Geology of the Caucasus: A Review

Abstract

The structure and geological history of the Caucasus are largely determined by its position between the stillconverging Eurasian and Africa-Arabian lithospheric plates, within a wide zone of continental collision. During the Late Proterozoic-Early Cenozoic, the region belonged to the Tethys Ocean and its Eurasian and Africa-Arabian margins where there existed a system of island arcs, intra-arc rift s, back-arc basins characteristic of the pre-collisional stage of its evolution of the region. The region, along with other fragments that are now exposed in the Upper Precambrian- Cambrian crystalline basement of the Alpine orogenic belt, was separated from western Gondwana during the Early Palaeozoic as a result of back-arc rift ing above a south-dipping subduction zone. Continued rift ing and seafloor spreading produced the Palaeotethys Ocean in the wake of northward migrating peri-Gondwanan terranes. The displacement of the Caucasian and other peri-Gondwanan terranes to the southern margin of Eurasia was completed by ~350 Ma. Widespread emplacement of microcline granite plutons along the active continental margin of southern Eurasia during 330-280 Ma occurred above a north-dipping Palaeotethyan subduction zone. However, Variscan and Eo-Cimmerian-Early Alpine events did not lead to the complete closing of the Palaeozoic Ocean. The Mesozoic Tethys in the Caucasus was inherited from the Palaeotethys. In the Mesozoic and Early Cenozoic, the Great Caucasus and Transcaucasus represented the Northtethyan realm - the southern active margin of the Eurasiatic lithospheric plate. The Oligocene-Neogene and Quaternary basins situated within the Transcaucasian intermontane depression mark the syn- and post-collisional evolution of the region; these basins represented a part of Paratethys and accumulated sediments of closed and semiclosed type. The final collision of the Africa-Arabian and Eurasian plates and formation of the present-day intracontinental mountainous edifice of the Caucasus occurred in the Neogene-Quaternary period. From the Late Miocene (c. 9-7 Ma) to the end of the Pleistocene, in the central part of the region, volcanic eruptions in subaerial conditions occurred simultaneously with the formation of molasse troughs. The geometry of tectonic deformations in the Transcaucasus is largely determined by the wedge-shaped rigid Arabian block intensively indenting into the Asia Minor-Caucasian region. All structural-morphological lines have a clearly-expressed arcuate northward-convex configuration reflecting the contours of the Arabian block. However, farther north, the geometry of the fold-thrust belts is somewhat different - the Achara-Trialeti fold-thrust belt is, on the whole, W-E-trending; the Greater Caucasian fold-thrust belt extends in a WNW-ESE direction.

Full text

S. ADAMIA ET AL.
489
Geology of the Caucasus: A Review
SHOTA ADAMIA
1
, GURAM ZAKARIADZE
2
, TAMAR CHKHOTUA
3
,
NINO SADRADZE
1,3
, NINO TSERETELI
1
, ALEKSANDRE CHABUKIANI
1
&
ALEKSANDRE GVENTSADZE
1
1
M. Nodia Institute of Geophysics, 1/1 M. Alexidze str., 0171, Tbilisi, Georgia
(E-mail: sh_adamia@hotmail.com)
2
Vernadsky Institute of Geochemistry and Analytical Chemistry, RAS, 119991, Moscow, Russia
3
Al. Janelidze Institute of Geology, 1/9 M. Alexidze str., 0193, Tbilisi, Georgia
Received 15 May 2010; revised typescripts receipt 30 January 2011 & 14 January 2011; accepted 11 April 2011
Abstract:  e structure and geological history of the Caucasus are largely determined by its position between the still-
converging Eurasian and Africa-Arabian lithospheric plates, within a wide zone of continental collision. During the
Late Proterozoic–Early Cenozoic, the region belonged to the Tethys Ocean and its Eurasian and Africa-Arabian margins
where there existed a system of island arcs, intra-arc ri s, back-arc basins characteristic of the pre-collisional stage of
its evolution of the region.  e region, along with other fragments that are now exposed in the Upper Precambrian–
Cambrian crystalline basement of the Alpine orogenic belt, was separated from western Gondwana during the Early
Palaeozoic as a result of back-arc ri ing above a south-dipping subduction zone. Continued ri ing and sea oor
spreading produced the Palaeotethys Ocean in the wake of northward migrating peri-Gondwanan terranes.  e
displacement of the Caucasian and other peri-Gondwanan terranes to the southern margin of Eurasia was completed
by ~350 Ma. Widespread emplacement of microcline granite plutons along the active continental margin of southern
Eurasia during 330–280 Ma occurred above a north-dipping Palaeotethyan subduction zone. However, Variscan and
Eo-Cimmerian–Early Alpine events did not lead to the complete closing of the Palaeozoic Ocean.  e Mesozoic Tethys
in the Caucasus was inherited from the Palaeotethys. In the Mesozoic and Early Cenozoic, the Great Caucasus and
Transcaucasus represented the Northtethyan realm – the southern active margin of the Eurasiatic lithospheric plate.
 e Oligocene–Neogene and Quaternary basins situated within the Transcaucasian intermontane depression mark
the syn- and post-collisional evolution of the region; these basins represented a part of Paratethys and accumulated
sediments of closed and semiclosed type.  e  nal collision of the Africa-Arabian and Eurasian plates and formation
of the present-day intracontinental mountainous edi ce of the Caucasus occurred in the Neogene–Quaternary period.
From the Late Miocene (c. 9–7 Ma) to the end of the Pleistocene, in the central part of the region, volcanic eruptions in
subaerial conditions occurred simultaneously with the formation of molasse troughs.
 e geometry of tectonic deformations in the Transcaucasus is largely determined by the wedge-shaped rigid
Arabian block intensively indenting into the Asia Minor-Caucasian region. All structural-morphological lines have
a clearly-expressed arcuate northward-convex con guration re ecting the contours of the Arabian block. However,
farther north, the geometry of the fold-thrust belts is somewhat di erent – the Achara-Trialeti fold-thrust belt is, on the
whole, W–E-trending; the Greater Caucasian fold-thrust belt extends in a WNW–ESE direction.
Key Words: Caucasus, convergence, collision, Eurasia, Gondwana, volcanism
Ka asların Jeolojisi
Özet: Ka asların yapısını ve jeolojik tarihini denetleyen ana unsur birbirine yaklaşan Avrasya ve Afrika-Arabistan
levhaları arasındaki konumudur. Geç Proterozoyik ile Tersiyer arasında Ka aslar, Tetis okyanusu ve bu okyanusun
Avrasya ve Afrika-Arabistan kıta kenarları içermekteydi; bu sistem içerisinde yer alan ada yayları, yay-içi ri ler, yay-ardı
havzalar Ka asların çarpışma öncesi jeoloji tarihinin bir parçasını teşkil eder. Erken Paleozoyik’te batı Gondwana’nın
altına güneye doğru dalan bir dalma-batma zonu üzerinde gelişen yay-ardı ri leşme ile Ka aslar, ve Alpin orojenik
kuşak içinde yer alan diğer üst Prekambriyen–Kambriyen kristalen temel parçaları, Gondwana’dan ayrılmıştır. Kuzeye
hareket eden bu Gondwana-çevresi (peri-Gondwana) mıntıkalarının güneyinde Paleotetis okyanusu açılmıştır. Ka asya
ve diğer Gondwana-çevresi mıntıkalarının Avrasya güney kenarını eklenmesi ~350 Ma’de tamamlanmıştır. Avrasya
kıta kenarının altına kuzeye doğru dalan bir dalma batma zonu üzerinde yaygın mikroklinli granitoid plutonlarının
yerleşimi 320–280 Ma aralığında gerçekleşmiştir. Tüm bu Variskan, Eo-Kimmeriyen ve erken Alpin olaylara rağmen
Ka asların güneyindeki Paleozoyik okyanusunun tamamen kapanmamış, ve Mesozoyik Tetis Paleotetis’ten miras
Turkish Journal of Earth Sciences (Turkish J. Earth Sci.), Vol. 20, 2011, pp. 489–544. Copyright ©TÜBİTAK
doi:10.3906/yer-1005-11 First published online 11 April 2011

THE GEOLOGY OF THE CAUCASUS
490
Introduction
 e structure and geological evolution of the
Caucasian segment of the Black Sea-Caspian Sea
region (Figure 1) are largely determined by its
position between the still converging Eurasian and
Africa-Arabian lithosphere plates, within a wide
zone of continent-continent collision. Problems of
Late Proterozoic–Phanerozoic development of this
area have been considered and discussed during
the past decades in a great number of publications.
According to some authors (Khain 1975; Adamia
1975; Adamia et al. 1977, 1981, 2008; Giorgobiani
& Zakaraia 1989; Zakariadze et al. 2007), the region
in the Late Proterozoic, Palaeozoic, Mesozoic, and
Early Cenozoic belonged to the now-vanished Tethys
Ocean (Prototethys, Palaeotethys, Tethys) and its
Eurasian and Gondwanan/Africa-Arabian margins.
Within this ocean-continent convergence zone,
there existed a system of island arcs, intra-arc ri s,
and back-arc basins etc. characteristic of the Late
Proterozoic–Early Cenozoic pre-collisional stage
of evolution of the region. During syn-collisional
(Oligocene–Middle Miocene) and post-collisional
(Late Miocene–Quaternary) stages of the Late Alpine
tectonic cycle, as a result of Africa-Arabia and Eurasia
collision back-arc basins were inverted to form
fold-thrust belts in the Great and Lesser Caucasus
and, in between, the Transcaucasian intermontane
depression. Normal marine basins were replaced by
semi-closed basins of euxinic type (Paratethys) and
later on (Late Miocene) by continental basins with
subaerial conditions of sedimentation (Milanovsky
& Khain 1963; Gamkrelidze 1964; Andruschuk 1968;
Azizbekov 1972; Geology of the USSR 1977; Jones &
Simons 1977; Eastern Paratethys 1985; Vincent et al.
2007; Adamia et al. 2008; Okay et al. 2010).
Main Tectonic Units
 e Caucasus is divided into several main tectonic
units or terrains (Figure 2).  ere are platform
(sub-platform, quasi-platform) and fold-thrust
units, which from north to south are: the Scythian
(pre-Caucasus) young platform, the fold-thrust
mountain belt of the Great Caucasus including
zones of the Fore Range, Main Range, and Southern
Slope, the Transcaucasian intermontane depression
superimposed mainly on the rigid platform zone
(Georgian massif), the Achara-Trialeti and the
Talysh fold-thrust mountain belts, the Artvin-Bolnisi
rigid massif, the Loki (Bayburt)-Karabagh-Kaphan
fold-thrust mountain belt, the Lesser Caucasus
ophiolitic suture, the Lesser Caucasian part of the
Taurus-Anatolia-Central Iranian platform, and
the Aras intermontane depression at the extreme
south of the Caucasus.  e youngest structural unit
is composed of Neogene–Quaternary continental
volcanic formations of the Armenian and Javakheti
plateaus (highlands) and extinct volcanoes of the
Great Caucasus – Elbrus, Chegem, Keli, and Kazbegi.
Within the region, Upper Proterozoic–
Phanerozoic sedimentary, magmatic, and
metamorphic complexes are developed.  eir
formation occurred under various palaeogeographic
and geodynamic environments: oceanic and small
oceanic basins, intercontinental areas, active and
kalmıştır. Mesozoyik ve erken Tersiyer’de, Büyük Ka aslar ve Transka asya, Avrasya’nın levhasının güney aktif kıta
kenarını, bir diğer ifade ile kuzey Tetis bölgesini temsil ediyordu.
Transka aya’nın dağ arası çöküntü bölgelerinde gelişen Oligosen–Neojen ve Kuvaterner havzalar bölgenin çarpışma
ve çarpışma sonrası evrimini temsil eder. Bu havzalar Paratetisin bir kesimini temsil eder ve sedimanları kapalı veya
yarı-kapalı havzalarda çökelmiştir. Afrika-Arabistan ve Avrasya levhalarının nihai çarpışması ve bugünkü kıtalararası
Ka aya dağ kuşağının oluşumu Neojen–Kuvaterner’de meydana gelmiştir. Geç Miyosen’den (9–7 Ma) Pleistosen’in
sonuna kadar geçen zamanda Ka a arın merkezi kesimlerinde volkanik faaliyetler meydana gelmiş ve molas havzaları
oluşmuştur.
Transka asya’daki tektonik deformasyonun geometrisini kontrol eden ana etken kama şeklinde sert Arabistan
blokunun Anadolu-Ka asya bölgesine saplanmasıdır. Buna bağlı olarak tüm yapısal-morfolojik çizgilerin, Arabistan
levhasının kuzey sınırını yansıtan bir şekilde, kuzeye doğru içbükey bir geometri gösterir. Buna karşın daha kuzeyde
kıvrım-bindirme kuşaklarının geometrisi farklıdır – Acara-Trialeti kuşağının yönü doğu-batı, Ka aslar kıvrım-
bindirme kuşağının uzanımı ise BKB-DGD’dur.
Anahtar Sözcükler: Ka aslar, yakınlaşan, çarpışma, Avrasya, Gondwana, volkanizma

S. ADAMIA ET AL.
491
passive continental margins – transitional zones
from ocean to continents.  e Late Proterozoic–
Phanerozoic interval is divided into two stages: pre-
collisional (Late Proterozoic–Early Cenozoic) and
syn-post-collisional (Late Cenozoic). During the
pre-collisional stage, there existed environments
characteristic of modern oceanic basins and zones
transitional from ocean to continent.
Geological Provinces
Existing data allow the division of the Caucasian
region into two large-scale geological provinces:
southern Tethyan and northern Tethyan located
to the south of and to the north of the Lesser
Caucasian ophiolite suture, respectively. During the
Late Proterozoic, the Southern Province distinctly
demonstrated Pan-African (Cadomian) tectonic
events, and throughout the Palaeozoic, it was a part
of Gondwana that accumulated mainly shallow-
marine platformal sediments. In the Palaeozoic,
the Northern Province is characterized by strong
manifestation of tectonic events: supra-subduction
volcanism, granite formation, deep regional
metamorphism, deformation and orogenesis.
 e Southern and Northern provinces di er each
from the other throughout the Mesozoic and Early
Cenozoic as well.  e boundary between them runs
along the North Anatolian (İzmir-Ankara-Erzincan)
– Lesser Caucasian (Sevan-Akera)-Iranian Karadagh
ophiolitic suture belt (see Figure 2).
Pre-collisional Stage: Late Proterozoic-Palaeozoic
Basement Rocks
Basement rocks are represented by regionally
metamorphosed (eclogite, amphibolite, epidote-
amphibolite and greenschist facies of high, moderate,
B L A C K
S E A
G R E A T C A U C A S U S
T R A N S C A U C A S U S
CAUCASUS
LESSER
EASTERN
P O N T I D E S
ANATOLIA
L. SEVAN
L. VAN
L.URUMIYEH
CAS PIAN
S E A
P R E C A U C A S U S
IRAN
Figure 1. Physical map of the Caucasus and adjacent areas of the Black Sea-Caspian Sea region (Adamia et al.
2010).

THE GEOLOGY OF THE CAUCASUS
492
and low pressure) sedimentary, volcanic and
plutonic rocks dated according to chronological
and palaeontological data. Magmatitic rocks
are represented by two main rock complexes of
(1) ultrabasic-basic-intermediate and (2) acidic
composition.  e former is a carrier of information
on the oceanic basins of Prototethys-Palaeotethys, it
outcrops within almost the all main tectonic zones of
the region (Abesadze et al. 1982), and is represented
by relatively small, dismembered, strongly deformed
and di erently metamorphosed fragments of basic
and ultrabasic rocks.
Rocks of pre-Mesozoic oceanic basins of the
region, generally, are closely associated with granite-
gneiss-magmatitic rock complexes of pre-Cambrian
MAIN TECTONIC UNITS
TECTONOSTRATIGRAPHIC UNITS (TSU)
Pc Mz
Pc Mz Kz
1
–
Sp Kz
2
Pc Kz
1
47 00’
o
Pc Pz
Alazani Fl
T a l y s h Z
Bechasin
Dz
Lo
Kh
Ah
As
Ts
Ch
La
Bu
Ka
Di
B PC- Pz
Kuban
Rioni
Terek
Aragvi
ophiolite suture belt: Sevan-Akera (SA)
Transcaucasian assif and forelands : Rioni (R) Kura (K) Alazani (Al) Aras (Ar)m its (Fd) ; ; ;
f (Fd) ; H ; ;oredeeps : Azov-Kuban Stavropol igh Terek-Caspian Gussar-Devichi
Fold-thrust mountain belts: Great Caucasus;
Achara-Trialeti; Talysh; Baiburt-Garabagh-Kaphan
Platforms: Scythian ;
Taurus-Anatolian-Central Iranian
(SC)
(TAI)
Neogene Quaternary subaerial volcanic area
–
c
a
b
pre-Cambrian-Palaeozoic basement
p- are collisional Pal eozoic of the Great Caucasus (a), Transcaucasus (b) and Lesser Caucasus (c)
p-re collisional Mesozoic
precollisional Mesozoic Early Cenozoic
–
p-re collisional Early Cenozoic
s-yn post collisional Late Cenozoic
–
Basement S
C
alients
Metamorphic omplexes
: Dzirula (Dz), Khrami (Kh),
Loki (Lo), Tsak uniats (Ts) Akhum(Ah),
Asrik hai( As).
: Chugush (Ch), Laba (La),
Buulgen (Bu),
Kassar (Ka), Dizi (Di).
,hk
-C
Gussar-Devichi Fd
Terek-Caspian Fd
Stavropol high
S c y t h i a n P l a t f o r m
Laba - Malka Z
Fore Range Z
Main Range Z
S
o u t h
e r n S
l o p e Z
S o u t h e r n S l o p e Z
Azov Kuban Fd-
Monocline Z
Daguestan Z
volcanic highlands, plateaus and extinct volcanoes: Kazbeg i (Kb), Keli (Ke)u
F or deep oreland one latform lateaud f e ; Fl f ; Z z ; Pt p ; Pl p
–––––
42 00’
o
SP Kz
2
40 00’
o
PC Kz
1
Pc Pz
Sp Kz
2
Aras Fl
Baku
Pc Mz-Kz
1
Pc -Kz
1
Sevan
Sp Kz
2
Kl
Sevan-Akera SA
Pc Mz-Kz
1
Kura
SA
Sp Kz
2
Taurus- Anatolian Central Iranian
49 00’
o
Pc Mz-Kz
1
Kura Fl
Tbilisi
Rioni Fl
A c h a r a -T r i a l e t i Z
Sp Kz
2
B PC-Pz
Grozni
Pc Mz
BPC-Pz
Pc Pz
Pc Mz-Kz
1
Pc Kz
1
42 00’
o
Pc Mz-Kz
1
Pc Mz-Kz
1
Pc Kz
1
43 00’
o
Pc Kz
1
Sp Kz
2
Pc Mz
PcMz- Kz
1
39 00’
o
41 00’
o
Novorossiisk
BLACK SEA
37 00’
o
44 00’
o
Aras
Loki - Gar abagh
Kaphan
Armenia Pl
Transcaucasian Massif TCM
42 00’
o
SP Kz
2
CASPIAN
SEA
40 00’
o
PC Kz
1
Pc Pz
Sp Kz
2
Aras Fl
Baku
Pc Mz-Kz
1
Pc -Kz
1
Sevan
Sp Kz
2
Kl
Sevan-Akera SA
Pc Mz-Kz
1
Kura
SA
Sp Kz
2
49 00’
o
Pc Mz-Kz
1
Kura Fl
Tbilisi
Rioni Fl
A c h a r a -T r i a l e t i Z
Javakheti Pl
Sp Kz
2
B PC-Pz
Pc Mz
BPC-Pz
Pc Pz
Pc Mz-Kz
1
K
Pc Kz
1
42 00’
o
Pc Mz-Kz
1
Pc Mz-Kz
1
Pc Kz
1
43 00’
o
Pc Kz
1
Sp Kz
2
Pc Mz
PcMz- Kz
1
39 00’
o
41 00’
o
BLACK SEA
37 00’
o
44 00’
o
Aras
Loki - Gar abagh
Kaphan
Armenia Pl
Transcaucasian Massif TCM
Figure 2. Tectonic map of the Caucasus (Adamia et al. 2010).

S. ADAMIA ET AL.
493
(Southern Province) and Palaeozoic (Northern
Province) basement, and represent rock associations
belonging to continental crust as well as to
transitional oceanic-continental crust.  e rocks are
strongly deformed: tectonic nappes, slices, tectonic
and sedimentary mélanges (Lesser Caucasus, Dzirula
massif), accretionary prisms etc (Great Caucasus) are
frequent.
Southern Province
In the Caucasian region, the oldest, Pan-African
(Cadomian–Neo-Proterozoic) basement of the
Central Iranian platform crops out north of Erevan
(Armenia, Tsakhkuniats massif, see Figure2). It
includes two Pre-Cambrian complexes: (1) Arzacan
(ensialic) and (2) Hancavan (ensimatic).
 e Arzacan ensialic complex consists of
paraschists (1500 m thick), which have undergone
metamorphism in almandine-amphibolite facies,
and of metavolcanics, phyllites, marbles, and schists
(2000 m thick) metamorphosed in greenschist facies.
 e complex is intruded by granites whose Rb/Sr
isochron age is 620 Ma and crust melt isotope initial
ratio of
87
Sr/
86
Sr= 0.7102 ± 0.0006 (Agamalian 2004).
 e lower unit of the Hancavan complex (1900
m thick), which during the Pan-African events was
obducted over the Arzacan complex, represents an
oceanic-crust-type assemblage and is dominated by
komatiite-basalt amphibolites with thin sedimentary
intercalations, while the upper unit (1000 m thick)
consists of metabasalt and metaandesite with beds
of marble and quartz-mica schists. Both parts of
the Hancavan complex contain tectonic lenses of
serpentinite.  e complex is cut by trondhjemite
intrusions whose Rb/Sr isochron age is 685±77 Ma,
with a mantle origin ratio of
87
Sr/
86
Sr= 0.703361
(Agamalian 2004).
Boundary Between Northern and Southern Provinces
 e Sevan ophiolite mélange contains di erent
exotic blocks represented by garnet-amphibolites
(Amasia – the westernmost part of the Sevan
ophiolite suture belt), amphibolites, micaschists
(Zod, Adjaris and Eranos – the eastern part of the
Sevan ophiolite suture belt) (Agamalian 2004), and
redeposited metamorphic rocks of continental
a nity: greenschists, marbles, limestones and
skarns (Geydara and Tekiakay in Karabagh Figure
3; Knipper 1991). Layers of pre-Carnian breccia-
conglomerates consisting of redeposited clasts
represented by tectonized harzburgites, layered-,
 aser- and isotropic gabbros, diabases, gabbro-
diabases, altered basalts, tectonized other basic
rocks, Upper Palaeozoic marbles, basaltic andesites,
phyllites, carbonatic scarn have been found in the
ophiolite mélange of the Lesser Caucasian suture
directly to the east of the Lake Sevan (Zod and Ipiak
nappes, r. Lev-chai; Knipper 1991). Available data
show that throughout the Mesozoic at the northern
edge of Palaeotethys occured destruction and erosion
of obducted ophiolites, accumulation of redeposited
ophiolitic clastics with admixture of continental ones.
According to Agamalian (2004), the Rb/Sr
age of the Amasia amphibolites is 330±42 Ma,
87
Sr/
86
Sr= 0.7051±0.003x±0.000292.  e Rb/Sr
age of a block of garnet gneiss (Zod) is equal to
296±9 Ma (
87
Sr/
86
Sr= 0.705357±0.000292), and for
metamorphic schists from the same localities 243±13
(
87
Sr/
86
Sr 0.706107±0.000156), 241±12 (
87
Sr/
86
Sr
0.707902±0.000417) and 277±44 Ma (
87
Sr/
86
Sr
0.704389±0.0003510).
 e Sevan ophiolite belt represents an easternmost
part of the İzmir-Ankara-Erzincan (or North
Anatolian) ophiolite suture belt, interpreted by many
authors as the main suture of the Paleotethys-Tethys
(e.g., Adamia et al. 1977, 1981, 1987).
Northern Province:  e Transcaucasian Massifs
(TCM)
Loki, Khrami, Dzirula, Akhum-Asrikchai Salients
of the Basement (see Figure 2)- All the above-
mentioned salients of the basement, except the
Akhum and Asrikchai ones, are mainly composed
of Variscian granitoids. Relatively small outcrops of
di erently tectonized and metamorphosed basic and
ultrabasic rocks are generally associated with pre-
Cambrian–Early Palaeozoic gneissose diorites and
plagiogranites.
 e Loki salient outcrops in the territory of Georgia
along the boundary with Armenia, within the Artvin-
Bolnisi massif of the Transcaucasian intermontane

THE GEOLOGY OF THE CAUCASUS
494
depression.  e structure of the Loki salient as well as
of the other salients of the Transcaucasian basement
seems to be more complicated than considered
earlier (Abesadze et al. 2002). Most of the salient is
composed of Upper Palaeozoic granitoids. Repeated
tectonic displacement has caused inter ngering
of metabasites and metapelites and formation of
tectonic sheets and slices (Figures 4 & 5).
 e Loki basement, evidently, was formed
during the Late Proterozoic–Early Palaeozoic.  e
metabasites, apparently, represent Prototethyan
fragments.  e metamorphic rocks along with
11
7
6
8
4
5
160
Ma
3
2
9
1
5
0
40
80
120
160
200
240
280
320
360
400
440
m
3
8
2
1
8
8
7
3
7
5
3
5
7
4
1
3
1
1
2
2
J
1
Tc
3
a
b
c
d
e
The Ipiak nappe (a,b,c,d):
1. arzburgite tectonite;
2. ayered gabbro;
3. laser gabbro;
4. sotropic gabbro;
5. lagiogranite dyke;
6. reccia and breccia-
conglomerate consisting of
gabbro and diabase redeposited
clastics;
7. Upper Triassic Cenomanian
volcanic rocks; 8. xotic limestone
blocks; 9. iabase dykes;
10. adiolarite; 11. Upper
Cenomanian flysch.
h
l
f
i
p
b
e
d
r
–
Zod(e): 1. abbro-diabase
breccia; 2. andstone layers
consisting of gabbro-diabase
clastics; 3. asalt and basaltic
andesite; 4. Carnian: pelite and
radiolarite; 5. adiolarite;
6. Toarcian radiolarite;
7. istal turbidite and conturite;
8. locks of Carnian limestone.
T c– Carnian; J – Lower Jurassic;
K cm– Cenomanian.
g
s
b
r
d
b
31
2
Figure 3. Pre-Upper Triassic and Upper Triassic-Jurassic sedimentary breccia in the ophiolite mélange of
the Sevan-Akera suture belt (Knipper 1991).

S. ADAMIA ET AL.
495
012
3
Km
41 15’
º
44 20’
º
R.Moshevani
0
1000 2000 m
SE
2000 m
1000
-1000
0
NW
Loqjandari
Eocene volcanic formation
Bajocian island-arc type
volcanic formation
Cenomanian terrigene clastics
and island-arc type volcanic formation
ous
Lower Jurassic terrigene clasticous s
tectonic slices of metabasite
and metapelite complexes
Upper Pal eozoic granitoidsa
Lower–Middle Pal eozoic tonalite-diorite gneisses and migmatitesa
The Loki salient
faults
cross-section
Figure 4. Simpli ed geological map and cross-section of the Loki salient (Abesadze et al. 2002; Zakariadze et
al. 2007).
gneiss-migmatite complexes of the Transcaucasian
massif bear resemblance to the immature continental
crust of the Nubian-Arabian shield, and in the Early
Palaeozoic, they were displaced to the southern edge
of the East-European continent (Baltica). All the
present-day geological structures were formed in the
Late Palaeozoic–Cenozoic (Figure 4; Abesadze et al.
2002).
 e Khrami salient situated to the north of the Loki
(Figure 5), is made up mainly of Upper Palaeozoic
(Variscan) granites. Plagiogneisses and migmatites
occupy a limited part and bear small bodies of
metabasites and serpentinites.
 e Dzirula salient is dominated by pre-Variscan
diorite-plagiogneiss-migmatite complex (‘grey
granites’) and Variscan granitoids (‘red granites’).

THE GEOLOGY OF THE CAUCASUS
496
012
Km
41º30’
44º10’
41º30’
41º35’
44º20’
R.Khrami
1400 m
1000
600
200
NW
SE
Khrami
Kldeisi
0
400 800 m
L Jurassic terrigen clastics. ous
The Khrami salient
Upper Cretaceous island-arc
type volcanic formation
Cenomanian basal formation
Upper Jurassic Lower Cretaceous
limestones and argillites
–
Lower Middle Carboniferous shallow-marine
and subaerial volcanic formations
–
abbro diorite-tonalite gneisses and migmatitesg-
Upper Pal eozoic rhyolites, granite-porphyry, and granitesa
faults
cross-section
Figure 5. Simpli ed geological map and cross-section of the Khrami salient (Abesadze et al.
2002; Zakariadze et al. 2007).

S. ADAMIA ET AL.
497
Basic-ultrabasic rocks are found mainly within the
 eld of diorite-plagiogneiss-migmatite complex, and
also within the tectonic mélange of the Chorchana-
Utslevi stripe cropping out along the eastern edge of
the Dzirula salient (Figure 6).
 e oldest basement unit consists of biotite
gneisses, plagiogneisses, amphibolites, and
crystalline schists subdivided into metabasic and
metasedimentary successions presented either as
irregularly piled-up tectonic slices or numerous
inclusions in later gabbroic, dioritic and quartz
dioritic intrusions.  e metabasic succession
includes various massive and banded amphibolites,
garnet amphibolites, metadiabases, and subordinate
subvolcanic bodies of metagabbro-metadiabase.
Polymetamorphism of the metabasic succession did
not exceed conditions of amphibolite and epidote-
amphibolite facies of moderate pressure.
 e Grey Granitoid complex incorporates
associated basic, dioritic and quartz dioritic
(tonalite) intrusions emplaced at various levels in the
oldest basement unit. Basic intrusions include dykes
and small stocks of diabases, gabbro-diabases, and
gabbro.
 e tectonic mélange zone consists of a number
of allochthonous tectonic slices of di erent age and
facies: phyllite schists, sheared Palaeozoic high-silicic
volcanics, sheared Upper Carboniferous microcline
granite, metabasite and serpentinite (Abesadze et
al. 1980). Metabasic slices consist of massive and
banded amphibolites, mylonitized amphibolites,
metagabbro-diabases, metadiabases and metabasic
tu s.  e ultrama c-ma c association of the
mélange zone is interpreted as dismembered Upper
Proterozoic–Lower Palaeozoic metaophiolite, and
phyllite slices as fragments of hemipelagic cover of
the paleooceanic basement.
Metabasic slices are associated with serpentine
bodies in the tectonic mélange zone. All these
ultrabasic-basic associations are considered as
a unique ancient ma c basement of the massif.
 e ultrabasic rocks are composed mainly of
harzburgite and dunite ubiquitously a ected by
polymetamorphism and extensive serpentinization.
Available data on geochronology and
biostratigraphy of the Transcaucasian massif
(TCM) basement unit, including three new Sm-Nd
isochrons were obtained in the Vernadsky Institute of
Geochemistry and Analytical Chemistry, Academy
of Sciences of Russia, Moscow (Zakariadze et al.
1998, 2007). An attempt to date the ma c foundation
of the TCM was based on the study of Nd-isotope
variation for the metabasic series of the tectonic
mélange zone, which despite narrow variation ranges
for major elements (Mg#= 0.58 ± 0.01) show strong
fractionation of incompatible trace elements and REE
in particular (Sm/Nd= 0.41–0.27).  e initial data
on Neoproterozoic–Cambrian (c. 750–500 Ma) age
limits of the dioritic intrusions of the Gray Granite
Basement Complex were derived from U-Pb studies
of zircon from gneissose granodiorite, quartz diorite-
plagiogranite and migmatite of the Dzirula salient
(Bartnitsky et al. 1990). New geochemical data,
together with new La-ICP-Ms zircon and electron
microprobe monazite age, are described from the
Dzirula massif. U-Pb zircon ages of ca. 540 Ma,
o en with 330 Ma rims are obtained from deformed
granodiorite gneisses; zircon and monazite data
date the metamorphic age of HT/LP migmatites and
paragneisses at ca. 330 Ma; some paragneisses contain
relict 480 Ma monazites implying a previous thermal
event (Treloar et al. 2009). Zircon and monazite
dates of ca. 330 Ma from unfoliated calc-alkaline to
high-K, I-type granodiorites, diorites and gabbros
intrusive into the gneisses and migmatites according
to Treloar et al. (2009) suggested that they represent
the heat source that drove the metamorphism.
 e whole stack of nearly vertical tectonic slices of
the Dzirula metamorphic complexes is hosted by Late
Palaeozoic granites. Middle–Late Carboniferous–
Permian an emplacement ages of the potassium (red)
granite is reliably constrained by stratigraphic and
various K-Ar and U-Pb data from micas and zircons
(Rubinshtein 1970; Zakariadze et al. 2007; Treloar et
al. 2009).
Small salients of the basement complexes of the
TCM are known to the north of the Sevan Lake
(Akhum, Asrikchay).  ey are represented mainly
by micaschists (Aslanian 1970; Azizbekov 1972).
 e Rb/Sr age of the quartz-micaschists according to
Agamalian (2004) is 293±7 Ma (87Sr/86Sr= 0.7057 ±
0.0016).

THE GEOLOGY OF THE CAUCASUS
498
100 100 300 500 m0
SE
NW
D
O(?)
C
2
J
2
J
1
J
1
J
2
S- D
31
Є
43 15’
o
43 30’
o
42 15’
o
42 00’
o
43 30’
o
0 5 10 km
R. Dumala
R. Dzirula
Middle Jurassic: Bajocian volcanic formation
The Dzirula salient
Lower Jurassic: conglomerates,
sandstones, argillites
Middle Carboniferous: rhyolitic subaerial
volcanic formation
Upper Silurian Devonian phyllites and
marbles
–
Ordovician (?): metarhyolites
and pudding conglomerates
Cambrian phylites and marbles (on the cross-section)
– undivided Cambrian Devonian phyllites (on the map)
–
Upper Pal eozoic: milonitized granitesa
Upper Pal eozoic granitesa
mylonitized rhyolites
Paleozoic gabbro
tonalite-granodiorite gneisses
Lower Middle Pal eozoic bi tite-sillimanit-cordierite schists, gneisses and migmatiteao
–
ultrabasites, serpentinites
Middle P l eozoica a amphibolites
cross-section
faults
Figure 6. Simpli ed geological map and cross-section of the Dzirula salient (Abesadze et al. 2002; Zakariadze
et al. 2007).

S. ADAMIA ET AL.
499
Great Caucasus, Main Range Zone, Ultrabasic-
basic Complexes
Within the Great Caucasus, pre-Mesozoic basic and
ultrabasic rocks crop out: (1) along the southern
margin of its crystalline core (Chugush, Laba,
Buulgen, and Kassar complexes), (2) at the western
submergence of the crystalline core (Belaya and
Kisha complexes), and (3) in the Fore Range Zone
(Blib, Atsgara, Arkhiz, Marukh complexes) (Figure
7).
 e southernmost strip of the crystalline core of
the Great Caucasus is represented by thrust slices
of metaophiolites (Adamia et al. 1978, 2004).  ey
consist of ultrabasic rocks, gabbro-amphibolites,
amphibolites and mica-schists, plagiogneisses,
marbles (Laba, Buulgen, Chugush, and Kassar
Groups, Figure 7). Mineral rock associations indicate
amphibolite facies of high and moderate pressure
metamorphism.  e presence of crinoidea in marbles
of the Laba Group indicates a post-Ordovician
(Early–Middle Palaeozoic) age of the rocks.  e
composition of the Palaeozoic metaophiolitic
complexes corresponds to that of oceanic spreading
centers (T-type MORB) and suprasubduction zones
(immature arc – back-arc association). Accretion
of the fragments of the oceanic and transitional
ocean/continent crust towards the eastern part of
BLACK
SEA
Sokhumi
Kh
Ch
FRZ
BeZ
FRZ
SSZ
MRZ
MRZ
Mz
Ps
Bl
Kf
Ar
So
La
Bu
Al
TD
Ma
Kv
Di
C
SA
Ka
Da
Os
Dh
Sa
Bs
Lh
Ur
Mk
Msp
Tb
SSZ
43
o
00’
Devonian Triassic deposits of the Dizi series
(Di) and Triassic of the Mzimta
–
Upper Palaeozoic deposits: Khuko (Kh),
Pseashko (Ps),Kvishi (Kv), and Oseti (Os)
Lower Middle Palaeozoic basite-ultrabasite-tonalite
metamorphic complexes: Belaia (Be), Chugush (Ch),
Laba (La), Buulgen (Bu), and Kassar (Ka);
–
Lower Middle Palaeozoic metapelite-gneiss-
migmatite Macera etc complexes (Mc)
–
Upper Palaeozoic (Variscan-Vs) granitic complexes
Palaeozoic Triassic volcanic and sedimentary
complexes
–
Lower Middle Palaeozoic basite-ultrabasite
metamorphic complexes: Blib (Bl), Dakhov (Dh),
Sahrai (Sa), and Beskes (Bs).
–
Lower Middle Palaeozoic ophiolites allochtones:
Kjafar (Kf), Arkhiz (Ar), Teberda (Tb). Bechasin
zone (BeZ)
–
Lower Middle Palaeozoic and Proterozoic (?)
metamorphic Chegem etc. complexes
–
Lower Middle Palaeozoic deposits: Urlesh (Ur),
Lahran (Ln) etc suits
–
Upper Palaeozoic Malka (Mk) granites
Malka serpentinites (Msp)
faults, thrusts
cross-sections
SSZ
FRZ
BeZ
MRZ
Southern Slope Zone
Main Range ZoneFore Range Zone
Bechasin zone
tectonic megaslices: Sofia (So), Teberda-Digor (TD), Shkhara-Adaihoh (SA) e c Elbrus (El) Chegem (C). xtin t volcanoes: ,
a
42 00’
o
KARACHAY
VLADIKAVKAZ
44 00’
o
Be
Figure 7. Schematic geological map of the pre-Jurassic complexes of the Great Caucasus. Abbreviations La, Bu and Kf indicate
locations of the Figure 8a, b & c, accordingly.

THE GEOLOGY OF THE CAUCASUS
500
the East European continent occurred during the
Middle Palaeozoic, apparently, at the Early–Middle
Carboniferous boundary (Adamia & Shavishvili
1982; Belov & Omelchenko 1986; Somin 2007b).
 irty seven samples of the Kassar Group
were studied in the palaeomagnetic laboratory of
the Caucasian Institute of Mineral Resources. In
amphibolites of this group, maghemite, magnetite
and titanomagnetite proved to be NRM-positive.
Calculated palaeo-latitude corresponds to 14° N,
whereas an age of magnetization, apparently, can be
attributed to Late Devonian–Early Carboniferous.
 at is in accordance with geological data on the
position and age of the initial rocks of metaophiolites
of the Laba and Buulgen Groups (Adamia et al.
2004a).
In the westernmost part of the Main Range Zone
of the Great Caucasus under Upper Palaeozoic
and Lower Jurassic deposits, there appear basic
and ultrabasic rocks represented by tectonic slices
of serpentinites, milonitized trondhjemites and
gabbro-diorites, strongly deformed banded gabbro
(with ultrabasic cumulatives), gabbro-diabases,
and phyllites (Adamia & Shavishvili 1982). A pre-
Mesozoic age for the basic-ultrabasic complexes of
the Main Range Zone is con rmed by stratigraphical,
palaeontological and isotopic geochronological data.
Based on the stratigraphical position they are dated
as pre-Middle Carboniferous (Andruschuk 1968;
Ajgirei 1976; Belov 1981; Somin 2007a). According
to palaeontological  nds (bluish-green algae and
crinoidea), the upper part of the Laba series is dated
as post-Middle Ordovician (Potapenko & Stukalina
1971; Adamia et al. 1973; Somin & Vidiapin, 1989).
 e absolute age results for the Laba- and
Buulgen complexes agree well with biostratigraphical
data. U-Pb data for zircon from microgneisses and
amphibolite microgneisses of the Laba series yield
534±9 Ma and 520 Ma ages (apparently, an age of
magmatic protolithes, Somin et al. 2004) and 345
Ma (an age of metamorphism, Somin et al. 2004).
U-Pb (SHRIMP) dating for magmatic zircons from
orthogneisses of the Buulgen complex yielded 381±3
Ma (Somin 2007a).  e same study gave an age of
metamorphism of 355–325 Ma.  ese data are in good
agreement with a Sm-Nd mineral isochron age for
garnet-biotite amphibolites of the Buulgen complex
(287±33 Ma, Somin 1991). According to data by
Hanel et al. (1993a, b), Gurbanov et al. (1995), an age
of amphibolites of the Buulgen complex is 600±15
Ma (melanosome) and 500±20 Ma (leucosome).
Great Caucasus, Main Range Zone, Gneiss-migmatite-
micaschist and Granitic Complexes
Rocks of the Granitic Complex, the granites
themselves
and various granitoids, granito-
gneisses, migmatites and quartz-mica crystalline
schists (amphibolitic, epidote-amphibolitic, and
greenschist facies), and also granite blastomilonites
and phyllonites are concentrated north of
metabasites-metaophiolites of the Laba-Buulgen-
Kassar accretionary complexes. Amphibolites are
subordinate and marbles are very scarce.  ese
complexes are made up of large tectonic slices in
the Main Range Zone: Sophia, Teberda-Digori,
Shkhara-Adaikhokhi (see Figure 7). Crystalline
schists, granite-gneisses and migmatites, known in
publications as the Makera, Gondaray and some other
groups, represent the environment accommodating
potassium-spar granites and associated granitoids
of the crystalline core – pre-Alpine basement of the
Great Caucasus (Gamkrelidze 1964; Andruschuk
1968; Somin 1971; Ajgirei 1976; Adamia et al. 1987;
Somin et al. 2007a). According to the mineral and
chemical composition, they are, generally, attributed
to calc-alkaline series, S- and I-granites, and also to
transitional from I-S-types of granites (Adamia et al.
1983; Potapenko et al. 1999; Somin 2007a).
 e age of the Metamorphic-Granitic
Complexes was determined geochronologically
and stratigraphically (Gukasian & Somin 1995).
Redeposited material of the metamorphic rocks as well
as granites is abundantly present in Upper Palaeozoic
molasse of the Great Caucasus. Geochronological
dating of granite-gneisses-migmatites (Gondaray
Complex) was obtained from detrital zircons (Somin
et al. 2007a). Most o en indicated values of 500±40
and 2000 Ma were obtained by the Pb/Pb evaporation
method for zircons from orthogneisses (Hanel et
al. 1993a, b). Dating of zircons from rocks of the
same locality using the traditional U-Pb method
provided an age of 400±10 Ma (Bibikova et al. 1991).
An U-Pb age of 386±5 Ma was obtained for similar
orthogneisses, and the U-PB dating of zircons from
migmatite leucosomes yielded 305 Ma (Somin et
al. 2007a). Data obtained for detrital zircons from

S. ADAMIA ET AL.
501
paragneisses fall in the Proterozoic–Lower Palaeozoic
interval (Somin et al. 2007b). Occurrence of detrital
zircons dated back to 470–480 Ma suggests that the
paragneisses are younger than Early Ordovician. 425
Ma SHRIMP dating of zircons from amphibolites,
intruded by orthogneisses, shows that the rocks
are not younger than Middle Silurian (Somin et al.
2007a). Rb/Sr isochron dating of potassium-spar
granites (Ullukam complex – the central part of
the Main Range Zone) gave values from 280 up to
300 Ma; K/Ar dating demonstrated an interval of
290–320 Ma (Gamkrelidze 1964; Andruschuk 1968;
Potapenko et al. 1999).
Great Caucasus Fore Range Zone: Basic and
Ultrabasic Rocks
Within the central (Tebaerd) and western parts
(Great Laba) of the Fore Range Zone, outcrops
of ophiolites are traced as strongly deformed
allochthonous tectonic sheets and slices.  ey
are underlain by Silurian–Devonian–Lower
Carboniferous volcanogenic-sedimentary island-
arc type deposits and overlain by Middle–Upper
Carboniferous molasse (neoautochthone).
There are several allochthonous sheets consstng
of ultrabasc rocks, gabbro-diabases, e usives
(basalts and andesitobasalts), terrigenous, carbonate
and volcanoclastic sediments (Grekov et al. 1974;
Kropachev & Grekov 1974; Ajgirei 1976; Khain
1984; Zakariadze et al. 2009; see Figures 7 & 8).  e
ophiolitic association is subdivided into the following:
mantle restites, cumulative complex, dyke complex,
volcanic series, and volcanogenic-sedimentary
series. According to rare  nds of fossil fauna (corals),
the age of the volcanogenic-sedimentary series is
identi ed as Middle Devonian (Grekov et al. 1974).
 e K/Ar age of amphibole from gabbro-pegmatite
is 457±13 Ma and 493±15 Ma (Khain 1984), and
SHRIMP zircon age of gabbroid rocks of the Maruh
ophiolite nappe is 416±8 Ma (Somin 2007a) that
agree well with data for a Lower–Middle Palaeozoic
age of the ophiolites of the Fore Range.
 e Blib complex represents an isolated outcrop
of metabasites and ultrabasic rocks tectonically
underlying Middle Palaeozoic sediments of the
westernmost part of the Fore Range Zone (Great
and Small Laba).  e complex represents an
alternation of amphibolites, amphibolite-gneisses,
plagiogneisses, and schists; garnet-epidote and albite
amphibolites predominate. Massive and banded
eclogites, and serpentinized ultrabasites alternating
with the garnet mica schists crop out (Andruschuk
1968). Sm/Nd dating of eclogite, with exception of
one pair of garnet rock, gave an age of 311±22 Ma,
and Lu-Hf garnet chronometer showed an age of
322±14, 316±5 and 296±11 Ma, which is constrained
to error limit of Ar-Ar age for phengite equal to
303±5 Ma (Perchuk & Phillipot 1997; Phillipot et al.
2001). Somewhat older mineral (amphibole, biotite,
muscovite) ages (374±30 Ma) were obtained by the
K-Ar method for amphibolites of the Blib complex
(Somin 2007a).
Within the Fore Range Zone of the Caucasus, the
Granitic Complex includes the upper part of the
Blib Complex consisting of garnet quartz-muscovite
schists, and granite-gneisses of the Armov ‘suite’
(Andruschuk 1968) that represents a tectonic
sheet located between the lower, ultrabasic-basic
(Balkan) part of the Blib Complex and the Middle
Palaeozoic metavolcanics of the Fore Range Zone.
Granitoids occupy a sizeable part of the complex
and are termed the Urushten Complex (Andruschuk
1968).  e complex is dominated by granodiorites,
plagiogranites, plagioalaskites belonging to I-type
of calc-alkaline series. Maximum values of K/Ar age
reach 370 Ma (Potapenko et al. 1999).
Several small outcrops of the basement complexes
termed as the Dakhov, Sakhrai and Beskes salients
(see Figure 7) form the partly exposed northern
margin of the Fore Range Zone of the Great
Caucasus (Ajgirei 1976; Somin et al. 2007b).  e
Dokhov salient is mostly composed of granitoids
intruded in metamorphic rocks.  e U-Pb age of
zircon grains from metaaplites has concordant ages
of 354±3 Ma and 353±3 Ma and these values are
considered to be the crystallization age of the aplites.
Also according to K-Ar dating, hornblende from
the unmetamorphosed granodiorite show an age of
301±10 Ma that constrains the upper age limit for
the Dakhov salient (Somin et al. 2007b).
Scythian Platform, Bechasin Zone: Metamorphic and
Granitic Complexes
Metamorphic and Granitic complexes outcrop in the
central part of the Bechasin Zone (see Figures 2 &
7).  e metamorphic rocks of greenschist facies are

THE GEOLOGY OF THE CAUCASUS
502
J
1
J
1
MBS
R
CB
MBS
S
S
G
A
BBROIC
-DIO
RITIC
LAYERED
S
E
QU
EN
CE
S
500 0 500
1000 m
2000
1000
Mk
SW
NE
M
M
D
D
L
J
1
PS
2500
2000
1500
1000
500
0
SW
NE
a
b
L
D
Ps
M
M
Mk
J
1
metapelites, marbles, Lashtrak suite (L)
metabasites , Damkhuths complex (D)
metaconglomerates or pseudoconglomerates (Ps)
mylonitized metabasites-plagiogneisses, Mamkhurts complex (M)
amphibolites, Klich complex
biotitised amphibolites
gabbro-diorite- tonalite-gneisses
rodingites
serpentinites
mylonitised granite-migmatite, Makera complex
Upper Pal eozoic granitesa
black slate-diabase formations, Lower Jurassic
faults
ghabbro-amp ibolites and amphibolites
diorites, quartz-diorites, tonalites -
Chilik massif
layered gabbro
volcanic complexes
my ylonites, blastom lonites,
gneisses
volcanic-sedimentary complex, Teberda suite
Devonian volcanic-sedimentary
complex and lim stonese
tectonized ultrabasites, allochtones
tUaectonized ultrabasites, allochtones pper Pal eozoic molasses, neoautochthon
faults, thrusts
2000
2500
3000
0
0
500
1500
1000
c
W E
Figure 8. Cross sections of the pre-Jurassic complexes of the Great Caucasus. Abbreviations of
La, Bu and Kh indicate location of the cross sections a, b and c, accordingly.

S. ADAMIA ET AL.
503
represented by micaschists, biotite-quartz schists,
metavolcanoclastics, sericite-chlorite schists etc.  e
U-Pb SHRIMP average age of detrital zircons from
metasandstones is 543 Ma (range= 573–579 Ma) and
the age of zircons from orthogneisses is 530±8 Ma
that indicate a Cambrian age of the complex (Somin
2007a). Metamorphic rocks of the Bechasin Zone are
intruded by Upper Palaeozoic granitoids. Massive
granites, granodiorites and quartz diorites, aplites
and granite-porphyry (Malka- and Kuban-types of
granitoids) are distinguished.  eir petrochemical
features indicate they are transitional from I- to
S-types and I granites (Potapenko et al. 1999).
Metamorphic and granite complexes of the Bechasin
Zone are unconformably (tectonically) covered by
Lower–Middle Palaeozoic sediments. In its turn, the
latter are covered by a thick body of allochthonous
ultrabasic rocks (serpentinites of the r. Malka, see
Figures 2 & 7).
Palaeozoic Sedimentary Cover
Palaeozoic sedimentary cover is represented
by various facies of terrigenous, carbonate, and
volcanogenic deposits within almost all tectonic
units of the Caucasus.
Southern Province
Within the Caucasian part of the central Iranian
platform, the Palaeozoic sedimentary cover is slightly
metamorphosed, deformed, and facially corresponds
to shallow-marine type. Continuous Devonian–
Carboniferous series of shelf deposits developed in
Nakhchevan (Azerbaijan) and southern Armenia and
mainly consist of coral-brachiopod limestones (o en
bituminous), quartzite sandstones, and argillites.
 e total thickness of the Devonian–Visean (Lower
Carboniferous) deposits ranges between 3000–4000
m (Figure 9).  ere are no deposits of Middle and
Upper Carboniferous age.  ick transgressive
Permian bituminous algal foraminifera limestones
(400–1000 m) containing corals, brachiopods,
ammonoids, and conodonts unconformably overlies
the Devonian and Carboniferous deposits (Aslanian
1970; Azizbekov 1972; Rustamov 2005).
Within the boundary zone, limestone blocks
with Middle Carboniferous–Permian conodonts
(Kariakin & Aristov 1990) are found in Karabagh
within the mélange of the Lesser Caucasian ophiolite
suture belt.
Northern Province
Within the Transcaucasian massif (TCM), Palaeozoic
deposits are known at the Khrami, Dzirula and
Asrik-Chai salients of the basement. At the Khrami
salient, they are represented by a shallow-marine
and continental volcano-sedimentary formation
with limestone lenses dated by corals, brachiopods,
conodonts, and fossil  ora as Upper Visean–
Namurian–Bashkirian (see Figure 5).  e formation
is 600–800 m thick. With this formation are
associated quartz porphyries and granite porphyries,
which together with volcanoclastics form a volcano-
plutonic formation. An analogous formation of
subaerial dacite-rhyolitic lavas and volcanoclastics
(1200 m thick) with rare andesitic and basaltic beds
outcrops within the Dzirula salient (Figure 6). One
more outcrop of a subaerial volcano-sedimentary
formation represented by andesite-basaltic volcanics
and containing remains of Upper Carboniferous
 ora (Gasanov 1986) is known north of Sevan Lake
(Asrik-Chai). According to petrochemical features,
Transcaucasian Upper Palaeozoic volcano-plutonic
complexes correspond to formations of mature
island-arc type.
Within the Southern Slope of the Great Caucasus,
Palaeozoic deposits are known as phyllites of the
Dizi series (1500–2000 m thick); they outcrop in
the central part of the zone and are represented
by strongly deformed rocks of relatively deep
open marine basin located between island-arc
morphostructural units of the Transcaucus and the
Great Caucasus. In continuous succession there
are alternations of pelite-siltstone and psammite-
turbidite terrigenous deposits intercalated with
chert, jasper, olistostromes, rarely volcanoclastics
of andesite-dacitic composition, and lenses of
recrystallized limestones (Figure 10).  e presence
of the Middle and Upper Devonian was established
by conodonts from cherts, corals, crinoids and
foraminifera from limestone (Kutelia 1983; Kutelia
& Barskov 1983). Metamorphism of the Dizi series
does not exceed greenschist-anchimetamorphism
degree (Adamia et al. 2011).

THE GEOLOGY OF THE CAUCASUS
504
STRATIGRAPHY
LITHOLOGY
LITHOLOGY
THICK
THICK
EOCENE
PA L E O
CENE
C R E T
A C E O U S
J U R A S S I C
TR
I A S S I C
MIDDLE
LOWER
UPPER
UPPER
LOW
LOWER
MID
UPPER
LOW
MID
LOW
UP
UP
PRIABONIAN
BARTONIAN
LUTETIAN
YPRESIAN
THANETIAN
DANIAN
MAASTRICHTIAN
CAMPANIAN
SANTONIAN
CONIACIAN
TURONIAN
CENOMANIAN
ALBIAN
APTIAN
BARREMIAN
HAUTERIVIAN
VALANGINIAN
BERRIASIAN
TITHONIAN
KIMMERIDGIAN
OXFORDIAN
CALLOVIAN
BATHONIAN
BAJOCIAN
AALENIAN
TOARSIAN
PLIENSBACHIAN
SINEMURIAN
HETTANGIAN
RHAETIAN
NORIAN
CARNIAN
LADINIAN
ANISIAN
SCYTHIAN
650
500
2000
2500
–
200 400–
400
100 300–
215
2
00
50
700
1000
1
00 3000
4
30
400 1000–
420
300
120
440 560–
AGE
SERIES
LITHOLOGY
THIKNESS
SYSTEM
DORASHAMIAN
DZHULFINIAN
MIDINIAN
MURGABIAN
KUBERGANDIAN
BOLORIAN
YACHTASIAN
STEPHANIAN
WESTPHALIAN
NAMURIAN
VISEAN
TOURNAISIAN
FAMENIAN
FRASNIAN
GIVETIAN
EIFELIAN
EMSIAN
PRAGIAN
LOKHOVIAN
WELIDAG
UNIT
BOGADJIKH
UNIT
PERMIAN
CARBONIFEROUS
DEVONIAN
CAMBRIAN-SILURIAN
P A L E O Z O I
C
400-1000
600
20
00-2300
14
00100
UPPER
UPPERMI
D
MIDDLE MIDDLE
LOWER
LO
a
b
c
LOW
UPPER
siltstones, shales, slates
sandstones
quartz sandstones, quartzites
limestones
onglomerates, gritstonesc
argillites, siltstones
andstoness
oalc
errigene clasticst
iabases, basaltsd
olomiteds
arlsm
limestones
clayey limestones
andy limestoness
dacite-rhyolites
olcanoclastics, shoshonitesv
andesites
andesites
Me ozoic Early Cenozoic (b, c)s–
Pal eozoic (a)a
Figure 9. Generalized and simpli ed lithostratigraphic columns of (a) Palaeozoic (Belov et al. 1989) and (b)
Mesozoic–Early Cenozoic pre-collisional units of the South Armenia and (c) Nakhchevan.

S. ADAMIA ET AL.
505
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BERRIASIAN
TITHONIAN
OXFORDIAN
CALLOVIAN
BATHONIAN
KIMMERIDGIAN
BAJOCIAN
AALENIAN
TOARCIAN
PLIENSBACIAN
SINEMURIAN
HETTANGIAN
RHAETIAN
NORIAN
LADINIAN
CARNIAN
ANISIAN
SCYTHIAN
TATARIAN
KAZANIAN
KUNGURIAN
ARTINSKIAN
SAKMARIAN
ASSELIAN
STEPHANIAN
WESTPHALIAN
NAMURIAN
VISEAN
TURNAISIAN
FAMENIAN
FRASNIAN
GIVETIAN
EIFELIAN
EMSIAN
CENTRAL GREAT CAUCASUS
STRATIGRAPHY
LITHOLOGY
THICK
m
1000 0012–
1000
0015
–
100 00520–
300 400–
300 400–
500 600–
600 700–
50 200–
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MIDDLE
MIDDLE
MIDDLE
MID
LOW
LOW
CR
LOWER
LOWER
LOWER
UPPER
UPPER
UPPER
UPPER
UPPER
TRIASSIC
PERMIAN
CARBONIFEROUS
DEVONIAN
J U R R A S S I C
//
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>
>
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>
calc-alcaline volcanics
carbonate turbidites
terrigene turbiditesous
lack slatesb
marmorized limestones
listostromeso
bedded cherts
>
volcanoclastics
tholeiitic basalts, black slates
Figure 10. Generalised lithostratigraphic column of the Palaeozoic and Lower–Middle Mesozoic units of
the central segment of the Great Caucasian Southern Slope Zone.

THE GEOLOGY OF THE CAUCASUS
506
Within the Main Range Zone, Upper Palaeozoic
sedimentary cover is composed of rocks accumulated
under subaerial and shallow-marine environments.
In the lower part of the Upper Palaeozoic section,
there occur coarse clastic continental molasses, locally
coal-bearing, with Middle Carboniferous  oral
fossils. Volcanics of quartz-porphyry composition
are reported here.  e higher horizons of the
section constrained according to brachiopods to
the Upper Carboniferous–Permian are represented
by shallow-marine terrigenous molasses (Figure
11).  e section is dominated by  nely fragmented
clastics and limestone lenses. Permian deposits,
apparently, should also be attributed to marine
terrigenous sediments. Terrigenous rocks alternate
with organogenic limestones, the amount of which
increases up-section. Fauna fossils in the limestones
are represented by corals, brachiopods, gastropods,
pelecypods, and foraminifera.  e thickness of the
deposits is 500–200 m (Andruschuk 1968; Somin
1971; Khutsishvili 1972; Belov 1981; Adamia et al.
2003).
 e Fore Range Zone of the Great Caucasus
con ned from the south by the Pshekish-Tirniauz
fault (see Figure 7) and representing a sub-lateral
narrow trough is a depositary of polyfacial Middle–
Upper Palaeozoic sediments.  e Middle Palaeozoic
of this zone (Silurian, Devonian and Lower
Carboniferous) relates to facies of relatively deep
sea, whereas the Upper Palaeozoic is represented
by continental or shallow-marine molasses.  e
structural position of the middle Palaeozoic rocks is
not quite clear: whether they are in autochthonous,
paraautochthonous or allochthonous position.
Many authors consider the Upper Palaeozoic as
neo-autochtonous cover locally disrupted by Late
Variscan and post-Variscan thrusts (Belov 1981;
Belov & Omelchenko 1986).
SW
NE
3500
3000
2500
2000
1500
500 0 500 1000 m
Mesozoic granitoides
Lower Jurassic black slates
Upper Carboniferous conglomerates,
gritstones, sandstones
Upper Carboniferous
Permian sandstones
–
Upper Carboniferous Permian
slates, limestones
–
faults
Lower Middle Pal eozoic:
gneisses, micaschists
a–
a
Figure 11. (a) Cross-section of the Kvishi formation (Khutsishvili 1972); (b) lithostratigraphic columns of the
Upper Palaeozoic units, Great Caucasian Main Range Zone (Belov et al. 1989).

S. ADAMIA ET AL.
507
Within the middle Palaeozoic section of the
Fore Range Zone, there is a distinguished deep-
water hemipelagic graptolite-siliceous-volcanogenic
formation with radiolaria (thickness more than 2500
m), argillite, siltstone, sandstone and siliceous schist
(Silurian), terrigenous turbidites with olistostromes,
and redeposited material of rocks of ophiolitic
association (Devonian–Lower Carboniferous
according to conodonts and other fossils).  e
Lower–Middle Devonian thick sequence plays
an important role as a structure that according to
its mineral-petrological features is attributed to
formations of island-arc – intra-arc ri s (Belov et
al. 1984; Adamia et al. 1987).  e section is capped
by a formation (up to 200 m thick) of terrigenous
turbidites, olistostromes and limestones of Late
Devonian–Early Carboniferous age (Figure 13).
Upper Palaeozoic molasses unconformably rest
either upon Middle Palaeozoic deposits of the Fore
Range Zone or upon ophiolitic allochthonous sheets
of the zone (Belov & Kizevalter 1962; Andruschuk
1968; Somin 1971; Ajgirei 1976; Khain 1984). In the
Fore Range Zone, they are represented by continental
molasse of Middle–Late Carboniferous and Permian
age ( ne-clastics – Middle Carboniferous, coarse
clastics – Upper Carboniferous, and red-coloured
clastics – Permian). Island-arc type subaerial volcanic
rocks are developed in the Middle Carboniferous
(rhyolites) and in the Permian (sub-alkali andesite-
dacites, thickness of 800 m) levels.  e age of the
deposits is established mainly by  oral fossils
(Andruschuk 1968; Belov 1981) belonging to the
North Tethyan palaeobiogeographic province.
Upper Permian strata, besides continental
molasses, comprises a carbonate-terrigenous
formation (~300 m) of marine deposits with
biohermal limestone bodies.  e formation is dated
on the basis of  ndings of brachiopods, corals,
pelecypods, algae, sponges, gastropods, ammonoides,
foraminifera etc.
Scythian Platform, Bechasin Zone– Within the
Bechasin Zone, Palaeozoic deposits (Silurian–
Middle Devonian) are represented by sandy-
argillaceous carbonatic shelf facies (up to 2400 m
thick) containing Silurian graptolites and Silurian-
Devonian conodonts (Belov et al. 1984; Figure
14b).  e Lower Palaeozoic, in particular Cambrian
deposits, apparently, were represented by carbonate
facies indicated by the presence of block limestones
with Cambrian trilobites and brachiopods (Ajgirei
1976).
Late Proterozoic–Palaeozoic Development
 e Gondwanan origin of pre-Cambrian crystalline
massifs in the Central European Variscides has
actively been discussed during recent decades
(Paris & Robardet 1990; Tolluoğlu & Sümmer 1995;
Stamp i 2000; Raumer et al. 2002). An interpretation
in favour of a Gondwanan origin of Late Proterozoic
Transcaucasian basement rocks was proposed by
Zakariadze et al. (1998) and for the Tsakhkuniats
massif (Armenia) by Agamalian (2004).  e Arzakan
and Aparan complexes (Tsakhkuniats) are considered
as formations of the northern active margin of the
Arabia-Nubian shield, which, at the end of the
Proterozoic, experienced granitization related to the
 nal stages of the Pan-African cycle of tectogenesis
(Agamalian 2004). In contrast to the Tsakhkuniats,
the Transcaucasian massif was not subjected to the
process, since it broke away from the Arabia-Nubia
shield and during Cambrian–Devonian time dri ed
deep into the Prototethys (Figure 15a) towards the
northern continent (Zakariadze et al. 1998).
During the Early–Middle Palaeozoic, in the wake
of northward migrating Gondwanan fragments
the Paleotethyan basin was formed and, in the
Ordovician, along its border with Transcaucasian
massif, there occurred the subduction of oceanic
crust accompanied by suprasubduction volcanic
eruptions of rhyolites, denudation of the massif,
and the formation of pudding conglomerates of
the Chorchana-Utslevi Zone of the Dzirula salient
(Abesadze et al. 1989).
Northward migration of the Transcaucasian
massif throughout the Palaeozoic caused narrowing
of Prototethys and its transformation into an oceanic
back-arc (Dizi) basin (Figure 15b). Fragments of
Palaeotethyan crust are met along the southern border
of the TCM, within the accretionary complexes of
the Sevan-Akera ophiolite suture, in the Pontides
(Nilüfer formation, Pulur massif, Demirkent and
Guvendic complexes – Yusufeli massif).

THE GEOLOGY OF THE CAUCASUS
508
At the western prolongation of the Sevan-Akera
suture, in the Sakarya Zone, there occurs pre-Liassic,
Upper Palaeozoic–Triassic series of metabasite-
marble-phyllite low-grade metamorphic complexes,
which are dated in the Pulur region as Late Permian
(ca. 260 Ma, Topuz et al. 2004a), whereas the high
temperature metamorphism in the same region is
Early Carboniferous (ca. 330 Ma) in age (Topuz et
al. 2004b). Metamorphic basic volcanic rocks in the
Amasya region (Tokat group) which are believed to
be equivalents of Agvanis and Yenişehir low-grade
metamorphic rocks, can be interpreted as arc-related
Q
Q
QQ
600
300 515–
600
~ 1000
520
120
210 390–
260 800–
220 330–
160 210–
130 160–
I
II
III
IV
Pz
2
C
2
P - P - P
123
T
1
Pz
2
C?
3
P
T ?
C
3
3
P ? - P
12
P
3
J
1
C? -
2
C?
3
P
1
P ? - P ?
23
T? - J
1
Pz
1
Pz
1
siltstones
shales, slates
andstoness
conglomerates and gritstones
c for F ure
a
olumns: I Khuko; II Pseashkho; III Kvishi; IV Oset ;
T J Triassic and Lower Jurassic; T Triassic; P Permian; C Carboniferous
Pz , Pal eozoic basement
i ( location see ig 5a )
;––
1
–– – –
–––
–
siliceous shales, jasper, phtanites
oalsc
limestones, marbles
acidic volcanoclastolites
acites, rhyolitesd
andesites
basalts
Figure 12. Lithostratigraphic columns of the Upper Palaeozoic units, Great Caucasian Main Range Zone (Belov et al. 1989).

S. ADAMIA ET AL.
509
STRUCTURAL - FACIES SUBZONES
KARDZHURT KENDELLAR URUP
FAMENNIAN
TOURNAISIAN
GIVETIAN
FRASNIAN
EMSIAN
EIFELIAN
imestonesl
argillaceous slates
siltstones
sandstones
conglomerates with
quartz pebbles
acid volcanics
basic and intermediate
volcanics
basic and andesitic
volcanics
black flints
basic volcanics
cid tuffs and lavasa
acid and intermediate
tuffs
tuff sandstones
conglomerates with granite
and volcanic pebbles
Figure 13. Generalised lithostratigraphic columns of the Palaeozoic units of in the Fore Range
(Belov et al. 1989).
basinal sequences metamorphosed during the Late
Palaeozoic (Göncüoğlu 1997; Okay & Şahintürk
1997). According to Topuz et al. (2009), the Kurtoğlu
(Gümüşhane) metamorphic complex is the oldest
rock assemblage known in the eastern Pontides, and
it represents the vestiges of Middle Devonian oceanic
subduction.  e Çal Unit in Pontides consists of
debris and grain  ows with Upper Permian limestone
and ma c pyroclastic  ows, calciturbidites and
radiolarian cherts dated as Late Permian.  e unit
may represent an oceanic seamount, which accreted
to the Laurasian margin during the Middle Triassic
(Okay 2000). Wall rock of the Demirkent dyke
complex is composed of gabbros, microgabbros, and
diabases. It can be supposed that some parts of these
rocks are of Early–Middle Carboniferous age (Konak
& Hakyemez 2001).
Relics of Palaeotethyan crust crop out in Iranian
Karadagh directly to east of the Lesser Caucasian
(Sevan-Zangezur) suture (Rustamov 2005).

THE GEOLOGY OF THE CAUCASUS
510
Palaeozoic ophiolites are known also near Rascht
(Majidi 1979; Davoudzadeh & Shmidt 1981), along
Alborz, and as far as Binalud (Lyberis & Manby 1999;
Zanchi et al. 2007).
Subduction of Palaeotethyan oceanic crust
beneath the Transcaucasian island-arc system was
going on. In the Late Palaeozoic, granite intruded
the island-arc (TCM), there occurred lava extrusions
and eruptions of volcanoclastics of island arc type
under subaerial and shallow sea environments (see
Figure 15).
 e Variscan granitoids of the TCM (Loki and
Khrami salients) correlate with leucogranites,
granite-gneisses and plagiogranites of S-type of the
Artvin salient, which are exposed in the easternmost
part of the Pontides (Turkey), along the Çoruh river
SYSTEM
DIVISION
STAGE,
SUBSTAGE
DEVONIAN
SI LURIAN
LOWER
UPPER
LOWER
CUVENIAN
DALEJANIAN
ZLICHOVIAN
PRAGIAN
LOCHKOVIAN
PRIDOLIAN
UPPER
LOWER
UPPER
MIDDLE
LOWER
UPPER
MIDDLE
LOWER
LUDLOVIAN
WENLOKIAN
LLANDOVERIAN
MIDDLE
D
1
Sp
2
Std
22
Sw
1
Stn
13
Stn
12
Stn
11
ULLU-LAKHRAN SUITE
AVARSIRT SUITE
Std
21
?
?
ULLU-LAKHRAN SUITE
MANGLAI SUITE
MAGLEI SUITE
URLESH SUITE
CHEGET-LAKHRAN
SUITE
?
III
II
I
limestones, dolomitized limestones, dolomites
silty clayey slates, siliceous-clayey slates, silty slates
lates with sandstone interbedss
sandstones
graptolites
onodontsc
Figure 14. Generalised lithostratigraphic columns of the Palaeozoic units in the Bechasin zone (Belov et al. 1989).

S. ADAMIA ET AL.
511
PAL EOTETHYSA
GONDVANA
EASTERN EUROPE
Po
Tc
DIZI
Mn
Ta
b
320 Ma
Ki
SS
10
30
50
GONDVANA
PAL EOTETHYSA
DIZI
C
2
320
Ma
GC
TC
400-500
Ma
Pz
1
600-800
Ma
Pt
3
ANS
PA
TC
NC
GC
MR
PROTOTETHYS
MR
FR
NC
GC
PROTOTETHYS
GC
BALTICA
ANS
TC
a
400 500 Ma–
BALTICA
GC
GONDWANA
ANS
PROTOTETHYS
PAL
EOTETHYS
A
50
10
Po
Tc
continents, continental crust
oceans, oceanic crust
upper mantle
ccretion wedgea
suprasubduction plutons
uprasubduction volcanisms
bduction, obducted crusto
id-oceanicm ridge
faults
spreading axes
subduction
a
M
a
bbreviations:
ANS, Arabian-Nubian shield
FR, Fore Range Zone, Great Caucasus
GC, Great Caucasus; Ki, Kırşehir
Mn, Menderes assif
MR, Main Range zone, Great Caucasus
NC, North Caucasus; PA, Pal eotethys
Po, Pontides; SS, Sanandaj-Sirjan zone
Ta, Taurus; TC, Transcaucasus
Figure 15. Late Proterozoic–Early Palaeozoic (a) and Late Palaeozoic (b) palaeotectonic reconstructions of the Black
Sea-Caspian Sea region.
valley, not far from the Georgia-Turkey border.  e
Artvin granitoids are unconformably overlain by the
Narlık anchimetamorphic formation of black slates,
sandy-argillaceous turbidites, cherts (with Lower
Jurassic radiolarians, Adamia et al. 1995), volcanic
and volcanoclastic rocks (Yılmaz et al. 2001).  e
Upper Palaeozoic granitoids of the TCM may also be
correlated with the Gümüşhane and other granites
of the eastern Pontides (Çoğullu & Krummenacker
1967), which are overlain by Upper Carboniferous

THE GEOLOGY OF THE CAUCASUS
512
shallow marine to continental terrigenous and
carbonate deposits alternating with dacite volcanics
(Okay & Şahintürk 1997).  e Gümüşhane granitoid
has given zircon ages of 324 Ma (Topuz et al. 2010).
 ere is no evidence for Variscan metamorphic
and magmatic events, folding and topographic
inversion within the Southern Slope Zone of the
Great Caucasus. Variscan and Eo-Cimmerian
events did not lead to closure of the Dizi back-
arc basin. During the Middle–Late Palaeozoic,
within the Dizi basin, thick terrigenous turbidites,
pelagic and hemipelagic deposits, andesite-dacite
volcanoclastics, and carbonates were accumulated
under deep-marine environment.  e accretional
prism consisting of tectonic slices of oceanic crust
and island-arc was formed in a transitional back-arc
to island-arc zone of the Great Caucasus. Obducted
metaophiolitic sheets shi ed from the root zone
located along the southern margin of the island arc
northward to the Fore Range Zone. Widespread
emplacement of microcline granite plutons along
the active continental margin of southern Eurasia
during 330–280 Ma occurred above a north-dipping
Paleotethyan subduction zone. Carbonate platform
lasted in the southern province of the Caucasus
(South Armenia-Nakhchevan) throughout the
Palaeozoic (see Figure 9).
Mesozoic–Early Cenozoic Development
Division of the Caucasus into northern and
southern provinces was also distinct throughout
the Mesozoic–Early Cenozoic. In the extreme south
of the region (Nakhchevan) and in the southern
Armenia, a platformal regime remained with the
accumulation of uniform, mainly carbonate shelf
sediments.  e ophiolite belt of the Lesser Caucasus
is represented by rocks of the Tethyan oceanic basin;
the Northern Province is represented by developed
facies characteristic of active continental margins
similar to Asiatic-margin-type of the present-day
Paci c: island-arc, back-arc, continental shelf.
Southern Province
Triassic sediments of the Southern Province are
dominated by shelf organogenic limestones, marls,
and dolomites (south Armenia, Nakhchevan),
while the northern part of the Province (Jermanis,
Armenia) is represented by sediments of Upper
Triassic shallow-marine terrigenous-coal-bearing
formations (Aslanian 1970; Azizbekov 1972). Lower
Triassic deposits are similar to shelf limestones of
Permian age.  e Late Triassic age of the terrigenous
units was identi ed by molluscs and  ora fossils (see
Figure 9b).
Jurassic deposits in the Southern province are
rare and are represented by shelf facies. In the near-
Araksian part of the province (Julfa-Ordubad),
Triassic limestones are overlain by the following
formations: (1) diabasic porphyrites with interbeds
of tu s, thickness of 120 m (Lias–Dogger); (2)
sandy-argillaceous deposits with interbeds of
tu ogenic sandstones with pelecypods indicating
an Aaleanian–early Bajocian age (50–100 m thick);
(3) sandy-argillaceous-carbonate formation (over
200 m thick) with Upper Bajocian, Bathonian,
Callovian ammonites (Azizbekov 1972). K-Ar
age of gabbrodiabasic intrusions of the Julfa area
varies between 175–186 Ma (Early–Middle Jurassic,
Abdullaev & Bagirbekova 2007).
Data on Early Cretaceous facial environments
are very scarce. Based on the features of Albian
deposits known in the near-Araksian part of the
Southern Province (sandstones, marls up to 200 m
thick) containing abundant mollusc fossils, it can
be considered that this domain during the Early
Cretaceous was a marine basin; Upper Cretaceous
deposits are widespread and also represented
shallow-marine formations consisting mainly of
organogenic-clastic limestones, sandy-argillaceous
limestones, and marls. All Late Cretaceous stages
are present.  e sediments are several hundreds
meters thick. Various levels bear conglomerates and
sandstones; frequent stratigraphic unconformities
indicate the shallowness of the basin. Fauna fossils
are represented by gastropods, large pelecypods,
rudistids and foraminifera (Aslanian 1970; Azizbekov
1972).
Paleocene (Danian,  anetian) deposits
represented by sandy-argillaceous-limestone shallow
marine facies (thickness 200–400 m) are similar to
Upper Cretaceous ones. Fossils are represented
by echinoids and foraminifera. Relations with
underlying formations are diverse: in some localities,

S. ADAMIA ET AL.
513
the transition is gradual, though unconformity and
basal conglomerates are also met. Unconformity is
also evident in Lower Eocene rocks represented by
shallow marine marls, organogenic limestones and
calcareous sandstones; the thickness of the deposits
ranges from 10’s to 1000 m.
 e environment of sedimentation within the
basins of the Southern Province signi cantly changed
in the upper part of the Eocene: from the end of Early
– beginning of Middle Eocene there started a period
of intensive submarine volcanic eruptions (see
Figure 9b). Lavas, pyroclastics (volcanic tu s), tu -
turbidites, more than 2000 m thick, accumulated
locally alternating with terrigenous and carbonate
deposits, which o en occur in the base of the Middle
Eocene forming together with conglomerates
basal-transgressive part of the section. Besides
nummulites, which allow con dent dating of
the rocks, these deposits contain large molluscs,
echinoids, brachiopods, corals, and some other fossils
indicating shallow sea environment (Aslanian 1970;
Azizbekov 1972). Eocene volcanism of the Southern
Province, as well as that of more northern zones of
the Caucasus, represent a part of the vast andesite
belt of the Middle East, running from Aegean Sea,
through Turkey, the Lesser Caucasus, Iran, and as far
as to Afghanistan. According to their petrochemical
characteristics the volcanics are attributed to island-
arc type.  ey are mainly represented by calc-alkaline
series, however, rocks of tholeiitic and shoshonitic
series are also present (Lordkipanidze et al. 1989;
Vincent et al. 2005).
Volcanic activity sharply decreased at the end
of the Late Eocene and under shallow-marine
environments there occurred the accumulation of
mainly sandy-argillaceous and carbonate sediments
including coral limestones. Upper Eocene volcanic
rocks are represented by thin andesitic bands and
their clastics.  e maximum thickness of the Upper
Eocene interval does not exceed 500–600 m (Aslanian
1970; Azizbekov 1972).
Boundary Zone: Ophiolitic Suture Belt
Allochthonous ophiolites of the Sevan-Akera Zone
include two types of series: tholeiitic and boninitic
(Zakariadze et al. 1993). Each one shows a complete
ophiolite sequence from ultrama c-ma c cumulates
to massive plutonics, dyke swarms, and pillow lavas.
An age of the boninitic plutons was reliably de ned
as Bathonian–Callovian (K-Ar, 168±8 Ma, biotite
and muscovite from plagiogranite, Morkovkina
& Arutiunian 1971; U-Pb 160±4 Ma, zircon from
quartz-diorite, Zakariadze et al. 1983). Sm and
Nd isotopes and obtained mineral isochrons for
two gabbro-norites from representative tholeiitic
gabbroic massifs (Lev-chai and Alticovshan-east of
Lake Sevan) show an Upper Triassic age (Carnian
–Norian) with rather low initial ε
Nd
values T=
226±13, ε
Nd
(T)+ 5.1±0.4 (Lev-chai) and T= 224±8.3
ε
Nd
(T)= +4.0±0.3 (Altikovshan). Petrological and
geochemical data show that the tholeiitic sequence
of Sevan-Akera Zone has a supra-subduction origin
(Bogdanovsky et al. 1992).
Mesozoic (?) and pre-Mesozoic sedimentary and
magmatic rocks of the suture belt are met in the
mélange as clastic-blocks of various dimensions.
Among them are blocks of Upper Triassic limestones
and calcareous sandstones with ammonites (Solovkin
1950), basaltic volcanic rocks, and radiolarite
associations (see Figure 3) with Late Triassic, Lower
and Middle Jurassic–Lower Cretaceous radiolarians
(Knipper 1980, 1990; Zakariadze et al. 1983).  e
e usive-radiolarite part of the ophiolitic association,
in some localities, includes lenses of Upper Jurassic–
Neocomian reef limestones (Gasanov 1986). Lower,
Middle and Late Jurassic as well as Lower Cretaceous
radiolarians assemblages are known from several
places of the Sevan-Akera ophiolite belt (Zakariadze
et al. 1983; Knipper 1990).  e younger ophiolitic
association starts with the transgressive Albian–
Senomanian, which is represented by  ysch and
olistostromes. At higher levels they are followed by
basalts and Albian–Lower Coniacian radiolarites
(Sokolov 1977).
Data from recent studies concerning ages and
composition of Lesser Caucasian ophiolites of
Armenia agree well with previous results.  e
investigation of Jurassic ophiolites from NW
Armenia evidence the occurrence of several suites
comprising rock representatives of slow-spreading
ophiolite type, of a remnant oceanic plateau, and arc-
type volcanic rocks of probable Upper Cretaceous
age (Galoyan et al. 2007).

THE GEOLOGY OF THE CAUCASUS
514
Radiolarians from radiolarites associated with
ophiolitic volcanic rocks from three ophiolitic units
cropping out in NW Armenia, east of Lake Sevan and
in central Armenia suggest Middle–Upper Jurassic
and Lower Cretaceous ages of the rocks (Danelian et
al. 2007).
 e
40
Ar/
39
Ar age of amphibole-bearing gabbros
of the Sevan-Akera ophiolites of north Armenia
evidence a Middle Jurassic age (165.3±1.7 Ma)
for oceanic crust formation (Galoyan et al. 2009).
40
Ar/
39
Ar phengite ages obtained for the high-
pressure assemblages (glaucophane-aegirine-
clinozoisite-phengite) of the tectonic mélange (NW
Armenia) range between 95 and 90 Ma, while ages
of epidote-amphibolite retrogression assemblages
are 73.5–71.0 Ma (Rolland et al. 2009). According to
Rolland et al. (2009a), the Lesser Caucasus (Sevan,
Stepanavan and Vedi) demonstrates evidence for a
slow-spreading oceanic environment in the Early
to Middle Jurassic.  e oceanic crust sequence is
covered by OIB alkaline lavas.
40
Ar/
39
Ar dating of
amphibole provides a Early Cretaceous age of the
rocks (117.3±0.9 Ma).
 e neoautochthonous complex of the ophiolitic
belt starts with the transgressive formation of
Coniacian–Santonian clastics; this indicates
shallowing and closing of the deep-water basin and
its replacement by a back-arc one.  e younger
Senonian–Lower Paleogene limestone formations
were formed in the shallow basin, as well as sandy-
argillaceous deposits of the Paleocene–Lower Eocene
and calc-alkaline andesitic volcanic formations,
terrigenous clastics and carbonates of the Middle
and Upper Eocene.
Northern Province
Transcaucasian Massif– Within the Triassic–
Eocene, the extreme southern tectonic unit of the
Northern Province, i.e. the Transcaucasian massif
(south Caspian-Transcaucasian massif according to
Rustamov 2005), developed as a relatively upli ed
structural-morphological island-arc type unit.
Within its central part (Georgian, Artvin-Bolnisi
and Azerbaijan massifs), the accumulation of mainly
shallow-water, lagoonal-lacustrine, coal-bearing and
salt-bearing deposits of variable thickness occurred
accompanied by island-arc type volcanic eruptions
(Figure 16).
At the Georgian massif, the Mesozoic sedimentary
cover begins with subaerial volcanoclastics of rhyolitic
composition (about 800 m) containing Upper Triassic
 ora of North-Tethyan palaeobiogeographical
domain (Svanidze et al. 2000; Lebanidze et al. 2009).
 e Lower Jurassic and Aalenian are built up of arkosic
terrigenous clastics and shallow-water organogenic
limestones (‘red ammonitic limestones’) containing
in addition to ammonoids, abundant crinoids
and brachiopods, which also belong to the North-
Tethyan palaeobiogeographical domain (Lebanidze
et al. 2009).  e Bajocian is almost fully represented
by tu -turbidites with rare bands of calc-alkaline
andesite-basalts (Gamkrelidze 1964; Moshashvili
1982; Beridze 1983).  e Bathonian is composed
of freshwater-lacustrine coal-bearing sandy-
argillaceous rocks followed by variegated lagoonal
Callovian–Upper Jurassic deposits containing bands
of coal, gypsum, and anhydrite. In the bottom of
the salt-bearing variegated formation, there is a
thick strata of sub-alkaline-alkaline basalts, which,
according to its stratigraphic position, is attributed
to the Upper Jurassic.  e thickness of the Jurassic
deposits varies, and locally reaches 3000–4000 m
(Gamkrelidze 1964; Azizbekov 1972; Moshashvili
1982; Lordkipanidze et al. 1989).
During the Jurassic, along the southern and
northern margins of the Artvin-Bolnisi, Azerbaijan
and Georgian massifs, the environment of
sedimentation has signi cantly changed: thickness
increased, and Lower Jurassic–Aalenian limestone
facies were replaced by deep-sea terrigenous
turbidites. Bajocian tu -turbidites were replaced
by coarse volcanoclastics and lavas of andesite-
basaltic and dacite-rhyolitic composition; folding
of the deposits is more expressed. On the basis of
these features the margins of the Artvin-Bolnisi,
Azerbaijan and Georgian massifs are considered
to be individual zones: Loki (Bayburt-Somkhiti)-
Karabagh (in the south) and Gagra-Java (in
the north) (Gamkrelidze 1964; Aslanian 1970;
Azizbekov 1972). Within the Loki-Karabagh Zone,
Bathonian–Callovian–Upper Jurassic facies also
underwent signi cant changes. Carbonate and salt-
bearing formations were replaced by normal-marine

S. ADAMIA ET AL.
515
.
.
. . .
++++
+++
++++
++++
+++
+++
++++
+++
++++
+++
.
.
.
+
+
++++
++++
UPPER
EOCENE
PALEO-
CENE
CRETACEOUS
JURASSIC
TRI
ASSIC
PALEOZOIC
UPPER
UP
LOWER
LOW
MID
UP
UP
MID
LOW
STRATIGRAPHY
THICK
m)(
THICK
m()
THICK
m()
LITHOLOGY
LITHOLOGY
LITHOLOGY
100
250
–
200-
400
200
500
–
150
250
–
360
300 700–
700 1200–
500 600–
1000-1500
300 600–
1000 1500–
700 1800–
100
150
500
–
500 800–
1000
500 1200–
300 1300–
300 1000–
>3000
PRIABONIAN
LUTETIAN
YPRESIAN
THANETIAN
DANIAN
MAASTRICHTIAN
SENONIAN
SENOMANIAN
TURONIAN
APTIAN
ALBIAN
NEOCOMIAN
MALM
DOGGER
LIAS
NORIAN
CARBONIFEROUS
ARTVIN-BOLNISI
MASSIF
GEORGIAN
MASSIF
AZERBAIJANIAN
MASSIF
g
g
sandstones, siltstones, claystones
andstones, gritstoness
conglomerates gritstones,
sandstones
,
terrigene clastics
rgillitesa
layey limestones, marlsc
limestones
olomitesd
sandy limestones
layc
glauconite
sland-arc and within plate-type volcanismi
dacites-rhyolites
andesites
ak kl aline-subal aline andesites and basalts
ubal ali basaltic andesitessk
rhyolites, granitoporphyres,
granites
Figure 16. Generalised and simpli ed lithostratigraphic columns of the pre-collisional units of the western Transcaucasus: (a)
Georgian and (b) Artvin-Bolnisi massifs and (c) Eastern Transcaucasus (Azerba ijanian massif).
terrigenous-carbonate (locally reef limestones)
rocks and by thick volcanic rocks of basalt-andesite-
dacite-rhyolite composition of calc-alkaline series
(Aslanian 1970; Azizbekov 1972; Lordkipanidze et
al. 1989). Upper Jurassic–Neocomian calc-alkaline
series were replaced by tholeiites of MORB-type and
by association of alkaline basalts in the immediate
contact between the Bayburt-Karabagh Zone and

THE GEOLOGY OF THE CAUCASUS
516
Lesser Caucasian ophiolitic belt; the Bajocian
contains rocks of boninitic series (Zakariadze et al.
1983; Lordkipanidze et al. 1989).
Lower Cretaceous facies of the Trancaucasian
massif are rather uniform (see Figure 16). Within the
Georgian massif, there occurs a transgressive basal
conglomerate-quartz sandstone formation, which
is followed by shelf carbonate sediments (Eristavi
1962): dolomites, limestones of the Urgonian facies,
organogenic limestones and marls (thickness from
hundreds to 2500 m). In the Bayburt-Karabagh Zone,
limestones are replaced by basalt-andesite-dacite-
rhyolitic volcanic rocks of island-arc and intraplate
types (Lordkipanidze et al. 1989).
Within the Georgian massif, Upper Cretaceous,
Paleocene and Eocene deposits built up mainly of
neritic organogenic limestones and marls are also
facially uniform; their thickness in some places
exceeds 2000 m. Formations of alkaline basalts and
volcanoclastics stratigraphically constrained to the
Turonian–Senonian stages are locally developed.
Glauconitic sandstones predominate at the base of
the Upper Cretaceous. However, to the south, within
the Artvin-Bolnisi massif, the Upper Cretaceous
section is dominated by volcanic rocks: basalts,
andesites, dacites and rhyolites (lavas, pyroclastics)
of calc-alkaline series.  eir thickness reaches
3000–4000 m. Volcanic rocks are of shallow marine-
subaerial type, ignimbrites are frequent. Volcanic
eruptions have ceased in the Late Senonian, and
throughout Maastrichtian and Early Paleocene at
the whole territory of the Transcaucasian massif
(as well as in the Sevan ophiolitic belt and Southern
Province), uniform limestone-marly facies of shelf-
sea have been formed.
In the Paleocene–Eocene, within the
Transcaucasian massif (island-arc), north of the
Early Paleogene andesitic belt of the Middle East,
basaltic troughs (ri s) originated (Lordkipanidze et
al. 1989): Talysh and Achara-Trialeti dividing the
Transcaucasian massif into the Georgian (in the
north) and Artvin-Bolnisi (in the south) massifs
(Figure 17). Within these troughs, the Paleocene–
Lower Eocene is represented by thick formation (up
to 1500 m) of terrigenous turbidites (Borjomi Flysch
and its analogues), which, in some localities, is
associated with dacite-rhyolitic lavas and pyroclastics
(thickness of 100–300 m).  ey are overlain by the
Eocene formation of bimodal, calc-alkaline, sub-
alkaline and alkaline volcanic rocks (andesites,
shoshonites, basanites etc) whose maximal thickness
in Achara is 5000 m (Lordkipanidze & Zakariadze
1974, 1986; Banks et al. 1997; Nadareishvili &
Sadradze 2004). In Talysh, Eocene volcanism has
more alkali tendencies (trachybasalts-trachyandesite
basalts-phonolitic formation, Allen et al. 2003, 2004;
Mamedov 1998; Vincent et al. 2005; Rustamov 2005)
with which are associated intrusives of sub-alkaline
basic-ultrabasic formation: sub-alkali peridotites
(age 38–41 Ma) and gabbro-syenites (34–36 Ma).
In the Late Eocene, volcanic activity gradually
decreased.  is time ‘basaltic troughs’, accumulated
mainly terrigenous turbidites with admixtures of
volcanoclastic material.
Great Caucasus– Mesozoic–Early Cenozoic
basin of the Great Caucasus located behind the
island-arc of the Transcaucasus was developing,
at least, from Devonian, throughout Palaeozoic
and Mesozoic–Early Cenozoic (Figure 18). In the
upper part of the section cropping out within the
central segment of the Southern Slope Zone of
the Great Caucasus (Dizi series of Svaneti, river
Mzymta gorge), there occurs terrigienous-turbiditic
formation with intercalations of carbonate rocks
whose Late Triassic age was established by corals
and foraminifera (Andruschuk 1968; Saidova et
al. 1988). In transitional Triassic–Lower Jurassic
terrigenous turbidites E. Planderova reported the
presence of marine microfossils of Rhaethian and
Hettangian age (Adamia et al. 1990). Sinemurian
terrigenous turbidites and volcanoclastics of the
central part of the Southern Slope Zone conformably
follow Hettangian levels. However, Liassic deposits
transgressively overlie basement rocks along its
southern and northern margins. Within the basin of
the Great Caucasus, the Pliensbachian is generally
represented by black slate formation locally with
beds of diabase.  oleiitic basalts of MORB-type –
pillow lavas and agglomerates- are also con ned to
this level (Beridze 1983; Lordkipanidze et al. 1989).
Within the entire basin, the Toarcian–Aalenian is
composed of terrigenous proximal turbidites along
its border with the Transcaucasian massif (island-

S. ADAMIA ET AL.
517
ACHARA-TRIALETI EAST
TALYSH, AZERBAIJAN
LITHOLOGY
LITHOLOGY
Fm.
Thick
m()
Fm.
Thick
m()
limestones,
marls
terrigene
turbidite,
marls
uff, turbidites,
olistostroms
t
terrigene
turbidite,
dacitic
volcanics
500 1000–
200-
500
1000 1200–
Borjomi
Tbilisi
Daba-
khana
200
300
–
Tetri
Stratigraphy
ACHARA-TRIALETI WEST
LITHOLOGY
Fm.
Thick
m()
E O C E N E
P
ALEOC
C R E T A C E O U S
limestones,
marls
Dviri
Kvabis
khevi
Likani
Peranga
Borjomi
Tetrit-
skaro
Mar-
da
50
200
–
500 900–
500 900–
600 1000–600 1200–
300 500–
200
400
–
500
1500
–
150
200
–
LOWER
UPPER
LOW-
ER
DAN-
THAN
MIDDLE UP
CEN-MAA
ALBIAN
APT
terrigene
deposits
skubal alic
basaltic
volcanics
delenitic-
andesitic
volcanics
subalkalic
basaltic
volcanics
tufftur-
bidites
limestones,
volcanics
tholeiitic,
calc-alkalic
basaltic-
andesitic
volcanics
limestones,
volcanics
terrigene
turbidites,
Borjomi
flysch
Arkevan
250 1400–
Peshtasar
Neslin
Gosmalyan
Astara
1000
100
Sim
a
lkalic-subalkalic andesibasaltic
volcanics
terrigene
clastics
terrigene turbidites, tuff,
turbidites
terrigene-
carbonat
turbidites
alkalic-subalkalic
a
ndesibasaltic volcanics
t
yc
e
rrigene and turbidites
(fl s h)
Figure 17. Generalised and simpli ed lithostratigraphic columns of the pre-collisional units of the Achara-Trialeti: west (a), east (b)
and Talysh (c) basins.
arc), and distal turbidites in the axial part of the
Southern Slope Zone. Paroxysms of volcanic activity
are periodically evident throughout the Liassic
that is con rmed by the presence of admixtures,
intercalations, and volcanic formations (basalts,
keratophyres) in Sinemurian, Toarcian and Aalenian
deposits (Lomize 1969; Beridze 1983; Ali-Zade 2003;
Panov & Lomize 2007; Tuchkova 2007). During the
Aalenian, volcanic eruptions under deep marine
environment also bear the features of MORB-type;
however, they also show resemblance to the island-
arc type (Lordkipanidze et al. 1989).
It was mentioned that Bajocian lavas and
volcanoclastics represented by calc-alkaline andesite-
basalts are widely spread along the southern margin
of the Southern Slope Zone, at its border with
the Transcaucasian massif (Gamkrelidze 1964;
Andruschuk). Northward, the Bajocian lava and
pyroclastics grade into tu -turbidites, and further
on, into terrigenous turbidites (Beridze 1983). Black
slate, terrigenous-turbiditic, and volcanogenic
formations of the Southern Slope Zone (thickness
more than 5000 m) are dated predominantly by
ammonites, though, some limestone lenses host also
pelecypods and brachiopods.
A er the Bajocian, the environment of back-arc
basin of the Great Caucasus has signi cantly changed:
volcanic eruptions ceased, along the southern side of
the basin there were deposited marine Bathonian,
Callovian and Lower Oxfordian terrigenous sandy-

THE GEOLOGY OF THE CAUCASUS
518
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PRIABONIAN
BARTONIAN
LUTETIAN
YPRESIAN
THANETIAN
DANIAN
MAASTRICITIAN
TURONIAN
SANTONIAN
CONIACIAN
CAMPANIAN
BARREMIAN
HAUTERIVIAN
VALANGINIAN
BERRIASIAN
CENOMANIAN
ALBIAN
APTIAN
KIMMERIDJIAN
OXFORDIAN
CALLOVIAN
BATHONIAN
BAJOCIAN
AALENIAN
TOARSIAN
PLIENSBACHIAN
SINEMURIAN
HETTANGIAN
RHAETIAN
NORIAN
WESTERN GREAT CAUCASUS
STRATIGRAPHY
LITHOLOGY
THICK
(m)
600
500
600
–
1000 4000–
500 1800–
1000 1300–
2000 2200–
1500 2000–
450 600–
TITHONIAN
EASTERN GREAT CAUCASUS
STRATIGRAPHY
LITHOLOGY
THICK
(m)
UP
UP
MID
LOW
LOW
LOWER
LOWER
UPPER
PAL O-
CENE
EOCENE
UPPER
UPPER
TRIASSIC
J U R R A S S I C
C R E T A C E O U S
MIDDLE
UP
MID
LOW
LOW
LOWER
LOWER
UPPER
PAL O-
CENE
UPPER
J U R R A S S I C
C R E T A C E O U S
MIDDLE
EOCENE
UP
DANIAN
THANETIAN
YPRESIAN
PRIABONIAN
BARTONIAN
LUTETIAN
MAASTRICITIAN
CAMPANIAN
SANTONIAN
CONIACIAN
TURONIAN
CENOMANIAN
ALBIAN
APTIAN
BARREMIAN
HAUTERIVIAN
VALANGINIAN
BERRIASIAN
HETTANGIAN
SINEMURIAN
PLIENSBACHIAN
TOARSIAN
AALENIAN
BAJOCIAN
BATHONIAN
CALLOVIAN
OXFORDIAN
KIMMERIDJIAN
TITHONIAN
200
3
00 550–
300 100–
200
150 200–
600 900–
1
500 2000–
1000 1500–
1500
1000
1400
–
150
200
–
.
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.. .
>
>
>
>
>
>
>
>
>
>
>
>
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.. ..
>
>
>
>
.
terrigene and carbonate turbiditesous
carbonate turbidites
terrigene turbiditesous
black slates
bedded cherts
terrigene clasticsous
tholeiite basalts and black slates
calc-alkaline volcanics
olistostromes
coral limestones
Figure 18. Generalised and simpli ed lithostratigraphic columns of the Mesozoic–Lower Cenozoic units of the
Great Caucasian Southern Slope zone (western and eastern segments).

S. ADAMIA ET AL.
519
argillaceous sediments, which northward gain the
features of terrigenous and carbonate turbidites
(Adamia 1977, 1989).  ere were developing two,
en échelon  ysch basins: eastern and western
ones, in which turbiditic sedimentation lasted
almost uninterruptedly throughout Late Jurassic,
Cretaceous, Paleocene, and Eocene. Here, thick
formations of predominantly carbonate turbidites
(Oxfordian–Valanginian, Turonian–Senonian)
alternate with terrigenous turbidites (Hauterivian–
Senomanian, Paleocene–Eocene) and olistostromes
(Maastrichtian, Priabonian).  e total thickness of the
whole Jurassic–Cretaceous–Paleogene sedimentary
complex, apparently, exceeds 10000 m (12–15 km
according to Saintot et al. 2006). Rocks are strongly
deformed: isoclinal folds and steep south-vergent
thrusts-overthrusts are common; cleavage and
boudinage are strongly developed. Small-scale nappe
structures are known only on the southernmost strip
of the Southern Slope Zone.
 e Northern Slope of the Great Caucasus –
Southern Margin of the Scythian Platform: Laba-
Malka Zone–  e northern edge of the Great
Caucasus, which is known as the Laba-Malka Zone
(Milanovsky & Khain 1963), during the Mesozoic–
Early Cenozoic, is featured by development of
continental-shelf deposits. Triassic, Jurassic,
Paleocene, and Eocene deposits are represented by
shallow-marine and continental facies (Milanovsky
& Khain 1963; Andruschuk 1968; Ajgirei 1976).
Gaps, stratigraphic and angular unconformities are
frequent (Figure 19).  e Lower and Upper Triassic
in the western part of the basin is represented by
carbonate rocks with crinoids, corals, sponges,
ammonoids, pelecypods, brachiopods, and
foraminifera.  e Middle Triassic is dominated by
terrigenous clastics.  ickness of the Triassic ranges
from 300 to 1500 m (Andruschuk 1968; Ajgirei
1976; Saintot et al. 2006). Palynomorph-bearing red-
coloured continental molasse of the central part of
the Northern Slope indicate a Triassic age.
Lower and Middle parts of the Jurassic series of
the Northern Slope of the Great Caucasus are mainly
composed of terrigenous clastic rocks. Shallow-
marine facies with ammonites, brachiopods, and
pelecypods alternate with continental coal-bearing
facies.  e Pliensbachian, Toarcian and Bajocian
include thin horizons of crinoidal limestones. Gaps
in the sedimentation are frequent; stratigraphic
unconformities are present.  e total thickness
of the deposits within the Western Caucasus is
several thousands metres. In the central part of
the Northern Slope, their thickness decreases and,
at the Pliensbachian level, there occur formations
of calc-alkaline andesitic and dacitic lavas and
volcanoclastics (thickness up to 200 m).  e thickness
of Lower–Middle Jurassic deposits increases in the
eastern part of the Northern Slope – the Limestone
Dagestan Zone (up to 10000 m – Lower Jurassic, and
up to 5000 m – Middle Jurassic; Kakhadze et al. 1957;
Andruschuk 1968; Panov & Lomize 2007; Tuchkova
2007).
 e next time-stage of the development of the
basin of the Northern Slope of the Great Caucasus
(Scythian platform) begins with the Callovian.
Within the period starting in the Callovian and going
on throughout Late Jurassic, Cretaceous, Paleocene,
and Eocene, a shallow-marine environment ranged.
 e base of the Callovian is represented by the
basal formation that marks a beginning of marine
transgression.  e Callovian is usually represented
by terrigenous-carbonate shallow-water deposits
with ammonites, bivalve molluscs, and gastropods.
 e Oxfordian and Kimmeridgian are dominated by
dolomites and reef limestones.  e Upper Jurassic
section is capped with predominantly lagoonal
facies represented by terrigenous-carbonate salt-
bearing variegated formation.  e thickness of the
Callovian–Tithonian deposits ranges from some tens
to 2300 m (Andruschuk 1968). Cretaceous deposits
of the Northern Slope Basin are facially very diverse.
Almost complete sections are replaced by the ones
showing a lot of stratigraphic unconformities; their
thickness varies from tens to some thousands of
metres.  e Lower Cretaceous is dominated by
sandy-argillaceous rocks (Hauterivian–Albian), and
only within its base, there are marls and limestones
(Berriasian–Valanginian–Hauterivian) containing
an abundant fauna.  e Upper Cretaceous, at the
extreme west of the Southern Slope, is represented
by a thin carbonate formation unconformably
overlying Lower Cretaceous rocks.  e sections
o en show unconformities.  e Upper Cretaceous
is dominated by limestones and marls related to the
facies of shallow marine basin. Terrigenous clastics

THE GEOLOGY OF THE CAUCASUS
520
140
155
50 60–
10 20–
190
360
60 70–
900
550
900 1100–
150
15 40–
370 555–
10 15–
280 420–
250
340
600
900 950–
640 1700–
600 950–
170 260–
6000 10000–
1500
.
.
.
STRATIGRAPHY
LITHOLOGY
LITHOLOGY
LITHOLOGY
THICK
THICK
THICK
EOCENE
PALEO
CENE
C R E T A C E O U S
J U R A S S I C
T R I A S S I C
MIDDLE
LOWER
UPPER
UPPER
LOW
LOWER
MID
UPPER
LOW
MID
LOW
UP
UP
PRIABONIAN
BARTONIAN
LUTETIAN
YPRESIAN
THANETIAN
DANIAN
MAASTRICHTIAN
CAMPANIAN
SANTONIAN
CONIACIAN
TURONIAN
CENOMANIAN
ALBIAN
APTIAN
BARREMIAN
HAUTERIVIAN
VALANGINIAN
BERRIASIAN
TITHONIAN
KIMMERIDGIAN
OXFORDIAN
CALLOVIAN
BATHONIAN
BAJOCIAN
AALENIAN
TOARSIAN
PLIENSBACHIAN
SINEMURIAN
HETTANGIAN
RHAETIAN
NORIAN
CARNIAN
LADINIAN
ANISIAN
SCYTHIAN
WESTERN SEGMENT CENTRAL SEGMENT EASTERN SEGMENT
limestones
arlsm
sandy limestones
clayey limestones
oolitic limestones
dolomites
oalc
dacitic volcanic rocks
andesitic volcanoclastics and lavas
sandstones
argillites, siltstones
onglomerates, gritstones, sandstonesc
sandstones and argillites
gypsum
glauconite
listostromso
concretions
coral limestones
Figure 19. Generalised and simpli ed lithostratigraphic columns of the Mesozoic–Lower
Cenozoic units of the Laba-Malka, Monocline, and Dagestan zones.

S. ADAMIA ET AL.
521
are characteristic of the Senomanian (glauconitic
sandstones). Glauconite is, generally, characteristic
of the Upper Cretaceous–Lower Paleocene deposits
(Andruschuk 1968; Khutsishvili 1972).
In the Paleocene–Eocene, shallow marine
sedimentation continued across a vast shelf along the
southern margin of the Eastern European continent.
Upon the shelf, there accumulated deposits
represented by marly, argillaceous-marly, and sandy-
marly facies with a thickness of some hundreds of
metres; dated, predominantly, by foraminifera and
echinoids fossils (Andruschuk 1968; Saintot et al.
2006).
Mesozoic–Early Cenozoic Development
In the Late Palaeozoic–Early Mesozoic (250–270
Ma), the oceanic basin separating the Africa-Arabian
continent from the Tauro-Anatolian-Iranian
platformal domain was gradually extending (Stamp i
2000; Babaie et al. 2005). However, according to
the reconstructions proposed by some authors (for
example, Stamp i 2000; Golonka 2004; Robertson et
al. 2004; Barrier & Vrielynck 2008), only the Central
Iranian terrain (CIT) was separated from Gondwana
and was displaced northward and collided with the
Eurasian continent in the Late Triassic.  e Taurus-
Anatolian terrains (TAT) separated from Gondwana
later, in the Early–Middle Jurassic (c. 180–160 Ma).
Neotethys was formed in the Middle–Late Mesozoic
(Figure 20). Northward displacement of the Taurus-
Anatolian terrains resulted in their gradual migration
towards the Pontian-Transcaucasian-Iranian active
continental margin, the narrowing of Palaeotethys-
Tethys and its transformation into a back-arc basin,
and the formation of the suture belt between the
TAT and CIT (Barrier & Vrielynck 2008).  e suture
belt, apparently, is marked by fragments of ophiolite
mélange of the Lake Van region.
 e TCM during the Mesozoic represented an
island-arc-type structure that accumulated mainly
shallow-marine carbonate, lagoonal and lacustrine-
continental gypsiferous and coal-bearing terrigenous
clastics. Suprasubduction extrusive and intrusive
activities lasted throughout the entire Mesozoic.
Back-arc basins of the Great Caucasus separated
the TCM from the southern shelf of the Scythian
platform (Adamia 1975; Adamia et al. 1977, 1981,
1983; Dercourt et al. 1986, 1990).
At the Cretaceous–Paleogene boundary within the
study area of the Great Caucasus and Transcaucasus,
there existed the following basins (from south to
north): shallow water, normal marine island-arc-
type, Artvin-Bolnisi (and Loki-Karabagh) basin that
accumulated calc-alkaline volcanics, limestones and
marls; deeper Achara-Trialeti and Talysh troughs
superimposed on the Transcaucasian island arc as
a result of the Cretaceous–Eocene ri ing (Adamia
et al. 1974, 1977, 1981; Lordkipanidze et al. 1989;
Kazmin et al. 2000); shallow-water, island-arc type,
normal-marine basin of the Georgian massif showing
predominantly carbonate sedimentation; the back-
arc basin of the Great Caucasus demonstrating
sedimentation of mainly deep-marine terrigenous
and carbonate turbidites and shallow-marine basin
of the pre-Caucasus (Laba-Malka Zone) representing
a wide shelf at the southern edge of the Eastern
European continent (Figure 21).
 e Eocene is especially important as a time of
intensi cation of ri ogenesis in the Achara-Trialeti
and Talysh basins and further evolution of intraarc
deep-marine troughs with accumulation of thick
sequences of basaltic volcanics, terrigenous and
tu ogenous turbidites (Adamia et al. 1974).
Late Cenozoic: Syn to Postcollisional Stage
 e Oligocene is traditionally considered as a
beginning of syn-collisional (or orogenic) stage
of development of the Caucasus (Milanovsky &
Khain 1963; Gamkrelidze 1964; Andruschuk 1968;
Aslanian 1970; Azizbekov 1972; Saintot et al. 2006;
Vincent et al. 2007; Adamia et al. 2008). By this time,
the palaeogeographic environment has signi cantly
changed. First of all this became apparent in
inversion of the relief: in the place of deep-water
basins there were formed mountain ranges of
the Great Caucasus, Achara-Trialeti, Talysh, and
Lesser Caucasus (Somkhiti, Bazum, Halib, Murguz,
Pambak, Shahdag, and Mrovdag ranges).  e
domains of shallow-marine basins of platformal
type of pre-collisional stage (Scythian platform,
Georgian massif, Artvin-Bolnisi massif, Caucasian
parts of the Taurus-Anatolian and Central Iranian

THE GEOLOGY OF THE CAUCASUS
522
PANGEA
PAL EOTETH SAY
MC
Di
WP
EP
TC
CI
SS
Ar
SP
GC
PAL EOTETH SAY
TC
Di
GC
TAP
ARABIA
Norian
205 aM
Po
TC
ArP
LAURASIA
TETHYS
TAP
GC
MC
Di
CIP
SS
NA
KR
NT
TETHYS
TC
Di
GC
TAP
ArP
Middle Late
Jurassic
160 - 170 aM
–
a
Black Sea
W
bbreviations:
Ar, ARP, Arabian platform and Central
Iranian platform; Di, Dizi basin;
EP, eastern Pontides; GC, Great Caucasus;
KR, rift basin;
MC, Mountainous Crimea basin;
NA, Nakhchevan and South Armenia;
NT, Neotethys; SP, Scythian platform;
SS, Sanandaj-Sirjan volcanic arc;
TAP, Taurus-Anatolian platform;
TC, Transcaucasus; WP, estern Pontides
continents, island-arcs,
continental crust
oceans, oceanic crust
back-arc basins
upper mantle
accretion wedge
suprasubduction plutons
suprasubduction volcanism
middle oceanic high
subduction
spreading axes
faults
ross-sectionsc
Figure 20. Norian and Late Jurassic tectonic reconstructions of the Black Sea-Caspian Sea region.

S. ADAMIA ET AL.
523
LATE
CRETACEOUS
80 90 Ma–
BS
TAP
SR
IAE
SS
WP
TETHYS
TC
AFRICA-ARABIAN
PLATFORM
TAURUS-ANATOLIAN
PLATFORM
NT
EP
EURASIA
GC
SA
ABB
WBS
SC
SP
EBS
MC
CIP
NA
ZG
NEOTETHYS
GC
ABB
GB
TAP
AAP
SSB
SA
GC
TC
EOCENE
35 55 Ma–
EA
TC
BS
ANATOLIA
UD
SPM
SG
SS
An
WP
MEDITERRANEAN
OCEAN
Tl
AFRICA-ARABIA
AFRICA-ARABIA
TAURUS-ANATOLIAN
PLATFORM
Al
RM
EP
EURASIA
GC
SR
ABB
WBS
SC
EBS
continents, island-arcs,
continental crust
oceans, oceanic crust
back-arc basins
upper mantle
accretion wedge
suprasubduction plutons
suprasubduction volcanism
middle oceanic high
subduction
spreading axes
faults
ross-sectionsc
a
P
İc
h
bbreviations:
AAP, Africa-Arabian platform;
ABB, Artvin-Bolnisi Block; Al, Alborz;
An, Andrusov high; AT, Achara-Trialeti
BS, Black Sea, CIP, Central Iranian platform;
EBS, Eastern Black Sea; E , Eastern Pontides;
GB, Georgian Block, GC, Great Caucasus;
IAR, zmir-Ankara-Erzin an ocean;
MC, Mountainous Crimea basin;
Na, Nakhchevan-South Armenia; NT, Neotethys;
RM, R odope Massif;
SC, South Caspian back-arc basin;
SG, Srednogorie; SA, Sevan-Akera ocean;
SP, Scythian platform;
SPM, Serbian-Pelagonian massif;
SR, Shatsky ridge;
SS, Sanandaj-Sirjan volcanic arc;
SSB, Southern Slope back-arc basin;
TAP, Taurus- Anatolian-Iranian platform;
Tl, Talysh; WBS, Western Black Sea;
WP, Western Pontides;
ZG, Zangezur-Garadagh ocean
Figure 21. Late Cretaceous and Eocene tectonic reconstructions of the Black Sea-Caspian Sea region.

THE GEOLOGY OF THE CAUCASUS
524
platforms) sank forming foredeep and intermontane
depressions that accumulated molasse deposits – the
products of denudation of arising mountain ranges
(Gamkrelidze 1964; Andruschuk 1968; Azizbekov
1972; Geology of the USSR 1977).
Oligocene–Lower Miocene deposits resulted
from accumulation in semi-closed euxinic basins of
the Paratethys at the most part of the territory of the
Caucasus are represented by uniform argillaceous-
sandy gypsiferous facies termed the Maykopian
series.  e main characteristic features of these rocks
are their brown colour, lack of carbonate content,
scarcity of fossils (except for  sh scales), abundance
of jarosite on bedding planes, and intralayers and
veinlets of gypsum. Disk-shaped concretions-septaria
of spherosiderite, up to 0.5–3.0 m in diameter are
very frequent, and they, as a rule, are located along
the bedding planes; locally thin beds and lenses of
hematite are observed.  e Oligocene only locally
is represented by other facies: siliceous (Dzirula
massif), normal-marine terrigenous (Western Great
Caucasus) continental coal-bearing, (Akhaltsikhe
basin) volcano-sedimentary, normal-marine with
corals and lagoonal multicolour terrigenous clastics
(Southern Armenia, Nakhchevan).
 e accumulation of molasse (maximum
thickness several km), predominantly shallow-sea
and lagoon-lacustrine terrigenous clastics with layers
of organogenic carbonate rocks (coquina), lasted
almost throughout the Miocene. Only at the end of
the Miocene (Tortonian, c. 7 Ma), were shallow-sea
environments replaced by subaerial surroundings
and simultaneously clastic material became coarse.
Marine environments of sedimentation remained
only within the territories adjacent to the Black,
Azov, and Caspian Sea basins.
Presented geological timescale (Figure 22) showing
correlation of the Oligocene–Quaternary stages of
the Caucasus with those of the Mediterranean area is
based on data of longterm investigations.
Starting from the Late Miocene (c. 9–7 Ma) and as
far as the end of the Pleistocene, in the central part of
the region, occurred volcanic eruptions in subaerial
conditions going on simultaneously with the
formation of molasse troughs and the accumulation
of coarse molasse.
PERIOD
AGE
STAGE
EPOCH
SERIES
MEDITER-
RANIEN
BLACK
SEA
CASPIAN
SEA
HOLOCENE
Q
2
PLEISTOCENE
Q
1
CHAUDIAN
GURIAN
BAKUNIAN
APSHERONIAN
QUATERNARY
NEOGENE
GELASIAN
PIACHENZIAN
ZANCLEAN
KIMMERIAN
PLIOCENE
N
2
MIOCENE
N
1
MESSINIAN
TORTONIAN
SERRAVALIAN
LANCHIAN
BURDIGALIAN
AQUITANIAN
OLIGOCENE
E
3
C H A T T I A N
R U P E L I A N
K H A D U M I A N
33.7
28.0
23.8
UPHLISTSIKHEAN
KOZAKHURIAN
SAKARAULIAN
19.1
16.4
13.6
1.80
3.60
5.33
7.11
11.0
2.58
PO NTIAN
M E O T I A N
AKCHAGILIAN
PALEOGENE
SAR MATIAN
K O N K I A N
KARAGAN IAN
C H O K R A K I A N
T A R K H A N I A N
AGES MA
SIC
EGRISSIAN
KUYALNIKIAN
0.01
0.08
0.41
0.70
1.0
KHAZARIAN
KVALINIAN
GIRKAN
UZUNLARIAN
KARANGATIAN
NEOEUXINIAN
3.0
Figure 22. Correlation of the Upper Miocene–Pleistocene
stratigraphic schemes of the Mediterranean and
Black Sea-Caspian Sea regions (Haq & Van Eisinga
1987; Remane & Four-Muret 2006; Adamia et al.
2008).

S. ADAMIA ET AL.
525
Aras Basin
In the Aras basin, the Oligocene is represented by two
facies accumulated in shallow-marine environment
(Figure 23).  e  rst facial type sandy-argillaceous
 ne- and coarse-grained terrigenous clastics
(thickness ~1000 m) with coral limestones are
exposed mainly in the W–NW part of the basin.  e
second facial type of the Oligocene, exposed mainly
in the eastern part of the Aras basin, is represented
by subalkali-alkali-basalt-andesitic and dacite
rhyolitic lavas and volcanoclastic rocks (thickness
~1000 m).  e Oligocene age of these formations was
established using molluscs, foraminifera, and corals
(Aslanian 1970; Azizbekov 1972). Lower Miocene
deposits of the Aras basin, represented by lagoonal,
salt-bearing multicolour sandy-argillaceous  ne-,
medium- and coarse-grained terrigenous clastics
(thickness ~400 m), rest unconformably upon older
(Oligocene and older) formations. Middle and Upper
Miocene sediments in the Lesser Caucasian part
of the Taurus-Anatolian-Central Iranian Platform
(South Armenia and Nakchevan) are widespread
mainly within the Aras basin and are represented by
lagoonal gypsiferous-salt-bearing terrigenous clastics
and shallow-marine terrigenous and carbonate rocks
dated by molluscs, foraminifera, ostracods, corals,
and plant fossils; thickness ~1000–1300 m (Aslanian
1970; Azizbekov 1972).
Upper Miocene and Pliocene sediments within
the Aras basin (Sarmatian, Pontian, and Meotian
stages) are represented by shallow marine, lagoonal
and continental, mainly,  ne-grained terrigenous
molasse, also by carbonate and gypsiferous deposits
(thickness ~1000 m).  e thickness of the Oligocene–
Quaternary sediments in easternmost part of the
Kura basin, at the south Caspian seashore reaches
~2 km (Brunet et al. 2003).  eir biostratigraphic
subdivision is based on the data of marine molluscs
and foraminifera.
Transcaucasian Basins
 e formation of the Transcaucasian foreland started
in the Late Pliocene; it was divided by the Dzirula
massif that resulted in formation of the Rioni basin
(-Black Sea) in the west and the Kura basin (-Caspian
Sea) in the east (see Figures 2, 23 & 24).
Rioni-Kura Basin-  e Oligocene–Lower
Miocene (Maykopian series) is represented mainly
by alternation of gypsiferous clays with sandstones
(Gamkrelidze 1964; Andruschuk 1968; Azizbekov
1972).
Maykopian deposits in some localities
conformably follow Late Eocene sandy-clayey
sediments.  eir maximal thickness is 2.5–3.0 km.
In the ascending section one can observe the gradual
transformation from more sandy varieties to more
clayey rocks in the middle part and again more
sandy rocks in the top of the section (Uplistsikhe,
Sakaraulo, and Kotsakhuri stages).
Middle Miocene (Tarkhanian, Chokrakian,
Karaganian, and Konkian Stages): Late Miocene
(Early and Middle Sarmatian Stages)– At this time,
a sublatitudinal marine basin was developing within
the area between the Southern Slope of the Great
Caucasus in the north and the Achara-Trialeti belt
in the south.  e maximal thickness of the Middle–
Upper Miocene sediments achieves 1500–3500
m. In the axial parts of these subsided structures,
deep-marine carbonate clays and sandstones with
marls were accumulated; in their marginal zones,
shallow-marine terrigenous-carbonate rocks of
limited thickness were deposited (Gamkrelidze 1964;
Azizbekov 1972; Eastern Paratethyan 1985).
 e abundance of various marine fossils
(molluscs, foraminifera etc) observed from the outset
of the Middle Miocene (Tarkhanian stage) indicates
the establishment of wide connections of the basin
with the global ocean and the replacement of
euxinic environments by normal marine conditions.
However, later on, the connections with oceanic
basins periodically either ceased (Chokrakian,
Karaganian stage, Middle–Sarmatian times) or
were impeded (the end of the Karaganian, the onset
and the end of the Konkian; the end of the Middle
Sarmatian) (Maisuradze 1971; Popkhadze 1983;
Eastern Paratethyan 1985).
In the Late Sarmatian, there began the
transformation of nearly all of the Caucasus into a
dry land except for some small areas.  e continuing
development resulted in the further upli of
clastic source areas and subsidence of subaerial-
sedimentation ones dominated by coarse molasses
with subdued sandstones and clays. According

THE GEOLOGY OF THE CAUCASUS
526
.
.
.
.
.
.
.
.
.
.
.
.
ARAS
FORLAND
KURA
FOR LANDE
TEREK-CASPIAN
FOR DEEPE
RIONI
FOR LANDE
AZOV-KUBAN
FOR DEEPE
LITHOLOGY
LITHOLOGY
LITHOLOGY
LITHOLOGY
LITHOLOGY
CASPIAN SEA
BASIN
STAGE, AGE
KVALINIAN
GIRKAN
KHAZARIAN
BAKUNIAN
APSHERONIAN
AKHCHAGILIAN
KIMMERIAN
PONTIAN
MEOTIAN
SARMATIAN
KONKIAN
KARAGANIAN
CHOKRAKIAN
TARKHANIAN
KOZAKHURIAN
SAKARAULIAN
UPLISTSIKHIAN
CHATIAN
RUPELIAN
EPOCH
HOLO-
CENE
PLEISTOCENEPLIOCENE
MIOCENE
OLIGOCENE
LOWER
MIDDLE
UPPER
STAGE,AGE
BLACK SEA
BASIN
HOLO-
CENE
PLEISTOCENE
NEOEUXINIAN
KARANGATIAN
UZUNLARIAN
CHAUDIAN
GURIAN
EGRISSIAN
KUALNIKIAN
KIMMERIAN
PONTIAN
MEOTIAN
SARMATIAN
KONKIAN
KARAGANIAN
CHOKRAKIAN
TARKHANIAN
KOZAKHURIAN
SAKARAULIAN
UPLISTSIKHIAN
LO
WER
MIDDLE
UPPER
MIOCENE PLIOCENE
CHATIAN
RUPELIAN
OLIGOCENE
110
0
110
700 1300– 600 950–
2000 600 2000
2300 3000–
1500-1600
200-450
450
-1700
100 1000–
1500 3000– 100 1500
–
300-700
100-
1000
2800
50
50-100
THIKNESS
THIKNESS
TH
IKNESS
TH
IKNESS
T
HIKNESS
100
50
100–
100 150
–
20 30–
400 1000–
370
65
0 1400
–
400 600–
400 1500–
1000
400 600–
500
100 500
–
330 820
–
gritstones
sandy argillites
conglomerates, gritstones, sandstones
arine and river terrace depositsm
spongilites, opoka
breccias, olistostromes
siltsones
claystones, argillites, siltsones
limestones
marls
sandy limestones
sandy marls
clayey limestones
coquina
alternation, facial transition
clays with jarosite and gypsum
carbonaceous clays
lignites, coal
gypsum, salt
siderite concretions
rhyolitic and dacitic volcanic rocks
ndesitic volcanic rocksa
unconformity
volcanoclastic rocks
basaltic volcanic rocks
ostracodes
Figure 23. Generalised and simpli ed lithostratigraphic columns of the syn- and post-collisional units of the Caucasus.

S. ADAMIA ET AL.
527
Odishi piggyback basin
-1
-2
-3
-4
-5
-6
-7
-8
-9
0
K
K
K
K
K
K
0
K
Ns
1
N
s
1
N
s
1
N s
1
K
K
05
10 km
?
S N
Q
Q
Q
Q
N
2
N
2
J
J
Basement
N
2
N
2
km
?
J
#1 Didi Shiraki
0
+1
-1
-2
-3
-4
-5
-6
-7
Q
Q
km
0
510km
Kura Basin
N
2
J
3
Q
N ak+ap
2
Nmp
1
Ns
1
Ns
1
Ns
1
Nmp
1
Nmp
1
Ns
1
Ns
1
Seismic reflection profile (99003)
Ns
1
Ns
1
Nmp
1
N ak+ap
2
Ns
1
Didi Shiraki piggyback basin
SWS
NEN
Nmp
1
Ns
1
Nmp
1
N ak+ap
2
N
1
2
Alazani piggyback basin
A c h a r a - T r i a l e t i t h r u s t f r o n t
R i o n i B a s i n
J, Jurassic; J , Upper Jurassic; K, Cretaceous; P, Paleogene; N , Lower–Middle Miocene; N ,Middle Miocene; N S, Upper
Miocene-Sarmatian rs; N mp, Upper Miocene, Meotian, Pontian rs; N , Pliocene; N ak+ap,Upper Pliocene-Akchagylian rs
and Lower Pleistocene-Apsheronian rs; Q, Quaternary. Red lines – faults; black vertical lines – wells
3 1-2 1 1
1 22
2
P
P
P
N
1-
2
P
Figure 24. Cross-sections across Rioni and Kura basins (compiled by V. Alania).

THE GEOLOGY OF THE CAUCASUS
528
to the composition of clastic material, one can
easily recognize the northern (mainly Cretaceous–
Paleogene  ysch of the Great Caucasus) and southern
and southwestern source areas (Mesozoic–Cenozoic
volcanic rocks of the Lesser Caucasus).
In the central and southern parts of the Kura
depression, the Upper Sarmatian (thickness ~200
m) is represented by variegated clays, cross-bedded
sandstones, gritstones, containing pebbles of
metamorphic, and crystalline rocks of the Lesser
Caucasus. Upper Sarmatian rocks are highly
gypsiferous.  e rocks show no marine fauna and
their age is determined on the basis of mammal
relicts (Eastern Paratethyan 1985; Chkhikvadze et al.
2000).
Marine Meotian rocks are predominantly
represented by coastal shallow water deposits.
 ey transgressively overlap Sarmatian and older,
Cenozoic and Mesozoic, rocks and, in turn, are
overlain by Pontian and younger beds.  ickness of
the Meotian and Pontian sediments varies from a
few to several hundred meters sometimes achieving
even 1500–2000 m.  e most complete sections
include rich and variable assemblages of molluscs,
foraminifera, ostracods, and sponge spicules
(Gamkrelidze 1964; Azizbekov 1972; Popkhadze
1975; Eastern Paratethyan 1985; Maisuradze 1988;
Jones & Simmons 1997; Adamia et al. 2008, 2010).
 e Pontian is regressive, its individuality
is manifested by molluscs including not only
forms common for the Black Sea realm, but
also species, frequent in Dacian and Pannonian
basins (Gamkrelidze 1964; Chelidze 1973; Eastern
Paratethyan 1985). Upper Pontian section is
represented by shallow water and relatively deep
water facies. Meotian and Pontian ages of the
continental formations have been established on the
basis of mammal fossils (Chkhikvadze et al. 2000)
and fossil tortoises (Gabashvili et al. 2000).
Pliocene (Kimmerian Stage)– Like the Pontian
stage, the Kimmerian one has much in common
with other coeval formations of the Black Sea area,
although showing some individual features.  e
Kimmerian stage consists mainly of sandstones,
claystones, and conglomerates (thickness ~200–300
m). Mollusc assemblage includes several endemic
forms evidencing decreasing salinity in several
parts of the Rioni Basin (Gamkrelidze 1964; Eastern
Paratethyan 1985; Taktakishvili 1984, 2000).
Rioni Basin– Kuyalnikian stage (terrigenous
clastics, thickness ~200 m) is characterized by
complete pro les and richer brackish mollusc
assemblages. Recent investigations have shown the
greater presence of the western Georgian Kuyalnikian
stage as compared to the other parts of the euxinian
basin due to the presence of transitional, Kimmerian-
Kuyalnikian beds that are almost completely absent
in other parts of the Black Sea area (Gamkrelidze
1964; Taktakishvili 1984, 2000; Eastern Paratethyan
1985).
Pleistocene and Holocene: (Gurian, Chaudian,
Uzunlarian, Karangatian, and Neoeuxinian Stages)
Rocks of the Gurian (Eopleistocene) stage crop out
only in Guria (south-western part of the Rioni basin),
although, it was penetrated by boreholes in other
areas of the Rioni basin.  ese are sandy clayey rocks
(thickness ~100–500 m) with homogenous but poor
mollusc fauna (Gamkrelidze 1964; Taktakishvili
1984, 2000; Eastern Paratethyan 1985).
Chaudian, Uzunlarian, Karangatian (Pleistocene)
and Neoeuxian (Holocene) marine deposits of
the Rioni foreland are spread only within the
areas adjacent to the Eastern Black Sea.  ey are
mainly represented by sandy-argillaceous  ne-
grained clastics alternating with coarse-grained
and carbonate rocks (according to well data).
 ese deposits achieve their maximal thickness
of ~600–800 m in the central part of the foreland.
Fossil molluscs and ostracods indicate Middle–Late
Quaternary age of these deposits (Gamkrelidze 1964;
Kitovani et al. 1991).  e age of Neoeuxinian marine
clays and sands alternating with peat beds and
containing brackish molluscs is equal to 31300 years
(Maisuradze & Janelidze 1987).
Kura Basin– Middle Pliocene productive series
(Kimmerian) exposed in the easternmost part of
the Kura (Caspian) basin and located mainly within
onshore and o shore zones of Azerbaijan contain
signi cant accumulations of oil and gas in  uvial-
deltaic and lacustrine sediments.  e maximal
thickness of the productive series in the Kura
basin reaches ~3500–4500 m (Gamkrelidze 1964;
Azizbekov 1972; Abrams & Narimanov 1997; Devlin
et al. 1999).

S. ADAMIA ET AL.
529
Akchagylian and Apsheronian stages are
represented by continental and shallow marine
molasse unconformably overlying older rocks
(maximal thickness ~1500 m). Marine facies of
the lower part of the section is made up of sandy-
clayey rocks; it’s upper part – of sandstones and
conglomerates (Gamkrelidze 1964; Azizbekov 1972).
Fossil fauna are represented by endemic brackish
molluscs of Caspian type, and also by ostracods and
foraminifera. Along with marine molluscs, there were
found relicts of fossil mammals (Eastern Paratethyan
1985; Adamia et al. 2010).
Continental facies of the Akchagylian and
Apsheronian stages are dominated by conglomerates
with insigni cant sandstones and sandy clays.  in
layers of volcanic ash are locally present (Gamkrelidze
1964; Azizbekov 1972).
Pleistocene and Holocene (Bakunian, Khazarian,
Girkan, and Khvalinian Stages)–  ese deposits
attributed to the Caspian Sea domain are represented
by shallow marine  ne-, medium-, and coarse-
grained terrigenous facies (clay, sand, sandstone,
gravelstone, conglomerate, volcanic ash), their
thickness varies from ~150 up to 1000 m.  e amount
of coarse-grained clastics grows from the axial zone
of the foreland towards its borders and marine facies
are replaced by continental ones. Marine fossils are
represented mainly by molluscs. Continental deposits
of the Pleistocene–Holocene stages of the eastern part
of the Kura foreland are dated mainly by remnants
of mammalia (Gamkrelidze 1964; Azizbekov 1972;
Maisuradze & Janelidze 1987; Kitovani et al. 1991).
Dzirula High– Within the Dzirula salient, the
Oligocene–Lower Miocene is represented by a
thin (200–375 m) manganese-bearing formation
of spongilitic sandstones and clays with opoka and
chalcedony.  e formation unconformably rests on
Cretaceous deposits (Gamkrelidze 1964).
 e Middle Miocene, starting with the Tarkhanian
stage, conformably follows the Lower Miocene and is
represented by sandstones, clays, and marls (thickness
1–30 m).  e Chokrakian deposits unconformably
overlie older sediments.  e Chokrakian stage is
followed by Karaganian and Konkian ones having
aggregate thickness 20–30 m.  ey are represented
by shallow-sea, o en variegated, sandstones,
gravelites, clays, sandy, and oolitic limestones.  eir
Middle Miocene age was, generally, established using
mollusc fossils (Gamkrelidze 1964; Ananiashvili &
Sakhelashvili 1984; Eastern Paratethyan 1985) and
foraminifera (Janelidze 1970, 1977).
Akhaltsikhe Basin–  e Oligocene section of the
Akhaltsikhe depression (the southern part of the
central Achara-Trialeti basin) is complete and well-
dated by fauna (mainly by marine molluscs).  e
Oligocene deposits of the Akhaltsikhe depression are
subdivided into several suites (Yılmaz et al. 2001).  e
lowermost suite is represented by calcareous clays
and sandy clays comprising interlayers and wedges
of siltstones and marls. Lower Oligocene mollusc
assemblages occur at all levels of the suite (Tatishvili
1965; Kazakhashvili 1984). Microforaminifera of
Early Oligocene age are also met (Kacharava 1977)
as well as  sh fossils.  e thickness of the suite is
600–700 m. Fish fossils, microforaminifera, and
molluscs of Oligocene age were found in the upper
part of the sandstones.  e Lower Oligocene age of
the suite was also proved by microforaminifera and
 sh fossils.  e following suite is built up of clays,
siltsones, conglomerates, and sandstones containing
brackish molluscs (Kazakhashvili 1984).
 is is followed by a coal-bearing suite up to 150
m thick represented by clays with interlayers and
succession of sandstones, siltstones, and lignite with
mollusc fossils.  ese deposits were formed under
conditions of tropical-to-subtropical climate in the
lagoon surrounded by swampy forests.  e following
suite is dominated by thick-bedded sandstones with
fossil molluscs (Kazakhashvili 1984).  e thickness is
25–50 m.  e uppermost suite is built up of reddish-
grey, grey and greenish-grey clays with sandstone
beds.  e thickness is 400–450 m.  e sandstone
succession includes terrestrial vertebrates (Gabunia
1964).
Great Caucasus– Syn- and post-collisional molasse
formations exposed at the western and eastern
periclines of the Great Caucasian anticlinorium are
represented by facies analogous with those of the
Transcaucasus foreland and pre-Caucasus foredeeps
(Andruschuk 1968; Azizbekov 1972; 1:1 000 000
scale geological map (L36, 37) of the USSR, 1983; 1:1
000 000 scale geological map of Azerbaijan 1971).
Outcrops of the Upper Sarmatian shallow-marine
deposits are reported in the Shakhdag Mountains,

THE GEOLOGY OF THE CAUCASUS
530
on the crest of the Great Caucasus at about 3550 m
above sea (Budagov 1964).
Scythian Platform–  e pre-Caucasian part of the
Scythian platform is almost completely covered by
thick layer of Oligocene–Neogene and Quaternary
molasse deposits that reach their maximal thickness
in the axial zones of the Azov (Indol)-Kuban (~ 4400
m), Terek-Caspian (~4700 m), and Gussar-Devichi
(~6000 m) foredeeps, while their minimal thickness
is reported in Stavropol arch (~1600 m) separating
the Azov-Kuban foredeep from the Terek-Caspian
one (Milanovsky & Khain 1963; Andruschuk 1968;
Azizbekov 1972; Ajgirei 1976; Ershov et al. 2003).
 e Oligocene–Lower Miocene Maykopian series
outcrops along the southern margin of these foredeeps
(see Figures 2 & 23) and is termed a er the Maykop
city located in the westernmost part of the pre-
Caucasus. Details of the Maykopian stratigraphy of
the region have been discussed in various publications
(see Milanovsky & Khain 1963; Andruschuk 1968;
Jones & Simmons 1997; Mikhailov et al. 1999).  e
Oligocene–Early Miocene age of the series is chie y
based on foraminifera, nannoplankton, ostracods,
and molluscs.  e thickness of the formation varies
from 800 to 1500 m in axial zones of the foredeeps
up to some tens of hundreds metres at their borders
(Andruschuk 1968; Azizbekov 1972).
Middle Miocene (Tarkhanian, Chokrakian,
Karaganian and Konkian stages), and Upper Miocene
(Sarmatian, Pontian, and Meotian stages) deposits
of the pre-Caucasus are represented mainly by  ne-
and medium-grained sandy-argillaceous clastics
with subordinate coarse-grained rocks, limestones,
and marls. In some localities, dolomites, coquina,
bioherms of bryozoan limestones, gypsiferous
and bituminous terrigenous clastics are found.
 e thickness of these deposits, which are mainly
shallow-marine and also lagoonal-continental, varies
from some hundreds of metres within the periphery
of the foredeeps up to 1000–2000 m in their axial
parts (Andruschuk 1968; Azizbekov 1972).
Pliocene, Pleistocene and Holocene– Two foredeeps
(Azov-Kuban and Terek-Caspian–Gussar-Devichi)
separated by the Stavropol high were continuously
developing in shallow-marine, lagoon-lacustrine
continental environments during the Pliocene and
Early Pleistocene.
Kimmerian, Kuyanlikian, and Gurian
(Tamanian) stages (Western pre-Caucasus) and
Kimmerian, Akchagylian, and Apsheronian stages
in the Eastern pre-Caucasus are represented mainly
by sandy-argillaceous clastics, marls, coquina,
dolomites, brown iron ore, oolitic iron ore, and
rare conglomerates.  e age of marine deposits is
determined by molluscs, ostracods; continental
deposits were dated by mammal fossils.  e
maximum thickness of Pliocene–Eo-Pleistocene
deposits within the axial zone of the foredeeps varies
from 1100 m (western pre-Caucasus) to 800 m,
(eastern pre-Caucasus) and 2700 m in the Gussar-
Devichi foredeep (Andruschuk 1968; Azizbekov
1972).
During the Late Pleistocene and Holocene,
division of the pre-Caucasus into the Black Sea and
Caspian Sea domains remained. Marine deposits
are found in the immediate proximity to the
seashore. Within the Black Sea domain, the Late
Pliocene–Holocene is subdivided into the Chaudian,
Uzunlarian, Karangatian, and Neoeuxinian stages,
while the Caspian Sea domain – into the Bakunian,
Khazarian, Girkan, and Khvalynian stages.  ey
contain sands, clays, conglomerates, limestones
with molluscs of Mediterranean type.  e Late
Pleistocene–Holocene contains marine molluscs of
Apsheronian type.  is time, most part of the pre-
Caucasus is represented by land (Andruschuk 1968;
Azizbekov 1972; Avanessian et al. 2000).
Late Cenozoic Syn- and Post-collisional Magmatic
Formations
Late Cenozoic syn- and post-collisional intrusive
and extrusive formations are widespread in the
Black Sea-Caspian Sea continent-continent collision
zone. Oligocene, Neogene, and Quaternary ages
of these formations are reliably dated on the basis
of geomorphological, structural, biostratigraphic,
geochronological, and magnitostratigraphic data
(Adamia et al. 1961; Milanovsky & Khan 1963;
Gamkrelidze 1964; Andruschuk 1968; Arakelyants et
al. 1968; Aslanian 1970; Azizbekov 1972; Rubinstein
et al. 1972; Vekua et al. 1977; Khaburzania et al.
1979; Maisuradze et al. 1980; Aslanian et al. 1984).
 e Upper Cenozoic calc-alkali to shoshonitic
volcanic belt runs from Turkey via Caucasus into

S. ADAMIA ET AL.
531
30
o
35
o
40
o
45
o
50
o
40
o
35
o
B L A C K S E A
CASPIAN SEA
MEDITERRANEAN SEA
ISTANBUL
TBILISI
E
Ch
Ka
Ke
B
JAVAKHETI
Pt
Urmieh- Dokhtar magmatic belt
MO
M
a
i
T
n
h
ru
s
t
I
n
n
e
r
T
a
u
r
i
d
e
S
u
t
u
r
e
Neogene and Quaternary formation
Pt– Pjatigorsk; E– Elbrus; Ch– Chegem ;Ka– Kazbegi; Ke– Keli; B Borjomi ; MO– Megri-Ordubad–
Oligocene Early Miocene formation–
boundaries of main tectonic units (terranes)
Ankara-Erzincan suture
Figure 25. Late Cenozoic syn- and post-collisional intrusive and extrusive formations in the Black Sea-Caspian Sea continent-
continent collision zone (modi ed from Okay 2000; Robertson 2000; Altıner et al. 2000).
Iran. Outcrops of these magmatic rocks are exposed
along the boundaries of the main tectonic units
(terranes) of the region. In Turkey, they construct
two branches.  e northern branch roughly coincides
with the İzmir-Ankara-Erzincan suture (Tethys); the
southern branch – with the Antalya (Pamphylian)-
Biltis (Southeast Anatolia) suture (Neotethys). In
the Lesser Caucasus, syn/post-collisional magmatic
rocks crop out along the Sevan-Akera ophiolite
suture, and in the northernmost Iran, along the
Karadagh-Rascht-Mashhad suture (Tethys), forming
the Alborz magmatic belt.  e southern magmatic
branch of Turkey extends into Iran along the Zagros
suture (Neotethys) and forms the Urmieh-Dokhtar
magmatic arc (Figure 25).
All the above-mentioned sublatitudinal branches
of syn/post-collisional magmatic formations are
gathered in the region surrounding Lakes Van and
Urmieh (Van triangle or Van knot). From here, the
submeridional volcanic branch extended northward
forming the East Anatolian, Armenia-Azerbaijan
and South Georgian volcanic highlands and
chains of extinct volcanoes of the Lesser Caucasus-
Transcaucasus.  e northernmost relatively short
sublatitudinal (WNW–ESE) branch of syn/post-
collisional magmatic formations located in the
central segment of the Great Caucasus is connected
to the boundary zone between the Great Caucasus
fold-and-thrust mountain belt and the Scythian
platform.
More or less intensive manifestations of syn/
post-collisional magmatic activity are found within
all tectonic units of the Caucasus, however, the most
intensive magmatic occurrences show up within the
rigid platformal units: (1) in the Lesser Caucasian
part of the Taurus-Anatolian-Iranian platform

THE GEOLOGY OF THE CAUCASUS
532
(TAIP and Aras foreland), and (2) in the Artvin-
Bolnisi rigid unit of the Transcaucasian massif –
TCM (see Figure 2).
 ree main stages of syn/postcollisional
magmatism are distinct: Oligocene–Miocene,
Miocene–Pliocene and Quaternary.
Oligocene-Miocene Magmatism–  e
southernmost part of the Lesser Caucasus and the
boundary zone between the Great Caucasus and pre-
Caucasus show evidence of syn-collisional intrusive
activity. Oligocene–Lower Miocene intrusions (32–
17 Ma) are widespread within the Aras foreland
and Taurus-Anatolian-Iranian platform, along
the border with the Lesser Caucasian (Sevan-
Akera-Zangezos-Karadagh) ophiolite belt, as well
as in the southernmost tectonic units of the TCM
(Karabagh, Talysh). Intrusive bodies are composed
of the following groups: gabbro, monzonite, syenite,
diorite and granite (Megri-Ordubad – le bank of the
river Araks, Tutkhun and other plutons and dykes;
Aslanian 1970; Azizbekov 1972; Aslanian et al. 1984;
Rustamov 1983, 2007; Nazarova & Tkhostov 2007;
Azadaliev & Kerimov 2007).
In the southernmost part of the Scythian platform,
at its border with the Great Caucasus, there occur the
Beshtau (Pjatigorsk) group of the Oligocene–Lower
Miocene alkali intrusive bodies of granite-porphyry,
granosyenite-porphyry, and quartz syenite-porphyry
composition that are intruded in Oligocene–Lower
Miocene sediments and their redeposited material
is found in Upper Miocene (Akchagylian) deposits
(Andruschuk 1968). However, K-Ar data (c. 8–9
Ma) indicate a Late Miocene age of these intrusions
(Borsuk et al. 1989).
Late Miocene–Quaternary Magmatism– Late
Miocene–Quaternary volcanic activity in the region
took place within a broad S–N-trending belt extending
from Central Anatolia to the Great Caucasus-pre-
Caucasus.  e belt is related to transverse Van-
Transcaucasian upli (Lordkipanidze et al. 1989). In
some localities, volcanic products exceed a kilometre
in thickness and cover a wide compositional spectrum
from basalt to high-silicic rhyolite. Two main stages
of volcanic activity are present: (1) Late Miocene–
Early Pliocene and (2) Pliocene–Quaternary. Lavas
predominate over volcanoclastics, especially during
the second phase of eruptions. According to their
mineral-chemical compositions, rocks of the both
stages are attributed to calc-alkaline, alkaline and
subalkaline series. Data on absolute age demonstrate
that the  rst stage of eruption in the Caucasus
happened ~13–4.5 Ma while the second one c. 3.5–
0.01 Ma (Rubinstein et al. 1972; Maisuradze et al.
1980; Camps et al. 1996; Ferring et al. 1996; Mitchel
& Westaway 1999; Lebedev et al. 2004, 2008).
Upper Miocene–Lower Pliocene formations are
known only in the Lesser Caucasus-Transcaucasus
where they are represented by basalt-andesite-dacite-
rhyolitic subaerial lava sheets and volcanoclastics.
Basaltic lavas and pyroclastic rocks are represented in
the lower, basal level of the formation. In some places,
the formation contains economic diatomite deposits.
 e middle part of the section is represented mainly
by volcanoclastic rocks. Pyroclastic rocks in the
vicinity of the Goderdzi pass (Artvin-Bolnisi massif-
ABM) contain remains of petri ed subtropical wood,
which date the rocks as Upper Miocene–Pliocene
(Uznadze 1946, 1951; Gamkrelidze 1964; Uznadze &
Tsagareli 1979). K-Ar dating of tu s indicate a Late
Miocene age (9.8 Ma, Aslanian et al. 1984).
Laminated and/or banded andesite and dacite
lavas with volcanoclastic interlayers are common
in the upper part of the formation. Andesite is a
dominant rock unit. K-Ar ages of the andesites and
dacites according to Aslanian et al. (1984), Lebedev et
al. (2004) vary from 9.4 Ma to 7.0 Ma.  e K-Ar age
of calc-alkaline, sub-alkaline and alkaline basaltic,
andesitic, dacitic, and rhyolitic volcanic rocks of the
TAIP (Armenia) yielded c. 13–3.5 Ma age interval
(Aslanian et al. 1984; Jrbashian et al. 2002).
Upper Pliocene–Holocene formations are
widespread within the TAIP and ABM. Basaltic
(doleritic) lavas are the dominant rock units in the
lower part of the formation. In some places, they
contain lenses of  uviatile to lacustrine and alluvial
deposits, and also pyroclastic rocks; andesitic basalts
are subordinate, more felsic rocks are rare. Because
of its low viscosity, lava could spread over a large
area. It covered an ancient relief forming an extensive
 at plateau.  e total thickness of the formation is
approximately 100–300 m.  e age of the lower part
of the formations is identi ed by mammalia fauna
as Late Pliocene–Pleistocene (Gamkrelidze 1964;
Andruschuk 1968; Azizbekov 1972; Adamia et al.

S. ADAMIA ET AL.
533
1961; Gabunia et al. 1999; La Georgie 2002; Vekua
et al. 2002).
Magnetostratigraphic investigations carried
out during the last decade (Vekua et al. 1977;
Khaburzania et al. 1979; Djaparidze et al. 1989;
Sholpo et al. 1998) have recognized within the Upper
Miocene–Quaternary sequence of volcanic rocks
all the known standard palaeomagnetic chrons and
subchrons: Brunhes, Matuyama (with Jaramillo,
Cobb Mountain, Olduvai, Reunion 2 and Reunion 1
subchrons), and Gauss (with Kaena and Mammoth
subchrons).  ese data place basalts of the ABM at
the top of the Akchagylian stage (c. 1.8 Ma).
Andesites, andesite-dacites, and dacites crown the
section of the Lower Pliocene–Quaternary volcanic
formations of the TAIP and ABM. According to
K-Ar dating, in Javakheti, the oldest rocks of dacitic
composition are lavas (c. 760000 a).
 e younger rocks (400 000–170 000 yr) are
found in the central part of the Javakheti highland
(Abul mountain, lake Paravani, caldera Samsari
etc). Volcanic activity in the region came to a halt,
probably, at the end of the Pleistocene, about 30 000
a (Lebedev et al. 2004) – Holocene (Afanesian et al.
2000).
 e central, mostly upli ed segments of the
Great Caucasus contain only Pliocene–Quaternary
volcanic and plutonic formations. Products of
post-collisional volcanism of the Elbrus, Chegem,
and Keli-Kazbegi centers of extinct volcanoes are
represented mostly by lava  ows of calc-alkaline-
subalkaline andesite-basalt, andesite-dacite rhyolite
composition (Tutberidze 2004; Koronovsky &
Demina 2007). Neogene–Quaternary intrusives
of the Great Caucasus also crop out in the same
regions and are represented by hypabyssal bodies.
A number of geochronological data indicate a Late
Pliocene–Quaternary age of this volcanic-plutonic
formation (Borsuk 1979; Chernishev et al. 2000).
Two radiocarbon data (5950±90 a and 6290±90 a)
were obtained from wood fragments collected from
the lake beds near the volcano Kazbegi.  ese data
indicate that the lake beds and lava  ow may be
attributed to Middle Holocene age (Djanelidze et al.
1982).
In the geological literature, migration of magmatic
activity of the Javakheti highland is described as
‘dominoes e ect’, i.e. attenuation of volcanism
within one zone results in formation of another,
‘shi ed’ in submeridional direction magmatically
active extension zone (Lebedev et al. 2008).  e
geodynamical regime of collisional volcanism of the
Caucasian segment is characterized by compression
at the depth and uneven extension within the
upper part of the Earth’s crust. (Koronovsky &
Demina 1996); petrochemical features of basalts of
eastern Anatolia and the Lesser Caucasus points to
propagation of ri volcanism from the Levant Zone
northward. In other words, the ri does not exist
yet, but a deep mechanism for its formation already
exists (Koronovsky & Demina 2007).
Several geodynamic models have been proposed
for the genesis of collision-related magmatism in
continental collision zones, in particular, for the
Eastern Anatolian Plateau (Pearce et al. 1990; Keskin
et al. 1998; Şengör et al. 2008; Dilek et al. 2009;
Kheirkhah et al. 2009), whose direct prolongations
are represented by volcanic high plateaus of Southern
Georgia. Some of them may be relevant to the Eastern
Anatolian-Caucasian Late Cenozoic collision zone
– for example, the detachment model (Innocenti
et al. 1982) of the last piece of subducted oceanic
lithosphere to explain the Late Miocene–Quaternary
calc-alkaline volcanism of southern Georgia, and the
lithosphere delamination (Pearce et al. 1990; Keskin
et al. 1998) model for explanation of the Pleistocene–
Holocene volcanism of the Central Great Caucasus.
Recent Geodynamics
 e recent geodynamics of the Caucasus and
adjacent territories is determined by its position
between the still converging Eurasian and Africa-
Arabian plates. According to geodetic data, the rate
of the convergence is ~20–30 mm/y, of which some
2/3 are likely to be taken up south of the Lesser
Caucasian (Sevan-Akera) ophiolitic suture, mainly
in south Armenia, Nakhchevan, northwest Iran and
Eastern Turkey.  e rest of the S/N-directed relative
plate motion has been accommodated in the South
Caucasus chie y by crustal shortening (Jackson
& McKenzie 1988; DeMets et al. 1990; Jackson &
Ambraseys 1997; Reilinger et al. 1997, 2006; Allen et
al. 2004; Podgorsky
et al. 2007; Forte et al. 2010).

THE GEOLOGY OF THE CAUCASUS
534
Tectonic stresses caused by the northward motion
of the Arabian Plate are adsorbed to a considerable
degree in the Antalya-Bitlis (Periarabain) ophiolitic
suture and in the Zagros fold-thrust belts (DeMets
et al. 1990; Jackson & Ambraseys 1997; Allen et al.
2004; Reilinger 2006). North of these structures the
stresses are propagated towards the Central Caucasus
by means of a relatively rigid block (Van Triangle)
whose base is located south of the Lakes Van and
Urumiech along the PAOS and its apex lies in the
Javakheti highland. Within the rigid block, there
occur intensive eruptions of Neogene–Quaternary
lavas in eastern Anatolia, Turkey, Armenia (Aragats,
etc), Georgia (Javakheti, Abul-Samsar, Kechut
ranges). Neogene–Quaternary volcanoes are also
known in the central part of the Transcaucasian
foreland and in the Main Range of the Great Caucasus
(Elbrus, Chegem, Keli, Kazbegi). It is noteworthy
that the strongest Caucasian earthquakes occurred
within this area (Figure 26) – 1988 Spitak (Armenia)
and 1991 Racha (Georgia).
A complex network of faults determines the
divisibility of the region into a number of separate
blocks (terrains) of di erent orders, varying one
from another by their dimensions, genesis, and
geological nature. Geological, palaeobiogeographical
and palaeomagnetic data provide evidence that
these terrains before being accreted together in a
single complicated fold-thrust belt have undergone
long-term and substantial horizontal displacements
within the now-vanished oceanic area of the Tethys
(e.g., Dercourt et al. 1986, 1990; Stamp i 2000;
Barrier & Vrielynk 2008).  e boundary zones
between these terrains represent belts of the strongest
geodynamic activity with widely developed processes
of tectogenesis (folding and faulting), volcanism,
and seismicity. As a result of continuing northward
movement of the Africa-Arabian plate in Oligocene–
post-Oligocene time, the region turned into the
intracontinental mountain-fold construction.  e
process of formation of its present-day structure
and relief (high-mountain ranges of the Caucasus
foredeeps, and intermontane depression of the
Transcaucasus, volcanic highlands) has especially
intensi ed since Late Miocene (Late Sarmatian, c.7
Ma). Syn-, post-collisional sub-horizontal shortening
of the Caucasus caused by the northward propagation
of the Africa-Arabian plate is estimated at about
hundreds km. Such a considerable shortening of
the Earth’s crust has been realized in the region
through di erent ways: (1) crustal deformation
with wide development of compressional structures
– folds, thrusts; (2) warping and displacement
of crustal blocks with their upli ing, subsidence,
underthrusting (a process sometimes referred to
as continental subduction) and (3) lateral escaping
(Adamia et al. 2004c).
 e geometry of tectonic deformations in the
region is largely determined by the wedge-shaped
rigid Arabian block intensively intended into the
relatively mobile Middle East-Caucasian region.
In the  rst place, it in uenced the con guration of
main compressional structures developed to the
north of the Arabain wedge (indentor) -from the
Periarabic ophiolite suture and main structural lines
in East Anatolia to the Lesser Caucasus (Koçyiğit et
al. 2001), on the whole, and its constituting tectonic
units including the Bayburt-Karabakh and Talysh
fold-thrust belts. All these structural-morphological
lines have clearly expressed arcuate northward-
convex con guration re ecting the contours of
the Arabian Block (see Figure 1). However, further
north, the geometry of the fold-thrust belts is
somewhat di erent – the Achara-Trialeti belt has,
on the whole, W–E trend (although, individual faults
and folds are oblique, NE–SW-trending in regard to
the general strike of the belt).  e Great Caucasus
fold-thrust belt extends in WNW–ESE (300°–120°)
direction, while the chains of young Neogene–
Quaternary volcanoes are oriented in submeridional
(N–S) direction that is also in compliance with
general NNE–SSW sub-horizontal compression
of the region.  ree principal directions of active
faults compatible with the dominant near N–S
compressional stress produced by the Arabian Plate
can be distinguished in the region (Koçyiğit et al.
2001) – longitudinal (WNW–ESE or W–E) and two
transversal (NE–SW and NW–SE).  e  rst group
of structures is represented by compressional ones
– reverse faults, thrusts, overthrusts, and related
strongly deformed fault-propogation folds. Unlike
the compressional faults, the transversal ones are
mainly extensional structures having also more or
less considerable strike-slip component (see Figure
26).  e tensional nature of these faults is evidenced
by intensive Neogene–Quaternary volcanism related

S. ADAMIA ET AL.
535
B L A C K
S E A
CAS PIAN
S E A
TURKEY
IRAN
40 E
45 E
40 N
RUSSIAN
FEDERATION
Tirniauz
Main Thrust
Gagra
Gali
R
Siazan
Odishi
Racha
Kelkit-Choruh
Dumlu
Bakuriani
Guria
Achara-trialeti
Orkhevi
Chatma
Spitak
Akhurian
Sarighamish
Barisakho
Lesser Caucasus
Kelbajar
Garni
Kura
Aras
Astara
Giratakh
Salvard
Yereven
Pre
S
Ag
Ar
faults
reevers
wrench
strike-slip sinistral
strike-slip dextral
reevers and strike-slip
Figure 26. Schematic map of the seismic sources of the Caucasus according to A. Arakelyan, S. Nazaretyan, A.
Karakhanyan (Armenia and adjacent areas of Turkey and Iran); B. Panakhi, T. Mamadly (Azerbaijan) and
Sh. Adamia (Georgia, adjacent areas of Turkey and North Caucasus), Compiled in the frame of Internatuinal
Scienece and Technology Center Project GA-651 ‘Caucasian Seismic Information Network for Hazard and
Risk Assessment (CauSIN), 2005, Report. Epicenters: R– Racha, S– Spitak earthquakes; extinct volcanoes:
Ar– Aragats, Ag– Ağrı Dağı.
to these faults in some places of the region – in
Armenia, Azerbaijan, Southern Georgia (Javakheti
highland), Transcaucasus and the Great Caucasus.
NE–SW le -lateral strike-slip faults are main
seismoactive structures in NE Turkey that borders
on SW part of Georgia. Right-lateral strike-slip
faults and fault zones are also developed in South
Armenia, Nakhchevan and NW Iran.  e analysis
of focal mechanism of some strong earthquakes in
the Caucasus shows that crustal blocks located to
the west of submeridional line running across the
Javakheti highland, volcano Aragatz in Armenia and
Agridag in Turkey have experienced westward lateral
escaping, whereas the crustal blocks east of this
line evidence for ESE-directed displacement.  ese
data are well corroborated by GPS measurements
(McClusky et al. 2000).
Seismicity
Two large devastating earthquakes occurred in
the Caucasus in the last 20–25 years.  e  rst
one was the magnitude 6.9 Spitak Earthquake on
December 7, 1988 whose epicenter located within
the Lesser Caucasus-Northern Armenia near the
Georgian border.  e earthquake became widely
known due to the immense losses it caused – no
less than 25 000 people were killed, some 500 000
le homeless, property damage was estimated at
about 8 billion USD.  e epicenter of the Spitak

THE GEOLOGY OF THE CAUCASUS
536
References
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Sevan fault, constituting a branch of the Sevan-
Akera ophiolite suture. Another large seismic event
was the magnitude 7.2 Racha earthquake on April
29, 1991.  is earthquake, the strongest one ever
recorded in Georgia, was located in Central Georgia
in the southern foothills of the Great Caucasus at
its junction with the Transcaucasian intermontane
foreland (see Figure 26).  e earthquake took about
a hundred human lives and caused great damage
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Conclusions
Starting from the end of the Proterozoic and the
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In present-day structure, relics of the crust of
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of Iranian Karadagh. Final collision of Africa-
Arabian and Eurasina lithospheric plates closing of
Neotethys branches and formation of the Caucasian
zone of continent-continent collision happened in
Oligocene–Early Miocene.
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