 Ma
(Kounov & Schmid 2013), the thermal imprint recorded by the
samples MR89 and MR100 occurred during Early Cretaceous
times, namely during an early stage of D2 or already during
D1 (sensu Reiser et al. 2016; i.e. presumably E or NE directed
deformation following the obduction of the South Apuseni
Ophiolites
).
Conclusions
The new isotopic and geochemical dataset in combination
with field observations on the stratigraphic sequences and the
correlation with Mesozoic sequences in the CircumPanno
nian region allow for an attribution of the siliciclastic and car
bonatic lithologies of the VultureseBelioara Series to different
depositional periods during the Permo–Mesozoic interval.
Srisotope analyses from pure white marbles of the
VultureseBelioara Series provide evidence for a Middle/Late
Triassic or a Jurassic deposition. However, the results of this
study can only provide basic information on the depositional
age of the Vulturese Belioara Series. In order to provide
a detailed stratigraphy, a larger number of samples has to be
analysed. The Biharia Nappe s.str. experienced greenschist
facies metamorphic overprint and largescale folding of the
VultureseBelioara Series around NESW trending fold axes
during late Early/early Late Cretaceous, topNW directed
nappe stacking (D2). The results from other marble sequences
(Vidolm and Baia de Arieș nappes) do not allow for a clear
Fig. 9. Stratigraphic columns to allow for a tentative correlation of the
sedimentary sequences of the Biharia Nappe System. Dashed lines
indicate tentative correlations between the lithostratigraphic units.
For the Vidolm occurrences, only the relative succession is given in
the figure.
162
REISER, SCHUSTER, TROPPER and FÜGENSCHUH
GEOLOGICA CARPATHICA
, 2017, 68, 2, 147 – 164
attribution; however the new data might provide helpful infor
mation for future studies. Correlating the thermal data from
the marble sequences with the tectonothermal evolution of the
Apuseni Mountains constrains greenschistfacies conditions
during the Alpine event in late Early/early Late Cretaceous
times.
Acknowledgements: Fruitful discussions with Stefan M.
Schmid, Liviu Matenco, Alex Kounov and Hannah Pomella as
well as support in the field from Emanoil Sasaran and Ioan
Balintoni are highly appreciated. We thank Manuela Wimmer
for help with the C and O isotope studies, Richard Tessadri for
help with the XRFanalyses and Monika Horschinegg for Sr
isotopic analysis. The authors would like to thank the reviewers
for comments and suggestions that have significantly improved
the manuscript. Financial support by the Austrian Science
Fund (FWF): I138N19 granted to Bernhard Fügenschuh and
through the doctoral grant by the University of Innsbruck
(office of the vice rector for research) is gratefully
acknowledged.
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i
MARBLES OF THE BIHARIA NAPPE SYSTEM, APUSENI MOUNTAINS, ROMANIA
GEOLOGICA CARPATHICA
, 2017, 68, 2, 147 – 164
Supplementary data
Table S1: Representative microprobe analyses of calcite and dolomite.
Tect. Unit
Vidolm Nappe
Biharia Nappe s.str.
Sample #
MR89
MR100
MR161
MR26
cc
dol
cc
dol
cc
dol
cc
dol
oxide wt %
Na
0.0204
0.0374
0.0087
0.0279
0.0188
0.026
0.0223
0.0146
Mg
0.7792
20.33
0.8879
20.1
0.6360
20.17
0.7174
21.91
K
0.0464
0.1338
–
–
–
0.0022
0.021
0.001
Ca
56.4
30.67
56.5
33.81
53.08
28.17
55.82
29.63
Fe
0.1557
1.5
0.0608
–
0.1479
1.87
0.0179
0.0165
Si
0.0564
0.082
0.0215
0.0577
0.0616
0.0888
0.0737
0.0468
Al
–
0.0012
–
–
–
–
–
–
Cr
–
–
–
–
–
–
–
–
Ti
0.0067
0.0111
0.0043
0.007
–
0.0028
–
–
Mn
0.1041
0.0993
0.0253
–
0.004
0.4822
–
–
P
–
–
–
–
0.0172
–
–
–
Zn
–
–
–
–
0.0429
0.0224
0.1053
0.0180
O
–
–
–
–
–
–
–
–
Total
57.57
52.87
57.51
54.00
54.01
50.84
56.78
51.64
formula calculation based on 1 oxygen
Na
0.0063
0.0011
0.0003
0.0008
0.0006
0.0008
0.0007
0.0004
Mg
0.0187
0.467
0.0213
0.4515
0.0163
0.481
0.0175
0.506
K
0.0009
0.0026
–
–
–
–
0.0004
–
Ca
0.975
0.161
0.977
0.546
0.978
0.483
0.978
0.492
Fe
0.0021
0.0193
0.0008
–
0.0021
0.025
0.0002
0.0002
Si
0.0009
0.0013
0.0003
0.0009
0.0011
0.0014
0.0012
0.0007
Cr
–
–
–
–
–
–
–
–
Ti
0.0001
–
0.0001
0.0001
–
–
–
–
Mn
0.0014
0.0013
0.0003
–
0.0001
0.0065
–
–
P
–
–
–
–
0.0003
–
–
–
Zn
–
–
–
–
0.0005
0.0003
0.0013
0.0002
O
1.000
1.000
1.000
1.000
1.000
1.000
1.000
1.000
Total
0.999
1.000
0.999
0.999
0.999
0.999
0.999
1.000
ii
REISER, SCHUSTER, TROPPER and FÜGENSCHUH
GEOLOGICA CARPATHICA
, 2017, 68, 2, 147 – 164
Table S2: Supplementary data. Chemical composition of marbles used for Srisotope analyses.
Sampl
e
MR83
MR99
MR102
MR100
MR9
MR13
MR23b
MR26
MR27
LLD
SiO2
0.01 %
0.49
0.13
0.24
0.08
0.03
0.04
4.86
0.24
0.09
Al2O3
0.01 %
0.15
< 0.01
0.04
< 0.01
< 0.01
< 0.01
0.47
0.18
0.09
Fe2O3
0.01 %
0.08
0.03
0.06
0.02
< 0.01
< 0.01
0.29
0.01
< 0.01
MnO
0.01 %
0.01
0.01
0.02
0.01
0.01
0.01
0.09
0.01
0.01
MgO
0.01 %
0.34
0.40
0.37
15.85
0.46
0.51
16.88
0.92
0.61
CaO
0.01 %
53.59
53.79
53.39
31.00
54.69
54.66
28.77
53.59
53.88
Na2O
0.02 %
0.05
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
K2O
0.01 %
0.08
< 0.01
0.01
< 0.01
< 0.01
< 0.01
0.05
< 0.01
< 0.01
TiO2
0.01 %
0.02
< 0.01
< 0.01
< 0.01
< 0.01
< 0.01
0.01
< 0.01
< 0.01
P2O5
0.01 %
0.11
0.03
0.07
0.04
< 0.01
< 0.01
0.06
< 0.01
< 0.01
L.O.I.
0.01 %
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
n.d.
Total
- - - - -
54.92
54.39
54.20
47.00
55.19
55.22
51.48
54.95
54.68
As
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Ba
10 ppm
< 10
< 10
< 10
< 10
< 10
< 10
< 10
< 10
< 10
Bi
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Br
1 ppm
1
1
1
1
2
1
1
2
2
Cl
10 ppm
80
60
80
50
100
60
40
50
50
Co
1 ppm
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
Cr
1 ppm
6
6
5
5
< 2
2
4
3
< 1
Cu
1 ppm
4
< 1
< 1
3
< 1
< 1
2
2
2
Ga
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Ge
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Hf
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Mo
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Nb
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Ni
1 ppm
< 1
< 1
< 1
< 1
< 2
< 2
4
< 1
< 1
Pb
1 ppm
4
3
3
2
5
5
3
2
3
Rb
1 ppm
4
1
1
< 1
1
1
2
1
1
S
10 ppm
50
60
60
140
70
40
20
40
50
Sb
3 ppm
< 3
< 3
< 3
< 3
< 3
< 3
< 3
< 3
< 3
Se
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Sn
3 ppm
< 3
< 3
< 3
< 3
< 3
< 3
< 3
< 3
< 3
Sr
1 ppm
160
244
207
45
169
177
106
184
153
Ta
2 ppm
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
< 2
Th
1 ppm
4
4
2
1
< 1
2
1
3
3
Tl
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
U
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
V
2 ppm
6
< 2
6
< 2
< 2
< 2
8
< 2
< 2
W
2 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
Y
1 ppm
5
1
3
< 1
4
3
< 1
1
< 1
Zn
1 ppm
6
3
3
8
10
7
22
8
5
Zr
1 ppm
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
< 1
EDXRFA (SpectroXepos), calibration: SRMs – LucasToothModell, samples: glass discs and/or powder pellets
major elements as oxide wt. %, Fe as Fe
2
O
3
tot., trace elements in ppm, L.O.I. at 1000 °C/2h, analysis on dry basis (105 °C/24h)
L.O.I. = loss on ignition, LLD = Lower Limit of Detection, n.d. = not determined