Geology of Georgia

The territory of Georgia occupies the central part of the Black Sea - Caspian Sea basin. The latter represents a Late Alpine collision structure that was formed in the place of the ancient ocean Tethys and its northern and southern continental framings as a result of the collision between Afro-Arabian and Eurasian continents. At the same time the Black Sea - Caspian Sea region is a connecting link between the European and Asiatic parts of this collisional structure known in traditional geology under the name of the Alpine - Himalayan Mountain - fold belt. The uniqueness of this belt consists in the fact that here the collision between the two continents during the Alpine cycle of tectogenesis has been realized in its entirety. The central part of the Black Sea - Caspian basin within the limits of which lies the whole Transcaucasia, including all the territory of Georgia, in contrast to the western and eastern parts of the basin, gives a possibility of compiling continuous cross sections - transects along the whole collisional structure, from the Arabian wedge up to the European continent inclusive. Apart from a unique possibility of studying the continent/continent collisional structure given by the Black sea - Caspian Sea region, the latter attracts a great interest by some problems of practical character. These are, in the first place, rich natural resources of various metallic and non-metallic minerals, including gigantic oil-and gas deposits. On the other hand, being a part of the Alpine - Himalayan seismic belt, the region is distinguished by a high level of seismic activity which, along with the other evidences of recent geodynamic activity (folding, faulting, mountain-building), make the region highly susceptible and vulnerable to various natural hazards inflicting considerable damage to the environment.

According to the results of Georgian scientists, published during the last two decades (including foreign editions), the Black-Sea-Caspian region on the whole, and adjacent territories of the Eastern Mediterranean are regarded as an accretional mosaic of terrains of Gondwanian, Tethyan, Eurasian and sometimes controversial origin [4]. Within this accretional complex it is possible to identify both: South-Tethyan and North-Tethyan terrains represented by fragments of rocks characteristic to mature and immature island arcs, intra-arc and back-arc basins, oceanic islands, mid-oceanic ridges, and micro-continents. It has been suggested that the accretion of terrains took place repeatedly in the Phanerozoic, but the continent/continent collision in the Caucasian intersection occurred only once, at the final stage of the Alpine plate tectonic cycle, in the Late Cenozoic time. Therefore the terms Paleotethys, Mesotethys, Neotethys signify not different oceans but the different stages of evolution of the same ocean that existed, at least during the whole Paleozoic, Mesozoic and Early Cenozoic. The main suture zone marking the location of oceanic Tethys, in the opinion of Georgian geologists, is the ophiolitic suture of North Anatolia-Lesser Caucasus. Recent high geodynamic activity of the region expressed by both seismic and aseismic deformations (faulting, folding, vertical and horizontal displacement of blocks, their rotation, etc.) is conditioned by still ongoing convergence of lithospheric plates and northward propagation of the Afro-Arabian continental block at a rate of several cm/year [1-11].

The territory of Georgia during its historical past was repeatedly subjected to destructive impact of strong and major earthquakes causing tremendous material damage and numerous loss of human lives. Among the most catastrophic events of the recent time was the Spitak 1988 earthquake (in North Armenia near Georgian border) and the Racha 1991 earthquake in Central Georgia. The high seismic activity is attributed to active manifestation of post-collisional tectogenesis  within the region. The intensive uplift of thrust-fold mountain belts of the Greater and Lesser Caucasus and no less intensive subsidence of adjacent intermontane depressions, formation of young folds and faults, wide spread of young volcanism along with high seismic activity – all these evidences indicate the ongoing tectonic activity of the region on its recent stage of evolution. The earthquake epicenter map shows that distribution of earthquakes has a wide-spread pattern that is characteristic of areas of intraplate compression consisting of a great number of constituting small plates and blocks. Fig.1. depicts the major faults on the territory of Georgia with epicenters of strong earthquakes (with magnitude more than 5). Besides, the map shows some paleodislocations which, according to some scientists, were originated as a result of very strong earthquakes of the past. The combined analysis of geological and seismic data has given possibility of identifying on the territory of Georgia a number of seismoactive zones related to the major fractures in the earth's crust. Seismoactive faults of the region have northwest-southeast or nearly sub-latitudinal strike coinciding with the trend of main geological structures. These faults reveal seismicity along their whole length but the maximal activity is usually observed at their intersection with the Caucasian Transversal Uplift (CTU). It is this belt where main seismoactive areas of the region are located. These are the Javakheti and Kazbegi seismoactive areas in Georgia, Spitak and Erevan-Ararat areas in Armenia, south of Georgia, and Grozni seismoactive area north of Georgia. The distructive Racha 1991 earthquake occurred at the western periphery of the CTU.

Two large submeridional seismoactive  faults: Abul-Samsar and Kechuti – are situated within the limits of the CTU in the Djavakheti volcanic highland (south Georgia). The first of them extends in SSW direction to the territory of Turkey where, near the village of Varto, it merges with the East Anatolian fault – one of the branches of  the global Levant zone of strike – slip faults. On the southern continuation of the Kechuti fault there are situated major earthquakes of the Spitac, Erevan and Ararat seismoactive areas.

Focal mechanisms of some Caucasian earthquakes confirm the concept of collision of Eurasian and Arabian plate causing the compression and squeezing of the Caucasia isthmus. Mechanisms of the majority of earthquakes related to faults of "Caucasian" (NW-SE) strike are characterized by compresscanal  stress, main axes being orientated in horizontal planes perpendicular to structural lines. Movements in earthquake sources of this type are realized in the form of thrusts and reverse faults leading to horizontal shortening of the earth's crust. Focal mechanism of earthquakes associated with transversal faults reveal more or less considerable strike-slip component.

Of considerable interest is the distribution of earthquake sources in depth. The overwhelming of Caucasian earthquakes are shallow (crystal). Minimal depths (up to 10-15 km) have. as a rule, strike-slip earthquakes whereas shocks connected with thrusts and reverse faults are sometimes located at much greater depths (up to 30-50 km). Sometimes, within a single focal zone one can observe the increase of earthquake depths in northward direction. This fact may be interpreted as under thrusting of southern blocks beneath the northern ones (2, 6, 7, 8, 16, 17). Prof. Sh. Adamia

Geologic evolution

The geological evolution of Georgia is closely related to the development of the entire Caucasus segment of the Mediterranean belt; therefore it is considered against the background of this region as a whole. A new material obtained in recent years concerning the definition of paleolatitudes provides not only qualitative but also quantitative characteristics of horizontal displacements of the Earth’s crust. Suggested palinspastic profiles have been compiled in terms of these data (Fig. ).

As a result of horizontal displacements of the certain lithospheric plates within the Mediterranean belt during the Precambrian-early Mesozoic, the generation and development of oceanic basins took place the present structure of these basins is marked by rocks of ophiolitic association.

Judging by the latest data on ophiolites of the Dzirula Massif  (Gamkrelidze et al. 1981) and also by paleomagnetic data, the most ancient of these oceans, Prototethys  (or Paleotethys) developed in the course of time the Precambrian up to the Middle Jurassic. At this time the Caucasian province and Greater Caucasian island arcs with an interarc rift of Fore range and Greater Caucasian and Precaucasus marginal basins (Adamia, 1984; Fig. ). According to other opinion, the southern, Lesser Caucasus paleotethys and belonged to the N margin of the Iran-afghan Plate (Gamkrelidze,1986).

In the rear of the gradually closing paleotethys, the joining together of Iran and Arabia and generation of Mesotethys had been taking place already since the Triassic (Fig.  ).

The next extension of Mesotethys occurred during the early Jurassic and beginning of the Middle Jurassic. At the N active margin of Paleotethys (a margin of Mesotethys according to Adamia, Zakariadze and lordkipanidze (1977), the Transcaucasus island arc and marginal sea of the Greater Caucasian can be discerned (Fig.    )).

In terms of geological data, Paleotethys became Phase of compression (Fig.  ). The suture of the closed paleotethys is assumed to be somewhere to the N of the Locki massif (Gamkrelidze, 1986; Fig.   ). These movements were accompanied by granite formation.

One can suppose that the Lesser Caucasus branch or bay of Tethys  was formed in the rear ef the closure of paleotethye since the end of the Middle Jurassic. 

(Prof. I. Gamkrelidze)

Georgia

Introduction

The republic of Georgia is located in the central and W part of Transcaucasus. The W and E boundaries lie at latitude 40* 05’ and 46*44’ E, the S and N ones at 41*07’ and 43*35’ N. Georgia borders Russia to the Caucasus Ridge, Azerbaijan to the E, Armenia to the Turkey to the SW. It’s W margin borders the Black sea. Georgia is 69 500 km² in area; its population totals 5 million. Representative of more than 100 nations and nationalities live in the republic. More then two-thirds of the populations are Georgians.

Georgia is characterized by rough topography; almost two-thirds of its territory is mountains. The main orographic unites are the elevation of Greater Caucasus, the intermontane area divided by Likhi Ridge into the Kolkheti (Rioni) and Iveria (Kura) lowlands, the Meskheti and Trialeti and ridges, the volcanic highland of the S Georgia and a part of the Lesser Caucasus elevation.

The climate in Georgia is divers due to its location in the subtropical zone at a boundary of the Aral-Caspian arid region and continental highland Caucasian. Western Georgia is characterized by a most subtropical climate, the E one by a dry, temperate to moist subtropical climate. The climate in S Georgia is continental.

Due to the diversity of climatic conditions, the network of rivers and their discharge is irregular. The network of rivers in W Georgia is denser then in its E part. Among the rivers of W Georgia, belonging to the Black Sea Basin, the Rioni has the largest runoff. Other major rivers are the Inguri, Kodory, Bziby, Tskenistskali (the right tributary of the Rioni; ( fig1).

Almost all the river of Georgia forms a common system of the Kura River and meets the Caspian Sea. The largest river of Georgia and Caucasus is the Kura (with an outflow in Turkey). The main tributaries are the Liakhvi, Ksani, Aragvi, Khrami and Alazani (together with the river Iori).

To the Caspian Sea basin also belongs River Tergi, which for 85 km flows near the border of Georgia and then breaks through the Caucasus ridge.

The capital of Georgia is Tbilisi (1.25 million residents). Other significant settlements are Kutaisi, Batumi, Poti, Gagra, Borjomi, Gori, Mestia, Kazbegi, Tianeti, Lagodekhi and Djava (fig.1).

History of geological study

Georgia, as well as the Caucasus as whole, was of great interest to naturalists, mainly geologist. For almost 150 years, it has been an object of geological study. From the beginning the initiative and guidance, was in the hands of explorers from W Europe. Fr.Dubois de Montpereu, H.Abih, E. Favre and E.Fournier were among the first researchers. H.Abih is justly repeated as a pioneer of the study of Caucasus geology.

The promotion of the study of Caucasian geological structure is connected with geologists of the Caucasus Mining Department, including S.Simonovich, A.sorokin, L.Batsevich, G.Tsulukidze, and L.Konushevski, and in the 1920s, E.Rengarten, I.kuznetsov, B.Meffert, N.Pafenholtz and A.Agalin. At the same time, the 1920s should be considered as the years of inception of Georgian geology study. At that time quite young geologists A.Janelidze, A.Tvalchrelidze  and K.Gabunia, founders of the Georgian geological School, began their activities. Since then their direct pupils, Georgian geologists I.Kacharava, I.Kahadze, G.Dzocenidze, A.Tsagareli, G.Tvalchrelidze, G.Zaridze, N.Tatrishvili, N.Schirtladze, M.Eristavi, I.Buachidze, G.Gvaxaria, M.Rubinshtein and their disciples have made a valuable contribution to Geological science, and the study of Georgia’s geological structure and mineral resources.

An important role has also been by outstanding Russian geologists V.Belousov, E.Khain, E.Milanovski, V.Muratov and others in the geological study of Georgia and Caucasus.

At present geological study in Georgia is carried out in every branch. A geological survey of the entire territory of Georgia has been accomplished at a scale of 1:50 000.

It should be noted that in the early 1970s, Georgian geologists were among the first to consider the evolution of Georgia, and Caucasus in general, on the basis of the theory of plate tectonics (Sh.Adamia, I.Gamkrelidze, M.Lortkipanidze, G.Zakariadze). At present geological studies in many branches are carried out mainly against a background of the theory.

Regional geology

Georgia as a part of Caucasus of the Caucasus is located between the Eurasiatic and Afro-Arabian plates at the junction of European and Asiatic branches of the Mediterranean (Alpine-Himalayan) fold belt. Its geological structure is built up mainly by Mesozoic and Cenozoic deposits. Early Precambrian and Paleozoic formations spread over a smaller area.

The following tectonic units of the recent geologic structure of Georgia can be distinguished according to the degree of dislocation of the Earth’s crust and taking into account geologic peculiatorities and evolution (fig.. ):

1.      Fold system of the Greater Caucasus (in the geological past a marginal sea),

2.      The Transcaucasian intermountain area (in geological past a N part of the Transcaucasian island arc);

3.      The fold system of the Lesser Caucasus (in geological past a S part of the Transcaucasian island arc).

Each of these tectonic units in their turn consists of various (second and third) order tectonic units (fig….)

Stratigraphy

The oldest – Precambrian and Lower – Middle Paleozoic – rocks are exposed in all the tectonic units (fig…). They are represented by gneisses, migmatites, crystalline schists and amphibolites within the Main Range zone of the fold system of the Greater Caucasus, the Georgian Block (in the so–called Dzirula massif) and the fold system of Lesser Caucasus (in the so-called Khrami and Locki massifs; Adamia, 1984).

Paleozoic rocks are exposed in the central part (Svaneti Zone) of the S slope of the Greater Caucasus. They are represented mainly by black shales, phthanites (cherts), sandstones, turbidities, olistostromes, lenses of marbles and calc-alkaline andesite-dacitic volcaniclastics. Their visible the thickness reachs 2000 cm. This is so called Dizi Series, in which faunally (by corals, foraminifer and conodontas) the Devonian, Carboniferous and Permian are established. Comparatively weakly metamorphosed Paleozoic sediments are exposed in Dzirula Massif as well. These are the allochthonous sliver of so-called “phyllitic suite” which are in contact with Upper-Paleozoic granitoids and Paleozoic and Precambrian gabbro-amphibolites and serpentinites. The latter are meta-ophiolites (Gamkrelidze et al., 1981).

The Upper Paleozoic rocs are also present in all tectonic units. In the Main Range zone crystalline rocks are overlain by weakly metamorphosed sandstones, conglomerates and argillites which contain Upper Carboniferous-Lower Permian marine fauna (marine molasses)

Continental and coastal calc-alkaline rhyolitic volcanic and coal-bearing argillites with lenses of reef limestone are known in the Dzirula and Khrami massifs. Lower-Middle Carboniferous corals, brachiopods, foraminifer and terrestrial flora have been found in this formation of Khrami Massif.

Triassic sediments are observed in the Dizi series of the Svanethi zone apart from the above-mentioned Upper Paleozoic deposits. To the Triassic also belong decitic-rhyolitic volcanic, quartz sandstones and siltstones with variable thickness (80-5000m), which crop out in the Dzirula Massif and contain flora of Triassic age.

Lower Jurassic-Aalenian sediments, which everywhere rest transgressively, are spread throughout all tectonic units of Georgia (Geology of USSR, 1964).

In the fold system of the Greater Caucasus these deposits, more then 5000m in thickness, are represented by black shales, sandstone turbidities, rhyolitic (in the lower part) and tholeiite-basaltic (in the upper part) lavas and their pyroclastics.

In the Georgian Block Lower sediments (80-90 m thick) crop out only along the edges of Dzirula Massif and are represented by arcosic sandstones, gravelstones, conglomerates, clays and red zoogenic limestones containing rich marine fauna (Ammonitico Rosso facies).

In the S part of Khrami and Locki massife the Lower Jurassic consists only of terrigenous deposits (120-600 m thick).

In the central part of the fold sistem of the Great Caucasus the Bajocian stage is represented by graywacke-siltstone flysch, shales and marls, and elsewhere by a thick (3500m) volcanogenic series, which contains marine fauna and consist mainly of calc-alkaline basaltic, andesite-bazaltic lavas and pyroclastics. Teproturbidites, graywackes and conglomerates are rather scarce.

The Batonian Stage in the fold system of Great Caucasus is represented by graywacke siltstone flysch, and by regressive coalbearing terrigenous deposits (65-200m) on its S slope (in the Gagra-Java Zone).

In the central and E parts of the S slope of the Greater Caucasus (Mestia-Tianeti Zone), the Upper Jurassic sediments which follow conformably Middle Jurassic slates consist mainly of clastic limestone flysch (1100-1500 m). on the rest of territory they lie transgressively and discordantly.

In W  and E parts of the Gagra-Java Zone an upper Jurassic marine facies is present. In the lower part it is represented by sandstones and clays (120-200 m)and in its upper part by reef limestones (400-900 m). a rich marine fauna (ammonites, corals, etc.) is found in these sediments. To the S and within the Georgian Block gypsumbearing lagoonal-continental terrigenous (Kimmerijian-Tithonian) deposits and to a losser extent alkaline basaltes and pyroclastics are present.

Upper Jurassic shallow-water limestones and marls, alternating with calc-alkaline basalt-andesite-dacite volcanics, are exposed at the W edge of Kharmi Massif and in the Lock-Karaback Zone also.

There is a variety of Cretaceous deposits in Georgia. Within the Greater Caucasus fold system (in the Mestia-Tianeti flysch zone) Lower Cretaceous is developed in the form of clastic limestone and greywacke siltstone flysch (750-1600 m) which conformably follow the Upper Jurassic flysch. In the S and within the Georgian Block the old formation, including crystalline rocks of the Dzirula Massif, is overlin transgressively by Lower Cretaceous rock (300-550 m). In the main, limestones are developed within this area. Only in the middle of a section apper marls and clays (Albian Stage) and glauconitic sandstones (Cenomania Stage). Reef limestone of Urgonian facies (Barrenian Stage) and ammonitic limestones (Aptian Stage) are distinguished in the Lower Cretaceous.

In the Upper Cretaceous sediments of the Mestia-Trileti, Flysch Zone greywacke siltstone (in the lower part) and clastic limestone (in the upper part) flysch (500-900 m) prevail. Within the Gagra-Djava Zone and Georgian Block, they are spread mainly as shallow-water limestones, marls and glauconitic sandstones (250-1200 m), whereas to the W in the dzirula massif, a alkali basalt-phonolitic series (70-300 m) occurs locally.

In Adjaria-Trialeti zone the Upper Cretaceous is represented by a volcanogenic suite with calc-alkaline basaltic composition, which in the lower part also contains the Albian Stage. Stratigraphically higher there then follow upper Turonian-Senonian limestones and marls (300-1200m).

In the Arthvin-Bolnisi Block and Lock-Karabach Zone transgressive upper Cretaceous sediments are present, which subdivide into three parts. A cenomanian volcanogenic-carbonate series (900-1200m) overlap directly the Khrami and Locki massifs and Jurassic rocks. In ascending section there follows a basalt-andesite-dacite-rhyolite series (1100-3300m) of Turonian-Santonian age. The uppermost part (Campanian-Maastrichtian) is represented by shallow-water limestones and marls with interlayers of acidic tuffs (300-350 m).

paleogene deposits are found in all tectonic units. In the S slope of the Greater Caucasus, the Paleocene-Eocene is represented by greywacke-siltstone flysch (600-850m). In the s part the Upper Eocene is built up of olistrostomes (10-400m).

In the Georgian block the Paleocene and Eocene consist of alternetion of limestones and marls (30-400m). In the middle part of the Lirolepis horizon, a horizon of marls is distinguished.

Tectonics

The territory of Georgia as a part of the Caucasus, underwent a long and complicated tectonic evolution and contains structures of various types, scales and genesis.

The northeastern tectonic unit of Georgia, the fold system of the Greater Caucasus, is characterized by a distinctly expressed asymmetry in its structure: S verging, often isoclinal folding on the S slope and quiet, poorly folded or monoclinal structures on the N slope and quiet, poorly folded or monoclinal structures on the N slope. Large, southeard-directed nappes are developed also on its S slope (Gamkrelidze, 1991). The above mentioned structures provide evidence of the leading role of late Alpine under thrusting of the comparatively rigid Georgian Block under the Greater Caucasus during its deformation (intraplate subduction (Gamkrelidze and Giorgobiani,1990).

The N boundary of the Georgian Block, in its W part, is by a deep fault, which in the sedimentary cover manifests itself as a regional flexure. Study of the structural peculiarities of the Georgian Block has shown that its central and W parts are caracterised by a mosaic block structure of the basement and occurrence of typical above-fault folds in the sedimentary cover. In the E area of subsidence of the Georgian Block its cover is detached and shifted and towards the S together with the nappes of the S slope of the Greater Caucasus (Gamkrelidze and Gamkrelidze, 1977; Khain, 1984; (fig…)

The adjara-Trialeti Zone of the Lesser Caucasus, wich is situated to the S of the Georgian Block, on the whole is an anticlinorium and is characterized by block-fold structures (fig.225). To the W from the Dzirula Massif along the N margin of this zone, an overthrust nappe is developed (fig.224).

The Artvin-Bolniosi block consists of two different tectonic units: The Javaxeti zone (in the W) and Bolnisi Zone (in the E). In the yang (Neogene Pleistocene) volcanic cover of the Javakheti Zone sublatitudinal gentles folds are observed. Two deep submeridional seismogenic faults are established which served as conduit channels for young lavas. The Bolnisi Zone includes the horst-like Khrami salient of pre-Alpine basement and the territory covered with Cretaceous and Paleogene volcanogenic rocks. Brachyanticlines and steep faults of various orientations are developed to the S in a sedimentary cover, which on the whole forms a gentle syncline (Gamkrelidze, 1984).

The NE wedge of the Locki-Karabakh Zone forms part of Georgia and is characterized by echelon-like disposition of internal anticlinoria. In the core of a sublatitudinal Locki anticlinorium the pre-jurassic crystalline basement is exposed. The axis of this structure plunges in both W and directins and causes periclinal closure of the sedimentary cover.

The fold and fault system of the Adjara-Trialeti and Lock-Karabach zones and the Artvini-Bolnisi Block were formed as a result of the manifestation of late Alpine (neogene) phase tectonic movements with the displasement of masses from S to N (Gamkrelidze, 1976).

Geological Evolution

The Geological history of the Caucasus region is complex, and is described by several investigators. It’s geological evolution is closely related to the development of the entire Caucasus segment of the Mediterranean belt; therefore it is considered against the background of this region as a whole.

Reconstractions of the history of movements of large blocks of the Earth’s crust are impossible at present without using kinematic and paleomagnetic methods, along with traditional geological investigations.

During the Precambrian time Caucasus with adjacent area were lie between two large continents: Evrasia and Afrika-arabia. was that territory one big continet’s part (megagea) or it was ocean prothotetis?

as a result of horizontal displacement of the ancient East-European and African platforms, as well as of certain lithospheric block (or plates) within the Mediterranean belt during the Precambrian-Early Mesozoic, the generation and development of oceanic baseins took place. In the present structures, these basins are marked by roks of ophiolitic association.

Judging by the latest data on ophiolites of the Dzirula Massif (Gamkrelidze et al.,1981) and also by paleomagnetic data (Asanidze and Pechorcky, 1979; Asanidze et al., 1980), the most ancient of these oceans, Prothotetys, developed from the late Precambrian apparently up to the middle Jurassic. The transcaucasian massif (of which the Dzirula massif is a part), that had a crust of transitional type till the Late Paleozoic, was a microcontinent, or an island arc within the large oceanic structure of the Prototethys (the same as th Paleotethys), consisting of a vast oceanic basin in the south and probably a narrower one (Greater Caucasian) in the North (fig…). In the middle of the early Carboniferous (Tournaisian?, Early and Middle Visean) there occurred a phase of compression that caused the overthrusting of ophiolites of the Fore Range of the Greater Caucasus and of the Dzirula massif and closere of the northern (Greater Caucasian) part of the Paleotethys ocean. Along with this, by the end of the Late Paleozoic, a vast marginal belt of calc-alkaline volcanics originated on the northern continental margin of the Paleotethys, structing from the Pyrenees in the west to the northeast of China in the extrem east and described for the first time by Mossakovsky (1970). This belt suggests the existence of a Benioff zone dipping northward under the Ciscaucasian (Scythian) plate and responsible for the volcanism (fig…). According to paleogeographic, paleofloristic, and paleomagnetic data, in the rear of the gradually closing Paleotethys, separation of Iran and Arabian and generation of the Mesotethys had been taking plase already since the Carboniferous. Despite some rather convincing data from some French Geologists concerning the North Anatolian origin of the Taurides or, perhaps, in part of the Iskenderun zone ophiolite nappes, geologic and paleogeographic andpaleobiogeographic data show that by the end of the Paleozoic (according to Flugel already since the Devonian) the future Central Anatolia had also been separated from Africa and was located within the oceanic structure of the Tethys (see fig…). The Mesotethys ocean in the present day structure is marced by an ophiolitic belt which is traced from the island of Crete and Carpathos, via Cyprus, the Iskenderun zone, Zagros and Oman, and further on to the Indus suture in the Tibetian Himalayas.

The closure of the Mesotethys ocean, as well as of the Paleotethys relic basin, occurred as a result of movements which spread from North to South. In particular, only the northern part of the Mediterranean belt was affected by Bathonian (Adygean), Late Cimmerian (pre-Cretaceouse) and Austrian movements. These epochs of tectonic activity are associated with intense manifestions of andesitic volcanism and granitoid plutonism, due to the processes of subduction on the continental margin of the oceanic basins (Gamkrelidze, 1974a,b,1976).