GeolCarp_Vol64_No4_255

www.geologicacarpathica.sk

GEOLOGICA CARPATHICA

, AUGUST 2013, 64, 4, 255—277 doi: 10.2478/geoca-2013-0019

Introduction

The  Istranca  (Strandja,  Strandzha)  “Massif”  is  a  NW-SE
trending,  almost  300 km  long  and  40 km  wide  Alpine  unit
that straddles across the Turkish-Bulgarian border in south-
eastern Balkan Peninsula (Figs. 1, 2 inset map). To the north,
it is bounded by a main thrust zone along which the “Massif”
is emplaced onto the volcano-sedimentary and igneous rocks
of  the  Late  Cretaceous  Srednogorie  Zone.  The  southern
boundary  is  covered  by  the  10 km  thick  Tertiary  sediments
of the Thrace (Trakya) Basin. The contact with the Rhodope
Unit, the other main crystalline unit of the Balkan Peninsula,
is covered by the western continuation of the Thrace Basin.

Apart from a few recent studies on the Bulgarian (Dabovski

et al. 2002) and the Turkish side (Okay et al. 2001; Elmas et
al. 2010) the tectonic units, their stratigraphy as well as their
structural relations are not known to the international com-
munity. Even if there are some detailed studies on litho-
stratigraphy (e.g. Ksiazkiewicz 1930; Ayd

n 1982;

Ça˘glayan

1996;

Ça˘glayan & Yurtsever 1998 in the Turkish side, and

Chatalov 1980, 1988, 1990; Gocev 1985; Dabovski & Savov

New age data from the tectonostratigraphic units of the

Istranca “Massif” in NW Turkey: a correlation with

SE Bulgaria

YAVUZ BEDI

, EMIL VASILEV

, CHRISTO DABOVSKI

, ALI

ERGEN

, CENGI

Z OKUYUCU

ADI

L DOG

, U. KAG

AN TEKI

, DARIA IVANOVA

, ILIANA BONCHEVA

, ISKRA LAKOVA

VALERI SACHANSKI

, I

SMAI

L KU CU

, ERCAN TUNCAY

, D. GÜLNUR DEMI

RAY

HAVVA SOYCAN

and M. CEMAL GÖNCÜOG

General Directorate of Mineral Research and Exploration (MTA), Department of Geological Research, Ankara;

yavuzbedi@gmail.com; okuyucucengiz@gmail.com

Bulgarian Academy of Sciences, Institute of Geology, Sofia; cdabovski@yahoo.com; v-sachanski@geology.bas.bg;

Hacettepe University, Department of Geological Engineering, Ankara; uktekin@yahoo.com

Middle East Technical University, Department of Geological Engineering, Ankara; mcgoncu@metu.edu.tr

(Manuscript received August 23, 2012; accepted in revised form April 15, 2013)

Abstract: The Istranca Crystalline Complex in NW Anatolia and SE Bulgaria includes structural units that differ in
lithostratigraphy, metamorphism, age and structural position. They are collectively named as the “Istranca nappes”
comprising from bottom to top the Sarpdere, Mahyada˘g and Do˘ganköy Nappes. The Sarpdere Nappe consists of Lower
Triassic arkosic metasandstones with slate interlayers, followed by Middle to Upper Triassic carbonates and an alterna-
tion of Upper Triassic clastics and carbonates. The Mahyada˘g Nappe comprises a low-grade metamorphic Late Paleo-
zoic—Triassic carbonate-siliciclastic sedimentary succession. The Do˘ganköy Nappe includes Precambrian?—Paleozoic
metasediments, intruded by Late Carboniferous-Early Permian calc-alkaline granitoids. Its Triassic cover comprises
metaclastics and metacarbonates. The Istranca nappes were juxtaposed at the end of the Triassic and transgressively
covered by Lower Jurassic coarse clastics, followed above by Middle to Late Jurassic carbonates, black shales and
carbonate-siliciclastic sedimentary succession. The phosphate concretions in black shales yielded radiolarian assem-
blages indicating Late Bajocian-Early Bathonian, Early Bathonian and Early Kimmeridgian ages. These nappes and
their Jurassic cover are unconformably overlain by the Cenomanian-Santonian volcano-sedimentary successions in-
truded by Santonian-Campanian Dereköy-Demirköy intrusive suite. The preliminary data suggest that the Variscan
basements of the Mahyada˘g and Sarpdere Nappes were juxtaposed prior to the Triassic and overridden by the Do˘ganköy
Nappe of possible Rhodopean origin from S to N during the Cimmerian compressional events.

Key words: NW Turkey, SE Bulgaria, Istranca Crystalline Complex, stratigraphy, nappes.

1988;  Gerdjikov  2005a;  Vasilev  &  Dabovski  2010  in  the
Bulgarian  side),  they  are  mostly  in  native  languages  and
hardly available. Moreover, no correlation is available on the
structural  and  lithostratigraphic  units,  and  the  available
small-scale geological maps for the Bulgarian (Cheshitev &
Kancev  1989)  and  Turkish  (Ça˘glayan  &  Yurtsever  1998)
side of the “Massif” do not match. To overcome these short-
comings and achieve a better understanding of the disputed
geological evolution of this less-known area, teams from the
General  Directorate  of  Mineral  Research  and  Exploration
(MTA) and the Geological Institute of the Bulgarian Academy
of Sciences have started in 2009 a bilateral mapping and cor-
relation  project  along  the  Bulgarian-Turkish  border.  The
present paper includes the new findings on the biostratigra-
phy,  structural  relations  as  well  as  a  correlation  of  the  rock
units  in  both  areas.  The  stratigraphic  nomenclature  in  this
paper is applied in a way that only the Bulgarian names are
used for formations with type localities in Bulgaria, whereas
Turkish  names  (with  the  Bulgarian  ones  in  brackets)  are
used if their type sections are established in Turkey. A corre-
lation chart of the very complicated nomenclature is given in

256

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et al.

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GEOLOGICA CARPATHICA, 2013, 64, 4, 255—277

Table 1. The corresponding lithostratigraphic units and their
names are marked in the explanations of Fig. 3 and related
columnar sections in Figs. 5, 7, 8 and 9.

Regional geology

In the Turkish side of the Istranca “Massif” the pre-Late Ju-

rassic overall stratigraphic picture based on previous data is a
pre-Triassic metamorphic basement intruded by Upper Paleo-
zoic metagranitoids/orthogneisses, unconformably overlain
by Triassic-Jurassic cover rocks (Ayd

n 1974, 1988; Aykol

1979; Ü ümezsoy 1982, 1990; Okay et al. 1995; Göncüo˘glu et
al. 1997; Ça˘glayan & Yurtsever 1998; Natal’in et al. 2005;
Okay & Yurtsever 2006). The basement together with the sed-

Fig. 1. Tectonic setting and geological map of Istranca Crystalline Complex. A – Alpine tectonic setting of the Balkan Peninsula (after
Dabovski & Zagorchev 2009), B – Geological map of the Istranca “Massif” and the neighbouring regions (Okay et al. 2001).

imentary  cover  was  intensely  imbricated  by  north-verging
thrusts  probably  during  the  Late  Jurassic—Early  Cretaceous,
accompanied  by  a  regional  metamorphism  affecting  the
whole  “Massif”  (Okay  et  al.  2001).  Actually,  it  has  already
been known since the 1930’s (e.g. Ksiazkiewicz 1930) that a
napped structure is present in the Istanbul, Istranca and Sakar
regions. This was further confirmed by  engör et al. (1984)’s
definition of the K

rklareli and Istranca nappes and Okay et al.

(2001)’s recognition of several north-vergent structural units
as products of thick-skinned tectonics. This structural model
was also the basis of the later geodynamic interpretations (e.g.
Okay et al. 2001; Sunal et al. 2006; Elmas et al. 2010).

In the Bulgarian part, however, the presence of coeval suc-

cessions with completely different formal lithostratigraphy
was recognized and attributed to long-distance-travel by al-

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lochthonous bodies or nappes (e.g. Chatalov 1980, 1985,
1988, 1990; Dabovski & Savov 1988; Dabovski et al. 1990,
2002). In the Dervent and Sveti Ilia Highs (Gocev 1985,
1991; Gerdjikov 2005b) and in Bulgarian Istranca (Chatalov
1980, 1985; Dabovski & Savov 1998; Dabovski et al. 1990,
2002; Gerdjikov 2005a) these nappes were described in con-
siderable detail. In E Bulgaria, Yanev et al. (2006) also rec-
ognized that some greenschist metamorphic Paleozoic rocks
within the Alpine allochthonous units are thrust over Trias-
sic-Jurassic rocks.

Previous tectonic scenarios (e.g. Chatalov 1980, 1985,

1988;  Okay  et  al.  2001;  Dabovski  et  al.  2002;  Sunal  et  al.
2011)  assume  that  the  juxtaposition  of  the  tectonic  units  in
Istranca  was  the  result  of  Late  Jurassic—Early  Cretaceous
compression.

The recent detailed mapping along the Turkish-Bulgarian

border (Fig. 3), presented in this study showed the presence
of at least three nappes and slices of them in thrust contact
with each other on the Turkish side. They completely differ
in stratigraphy (Fig. 4), lithology and metamorphic features
(Bedi et al. 2011a). These structural units in Turkey are here-

after  called  the  Istranca  nappes.  They  include  in  ascending
order  the  Sarpdere,  the  Mahyada˘g,  and  the  Do˘ganköy
Nappes.  Considering  their  Triassic  lithostratigraphy,  they
correspond to the Subbalkanide type, the Strandja type, and
the  Sakar  type  nappes  of  Chatalov  (1980),  respectively.
Based  on  the  new  data  from  the  Turkish  side,  these  three
nappes  are  sealed  by  Lower  Jurassic  clastics.  The  Jurassic
overstep sequence, on the other hand, is completely revised
by  this  study  on  the  basis  of  new  fossil  data  obtained  from
different nappes. The details of the Upper Cretaceous volca-
no-sedimentary successions are beyond the scope of this pa-
per and will be only evaluated briefly.

The Cimmerian Istranca Nappes

The lithostratigraphy, metamorphism and structural posi-

tion of the Triassic rocks are the main criteria to differentiate
the Istranca nappes. Therefore, we will emphasize the strati-
graphy and lithology of the Triassic rocks in the Turkish and
Bulgarian parts of the Istranca “Massif”. The ages of the

Fig. 3. Legend.

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Table 1: Correlation chart of the lithostratigraphic units in Bulgaria and Turkey.

lithostratigraphic  units,  the  most  critical  issue  in  this  study,
are  partly  new  findings  we  recently  obtained  during  this
study,  but  are  also  supported  by  published  (mainly  in  Bul-
garian  language)  and  unpublished  studies  for  the  Bulgarian
side. Considering that these structural units were initially im-
bricated  prior  to  the  Liassic  as  a  result  of  Cimmerian  events
they are named the “Cimmerian Istranca Nappes (CIN)”.

The Sarpdere Nappe

This unit is structurally the lowermost one in the Istranca tec-

tonic belt. Its pre-Triassic basement is not exposed in Turkish
part whereas it is thrust onto the other structural units (Fig. 5).

The succession in the Bulgarian part is represented by a

pre-Triassic  basement,  covered  unconformably  by  Triassic
(Subbalkanide  type  Triassic,  Chatalov  1980)  and  Jurassic
sediments,  which  were  considered  to  form  the  autochtho-
nous basement of the CIN (e.g. Chatalov 1980; Dabovski et
al.  1990;  Vasilev  &  Dabovski  2010).  The  pre-Triassic  se-
quences in the Bulgarian part show some differences. For ex-
ample,  the  Paleozoic  sequence  to  the  north  of  Topolovgrad
(Fig. 5,  column B)  comprises  a  metaclastic-dominated  suc-
cession with volcanic and volcaniclastic intervals (Chatalov
1983,  1985),  whereas  to  the  east  of  Golyamo  Bukovo  and
south-west of Zvezdets the Triassic sediments are tectonically
underlain by Carboniferous-Permian granitoids.

Subbalkanide type Triassic (Chatalov 1980)

Sarpdere Nappe (Bedi et al. 2011a,b)

Pitovo Fm (Chatalov 1985)

Harmantepe Fm (Bedi et al. 2011a,b)

Golyamo Bukovo Fm (Chatalov & Trifonova 1985)

Golyamo Bukovo Fm

Bosnek Fm (Tronkov, 1975)

Bosnek Fm

Lepen Member (Chatalov 1984)

Çağlay

k Fm (Bedi et al. 2011a,b)

Troyan Fm (Chatalov 1984)

Kurudere Fm (Bedi et al. 2011a,b)

Ambaritsa Fm (Chatalov 1984)

Ambaritsa Fm

Strandja type Triassic (Chatalov 1980)

Mahyadağ Nappe (Bedi et al. 2011a,b)

Zaberska Fm (Chatalov 1985)

Armutveren Fm (Bedi et al. 2011a,b)

Struvnitsa Member (Chatalov 1985)

Çukurp

nar Fm (Bedi et al. 2011a,b)

Kushliovo Fm (Vasilev 1998)

Lower part of Adatepe Fm (Bedi et al. 2011a,b)

Gramatikovo Fm (Chatalov 1985)

Upper part of Adatepe Fm (Bedi et al. 2011a,b)

Tolpan Fm (Vasilev 2001)

Tolpan Fm

Kalinachuka Fm (Vasilev 2001)

Kalinachuka Fm

Yazminski Fm (Vasilev 2001)

Yazminski Fm

Malko Tarnovo Fm (Chatalov 1983, 1985)

Karl

k Marble Member (Çağlayan & Yurtsever 1998), Karl

k Marble

(Okay & Yurtsever 2006), Karl

k Fm (Bedi et al. 2011a,b)

Sakar type Triassic (Chatalov 1980)

Doğanköy Nappe (Bedi et al. 2011a,b)

Zhaltychal Fm (Kozhoukharov 1987)

Tekedere Group (Çağlayan & Yurtsever 1998; Okay & Yurtsever 2006)

Lessovo Metagranitoid (Kamenov et al. 1986; Vergilov et al. 1986)

rklareli Metagranite (Ayd

n 1974, 1982), K

rklareli Group (Çağlayan

& Yurtsever 1998; Okay & Yurtsever 2006)

Sakar Pluton (Vergilov et al. 1986)

Hamzabeyli Metagranite (Çağlayan & Yurtsever 1998; Okay &
Yurtsever 2006)

Paleokastro Fm (Chatalov 1980)

Evciler Gneiss (Çağlayan & Yurtsever 1998; Okay & Yurtsever 2006),
Evciler Fm (Bedi et al. 2011a,b), Caferintaşlar

Metaconglomerates

Member (Çağlayan & Yurtsever 1998; Okay & Yurtsever 2006)

Fatmakaya Gneiss (Pamir & Baykal 1947), Fatmakaya Fm (Çağlayan &

Yurtsever 1998; Bedi et al. 2011b)

Ustrem Fm (Chatalov 1985)

Kocayaz

Fm (Bedi et al. 2011b)

Kerimarski Member (Chatalov 1985)

Yenice Member (Çağlayan & Yurtsever 1998)

Mramor Member (Chatalov 1985)

Kanl

dere Member (Bedi et al. 2011b)

Chanakl

Member (Chatalov 1985)

Sepetdere, Kay

nardere, Terzidere, Taştepe and Burcan

ktepe

Members (Bedi et al. 2010a,b), Terzidere Clayey Schist Member
(Çağlayan & Yurtsever 1998), Terzidere Fm (Okay & Yurtsever 2006),
Taştepe Phyllite Chalcschist Member (Çağlayan & Yurtsever 1998),
Taştepe Chalkschist (Okay & Yurtsever 2006), Çukurp

nar Chalkschist

Member (Çağlayan & Yurtsever 1998), Çukurp

nar Chalkschist (Okay

& Yurtsever 2006)

Srem Fm (Chatalov 1985)

Kapakl

Member (Çağlayan & Yurtsever 1998), Kapakl

Dolomite

(Okay & Yurtsever 2006)
Kapakl

Fm (Ayd

n 1988; Bedi et al. 2011a,b)

Jurassic Cover Units

Kostina Fm (Sapunov et al. 1967), Kubarelov Quartzitic Fm (Chatalov
1985)

Yuvarlaktepe Fm (Bedi et al. 2011a,b)

Ozirovo Fm (Sapunov et al. 1967), Kraynovo Fm (Chatalov 1985)

Domuzp

nartepe Fm (Bedi et al. 2011a,b)

Bliznak Fm (Chatalov 1985)

Gümüşalan Fm (Bedi et al. 2011a,b)

Zvezdets Fm (Chatalov 1985)

Balaban Member (Çağlayan & Yurtsever 1998), Balaban Fm (Okay &
Yurtsever 2006; Bedi et al. 2011a,b)

Kazanska Member (Chatalov 1985)

Uzundere Member (Bedi et al. 2011a,b)

Brashlyan Fm (Chatalov 1985)

Boztaş Fm (Bedi et al. 2011a,b)

Hranova Fm (Chatalov 1985)

Balc

tepe Fm (Bedi et al. 2011a,b), Yeşilce Fm

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Fig. 4. Correlation chart of the tectonostratigraphic units in the Istranca Crystalline Complex (Istranca “Massif”).

The Triassic succession of the Sarpdere Nappe displays

similarities along the Istranca belt on both sides of the Turkish-
Bulgarian border. It mainly crops out in the S of the recently
re-mapped area shown in Figure 3. In the Turkish part, from
bottom to top, the sequence comprises (Fig. 5) the following
formations: arkosic metasandstone, metasiltstone, metamud-
stone alternations of the Lower Triassic (Induan—Olenekian)
Harmantepe  Formation  (the  Pitovo  Formation  of  Chatalov
1985);  the  Olenekian-Anisian  Golyamo  Bukovo  Formation
(Chatalov & Trifonova 1985) including dolomite, dolomitic
limestone  and  recrystallized  limestone  with  greyish-pinkish
colour,  locally  thin-  to  thick-bedded  metasandstone  and

metasiltstone interbeds; the Anisian Bosnek Formation
(Tronkov 1975) with micritic dolomites and dolomitic lime-
stones. They are conformably overlain by the Ladinian
Ça˘glay

k Formation (the Lepen Member of the Radomir For-

mation of Chatalov 1984) that includes up to 10 m long do-
lomite and dolomitic limestone olistoliths of the Anisian
Bosnek Formation. The olistostromal Ça˘glay

k Formation

comprises in general red, brown, ferrous, spotted sandstones
with  siltstone  interbeds.  It  is  conformably  overlain  by  the
Upper  Ladinian-Lower  Carnian  Kurudere  Formation  (the
Troyan Formation of Chatalov 1984), which is composed of
grey,  beige,  light  grey  colour,  massive  in  general,  locally

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thick- to very thick-bedded, rarely thin- to medium- and regu-
larly-bedded dolomites and recrystallized limestones with mi-
critic texture. The age of this formation in the Turkish part is
given by the recent finding of a number of well-preserved fora-
minifers  such  as  Polarisella  ex  gr.  elabugae  (Cherdyntsev)
(Fig. 6A.6,  Table 2),  Endotriadella  wirzi  (Koehn-Zaninetti)
(Fig. 6A.8, Table 2), Turriglommina mesotriasica (Koehn-Za-
ninetti)  (Fig. 6A.9,  Table 2),  and  Lamelliconus  cf.  procerus
(Liebus)  (sample  09-KK-926;  Sarpdere  village,  at  K

rklareli-

E19-a4 quadrangle sheet, 41°51

’51” N/27°36’26” E UTM

Coordinates), in the recrystallized limestone levels. The top
of the sequence is conformably overlain by the Carnian-No-
rian Ambaritsa Formation (Chatalov 1984) composed of yel-
low,  grey  colour,  thin-  to  medium-  and  regularly-bedded
calcschist,  dolomite,  dolomitic  limestone  and  recrystallized
limestone  intercalation.  This  unit  is  not  observed  in  the
Turkish part.

The Mahyada˘g Nappe

According to the original definition of Chatalov (1990) in

the Bulgarian part, the Strandja type Triassic forms a distinct
nappe (the Zabernovo Nappe of Chatalov 1980) and was em-
placed from south to north over a pre-Upper Jurassic autoch-
thonous  or  para-autochthonous  basement  (also  including
Subbalkanide type Triassic), presumably during the Late Ju-
rassic-Early Cretaceous compressional events. According to
this  author,  the  succession  is  in  an  overturned  position;  the
base  of  the  nappe  consists  of  Upper  Triassic  followed  up-
wards  by  Middle  Triassic  very  low-grade  metasediments,
and the top is occupied by Lower Triassic greenschist facies
metasediments  with  sporadic  basic  and  acidic  metavolca-
nics.  Later  studies  (Nikolov  et  al.  1996;  Maliakov  1997;
Boncheva & Chatalov 1998), based on scarce fossil findings
(palynomorphs and conodonts data), suggest a Paleozoic age
for at least a part of these metasediments.

In the Turkish part, this structural unit is located between

the Sakar Nappe and the Sarpdere Nappe. It starts (Fig. 7) with
the  Devonian?-Permian  Armutveren  Formation  (Table 1,  the
Zaberska Formation in Chatalov 1985). The Devonian age of
this  formation  is  determined  on  the  basis  of  conodonts  from
thin  levels  of  recrystallized  limestones  in  the  metaclastics
around  Stoilovo  village  (Boncheva  &  Chatalov  1998).  The
Zaberska Formation (Table 1) is composed of alternating red-

dish,  yellowish,  thin-bedded  quartzite  with  interbeds  of
calcschist,  dolomite  and  recrystallized  limestone,  together
with  greenish-brownish  colour,  thin-  to  medium-bedded  and
well-foliated  quartzschists.  The  thickness  of  recrystallized
limestone  in  the  Armutveren  Formation  varies  between  0.5
and  10 m.  Upwards,  it  is  followed  by  the  10 m  thick  upper-
most  Permian—lowermost  Induan  (Okuyucu  et  al.  in  review)
Tütünlüktepe Formation. It displays discontinuous outcrops in
the study area and comprises an alternation of grey, dark grey
colour,  thin-  to  medium-  and  regularly-bedded  recrystallized
limestone with parts of shells of bivalves in places, and green
colour,  thin  foliated  metasiltstone.  This  unit  is  observed
around Tütünlüktepe Hill only on the road between Dereköy-
Ça˘glay

k in the Turkish part of the study area.

Both the uppermost Permian—lowermost Induan Tütünlük-

tepe and the Devonian—?Permian Armutveren Formations
are overlain with angular unconformity by the 250 m thick,
low-grade metamorphic Çukurp

nar Formation (Table 1, the

Struvnitsa Formation in Chatalov 1985) of Induan age. It is
composed  of  metasiltstone,  metaconglomerate  with  quartz-
schist interbeds, metamicroconglomerate and coarse-grained
metasandstone.  This  Triassic  unit  has  been  considered  a
member of the Paleozoic Zaberska Formation by Vasilev &
Dabovski (2010) in the Bulgarian part. Nikolov et al. (1996),
on  the  other  hand,  claimed  that  the  unit  corresponds  to  the
Triassic but does not provide any fossil data. The pebbles in
the Çukurp

nar Formation are polygenetic in character; they

are fine to coarse in size and consist of mainly quartz and
schist pebbles of the Armutveren Formation.

In Bulgaria, this unit is conformably overlain by the Kush-

liovo Formation (Vasilev 1998), which comprises dark grey
slate,  metasiltstone  and  metasandstone,  locally  interbedded
with  recrystallized  limestone.  In  this  study,  however,  these
metasediments are interpreted as the lower levels of the Ole-
nekian—Anisian Adatepe Formation (Table 1, the Gramatikovo
Formation in Chatalov 1985). This Lower Triassic carbonate-
siliciclastic intercalation is overlain by grey, dark grey colour,
very  thin-  to  thin-bedded  recrystallized  limestone  and  dolo-
mite alternating with metasiltstone interbeds, corresponding to
the upper levels of the Adatepe Formation. Upwards, the unit
conformably  passes  into  the  Anisian—Ladinian  Tolpan  For-
mation (Vasilev 2001), which is composed of grey, brownish
colour, thin- to medium-bedded phyllite, calcschist and grey,
dark  grey  colour,  thin-  to  medium-bedded  recrystallized

Table 2: Distribution of foraminiferal and radiolarian findings in the study area.

Foraminifera-bearing
samples

Sample locality

Unit

Age

10-KK-135 and 10-KK-144

Domuzp

nar Hill

(NE of Kofçaz village)

Domuzp

nartepe Fm

Early Jurassic

(Sinemurian–Pliensbachian)

10-KK-166

NE of Kula village

Kapakl

Fm in the Doğanköy Nappe

Anisian–Ladinian

10-KK-775

N of Taştepe village

Taştepe Member of Kocayaz

Fm in the

Doğanköy Nappe

Early Triassic

10-KK-34 and 10-KK-37

northwest of Byala Voda village

in Bulgaria

Yazminski Fm in the Mahyadağ Nappe

Carnian–Norian

09-KK-926

SE of Sarpdere village

Kurudere Fm in the Sarpdere Nappe

Ladinian–early Carnian

Radiolaria-bearing samples

Sample locality

Unit

Age

09-Gec-1

N of Geçitağz

village

Balaban Fm

Early Kimmeridgian

10-KK-363-J

SE of Kula village

Balaban Fm

Early Bathonian

10-KK-363-H

SE of Kula village

Balaban Fm

Late Bajocian–Early Bathonian

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Fig. 6A. Triassic Foraminifera and Dinoflagellata of the Istranca Crystalline Complex from Bulgaria and Turkey. 1 – Schmidita cf. inflata
Fuchs, 1967; sample 10-KK-166, Kapakl

Formation, Turkey. 2 – Pseudonodosaria obconica (Reuss, 1868); sample 10-KK-37, Yazminski

Formation, Bulgaria. 3 – Meandrospira cheni (Ho, 1959); sample 10-KK-775, Kocayaz

Formation, Tastepe Member, Turkey. 4 – Agatham-

mina cf. austroalpina Kristan-Tollmann & Tollman, 1963; sample 10-KK-34, Yazminski Formation, Bulgaria. 5 – Schizosphaerella sp. (cal-
careous dinoflagellate cyst); sample 10-KK-34, Yazminski Formation, Bulgaria. 6 – Polarisella ex gr. elabugae (Cherdyntsev, 1914); sample
09-KK-926, Kurudere Formation, Turkey. 7 – Earlandia dunningtoni (Elliott, 1958); sample 10-KK-775, Kocayaz

Formation, Ta tepe

Member, Turkey. 8 – Endotriadella wirzi (Koehn-Zaninetti, 1968); sample 09-KK-926, Kurudere Formation, Turkey. 9 – Turriglommina
mesotriasica (Koehn-Zaninetti, 1969); sample 09-KK-926, Kurudere Formation, Turkey. 10 – Aulotortus sinuosus Weynschenk, 1956;
sample 10-KK-166, Kapakl

Formation, Turkey. 11—16 – Aulotortus friedli (Kristan-Tollmann, 1962); sample 10-KK-166, Kapakl

For-

mation, Turkey. Scale bars for all figures 100 µm.

Fig. 6B. Lower Jurassic Foraminifera of the Istranca Crystalline Complex from Turkey. 1 – Trocholina umbo Frentzen, 1941; sample 10-KK-144,
Domuzp

nartepe Formation, Turkey. 2, 3 – Involutina gr. liassica (Jones, 1853); sample 10-KK-144, Domuzp

nartepe Formation, Turkey.

Continued on the next page.

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Fig. 6B. Continued: 4 – Semiinvoluta clari Kristan, 1957; sample 10-KK-144, Domuzp

nartepe Formation, Turkey. 5 – Ichthyolaria sac-

culus (Terquem, 1866); sample 10-KK-144, Domuzp

nartepe Formation, Turkey. 6 – Verneuilinoides mauritii (Terquem, 1866); sample

10-KK-144, Domuzp

nartepe Formation, Turkey. 7 – Geinitzinita pupoides (Bornemann, 1854); sample 10-KK-144, Domuzp

nartepe Forma-

tion, Turkey. 8 – Pseudonodosaria tenuis (Bornemann, 1854); sample 10-KK-144, Domuzp

nartepe Formation, Turkey. 9 – Ichthyolaria

cf. brizaeformis (Bornemann, 1854); sample 10-KK-144, Domuzp

nartepe Formation, Turkey. 10 – Nodosaria simoniana d’Orbigny, 1850;

sample 10-KK-144, Domuzp

nartepe Formation, Turkey. 11 – Dentalina cf. mauritii Terquem, 1866; sample 10-KK-144, Domuzp

nartepe

Formation, Turkey. 12 – Dentalina subsiliqua Franke, 1936; sample 10-KK-144, Domuzp

nartepe Formation, Turkey.

Fig. 7. Generalized stratigraphic columnar section of the Mahyada˘g (Istranca type Triassic, Chatalov 1980) Nappe (significantly modified
from Chatalov 1980; Vasilev & Dabovski 2010 by new data from Turkey).

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limestones. In the Bulgarian part, this unit is overlain by the
210—550 m  thick  Ladinian  Kalinachuka  Formation  (Vasilev
2001), which is composed of an intercalation of carbonaceous
sandstone,  siltstone  and  shale  with  limestone  interbeds.  This
unit  has  not  yet  been  observed  in  Turkey.  In  the  Bulgarian
part,  the  Kalinachuka  Formation  is  conformably  overlain  by
grey,  dark  grey  colour,  thin-  to  medium-  and  regularly-bed-
ded, Upper Ladinian—Norian Kaynakdere Formation (Table 1,
the Yazminski Formation in Vasilev 2001) comprising ammo-
nite-bearing  recrystallized  limestones,  rich  in  foraminifers
Agathammina cf. austroalpina Kristan-Tollmann & Tollman
(Fig. 6A.4,  Table 2),  Polarisella  ex  gr.  hoae  (Trifonova),
Pseudonodosaria  obconica  (Reuss)  (Fig. 6A.2,  Table 2),
Dentalina sp. and  Trocholina sp. (sample 10-KK-34; Malko
Tarnovo-Burgas road (north-west of  Byala Voda village in
Bulgaria),  42°10

’57” N/27°28’03” E UTM Coordinates,

sample 10-KK-37; Malko Tarnovo-Zvezdets road (north-west
of Byala Voda village in Bulgaria), 42°13

’14” N/27°25’37” E

UTM Coordinates) and Schizosphaerella sp. (calcareous di-
noflagellate cysts, Fig. 6A.5, Table 2) in the Bulgarian part of
the formation. The limestone is locally thin-bedded with lam-
inated shale interbeds. This unit also crops out 1 km north-
east of Kula village in the Turkish part. It is overlain by the
Upper Ladinian—Norian Karl

k Formation (Table 1, the Malko

Tarnovo Formation in Chatalov 1983, 1985) which laterally
passes into the Kalinachuka and Kaynakdere Formations. The
Karl

k Formation covers large areas in the study area. It was

considered to be of Jurassic age by Ça˘glayan & Yurtsever
(1998) and included in their Kapakl

Formation. The forma-

tion comprises reddish, pinkish, locally grey and white colour,
laminated, thick- to very thick-bedded recrystallized limestones
and  marbles  with  saccaroid  texture.  In  general  it  is  massive,
however,  regular  local  bedding  can  be  observed  in  the  unit.
Within the marbles, 1—4 m thick, green, yellowish-green colour,
medium-  to  thick-bedded  schist  and  yellow,  light  brown
calcschist  interbeds  can  also  be  observed.  The  recrystallized
limestones  and  marbles  can  locally  include  crinoid  fossils  as
for instance in the east of  Ça˘glayan and north of Çukurp

nar

villages (Fig. 3). The Karl

k Formation (Ça˘glayan & Yurtsever

1998) is the uppermost unit of the Mahyada˘g Nappe under Ju-
rassic cover. It has been thrust during post-Campanian time
upon the Santonian—Campanian granitoids of the Dereköy-
Demirköy pluton (Table 1, the Malko Tarnovo pluton) and has
caused local mylonitic deformation, as seen to the north-east of
Kula village.

The Do ˘ganköy Nappe

The Do˘ganköy Nappe is the uppermost structural unit of

the CIN and consists of a Precambrian—Lower Paleozoic base-
ment  and  its  Triassic  cover.  In  Bulgaria,  however,  Chatalov
(1980)  regards  it  as  autochthonous  and  includes  the  Triassic
rocks in his Sakar type Triassic. Gocev (1985) and Dabovski
et al. (1990) on the other hand consider this structural unit to
be allochthonous and place it between their autochthonous (?)
Subbalkanide  (the  Sarpdere  Nappe)  and  the  Zabernovo  Unit
(Strandja  type  Triassic)  as  an  intermediate  nappe.  While  the
Precambrian—Lower  Paleozoic  basement  rocks  together  with
the lower part of the Lower Triassic (Induan—Lower Olenekian)

cover  units  have  undergone  amphibolite  facies  metamor-
phism, the upper part of the Lower Triassic (Upper Olenekian)
and  the  Middle  Triassic  rock  units  were  affected  by  green-
schist facies metamorphism together with Sarpdere and Istranca
nappes  during  Dogger—Early  Cretaceous.  The  Precambrian
and the Lower Triassic rock units of the  Do˘ganköy  Nappe
were retrograded during this metamorphic event.

The Do˘ganköy Nappe comprises the Tekedere Group

(Ça˘glayan  &  Yurtsever  1998;  Okay  &  Yurtsever  2006)  in-
cluding Precambrian—Lower Paleozoic gneisses, schists, am-
phibolites, calcschists, quartzites, etc. (Fig. 8). The rocks of
the Tekedere Group are locally affected by partial melting to
produce migmatites with compositionally and texturally dif-
ferent  leucosomes.  In  these  basement  rock  units,  gabbroic,
granodioritic  and  granitic  intrusions  have  also  undergone
amphibolite facies metamorphism. These mafic and felsic in-
trusions may correspond to the Carboniferous orthogneisses
of Natal’in (2006) and the leucocratic gneisses of Sunal et al.
(2006). They have generated a garnet-rich contact-metamor-
phic aureole at the contact to the metasedimentary host-rocks
of the Tekedere Group.

The metasediments of the Tekedere Group and the Upper

Carboniferous—Lower Permian intrusive rocks are cut by the
granitoids of the K

rklareli Group (Ça˘glayan & Yurtsever

1998; Okay & Yurtsever 2006).

This crystalline basement is unconformably overlain by

conglomerates of the Lower Triassic Evciler Formation. The
pebbles are composed of polygenetic quartzite, schist, granitic
gneiss, amphibolite and elongated pebbles with gneissose tex-
ture. The Paleokastro Formation in Bulgaria (Chatalov 1980)
and the Caferinta lar

Metaconglomerate described by Ça˘glayan

& Yurtsever (1998) and Okay & Yurtsever (2006) in Turkey
are  not  distinct  metaconglomerate  levels,  but  correspond  to
the Evciler Formation. The Lower Triassic  ermat Quartzite,
Rampana  Quartzite  and  Çiftlik  Quartzite  around  K

lagaç

were  interpreted  as  having  lateral  and  vertical  transitions  to
the Evciler Gneiss (Ça˘glayan & Yurtsever 1998), but they do
not have direct stratigraphical relations based on the new field
observations.  Hence,  they  are  parts  of  a  completely  different
tectono-stratigraphic  unit  and  have  to  be  excluded  from  the
units of the Istranca Crystalline Complex. The metaconglom-
erates of the Evciler Formation are overlain by another Lower
Triassic  unit;  namely  the  Induan—Olenekian  Fatmakaya  For-
mation with local metaconglomeratic levels.

The Fatmakaya metaclastics are covered conformably by

the Lower Triassic (Olenekian) Kocayaz

Formation (Table 1,

the Ustrem Formation in Chatalov 1985). This formation is
the equivalent of the Mahya Schists of Ça˘glayan & Yurtsever
(1998) in the Turkish Istranca and includes the Yenice, the
Kanl

dere, the Sepetdere, the Kay

nardere, the Terzidere,

the Ta tepe and the Burcan

ktepe Members. It starts with the

Yenice Member (Ça˘glayan & Yurtsever 1998) at the bottom,
which is composed of quartzite, calcschist, garnet-staurolite-
biotite-bearing amphibole schist with marble intercalations.
The 25—200 m thick Kanl

dere Member (Table 1, the Mramor

Member  of  the  Ustrem  Formation  in  Chatalov  1985)  com-
prises grey, pink, white, bluish colour and thick- to very thick-
layered  to  massive  recrystallized  limestones  and  marble.  It
laterally  and  vertically  passes  into  the  underlying  Yenice

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thin-  to  medium-bedded  calcschists  with  crinoids,  gastropods
and bivalves at the top. Early Triassic foraminifers, such as
Meandrospira  cheni  (Ho)  (Fig. 6A.3,  Table 2),  Earlandia
dunningtoni  (Elliot)  (Fig. 6A.7,  Table 2),  Polarisella  ex  gr.
hoae (Trifonova), Hoyenella gr. sinensis (Ho), Spiroplectam-
mina  aff.  dobrudzhiana  Trifonova,  Ammodiscus  sp.  as  well
as  the  annelid  species  Spirorbis  phlyctaena  Brönnimann  &
Zaninetti (sample 10-KK-775, at Ta tepe village, at K

rklareli-

E18-a2 quadrangle sheet, 41°58

’27” N/27°08’15” E UTM

Coordinates) were determined from this member in the Turkish
part. The overlying Burcan

ktepe Member, approximately

100 m thick, is composed of calcschists and interbedded
metapelitic rocks with abundant crinoids (Table 1, the Keri-
marski Member of Ustrem Formation in Chatalov 1985).
The rocks of the Kocayaz

Formation are frequently intruded

by pegmatite, quartz veins and quartz porphyry dykes of
probable end-Triassic magmatism.

Ça˘glayan & Yurtsever (1998) assigned a Liassic age to the

crinoidal calcschists of the Burcan

ktepe Member (the Çuku-

nar Calcschist Member of Ça˘glayan & Yurtsever 1998)

with  the  help  of  crinoids.  In  a  recent  study  (Hagdorn  &
Göncüo˘glu 2007) the same rocks were dated by the presence
of  the  genus  Holocrinus, a  crinoid  clade  that  occurs  world-
wide  in  Lower  and  Middle  Triassic  sediments.  The  upper-
most  unit  of  the  Do˘ganköy  Nappe  is  the  Anisian-Ladinian
Kapakl

Formation (Table 1, the Srem Formation in Chata-

lov 1985) which is composed, from bottom to top, of dolo-
mite, dolomitic limestone, recrystallized limestone, marble
and up to 20 m thick calcschists. The dolomites and the do-
lomitic limestones observed at the basement of the Kapakl

Formation are grey, light grey in colour, thick- to very thick-
bedded and locally massive. They include abundant crinoids,
gastropods  and  some  undeterminable  algae.  The  overlying
recrystallized  limestone  and  marbles  are  bluish,  pinkish,
whitish in colour and massive in general and locally thick- to
very  thick-bedded.  The  recrystallized  limestone  levels  from
the  Turkish  part  include  the  Schmidita  cf.  inflata  Fuchs
(Fig. 6A.1,  Table 2),  Aulotortus  sinuosus  Weynschenk
(Fig. 6A.10,  Table 2), Aulotortus  friedli  (Kristan-Tollmann)
(Fig. 6A.11—16, Table 2),  Trochammina almtalensis Koehn-
Zaninetti,  and Nodosaria sp.  (sample10-KK-166,  north-east
of  Kula  village,  at  K

rklareli-D18-c4 quadrangle sheet,

42°00

’45” N/27°18’16” E UTM Coordinates) foraminiferal

association which indicates Middle—?Late Triassic age. The
calcschists that are located at the top of the formation are grey,
whitish in colour and thin- to medium-bedded. The Kapakl

Formation, which is determined as Jurassic by Ça˘glayan &

Yurtsever (1998) and Triassic—?Liassic by Okay & Yurtsever
(2006) is actually of Middle Triassic age. Our new crinoid
finding (H. Hagdorn, written communication, 2010) from the
dolomitic lower part suggests an Anisian—Ladinian age, which
is in accordance with Chatalov (1985)’s data from Bulgaria.

According to data from Turkish Istranca, the earliest com-

mon  overstep  sequence  of  rock  units  of  the  Do˘ganköy,  the
Mahyada˘g and the Sarpdere Nappes is the Yuvarlaktepe For-
mation  (Table 1,  the  Kostina  Formation  in  Sapunov  et  al.
1997)  of  Early  Jurassic  age.  It  overlies  the  older  units  and
their primary tectonic contacts with an angular unconformity
(Fig. 9A,B).  However,  the  following  compressional  events
resulted in re-arrangement of the structural units, where slices
of the Do˘ganköy Nappe are observed above the Jurassic cover
sequences (e.g. Fig. 9C).

Such an observation in Bulgaria led Gerdjikov et al.

(2005a) to attribute the Sakar Nappe in Bulgaria to the
Rhodope terrane.

Jurassic cover of the Cimmerian Istranca Nappes

(CIN) and their radiolarian assemblages

The Jurassic sequence sealing the first nappe movements

during the pre-Liassic and representing the common cover of
the CIN starts with the Early Jurassic Yuvarlaktepe Forma-
tion  (Table 1,  Kostina  Formation  in  Sapunov  et  al.  1967;
Sapunov 1999). It comprises red, yellowish, brownish, mas-
sive, and locally thick- to very thick-bedded conglomerates,
microconglomerates  and  coarse-grained  sandstones  (Fig. 10).
Pebbles of the conglomerate are composed mainly of quartz
but also include pebbles of the older units. This unit is over-
lain  by  the  Lower  Jurassic  Domuzp

nartepe Formation (Ta-

ble 1,  the  Ozirovo  Formation  in  Sapunov  et  al.  1967;
Sapunov 1999) which is composed of grey, white in general
massive  and  locally  thick-  to  very  thick-bedded  dolomite,
dolomitic  limestone  and  recrystallized  limestone  with  be-
lemnites, locally abundant crinoids, abundant and large pele-
cypod  and  gastropod  fossils.  The  foraminiferal  assemblage
Trocholina  umbo  Frentzen  (Fig. 6B.1,  Table 2),  Involutina
gr.  liassica  (Jones)  (Fig. 6B.2—3,  Table 2),  Semiinvoluta
clari  Kristan  (Fig. 6B.4,  Table 2),  Ichthyolaria  sacculus
(Terquem)  (Fig. 6B.5,  Table 2),  Verneuilinoides  mauritii
(Terquem)  (Fig. 6B.6,  Table 2),  Geinitzinita  pupoides
(Bornemann)  (Fig. 6B.7,  Table 2),  Pseudonodosaria  tenuis
(Bornemann)  (Fig. 6B.8,  Table 2),  Ichthyolaria  cf.  brizae-
formis  (Bornemann)  (Fig. 6B.9,  Table 2),  Nodosaria  simo-

Fig. 9. Geological cross-sections in the study area. A – Field photos showing the contact relationships between the Kapakl

Formation of

Do˘ganköy Nappe and overlying Jurassic cover units in the Yuvarlaktepe section, 2.5 km S of Kula village, Turkey (at K

rklareli-E18-b1

quadrangle sheet, 41°58

’54” N/27°18’58” E UTM Coordinates). B – The contact relation between Jurassic cover rock units on the Am-

baritsa Formation of the Sarpdere Nappe in the Zvezdets section, 1 km W of Zvezdets village, Bulgaria (between the UTM Coordinates:
starting at 42°06

’20” N/27°24’05” E; finishing at 42°06’44” N/27°25’04” E). C – The Ça˘glay

k section showing the nappe and thrust

structures in Ça˘glay

k village, Turkey (at K

rklareli-D18-c4 quadrangle sheet, between the UTM coordinates: starting at 42°02

’00” N/

27°19

’42” E; finishing at 42°01’12” N/27°21’51” E). D – The Kurudere section showing the imbricated structures in the SE Sarpdere

village, Turkey (at K

rklareli-E19-a4 quadrangle sheet, between the UTM coordinates: starting at; 41°51

’25” N/27°35’35” E; finishing at

41°51

’28” N/27°36’32” E). E – Figure showing the highly tectonized unit of the Üsküp-Çukurp

nar section between Üsküp and Çukurp

nar village (at K

rklareli-E18-b3 quadrangle sheet, between the UTM Coordinates: starting at 41°44

’35” N/27°24’30” E; finishing at

41°50

’20” N/27°28’00” E).

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niana  d’Orbigny  (Fig. 6B.10,  Table 2),  Dentalina  cf.  mau-
ritii   Terquem (Fig. 6B.11, Table 2), Dentalina cf. subsiliqua
Franke  (Fig. 6B.12,  Table 2),  Ophthalmidium  liasicum
(Kuebler  &  Zwingli),  and  Cornuspira  sp.  is  determined  in
samples  10-KK-135,  10-KK-144  from  Domuzp

nar Hill at

2.5 km north-east of the Kofçaz village (at K

rklareli-E18-a2

quadrangle sheet, 27°11

’13” N/41°58’10” E UTM Coordi-

nates; Fig. 3) and indicate an Early Jurassic (Sinemurian—
Pliensbachian) age.

Fig. 10. Stratigraphic section of the Jurassic rock units (significantly modified from Chatalov 1985; Sapunov 1999; Vasilev & Dabovski
2010 by new data from Turkey).

The unit laterally and vertically passes to the Sinemurian-

Lower Bajocian Gümü alan Formation (Table 1, the Bliznak
Formation in Chatalov 1985), which is an alternation of sand-
stone and siltstone. The Gümü alan Formation is olistostro-
mal in character and includes dolomitic and dolomitic
limestone olistoliths from various units, including the Kapakl

the Karl

k, and the Bosnek Formations of the CIN as well as

the underlying Domuzp

nartepe Formation. The sandstones of

the formation are thin- to medium-bedded and yellow, brown

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and red in colour. Locally this sandstone includes abundant
macrofossils such as bivalves (Pseudopecten) and belemnites.
The  siltstones  intercalated  with  sandstones  are  yellowish,
greenish, brownish in colour, thin-bedded and laminated. The
extensively folded formation passes into the Balaban Forma-
tion  (Table 1,  the  Zvezdets  Formation  in  Chatalov  1985).
A  42 m  thick  unit  begins  at  the  base  with  brown  –  light
brown and yellowish, medium- to thick- and regularly-bedded
quartzitic sandstones. It passes into black, dark grey, thin- to
very  thin-bedded  and  laminated  bituminous  shale  and  yel-
lowish-greenish colour, thin-bedded, laminated siltstones to-
wards  the  upper  part.  It  typically  includes  black  shale
intervals  with  large  (up  to  4 cm)  idiomorphic  pyrite  and
chalcopyrite crystals. At the top of the formation these shales
include phosphate concretions which are 2—80 cm in diame-
ter.  Three  spot  samples  from  these  phosphate  concretions
from  the  Balaban  Formation  have  yielded  radiolarian  as-
semblages. Two of them (09-KK-363-H and 09-KK-363-J)
collected  from  the  concretions  in  bituminous  shale  near
Kula  village  (at  K

rklareli-D18-c4 quadrangle sheet,

42°00

’02” N, 27°17’45” E and at K

rklareli-E18-b1 quad-

rangle sheet, 41°59

’41” N/27°17’57” E UTM Coordinates,

Fig. 3, Table 2) yielded diverse but moderately-preserved ra-
diolarians.  The  radiolarian  fauna  of  sample  09-KK-363-H
contains  the  following  taxa:  Pantanellium  sp.  (Fig. 11.3),
Triactoma  spp.,  Xiphostylus  spp.  (Fig. 11.4,5),  Homoepa-
ronaella  argolidensis  Baumgartner  (Fig. 11.24),  Hexasatur-
nalis suboblongus (Yao) (Fig. 12.8), Bernoullius rectispinus
delnortensis Pessagno, Blome & Hull (Fig. 12.11), Bernoullius
rectispinus  leporinus  Conti  &  Marcucci  (Fig. 12.13),  Hsuum
spp.  (Fig. 12.21)  and  Transhsuum  sp.  (Fig. 12.22).  Due  to
co-occurrence of two characteristic taxa (Homoeparonaella
argolidensis and Hexasaturnalis suboblongus (Yao), the age of
sample 09-KK-363-H is assigned as Late Bajocian—Early Ba-
thonian  corresponding  to  UA  4-5  (Baumgartner  et  al.  1995;
Dumitrică & Dumitrică-Jud 2005; Chiari et al. 2012; Fig. 13).

The radiolarian assemblage from sample 09-KK-363-J com-

prises  Gorgansium  sp.  aff.  G.  silviense  Pessagno  &  Blome
(Fig. 11.1),  Gorgansium  sp.  (Fig. 11.2),  Triactoma  jonesi
(Pessagno)  (Fig. 11.6,7),  Xiphostylus  sp.,  Angulobracchia
purisimaensis  (Pessagno)  (Fig. 11.9,10),  Emiluvia  premyogii
Baumgartner  (Fig. 11.16),  Emiluvia  spp.,  Higumastra  gra-
tiosa Baumgartner (Fig. 11.21), H. sp. cf. H. gratiosa Baum-
gartner  (Fig. 11.22),  H.  sp.  cf.  H.  inflata  Baumgartner
(Fig. 11.23),  Homoeparonaella  argolidensis  Baumgartner
(Fig. 11.24), Homoeparonaella elegans (Pessagno) (Fig. 12.1),
Tetraditryma  praeplana  Baumgartner  (Fig. 12.2),  Tetratrabs
sp. (Fig.12.3), Tritrabs simplex Kito & De Wever (Fig. 12.4),
Hexasaturnalis  nakasekoi  Dumitrică  &  Dumitrică-Jud
(Fig. 12.5—6),  Hexasaturnalis  suboblongus  (Yao)  (Fig. 12.7),
Spongosaturninus  bispinus  (Yao)  (Fig. 12.9),  Bernoullius
dicera (Baumgartner) (Fig. 12.10), B. rectispinus delnortensis
Pessagno, Blome & Hull (Fig. 12.12), B. rectispinus leporinus
Conti  &  Marcucci  (Fig. 12.14—15),  Perispyridium  sp.  cf.  P.
gujohachimanense  Takemura  (Fig. 12.16),  Perispyridium  sp.
(Fig. 12.17),  Parahsuum  officerense  (Pessagno  &  Whalen)
(Fig. 12.18),  Hsuum  spp.,  Napora  sp.,  Canelonus?  sp.
(Fig. 12.26),  Stichomitra (?)takanoensis  Aita  (Fig. 12.27).
Considering the ranges of two important taxa (Hexasaturnalis

nakasekoi and Hexasaturnalis suboblongus), an Early Batho-
nian age is assigned to sample 09-KK-363-J corresponding to
UA 5 (Baumgartner et al. 1995; Dumitrică & Dumitrică-Jud
2005; Chiari et al. 2012; Fig. 13).

Another sample from a phosphate concretion (09-Gec-1)

in shale near Geçita˘gz

village (at K

rklareli-E18-b1 quadran-

gle sheet, 41°57

’23” N/27°17’50” E and 41°57’27” N/

27°17

’53” E UTM Coordinates; Fig. 3, Table 2) yielded a

less-diverse and poor to moderately-preserved radiolarian as-
semblage. The radiolarian assemblage of sample 09-Gec-1 is:
Triactoma sp. (Fig. 11.8), Paronaella broennimanni Pessagno
(Fig. 11.11), Paronaella spp. (Fig. 12.12—15), Paronaella sp.
cf. P. mulleri Pessagno, Emiluvia sp. (Fig. 11.17), Higumastra
devilsgapensis  Pessagno,  Blome  &  Hull  (Fig. 11.18—20),
Homoeparonaella argolidensis Baumgartner (Fig. 11.26—27),
Hsuum  mclaughlini  Pessagno  &  Blome  (Fig. 12.19),  Hsuum
sp.  cf.  mclaughlini  Pessagno  &  Blome  (Fig. 12.20),  Hsuum
spp.  (Fig. 12.23—24),  Archaeodictyomitra  sp.  (Fig. 12.25).
The presence of Hsuum mclaughlini is crucial for dating. Al-
though  the  range  of  the  Hsuum  mclaughlini  was  reported  as
Late  Tithonian  by  Pessagno  et  al.  (1984),  the  total  range  of
this taxon was reported as Kimmeridgian to Berriasian in later
studies (e.g. Kiessling 1999). Together with the presence of this
taxa,  we  take  into  consideration  the  last  occurrence  of  Pa-
ronaella broennimanni, and assign the age of the 09-Gec-1 as
Early Kimmeridgian corresponding to UA10 by Baumgartner et
al. (1995 and the age data from the other studies, e.g. Pessagno
et al. 1984; Pessagno et al. 1993; Kiessling 1999; Fig. 13).

According to these radiolarian data, the depositional age in-

terval of the Balaban Formation in the Turkish side is Late Ba-
jocian  to  Early  Kimmeridgian.  In  Bulgaria,  a  Bajocian  age
was assigned to the equivalent unit (the Zvezdets Formation)
by Chatalov (1985) based on belemnites, bivalves, and gastro-
pods.  In  the  Turkish  part  of  Istranca  Ça˘glayan  &  Yurtsever
(1998) and Okay & Yurtsever (2006) assigned this unit to the
Balaban  graphitic  schists  of  their  Mahya  Formation.  Belem-
nite fossils were found in this formation in outcrops at about
1 km  to  the  NE  of  Bliznak  village  in  Bulgaria,  on  the
Dereköy-Geçita˘gz

road (at K

rklareli E-18-b1 quadrangle sheet,

41°56

’12” N/27°20’33” E UTM Coordinates, Fig. 3, Ta-

ble 2) and in the NW of Kofçaz (at K

rklareli quadrangle sheet,

41°58

’00” N/ 27°09’05” E UTM Coordinates in Turkey).

The Uzundere Member (Table 1, the Kazanska Member in

Chatalov  1985)  of  the  Balaban  Formation  is  composed  of  a
20 m  thick  brecciated  conglomerate.  In  bituminous,  black
shales  included  in  the  Balaban  Formation,  cordierite  and  an-
dalusite minerals were formed due to contact metamorphism re-
lated  to  the  intrusion  of  the  Upper  Santonian-Campanian
(Moore et al. 1980; Ayd

n 1982) the Dereköy-Demirköy pluton.

The Jurassic sequence at the top grades laterally and verti-

cally  into  the  Upper  Jurassic  (middle  Kimmeridgian—Titho-
nian?) Ye ilce Formation (Table 1, the Hranova Formation in
Chatalov 1985) comprising an intercalation of mudstone, calc-
phyllite,  recrystallized  limestone,  shale,  siltstone  and  then  to
(middle  Kimmeridgian—Tithonian?)  the  Bozta   Formation
(Table 1,  the  Brashlyan  Formation  in  Chatalov  1985),  which
consists  of  Fe-rich  silicified  limestone  and  sandstone  includ-
ing local conglomeratic channel fills. The limestones included
in the Bozta  Formation locally include crinoids. Although the

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Fig. 11. Scanning electron micrographs of Middle and Late Jurassic radiolarians from the phosphate nodules in black shales of the Balaban
Formation. Samples 09-KK-363-H and 09-KK-363-J were taken at K

rklareli-E18-b1 quadrangle sheet (with UTM Coordinates:

46°50

’39” N/05°24’44” E and 46°49’47” N/05°25’16” E; Fig.

2) and sample 09-Gec-1 is from the same lithologies taken from Geçita˘gz

village (at K

rklareli-E18-b1 quadrangle sheet, with UTM Coordinates: 46°45

’14” N/05°25’09” E and 46°45’02” N/05°25’03” E;

Fig. 2).  Scale = number  of  micrometers  for  each  figure.  1  –  Gorgansium  sp.  aff.  G.  silviense  Pessagno  &  Blome;  09-KK-363-J,  scale
bar = 135 µm. 2 – Gorgansium sp.; 09-KK-363-J, scale bar = 165 µm. 3 – Pantanellium sp.; 09-KK-363-H, scale bar = 130 µm. 4—5 – Xipho-
stylus spp.; both specimens from 09-KK-363-H, scale bar for both specimens = 330 µm. 6—7 – Triactoma jonesi (Pessagno); both specimens
from  09-KK-363-J,  scale  bar  for  both  specimens = 300 µm.  8  –  Triactoma  sp.;  09-Gec-1,  scale  bar = 160 µm.  9—10  –  Angulobracchia
purisimaensis  (Pessagno);  both  specimens  from  09-KK-363-J,  scale  bar = 400 µm.  11 –  Paronaella  broennimanni  Pessagno;  09-Gec-1,
scale bar = 230 µm. 12—15 – Paronaella spp.; all specimens from 09-Gec-1, scale bar for all specimens = 400 µm. 16 – Emiluvia premyogii
Baumgartner; 09-KK-363-J, scale bar = 270 µm.  17  – Emiluvia sp.; 09-Gec-1, scale bar = 160 µm. 18—20  – Higumastra devilsgapensis
Pessagno, Blome & Hull; all specimens from Gec-1, scale bar for all specimens = 400 µm. 21 – Higumastra gratiosa Baumgartner; 09-KK-363-J,
scale bar = 300 µm. 22 – Higumastra sp. cf. H. gratiosa Baumgartner; 09-KK-363-J, scale bar = 400 µm. 23 – Higumastra sp. cf. H. inflata
Baumgartner; 09-KK-363-J, scale bar = 300 µm. 24—27 – Homoeparonaella argolidensis Baumgartner. 24 – 09-KK-363-H, 25 – 09-KK-363-J,
26—27 – 09-Gec-1, scale bar for all specimens = 350 µm.

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Fig. 12. Scanning electron micrographs of Middle and Late Jurassic radiolarians from the Istranca “Massif”. The sample locations are the
same  as  in  Fig. 12.  Scale  =  number  of  micrometers  for  each  figure.  1  –  Homoeparonaella  elegans  (Pessagno);  09-KK-363-J,  scale
bar = 300 µm.  2  –  Tetraditryma  praeplana  Baumgartner,  09-KK-363-J,  scale  bar = 300 µm.  3  –  Tetratrabs  sp.;  09-KK-363-J,  scale
bar = 250 µm. 4 – Tritrabs simplex Kito & De Wever; 09-KK-363-J, scale bar = 200 µm. 5—6 – Hexasaturnalis nakasekoi Dumitrică &
Dumitrică-Jud;  09-KK-363-J,  scale  bar = 250  and  200 µm,  respectively.  7—8  –  Hexasaturnalis  suboblongus  (Yao);  7  –  09-KK-363-J,
8 – 09-KK-363-H, scale bar for both figures = 200 µm. 9 – Spongosaturninus bispinus (Yao); 09-KK-363-J, scale bar = 185 µm. 10 – Ber-
noullius dicera (Baumgartner);  09-KK-363-J, scale bar = 360 µm. 11—12 – Bernoullius rectispinus delnortensis Pessagno, Blome & Hull;
11 – 09-KK-363-H, 12 – 09-KK-363-J, scale bar for both specimens = 150 µm. 13—15 – Bernoullius rectispinus leporinus Conti & Mar-
cucci; 13 – 09-KK-363-H, 14—15 – 09-KK-363-J, scale bar for all specimens = 200 µm; 16 – Perispyridium sp. cf. P. gujohachimanense
Takemura; 09-KK-363-J scale bar = 200 µm. 17 – Perispyridium sp.; 09-KK-363-J, scale bar = 200 µm. 18 – Parahsuum officerense (Pes-
sagno & Whalen); 09-KK-363-J, scale bar = 100 µm. 19 – Hsuum mclaughlini Pessagno & Blome; 09-Gec-1, scale bar = 150 µm. 20 – Hsuum
sp. cf. H. mclaughlini Pessagno & Blome; 09-Gec-1, scale bar = 180 µm. 21, 23—24 – Hsuum spp.; 21 – 09-KK-363-H, 23—24 – 09-Gec-1,
scale bar for all specimens = 150 µm. 22 – Transhsuum sp.; 09-KK-363-H, scale bar = 150 µm. 25 – Archaeodictyomitra sp.; 09-Gec-1,
scale  bar = 150 µm.  26  –  Canelonus?  sp.;  09-KK-363-J,  scale  bar = 80 µm.  27  –  Stichomitra(?)  takanoensis  Aita;  09-KK-363-J,  scale
bar = 125 µm.

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age of these two formations have been reported as Bathonian
by Chatalov (1985) and Sapunov (1999), new radiolarian dat-
ing from the underlying Balaban Formation reveals that their
depositional ages could be as young as Late Jurassic. Crinoids
are abundant in outcrops N of Dereköy on the Turkish-Bul-
garian border which can be followed in Bulgaria.

Upper Cretaceous volcano-sedimentary cover

The Sarpdere and the Mahyada˘g Nappes, together with

their Jurassic cover, are overlain with angular unconformity
by rocks of the Cenomanian—Santonian I

˘gneada Group

(Ça˘glayan & Yurtsever 1998), which display characteristics
of a volcano-sedimentary succession (Ça˘glayan & Yurtsever
1998; Okay & Yurtsever 2006). This unit is the stratigraphic
equivalent to Varshilo (Petrova et al. 1980), Grudovo (Petrova

Fig. 13. Stratigraphic ranges of radiolarian taxa obtained from 09-KK-363-H, 09-KK-363-J and
09-Gec-1 from the Balaban Formation of the “Strandja Massif”. Grey area shows the determined
age of assemblages. Dotted lines show the supposed parts of stratigraphic intervals of taxa.

et al. 1980) and Michurin (Petrova
& Simeonov 1988) Groups in Bul-
garia. In the CIN, the Jurassic and
Cenomanian-Santonian  cover  units
were intruded by the Upper Santo-
nian-Campanian  Dereköy-Demir-
köy pluton, which includes granite,
granodiorite,  monzonite,  syenite,
gabbro,  monzodiorite  as  intrusive
bodies.  The  vein  rocks  observed
are diorite porphyry, diabase, peg-
matite and aplite.

Evaluation of the new data

and discussion

Stratigraphy

The new stratigraphic data ob-

tained  in  the  Turkish  Istranca  evi-
dence  the  presence  of  structural
units  with  different  lithostratigra-
phies,  ages  and  basements.  This
contrasts  with  the  suggestion  of
earlier  studies  (e.g.  Ça˘glayan  &
Yurtsever 1998; Okay & Yurtsever
2006 and others) who considered a
single  lithostratigraphic  succes-
sion all along the “Massif”.

To start with the dissimilarities in

the  pre-Triassic  basement  of  the
CIN,  the  basement  of  the  Subbal-
kanide  Autochthon  in  Bulgaria  is
not  observed  in  the  Turkish  part
due to the tectonic activities. More-
over,  the  low-grade  metamorphic
succession  in  this  unit  exposed
north  of  Topolovgrad  is  dissimilar
to the pre-Triassic basement of the
structurally  overlying  Mahyada˘g
Nappe,  especially  in  regard  to

lithostratigraphic  and  metamorphic  properties.  The  basement
rocks  of  the  Mahyada˘g  and  Do˘ganköy  Nappes  also  do  not
show any geological continuity. The former one characterizes
a Variscan continental margin deposition without the relicts
of  the  Late  Carboniferous—Early  Permian  calcalkaline  mag-
matism, which is the most striking feature of the overthrusting
Do˘ganköy  Nappe.  Moreover,  the  amphibolite-facies  meta-
morphic development of the pre-Triassic basement together
with its Lower Triassic cover in this nappe and the presence
of  the  Hamzabeyli  Metagranite  are  additional  supports  for
its  distinctive  geological  history.  Even  if  the  pre-Triassic
basements of the CIN were involved in the former Variscan
orogeny,  they  all  were  originally  in  completely  different
geological settings.

The recognition of the differences in the Triassic stratigra-

phy of the CIN and the new fossil data are the most critical
subjects of the present study. Overall, the Triassic succes-

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sions represent an overstep sequence on the aforementioned
Variscan  basements.  They  disconformably  commence  with
thick  basal  conglomerates  containing  pebbles  from  the  un-
derlying  crystalline  rocks  and  include  passive  margin  plat-
form sediments. A preliminary reconstruction based on rock
units  suggests  that  the  Olenekian-Norian  shallow-marine
carbonates of the Sarpdere Nappe were deposited in a more
proximal position on the platform then the carbonates of the
Mahyada˘g Nappe (Figs. 5 and 7).

The combined columnar section of the Do˘ganköy Nappe for

the Triassic (Fig. 8) in the Turkish and Bulgarian areas, how-
ever, shows a completely different geological evolution. Dis-
regarding  the  differences  in  metamorphism,  the  Do˘ganköy
Nappe includes a coarse clastic-dominated lower part (Induan
to  Olenekian),  followed  by  a  clastic-carbonate  deposition
with volcanic interlayers of Olenekian age and finally a shal-
low-marine  carbonate  succession  in  the  Anisian—Ladinian.
These stratigraphic disparities cannot be assigned simply to
lateral changes in depositional environment but would indi-
cate, together with the discrete metamorphic evolution, that
this unit was in a different geological position then the other
CIN during the Triassic.

The identification of all these differences in stratigraphy

was only possible by new fossil findings and one-to-one cor-
relation of the fossiliferous Triassic successions both in
Turkish and better dated (e.g. Sapunov et al. 1967; Dodekova
& Chatalov 1982; Chatalov 1983, 1985, 1990; Chatalov &
Trifonova 1985; Budurov & Trifonova 1991; Vasilev 1998,
2001; Boncheva & Chatalov 1998; etc.) locations in Bulgaria.
For example, the Jurassic carbonates (the Kapakl

Dolomites

of Ça˘glayan & Yurtsever 1998; Okay & Yurtsever 2006) are
proven to be Late Triassic (the Karl

k, the Kurudere and the

Kapakl

Formations of different nappes) in age. The Triassic

Mahya Schists of Ça˘glayan & Yurtsever (1998) covering
large areas close to the Turkish-Bulgarian border, on the other
hand, were shown to be Late Bajocian-Early Kimmeridgian
in age by radiolarians. The Anisian-Ladinian age determined
by Hagdorn & Göncüo˘glu (2007) from crinoids also show
that the Liassic age determined by echinoids in Ça˘glayan &
Yurtsever (1998) is not correct.

The Jurassic overstep sequence on the Cimmerian tectonic

units is rather uniform. It starts with basal conglomerates and
rapidly grades into Sinemurian carbonates, which are also ob-
served  as  olistoliths  in  the  Pliensbachian-Aalenian  clastics.
The  Late  Bajocian-Early  Kimmeridgian  period  is  character-
ized by a thick succession of pyrite-rich black shales including
levels of phosphate nodules that represent a change from an-
oxic to disoxic conditions, very probably in a restricted exten-
sional  basin.  Towards  the  end  of  the  Late  Jurassic  this  basin
closed and the basement rocks were imbricated by northward
thrusting  as  a  second  phase  (Fig. 9C,D).  This  event  very
probably resulted in crustal thickening and low-grade metamor-
phism that was followed after a considerable gap by Cenoma-
nian-Santonian volcaniclastic rocks of the Srednogorie arc.

In contrast to the over generalized age assignments in previ-

ous studies we found belemnites, crinoids, pelecypoda in the
Domuzp

nartepe Formation; belemnites, bivalves (Pseudopecten)

in the Gümü alan Formation; crinoids in the Bozta and the
Ye ilce Formations and belemnites and radiolarian fauna in

the Balaban Formation. In addition, Triassic foraminifers were
found for the first time in the Kurudere Formation (Fig. 6.19,
21—22) of the Sarpdere Nappe, in the Ta tepe Member
(Fig. 6.15, 20) and the Kapakl

Formation (Fig. 6.13, 20, 25—29)

and Jurassic foraminifers were found for the first time in the
Domuzp

nartepe Formation (Fig. 6.1—12).

Another important finding from the Turkish and the Bul-

garian  parts  is  that  all  the  units  described  are  definitely  of
continental  crust  type.  No  evidence  of  any  kind  of  oceanic
material that may represent an oceanic lithosphere has been
found within or between the tectonic units. This is critical to
note,  as  this  observation  contrasts  with  Natal’in  et  al.’s
(2005)  suggestions  on  the  presence  of  serpentinite  slices  in
the central part of the “Massif”.

Preliminary structural evaluation

The nappe structure of the Istranca units in Turkey was al-

ready  identified  by  engör  et  al.  (1984)  and  Okay  et  al.
(2001)  in  general  terms.  The  detailed  mapping  during  this
study has resulted in recognition of a very complex structure,
which will be presented in a forthcoming paper. The prelimi-
nary evaluation, however, indicates multiple periods of tec-
tonic  activities  and  thrusting.  We  therefore  propose  to  omit
the  term  “Istranca  Massif”  and  to  use  the  name  Istranca
Crystalline Complex (ICC) instead.

Conclusions

Geological mapping of the NW Turkish and SE Bulgarian

parts of the Istranca “Massif” resulted in recognition of several
tectonostratigraphic  units  with  different  Precambrian?-
Paleozoic  basements,  Triassic,  Jurassic  and  Upper  Creta-
ceous  overstep  sequences.  At  least  three  compressional
events – pre-Jurassic, post-Kimmeridgian and post-Campa-
nian, respectively, have caused an intensive imbrication and
created a very intricate structural complex of variable meta-
morphic  rocks.  We  therefore  suggest  abandoning  the  term
“Istranca  Massif”  and  applying  the  name  “Istranca  Crystal-
line Complex” for this unit.

As a result of detailed stratigraphic work based on a num-

ber of new fossil findings and a detailed correlation with the
better-dated formations in Bulgaria, three main tectonostrati-
graphic units were identified on the basis of different Trias-
sic successions. As their primary imbrication is end Triassic
in age, they were named as the Cimmerian Istranca Nappes
comprising from bottom to the top the Sarpdere, Mahyada˘g
and Do˘ganköy Nappes. The first two nappes have dissimilar
Variscan basements and a Lower Triassic cover, resembling
passive margin successions that correlate with the Fore-Bal-
kan terrane. The Do˘ganköy Nappe has a composite Variscan
basement with metamorphic rocks of ortho- and para-origin
and a Lower Triassic metasedimentary cover with medium—
high-grade metamorphism. This suggests that the Do˘ganköy
Nappe may represent a different unit, resembling the
Rhodope terrane. The vergence of the CIN is towards the N.

The first common cover or overstep sequence of the CIN is

the Lower Jurassic basement sediments. These platform type

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sediments laterally and vertically passes to the Gümü alan
Formation including an alternation of sandstone and siltstone
with olistostromes and olistoliths of different origins possibly
indicating an unstable platform margin.

The Jurassic rock units covering the CIN in Istranca have

lost their primary structural positions due to the nappe move-
ments that occurred in latest Jurassic-Early Cretaceous time.
As a result they have been overthrust by Triassic succes-
sions, which they primarily covered, or locally form tectonic
windows below them (Fig. 9C,D,E).

In brief, the preliminary data obtained by the recent field-

work  in  the  Istranca  Crystalline  Complex  revealed  new
stratigraphic  and  structural  implications.  Even  if  prelimi-
nary, this new data will contribute to reconsideration of the
previous  suggestions  and  provide  new  constraints  for  the
geodynamic  evolution  of  this  little  known  terrane  assem-
blage in a very critical area of the Alpine belt.

Acknowledgments: This study was carried out in context of a
joint project between the General Directorate of Mineral Re-
search and Exploration (MTA) and the Geological Institute of
the Bulgarian Academy of Sciences (BAS). The authors would
like to extend their thanks to Dr. Aral I

. Okay (ITU) for his

discussions during the field work, to Kemal Erdo˘gan and Sibel

ener (MTA) for their contribution to date the Mesozoic fora-

minifers. The authors also thank Dr. Halil Yusufo˘glu, Hüseyin
Öcal, Ezgi Ulusoy and Özgür Türkmen for their contribu-
tions. The authors gratefully acknowledge Dr. Špela Goričan,
Dr. Paulian Dumitrică, Prof. Eugen Grădinaru, Prof. Hans-
Juergen Gawlick and Prof. Dušan Plašienka for their construc-
tive reviews as well as scientific and linguistic contributions.

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