GeolCarp_Vol63_No6_453

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA

, DECEMBER 2012, 63, 6, 453—461 doi: 10.2478/v10096-012-0035-1

Remagnetization of Upper Jurassic limestones from the

Danubian Unit (Southern Carpathians, Romania):

tectonic implications

CRISTIAN G. PANAIOTU

, CRISTINA E. PANAIOTU

and IULIANA LAZĂR

University of Bucharest, Faculty of Physics, Paleomagnetic Laboratory, Bălcescu 1, Bucharest, Romania; cristian.panaiotu@gmail.com

University of Bucharest, Faculty of Geology and Geophysics, Mineralogy Department, Bălcescu 1, Bucharest, Romania;

cris.panaiotu@gmail.com

University of Bucharest, Faculty of Geology and Geophysics, Geology Department, Bălcescu 1, Bucharest, Romania;

iuliana.lazar@g.unibuc.ro

(Manuscript received December 9, 2011; accepted in revised form June 13, 2012)

Abstract: We present a pioneering paleomagnetic study on Upper Jurassic limestones from the Danubian Unit (Southern
Carpathians, Romania). Thermal and alternating field demagnetizations were applied to define the characteristic remanent
magnetization component in all six localities (81 samples). All samples have a normal polarity characteristic remanent
magnetization. Negative regional and local fold tests suggest that this remanent magnetization is in fact a remagnetization
produced by late diagenetic processes. The studied limestones were probably remagnetized during the collision of the
Getic Unit and Danubian Unit which took place during the long normal polarity Chron C34 (82—118 Ma). The area mean
direction (D = 75.5°, I = 50.0°,

= 10.2°, k = 44) implies about 75° clockwise rotation post remagnetization. Our paleo-

magnetic results further indicate the absence of significant relative rotation between the Getic Unit and the Danubian Unit
during the Cenozoic.

Key words: Upper Jurassic, Southern Carpathians, paleomagnetism, remagnetization, limestones.

Introduction

The Danubian Unit is considered a part of the European mar-
gin  scraped  off  the  Moesian  Platform  in  response  to  strong
collision with the Getic Unit during late Early Cretaceous (e.g.
Iancu  et  al.  2005;  Schmid  et  al.  2008).  After  this  collision
both  units  are  considered  part  of  the  Tisza-Dacia  Megaunit
(Csontos  &  Vörös  2004).  Whatever  model  is  adopted,  all  of
them invoke a Miocene retreat of the subducted oceanic slab
as the principal driving force for the final emplacement of the
continental ALCAPA and Tisza-Dacia Megaunits that occupy
the  internal  parts  of  the  Carpathian  loop  (Csontos  &  Vörös
2004; Fügenschuh & Schmid 2005; Ustaszewski et al. 2008;
Van Hinsbergen et al. 2008). Paleomagnetic results to support
these  models  are  available  only  from  internal  parts  of  the
Tisza-Dacia  Megaunit:  Apuseni  Mountains  (Pătra cu  et  al.
1990,  1994;  Panaiotu  1998)  and  Getic  Unit  (Pătra cu  et  al.
1992; Panaiotu & Panaiotu 2010). There is a broad agreement
between  paleomagnetic  data  and  geological  models  concern-
ing the sense of rotation and the timing, but not the amplitude
of rotation (Ustaszewski et al. 2008).

In this study we present the first paleomagnetic results

from the Danubian Unit. The initial purpose was to constrain
the Upper Jurassic position of the Danubian Unit prior to the
collision with the Getic Unit in terms of paleolatitude and
vertical axis rotation. We selected for sampling the carbonate
sequences developed within the Kimmeridgian—Tithonian of
the Danubian window in the Svini a area (western part of the
Southern Carpathians). Our study documented both the exist-
ence of a Cretaceous remagnetization, which obscured the

Upper Jurassic primary magnetization of the limestones, and
a subsequent clockwise rotation, which has implications for
the Southern Carpathians Tertiary geodynamic scenario.

Geological setting

The Southern Carpathians are built up of a succession of

nappes  and  thrust  sheets  with  a  complicated  geotectonic
structure  within  the  Carpathian  Folded  Belt  (Fig. 1).  The
studied Upper Jurassic sequence belongs to the sedimentary
cover of the Danubian Unit, one of the most complex geotec-
tonic  units  of  the  Marginal  Dacides  that  are  interpreted  as
part  of  the  strongly  deformed  European  continental  margin
(Săndulescu  1994).  The  Danubian  Unit  was  defined  first  as
the Danubian autochthonous and later as the Danubian nappe
complex  (e.g.  Iancu  et  al.  2005  and  references  therein).  The
Danubian  nappes  represent  the  most  external  Carpathian
units, which continue south of the Danube in Miroć (Serbia)
and  in  the  Stara  Planina  and  Prebalkan  (Bulgaria)  tectonic
units  (Săndulescu  1994;  Kräutner  1996;  Kräutner  &  Krstić
2002).  The  Danubian  Unit  is  composed  of  several  thrust
complexes:  Arjana,  Co u tea,  Upper  Danubian  and  Lower
Danubian (Iancu et al. 2005).

The studied sequence belongs to the Upper Danubian

nappe complex which is largely exposed in the western part
of the Danubian window in the Svini a area (western part of
the Southern Carpathians, Fig. 1) and is represented by car-
bonate sequences developed during the Kimmeridgian-Titho-
nian interval, belonging to Greben Formation. The Greben

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Formation  was  described  first  by  Răileanu  (1959)  who  de-
fined  within  this  formation  two  units:  “upper  nodular  lime-
stone  horizon”  and  “the  compact  limestone  horizon”.  The
lower  part  of  the  Greben  Formation  (20  to  30  meters  in
thickness)  consists  of  bedded  red  nodular  and  subnodular
limestone (10 to 150 cm the thickness of each bed) with vari-
ous  textural  and  structural  features.  The  upper  part  of  this
formation in the Svini a area (5 to10 meters in thickness) is
represented by grey sub-nodular and cherty limestones (each
bed  20—40 cm  thick)  alternating  with  thin  marls  and  marly
limestone beds.

From these nodular limestones a rich ammonite fauna,

which  proves  the  Late  Kimmeridgian  and  Early  Tithonian
age,  was  described  by  Răileanu  &  Năstăseanu  (1960)  and
Grigore  (1998).  They  identified  the  following  ammonite
zones: Acanthicum, Cavouri, Beckeri and Hybonotum. Later,

Grigore (2000) also demonstrates the presence of Verruciferum
and Richteri ammonite Zones. Thus, the studied sequences
that outcrop near the Svini a locality belong to the upper-
most Kimmeridgian—Lower Tithonian interval (Grigore 1998,
2000).

Sampling and laboratory procedures

We sampled 6 localities in the Upper Jurassic limestones

of the Greben Formation (Fig. 2). The lithology of the sam-
pled localities is dominated by red nodular limestones some-
times intercalated with grey limestones. In each locality we
collected several samples distributed along several meters of
stratigraphic section. At locality B9, however, we sampled 35
beds distributed on a 28 m stratigraphic section. Samples were

Fig. 1. Areas with paleomagnetic results within the Southern Carpathians: 1 – this study, 2 – Upper Cretaceous magmatic rocks (Pătra cu
et al. 1992), 3 – Ha eg Basin (Panaiotu & Panaiotu 2010). Arrows correspond to mean Late Cretaceous paleodeclination for each area.
Maps after Willingshofer et al. (2001).

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cored (2.54 cm in diameter) with a portable gasoline-powered
drill. They were oriented in situ with a magnetic compass. Lo-
cal declination was determined with a sun compass.

Cores were split in the laboratory into standard specimens

(2.2 cm  in  length)  for  paleomagnetic  measurements.  Pilot
specimens  from  each  locality  were  subjected  to  detailed  al-
ternating field (AF) demagnetization up to 140 mT and ther-
mal demagnetization up to 700 °C. Thermal demagnetization
was performed in 50° steps up to 400 °C and 25° steps up to
700 °C.  Around  half  the  specimens  were  measured  in  the
Paleomagnetic  Laboratory  at  the  University  of  Bucharest.
Remanences were measured with an Agico JR5 spinner mag-
netometer.  Thermal  demagnetization  was  performed  with  a
home built heater (triple mu-metal shields, non-inductive pro-
cessor  control  furnace).  For  AF  demagnetization  we  used  a
static  demagnetizer  (Magnon  International).  The  heater  and
the magnetometer are installed inside a set of three Helmholtz
coils  used  to  reduce  geomagnetic  field  in  the  working  area.
The degree of thermal alteration during laboratory heating was
monitored  by  measuring  magnetic  susceptibility  on  a  MS2B
Bartington system. The rest of the collection was measured in
the  Paleomagnetic  Laboratory  at  Utrecht  University  using  a
horizontal 2G Enterprise DC SQUID cryogenic magnetometer
and  a  laboratory-built  thermal  demagnetiser.  Paleomagnetic
analysis was performed using Randy Enkin’s paleomagnetic
software  (http://gsc.nrcan.gc.ca/sw/paleo_e.php)  and  Rema-
soft 3.0 (Chadima & Hrouda 2006).

In addition at the Paleomagnetic Laboratory of the Univer-

sity of Bucharest, we carried out a series of rock magnetic
analyses in order to characterize the nature of the main mag-

netic carriers at each sampling locality. We analysed the ac-
quisition of an isothermal remanent magnetization (IRM), in
a  succession  of  fields  up  to  2.5 T  using  a  pulse  magnetizer
MMPM10,  and  its  subsequent  back-field  demagnetization.
After each step remanent magnetization was measured with
JR5 magnetometer. The change of the magnetic susceptibility
during  a  heating-cooling  cycle  from  room  temperature  to
700 °C in argon was investigated using an AGICO CS-4 ap-
paratus  coupled  to  the  MFK1A  kappabridge.  On  selected
specimens  we  measured  the  hysteresis  properties  using  a
VSM  model  3900  (Princeton  Measurements)  with  a  maxi-
mum applied field of 1 T.

Complementary to the paleomagnetic study we did prelimi-

nary petrographic observation of polished thin sections using
polarized  microscope  and  cathodoluminescence  microscopy
(using  equipment  from  the  CITL  model  CCL  8200  MK3)  to
identify some peculiar aspects of the depositional and diage-
netic  processes  influencing  the  magnetic  minerals  from  the
studied limestones. We focussed on observing the depositional
texture and composition as well as the diagenetic compaction
and  chemical  dissolutions/precipitation  or  remobilization  of
iron bearing minerals.

Results

Rockmagnetic results

In red limestones IRM acquisition curves saturate in mag-

netic fields above 1.6 T (Fig. 3A) showing dominance of he-
matite  in  these  samples.  Coercivity  of  remanence  for  these
limestones  determined  from  back  field  demagnetization  of
saturation IRM ranges between 70 mT and 300 mT. In some
samples hematite is accompanied by magnetite. This is evi-
dent  both  in  IRM  acquisition  curves  and  hysteresis  experi-
ments.  After  diamagnetic  correction  some  hysteresis  loops
display  “wasp-waisted”  behaviour  (Fig. 3B).  This  type  of
hysteresis loop is likely associated with mixtures of hematite
and  magnetite  minerals  (Tauxe  et  al.  1996).  Variation  of
magnetic  susceptibility  with  temperature  is  in  agreement
with  IRM  experiments.  Some  samples  show  an  increase  of
magnetic  susceptibility  around  500 °C  before  a  significant
drop in magnetic susceptibility between 500 °C and 600 °C,
followed by the next fall after 600 °C. We interpret this be-
haviour as an indication of mixture of magnetite and hema-
tite  (Fig. 3C).  Other  samples  show  only  the  presence  of
hematite (Fig. 3D). During cooling, all samples show a large
increase  in  magnetic  susceptibility  showing  the  creation  of
new  magnetite  upon  heating  at  700 °C.  Partial  thermomag-
netic  runs  between  room-temperature  and  400 °C,  500 °C,
600 °C and 700 °C show that in most samples this alteration
appear after 600 °C (Fig. 3D).

In grey limestones the most effective method to identify

magnetic mineralogy was the acquisition and demagnetization
of IRM because their magnetic properties were significantly
weaker than those of red limestones. As can be seen from the
example presented in Fig. 3A the IRM curves is fully saturated
in 0.4 T showing the presence of a soft coercivity mineral.
Due to low values the magnetic susceptibility – temperature

Fig. 2. Position of the sampling localities in the Mesozoic lime-
stones of the Danubian Unit. Geological map is simplified after Ro-
manian Geological Map scale 1 : 200,000, sheet Turnu Severin.

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curves are noisy, but show a significant drop between 500 °C
and 600 °C suggesting that this magnetic mineral is probably
magnetite. Cooling curves always show an important in-
crease of magnetic susceptibility.

Paleomagnetic results

Typical examples of orthogonal projections after thermal

demagnetization are presented in Fig. 4. The samples fall into
two categories. The majority of samples, after removing one

tization (NRM). This behaviour is accompanied by mineralog-
ical  transformation  reflected  in  an  increase  of  both  magnetic
susceptibility  and  remanent  magnetization.  AF  demagnetiza-
tion  has  isolated  the  same  normal  polarity  component,  but  it
was less efficient in specimens where hematite was the main
magnetic  mineral.  For  this  reason  thermal  demagnetization
was the preferred technique to isolate the ChRM.

The ChRM directions were determined by principal compo-

nent analysis (Kirschvink 1980) in the temperature interval
between 300 °C and the temperature where directional insta-

Fig. 3. Examples of rockmagnetic results: A – IRM acquisition and backfield demagnetization; B – Hysteresis loop of a red limestone;
C – Variation of the low-field magnetic susceptibility during a heating-cooling cycle for a sample with magnetite and hematite; D – Par-
tial thermomagnetic runs at 600 °C (grey curve) and at 700 °C (black curve) for a sample with hematite.

Table 1: Paleomagnetic results from the Upper Jurassic limestones rocks of the Danubian Unit.

D and I are site-mean declination and inclination calculated before and after tectonic correction; k and

are statistical parameters after Fisher (1953); N is number of samples giving reliable results or

number of sites for the mean direction. Mean direction of characteristic remanent magnetization for
each locality is marked with bold letters.

or  two  low  temperature  compo-
nents  (below  250—300 °C),  have
thermal  demagnetization  diagrams
revealing  the  presence  of  a  stable
and  well-defined  directional  com-
ponent with normal polarity, going
toward the origin. The second cate-
gory  contains  samples  having  a
univectorial  characteristic  rema-
nent  magnetization  (ChRM)  also
with  normal  polarity  and  pointing
toward  origin.  All  samples  show
erratic demagnetization trajectories
starting  in  the  temperature  interval
500—600 °C  when  the  remanent
magnetization  is  less  than  95 %  of
the initial natural remanent magne-

In situ

Tilt corrected

Locality Geographical coordinates

N D(°) I(°) k α

(°) D(°) I(°) k α

(°)

44.632871°N 22.048401°E

6 59.5 59.1 28.3 12.8 104.5 38.9 14.7 18.1

44.612490°N 22.006762°E

11 79.9 63.7 131.2

4.0 89.6

6.6 36.1

7.7

44.609915°N 22.006956°E

4 75.3 47.0 194.7

6.6 15.4 54.0 194.7

6.6

44.501817°N 44.501817°E

35 83.6 37.4 70.8

2.9 72.8 53.5 75.9

2.8

B8B

44.518843°N 22.078713°E

8 87.6 44.1 60.1

7.2 89.0 52.3

9.0 19.5

17 62.9 31.5 19.8

8.2 72.7 52.7 28.4

6.8

B8A

44.519744°N 22.078084°E

58 % unfolding 62.9 46.2 50.5

5.1

Area mean

Remagnetized Upper Jurassic limestones

6 75.5 50.0 44.0 10.2 78.5 46.5

8.8 23.9

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bility  has  started.  The  line  fits  were  based  on  the  following
constraints: 1) minimum 4 demagnetization steps; 2) the Max-
imum  Angular  Deviation  was  less  than  10°.  The  decay  of
ChRM  during  thermal  magnetization  is  in  agreement  with  a
magnetic  mineralogy  dominated  by  magnetite,  in  grey  lime-
stones, and dominated by hematite, with distributed blocking
temperatures,  sometimes  combined  with  magnetite,  in  red
limestones.  Locality  mean  directions,  based  on  Fisher  statis-
tics (Fisher 1953), are presented in Table 1.

Petrographic results

Most of the analysed limestones are characteristic for deep

shelf  environment  with  dominant  pelagic  fauna  (mainly
crinoids  and  radiolarians),  ranging  from  fine-grained  mud-
stone to medium-grained packstone (Fig. 5A,B). Colour also
varies from light grey to dark red according to the amount of
iron oxide incorporated in the rock sample. The red coloured
limestone  shows  that  iron  oxide  was  incorporated  into  the

mud  either  in  the  matrix  or  filling  the  internal  cavities  and
pores of the bioclasts (within the network of crinoids, in en-
dolithic perforations within the macrofossils, inside foramin-
iferal  and  radiolarian  chambers).  Most  probably  this  iron
pigmentation has a bacterial origin (Preat et al. 1999; Mamet
& Preat 2006) with micrometric hematite. The grey coloured
limestone  does  not  have  hematite  and  also  does  not  have
mud matrix but calcite cement.

The observed effects of diagenesis include the syndeposi-

tional compaction with reorientation and aligning of the bio-
clasts  followed  by  reorganization  of  the  mud  and  possible
concentration of the hematite crystals along some weakly de-
veloped and undulating lamina surfaces. This is an early dia-
genetic  process  which  takes  place  while  a  large  amount  of
pore water still exists, allowing such reorganization. The en-
tire sequence of rocks contains no impermeable layer and the
sedimentation  was  almost  continuous  without  big  gaps,  in
such  conditions  the  pore  water  could  have  been  expelled
freely as the lithostatic pressure increased.

The chemical diagenetic overprints are either related to

early  diagenetic  processes  like  cementation  and  recrystalli-
zation  or  to  late  diagenetic  processes  after  a  tilting/folding
phase. All of these processes are responsible for the remag-
netization.  Early  diagenetic  cementation  affected  only  the
coarse-grained  grey  limestones  which  contain  large  amount
of echinoderms and other shells but less mud. Around echino-
derms there is often a thick rim of non-luminescent syntaxial
calcite  crystals  (Fig. 5C).  Later  burial  cementation  is  also
present and can be recognized from its bright/dull lumines-
cent  calcite  (Fig. 5C)  typical  for  anoxic  environments.  The
early and later cementation make the sediments less sensitive
to further compaction and limited the fluid flows and chemical
remagnetization.

Bacterial hematite from the red limestones is unstable dur-

ing burial conditions and its recrystallization into larger he-
matite  crystals  is  a  usual  process  which  can  produce  a
chemical remagnetization, obliterating the primary one. Late
chemical diagenetic processes are attributed to pressure dis-
solution  with  different  forms  of  stylolite  and  dissolution
seams. These are regarded as late diagenetic features because
they  cut  the  late  burial  cements  and  are  oblique  to  the  bed-
ding  reflecting  a  post  tilting/folding  event.  Stylolites  have
large  amount  of  insoluble  residue  like  iron  oxides,  organic
matter and clay along their irregular surfaces (Fig. 5D). The
iron oxide along these surfaces is still hematite, but the crys-
tals are larger and grouped together in lumps so this process
is responsible for a new chemical remagnetization.

Discussions

Origin of ChRM

Because the Late Jurassic is characterized by a relative

high frequency of reversals (e.g. Ogg 2004) we expected to
find many reversals in the 28 m thick B9 section. On con-
trary, both at this locality and other localities the ChRM has
only normal polarity. This characteristic suggests that the
ChRM is probably a remagnetization.

Fig. 4.  In  situ  orthogonal  plots  of  thermal  demagnetization:  multi-
component natural remanent magnetization (specimens B4-8, B8B-21,
B8A-13,  B9-05)  and  univectorial  natural  remanent  magnetization
(specimens  B6-5,  B5-2).  The  maximum  temperature  on  each  plot
marks the beginning of erratic demagnetization trajectories.

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To constrain the age of the ChRM we performed fold tests

both at locality level and regional level. In four localities (B4,
B5, B8A, B8B) we sampled both limbs of a mesoscopic fold
so it was possible to do local fold tests. We used two types of
fold  test:  proportional  fold  test  (Watson  &  Enkin  1993)  and
direction-correction  tilt  test  (Enkin  2003).  Proportional  Fold
Test evaluates the unfolding % which corresponds to the max-
imum Fisher precision parameter k as the data is progressively
unfolded. The direction-correction tilt test tests whether or not
the site mean directions are correlated to the bedding attitudes,
and also provides an analytical method which determines the
bedding  correction  which  renders  the  least  dispersion  of  the
directional data. Both fold tests are negative in three localities
(B4, B5, B8B) showing that the age of ChRM is post-folding
(Fig. 6A).  At  locality  B8A  both  tests  suggest  a  syn-folding
magnetization at around 58 % unfolding (Fig. 6B).

At a regional scale the direction-correction tilt test is nega-

tive for five localities (B4, B5, B6, B8A, B9). Both the direc-
tion-correction tilt test and proportional fold test suggest
optimal untilting at around 24 % untilting so we interpret the
ChRM as a post-folding magnetization. If we include the
syn-folding mean direction from locality B8A the direction-

correction tilt test is indeterminate, but the degree of optimal
untilting is also around 24 % (Fig. 7).

Since small vertical axis rotations between the sampling

localities  cannot  be  ruled  out  also  we  performed  the  block
rotation  Fisher  test  (BRF)  proposed  by  Enkin  &  Watson
(1996). The test is negative given the following results: geo-
graphical coordinates: mean inclination = 50.2°, k = 25;  strati-
graphic coordinates: mean inclination = 45.7, k = 6.

Taking into account both the lack of reversed polarity

magnetizations and the results of the fold tests we think that
the  ChRM  is  a  remagnetization  most  probably  acquired
mainly during the final stage of folding. Pervasive and wide-
spread remagnetizations are common in many orogens (e.g.
Oliva-Urcia et al. 2008; Grabowski et al. 2009; Meijers et al.
2011).  Several  mechanisms  and  settings  have  been  invoked
to  explain  remagnetizations  of  low  to  moderately  deformed
rocks in tectonic regimes, including thermal metamorphism,
migration of orogenic fluids, diagenetic mineral transforma-
tions  and  magnetic  reorientation  induced  by  pressure  solu-
tion  (McCabe  &  Elmore  1989;  Jackson  1990;  Menard  &
Rochette 1992; Katz et al. 1998; Oliva-Urcia et al. 2008). In
our  study  we  consider  that  remagnetization  is  produced  by

Fig. 5. Examples of sampled limestone types: A – Red laminated crinoidal packstone; B – Red radiolarian packstone; C – Non-lumines-
cent syntaxial calcite cement (white arrow) around echinoderms followed by luminescent pore cement (black arrow); D – Stylolites (white
arrow) with concentration of insoluble residue.

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Fig. 6. Examples of local fold tests for localities B8A and B8B: equal area projections of individual
samples in geographical and stratigraphic coordinates and incremental fold test (Watson & Enkin 1993)
showing the variation of precision parameter k during unfolding.

Fig. 7. Regional fold test: equal area projections of locality mean directions (1 = B9, 2 = B8B, 3 = B6,
4 = B4, 5 = B5, 6 = B8A) in geographical and stratigraphic coordinates and incremental fold test (Watson
& Enkin 1993) showing the variation of precision parameter k during unfolding.

the  late  diagenetic  processes
identified  in  the  studied
limestones.  As  observed  by
detailed  petrography,  the  re-
magnetization  was  probably
acquired  during  or  after  a
tilting/folding event by pres-
sure

dissolution

process

which liberated the magnetic
minerals  and  concentrated
them  along  the  stylolites  or
dissolution seams, similar to
the  process  described  in  the
Pyrenees  by  Oliva-Urcia  et
al. (2008).

We computed an area

mean  direction  based  on  the
syn-folding  direction  for  lo-
cality B8A and in situ direc-
tions for other localities. We
think  that  this  value  is  the
best estimation of area mean
direction  (Table 1).  In  geo-
graphical  coordinates  the
mean  inclination  of  the  area
mean  direction  is  practically
identical  with  the  mean  in-
clination  from  the  BRF  test
so  vertical  axis  rotations  be-
tween sampling localities are
probably not significant.

The sampling localities are

close  to  the  present  day
boundary  between  the  Getic
Unit  and  the  Danubian  Unit
in  the  western  part  of  the
Southern Carpathians (Fig. 1).
Most probably this normal po-
larity  remagnetization  was
produced  during  the  collision
of  the  Getic  domain  with  the
Danubian  domain.  This  colli-
sion took place during the late
Early  Cretaceous—early  Late
Cretaceous  (e.g.  Csontos  &
Vörös 2004; Iancu et al. 2005;
Schmid et al. 2008). The colli-
sion  period  corresponds  to
Chron C34 when the geomag-
netic field has only normal po-
larity  for  a  very  long  period
(Cande & Kent 1995).

Tectonic implications

In Fig. 8 we plotted to-

gether  area  mean  directions
from  this  study,  the  Upper
Cretaceous  sediments  from

460

PANAIOTU C.G., PANAIOTU C.E. and LAZĂR

GEOLOGICA CARPATHICA

GEOLOGICA CARPATHICA, 2012, 63, 6, 453—461

the Ha eg Basin (Panaiotu & Panaiotu 2010) and the Upper
Cretaceous magmatic rocks (banatites) from the western part
of the Southern Carpathians (Pătra cu et al. 1992). The am-
plitude of the clockwise paleomagnetic rotation with respect
to expected Cretaceous paleomagnetic direction from stable
Europe (Besse & Courtillot 2002) is similar for all three areas:
~70—85° (Table 2).

To estimate if there is any tectonic motion between these ar-

eas we calculated poleward displacements and rotations using
the method of Debiche & Watson (1995). The data presented
in Table

2 show that both poleward displacements and rota-

tions  are  not  significant.  These  results  confirm  the  geody-
namic models for the evolution of the Southern Carpathians,
which  suggest  coordinate  rotation  of  Getic  and  Danubian
Units around the corner of the Moesian Platform during the
Cenozoic  (e.g.  Csontos  &  Vörös  2004;  Fügenschuh  &
Schmid 2005; Ustaszewski et al. 2008; Van Hinsbergen et al.
2008). According to the paleomagnetic data, this rotation in
the western part of the Southern Carpathians took place with
little  internal  deformation  reflected  in  vertical  axis  rotations.

Table 2: Comparison of tectonic motion between terrains from the
Southern Carpathians and stable Europe.

Fig. 8.  Equal-area  projection  of  area-mean  directions:  1  –  this
study,  2  –  Upper  Cretaceous  sediments  from  the  Ha eg  Basin
(Panaiotu  &  Panaiotu  2010),  3  –  Upper  Cretaceous  magmatic
rocks (Pătra cu et al. 1992); Eu – expected European direction for
the  Late  Cretaceous  calculated  from  synthetic  European  paleopole
70 Ma  (Besse  &  Courtillot  2002)  for  geographical  coordinates:
45 °N, 22 °E.

Tectonic motion was computed for the first terrain with respect to the
second. Position of terrains is presented in Fig. 1: area 1 = Danubian (re-
magnetized limestones, this study); area 2 = Banatites (Upper Cretaceous
magmatic rocks); area 3 = Ha eg Basin (Upper Cretaceous sediments).

Terrains

Poleward displacement (°) Rotation (°)

Haţeg Basin — Danubian

8.5 ± 11.4

8.4 ± 13.2

Banatites — Danubian

7.4 ± 11.1

7.6 ± 13.0

Haţeg Basin — Banatites

1.9 ± 12.7

15.8 ± 14.2

Danubian — Europe

4.8 ± 8.4

72.4 ± 9.8

Haţeg — Europe

12.5 ± 9.4

70.1 ± 10.4

Banat — Europe

11.1 ± 10.3

85.2 ± 11.4

Our data show that the domain affected by large Cenozoic
clockwise rotation extend around 300

km in a N-S direction.

Conclusions

A remanent magnetization of normal polarity has been re-

covered in all strata sampled in the Upper Jurassic limestones
from the Danubian Unit. The lack of reversed polarity magne-
tizations and several negative fold tests suggests that this re-
manent magnetization is in fact a remagnetization acquired
probably in the last phase of folding. Most probably the studied
limestones were remagnetized at some stage in the collision of
the Getic Unit and Danubian Unit which took place during the
long normal polarity Chron C34 (82—118

Ma).

The area mean direction implies about 75° clockwise rota-

tion post remagnetization. This rotation is similar to that re-
corded by the Upper Cretaceous sediments and magmatic
rocks from the Getic Unit. Our new data show that the Ceno-
zoic rotation of the western part of the Southern Carpathians
around the Moesian Platform took place without major verti-
cal axis rotations between internal blocks.

Acknowledgments:  The  authors  thank  Cor  Langereis,  Wout
Krijgsman, Iuliana Vasiliev and Tom Mullender for their sup-
port  during  our  measurements  at  the  Fort  Hoofddijk  Paleo-
magnetic  Laboratory.  Useful  comments  from  the  two
reviewers (Jacek Grabowski and Dušan Plašienka) helped us
to improve the revised version of the manuscript. This work
was supported by CNCS—UEFISCSU, Project 1922 PNII—IDEI
1003/2008-2011.

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