







































Georgian Geographical Journal 2023, Vol.3 (1) 

 

 

3D Model and Structural-Kinematic Evolution of the Pre-Jurassic 

Crystalline Basement of the Western Georgia 
Levan Basheleishvili1, Giorgi Beridze1* 

Abstract 

The modern structure of Western Georgia is determined mainly by the meridional (sub-meridional) and 

latitudinal systems of faults covering different depths of the Earth's crust. The noted faults are often-sided 

boundaries of the blocks of the crystalline basement of the Earth's crust, creating a picture of its mosaic-block 

structure. The analysis of the lithofacies and thicknesses of the sedimentary cover developed within their limits, 

in several cases, indicating their autonomous and inversion nature of development. The comparison of 

geophysical and drilling data and applying the system analysis method of disjunctive structures made it possible 

to clarify some issues of the structural-kinematic evolution and morphogenetic of individual blocks and faults of 

the pre-Jurassic crystalline basement within the limits of the Southern Caucasus. A 3D physical model of the 

surface of the crystalline basement constructed by us within Western Georgia shows the spatial arrangement and 

the character of the inversion nature of individual blocks, indicating the manifestations of the Alpine and Late 

Alpine orogeneses. Analysis of the actual material, geophysical, and geological data for the intra-Caucasian 

intermountain area allows us to draw the following conclusions: the Georgian Block (a fragment of the 

Transcaucasian median massif, microplates, and terranes), with a pre-Jurassic crystalline basement exposed in 

its central part, is divided into the western and eastern subsidence zones, which in turn disintegrate into separate 

blocks. From the central zone of the uplift of the Georgian Block to the east and west, a gradual "stepwise" 

subsidence and tilting of the blocks of the crystalline basement is outlined. Similar structures are known in the 

literature as the so-called tilt blocks. 

Keywords: Georgia, crystalline basement, structural geology, 3D model 

Introduction 

 

Figure 1. Scheme of the fault tectonics of the crystalline basement of Western Georgia. Scale 1: 100 000. 

 
1 Al. Janelidze Institute of Geology, Iv. Javakhishvili Tbilisi State University, Tbilisi, Georgia,  

* Corresponding author: giorgi.beridzegeolinst@gmail.com 

 



Basheishvili and Beridze. Georgian Geographical Journal 2023, Vol.3 (1) 

 

The modern structure of Western Georgia is primarily determined by the meridional (sub-

meridional) and latitudinal systems of faults covering different depths of the Earth's crust. The noted 

faults are often the siding boundaries of the blocks of the crystalline basement of the Earth's crust, 

creating a picture of its mosaic-block structure [1-6]. The analysis of the lithofacies and thicknesses of 

the sedimentary cover developed within their limits, in several cases, indicating their autonomous and 

inversion nature of development. At the Early-Middle Jurassic stage, within the Colkheti depression, a 

clearly expressed Colkheti trough opened towards the eastern part of the Black Sea. At this time, two 

faults of the general Caucasian strike formed in the north. In the south of the basin, the northern 

Adjara-Trialeti fault also manifested a latitudinal strike. The only meridional structure at that time was 

the Tkibuli-Zestaphoni fault, from which the thickness of the Lower-Middle Jurassic formations 

sharply decreased to the east, apparently connected to the washout of the Dzirula land. At that time, 

the greatest sagging occurred in Samegrelo, where the thickness of the Lower-Middle Jurassic was 

3000–3500 m (Fig. 1). 

Results 

The Samegrelo trough continued to develop in the Early Cretaceous. At the same time, the Rioni-

Chaladidi trough was isolated distinctly for the first time. The entire western part of the Colkheti 

depression was cut off from the eastern one by the sub-meridional fault. Here, the eastern block is 

relatively elevated, where the thickness of the Lower Cretaceous is 2000 m. Thus, at that time, five 

uplifts and four troughs were isolated, and all these structures had a latitudinal and near latitudinal 

strike. 

In the Late Cretaceous, the paleotectonic plan of the Colkheti depression changed. The central 

Samegrelo depression takes on a sub-meridional strike; to the west and north of the indicated trough, 

the meridionally spreading, narrow so-called Salkhino uplift and the sub-latitudinal Anaklia-Jvari 

fault were formed. In the Pliocene-Eocene time, the Central Samegrelo trough and the Salkhino-

Kvaloni uplift acquire a distinctly meridional outline. At the same time, the Lessa and Dzirula uplifts 

of latitudinal strikes formed. 

The Maikopian time (Oligocene–Early Miocene) in the Caucasus is characterised by the onset of 

the early orogenic stage of development, at which the Central Samegrelo trough retains its meridional 

strike with the accumulation of up to 1000 m of Maikop deposits. At the same time, two meridional 

Satanjo and Tsaishi uplifts that represent the area of erosion were isolated. 

In the Middle-Late Miocene, the meridional Central Samegrelo trough continues to develop, where 

the thickness of the Miocene reaches 2000 m. At the same time, the axial line of the trough migrates 

to the northeast compared to the Maikopian. 

The Paleocene stage of the development of the Colkheti depression, compared with the previous 

one, was characterised by a change in the paleotectonic plan, and the inversion stage of development 

started. This is visible in the Central Samegrelo trough; after the accumulation of 200–300 m 

(Pontian) deposits, uplifting took place, transforming the area into the erosion area. At that time, the 

submeridional trough turned into a latitudinal one. 

In the Quaternary period, the final relief from the Colkheti Depression takes place. First, the broad 

Central Samegrelo uplift reappears and again acquires a meridional direction. The thickness of the 

deposits reaches 200 m. 

The meridional Saberio-Tsaishi uplift also formed, where Quaternary deposits are missing. This 

narrow uplift in the east takes a northeasterly direction and thus almost entirely isolates the Central 

Samegrelo trough from the rest of the Colkheti depression. 

Thus, the initiation and development of meridional structures in the Colkheti depression show that 

the structural plan was rearranged at least twice, and this was associated with the region's main 

tectonic phases of deformation. Such data analysis makes it possible to comprehend the mechanism of 

the formation of meridional (anti-Caucasian) structures within Western Georgia. Recent studies show 

that in the Colchis depression, according to seismic data, the crystalline basement subsided from east 

to west from 0 to 8–9 km (in the coastal part of the Black Sea). However, with general subsidence to 

the west (in some places in the basement), local uplifts are noted, which are quite clearly recorded on 

seismic profiles. In addition, these uplifts in the eastern part were exposed by boreholes. Here, Lower 

Cretaceous deposits directly overlie the basement rocks, and the thickness of the Mio-Pliocene 

deposits is 400–450 m. To the west, between the villages of Akhali Sviri and Vartsikhe, a trough is 



Basheishvili and beridze. Georgian Geographical Journal 2023, Vol.3 (1) 

 

noted, where the thickness of the Mio-Pliocene remains unchanged but the thickness of the Upper 

Cretaceous deposits doubles. The basement uplift was recorded in the village of Vartsikhe, well No. 

18, at a depth of 720 m. On a five-kilometre stretch of uplift, the thickness of the Mesozoic-Cenozoic 

cover is reduced to a minimum (700–750 m). To the west, in well No. 66 (Sakuliya), the thickness of 

the Miocene-Pliocene deposits doubles, and Chokrakian deposits directly overlie the Upper 

Cretaceous deposits. To the west of the village of Sakuliya, the basement submerges again. No. 1 

(Samtredia) in 2800–3045 m exposed the Middle Jurassic deposits. Here, deposits of the Meotian 

stage rest on the Upper Cretaceous deposits. Thus, along the latitudinal profile of Zestaphoni-

Samtredia (Fig. 2), the thickness of the Upper Cretaceous deposits does not exceed 250–200 m, 

except for the Akhali Sviri-Rodinauli area, where their thickness is 800 m, and the thickness of the 

Lower Cretaceous and Mio-Pliocene deposits does not change compared to neighbouring areas. To 

the west of the mentioned trough, geological and geophysical data record the uplifted Vartsikhe 

Block, which, as the drilling data show, is limited by faults penetrating at least to the bottom of the 

earth's crust from the west and east. From them, the western one within the Georgian Block caused a 

halving of the thickness of the Mio-Pliocene deposits. According to M. I. Ioseliani et al. [7], igneous 

bodies that are not exposed on the surface are confined to this fault within Ajara-Trialeti. The 

Vartsikhe fault, the eastern limit of the Vartsikhe uplift within the Georgian Block, is well recorded 

on satellite images as a profound fault. It may also have a right-shear component. Another fault of sub 

meridional strike is outlined along the Ozurgeti-Amtkheli line, which, in addition to the data of the 

seismic profiles of Anaklia-Zestaphoni and Sabazho-Simoneti, is also confirmed by the analysis of 

geological materials. In particular, within the Ajara-Trialeti zone, it corresponds to a meridional fault-

slip, along which the Upper Cretaceous and Middle Eocene deposits of the Guria Range come into 

contact with the Mio-Pliocene deposits. The vertical amplitude of this fault slip is more than 3000 m. 

Jurassic deposits are missing east of the Sakuliya village to the Dzirula massif (along the Samtredia-

Zestaphoni profile). West of Samtredia, according to seismic data, the basement is submerged to a 

depth of 8 km [7]. In the vicinity of the village of Lessa (Lanchkhuti district), deep wells (No. 2, 21) 

exposed a thick complex of Sarmatian and post-Sarmatian deposits. The Upper Cretaceous deposits 

gradually wedge out from north to south, and the Lower Sarmatian sandstones and conglomerates 

directly overlie the Albian-Cenomanian volcanogenic deposits. According to the data from well No. 

1, the sole of the Albian-Cenomanian volcanogenic sequence is recorded at a depth of 3450 m. 

According to seismic data, the marked area is within the Rioni-Supsa trough [9] or the Paliastomi 

graben [1, 8].  

 

Figure 2.Latitudinal geological profile (Samtredia-Dzirula) according to drilling data. 

The Rioni-Supsa trough is the most submerged part of the Colkheti depression, where the basement 

surface from east to west subsides to 6–8 km along seismic profiles. From the south, the noted trough 

is limited by the Guria depression, the deep structure of which is due to faults of latitudinal and also 

meridional and diagonal strikes. In the east of the depression (east of Chokhatauri), the basement is 

uplifted, and the absolute depth of its attitude is 3–4 km. The foundation is significantly higher in the 

south of this strip compared to its northern part. Thus, the noted Kobuleti-Zekari band is, according to 

all geological and geophysical features, a fault zone, which is also fixed on the map of the depths of 

the upper mantle surface compiled by M.A. Ioseliani et al. [7]. A diagonal (northeast strike) fault is 



Basheishvili and Beridze. Georgian Geographical Journal 2023, Vol.3 (1) 

 

outlined along the southeastern margin of the Guria depression. Both gravimetric and seismic studies 

argue for the fault. Seismic and seismic-geological sections compiled and interpreted by M.S. 

Ioseliani et al. [7] for various profiles of the Colkheti depression (Sukhumi-Batumi, Chaladidi-Jgali, 

Didi Kukhi-Zestaphoni, Vani-Besiauri, and Dzirula massif-Anaklia) lead to the conclusion about the 

confinement of marginal velocities to the surface of the crystalline basement. For the Colkheti 

depression, the regularity derived for most parts of the Kura depression, where the surface is confined 

to the volcanogenic Middle Jurassic, is generally not revealed. This difference is probably due to the 

fact that the processes of continental rifting were rather intensive in the Colkheti Depression during 

the Late Jurassic and Late Cretaceous (the latter formations include rocks of the Mtavari Suite). This 

process led to deconsolidation, fragmentation, and, in connection with this, a decrease in density and 

velocity in the underlying formations of the volcanogenic Middle Jurassic (Bajocian), as a result of 

which the rocks of the pre-Jurassic basement turned out to have higher density and velocity, which 

leads to the fact that the marginal velocities established for the basement rocks, in this case, 

correspond precisely to these rocks. The Odisha Block, structurally the most distinct unit, covers the 

Samegrelo syncline. In the Late Cretaceous, it experienced a change in the tectonic plan with the 

formation of the sub-meridional Central Samegrelo foredeep and the accumulation of deposits up to 

500 m thick. To the west and north of the trough, meridionally elongated, narrow uplifts are outlined, 

in which Upper Cretaceous deposits were not accumulated. At the same time, the accumulation of the 

Mtavari volcanic suite indicates the activation of the process of continental rifting, with a more or less 

meridional strike of this structure. In Paleocene-Eocene time, its meridional trough is outlined to the 

west (Odishi depression), where sediments with a thickness of more than 1000 m accumulate. 

According to estimations, the crystalline basement is located at a depth of 7000m. 

Conclusion 

The comparison of geophysical and drilling data and applying the system analysis method of 

disjunctive structures made it possible to clarify some issues of the structural-kinematic evolution and 

morpho-genetics of individual blocks and faults of the pre-Jurassic crystalline basement within the 

limits of the Southern Caucasus. A 3D plasticine model of the surface of the crystalline basement 

constructed by us within Western Georgia shows the spatial arrangement and the character of the 

inversion nature of individual blocks, indicating the manifestations of the Alpine and Late Alpine 

phases of ectogenesis (Fig. 3). 

 

Figure 3. 3D plasticine model of the pre-Jurassic crystalline basement of Western Georgia  

Scale – Horizontal 1:500 000; vertical 1:200 000 



Basheishvili and beridze. Georgian Geographical Journal 2023, Vol.3 (1) 

 

Thus, the Odisha Block, located approximately in the central part of the depression from the 

western and eastern sides, is bounded by faults of a strike-slip nature, above which in the sedimentary 

cover, supra-fault echelon folds are developed, indicating the right-lateral component of the faults. In 

general, the kinematics of the Odisha Block indicate its shift in the southwest direction; the Block is 

slightly inclined in the eastern part concerning the Askhi and Okriba Blocks. From the south, it is 

bounded by the Abasha Block, one of the most subsided structures of the Colkhida depression. 

Analysis of the actual material, geophysical, and geological data for the intra-Caucasian 

intermountain area allows us to draw the following conclusions: the Georgian Block (a fragment of 

the Transcaucasian Median Massif, microplates, terranes), with a pre-Jurassic crystalline basement 

(Dzirula uplift) exposed in its central part, is divided into the western and eastern subsidence zones, 

which in turn disintegrate into separate blocks. 

From the central zone of the uplift of the Georgian Block to the east and west, a gradual "stepwise" 

subsidence and tilting of the blocks of the crystalline basement is outlined. Similar structures are 

known in the literature as the so-called tilt blocks [3, 5, 10]. They are quite distinctly recorded on 

different geophysical profiles. In some cases, the transverse uplifts of the crystalline basement are 

recorded by drilling data. Several transverse faults are associated with earthquakes, which are 

characterised by tensile stress and, therefore, can have a fault character with the inclination of the 

shear planes towards the centres of maximum tension. As a result of gravitational modelling, it is 

established that the M-boundary within this profile is indicated by a local uplifting under the Central 

Black Sea and a comparative subsidence under the Dzirula uplifts. The above outlines two plans of 

structural symmetry in the modern structure of the pre-Alpine consolidated crust of the South 

Caucasus Median Massif. The first (latitudinal profile) is characterised by extensional structures, 

mainly stepwise tilting blocks, which transform into listric faults. The second (meridional) is 

characterised by tangential, sub-meridional compression of the region caused by the advancement of 

the Arabian inlier to the north with the formation of the Transcaucasian transverse uplift and other 

collision structures. 

  

Competing interests 

The authors declare that they have no competing interests. 

Authors’ contribution 

All authors provided critical feedback and helped shape the research, analysis and manuscript. 

 

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