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Main features of geological structure and a new tectonic map of Georgia

Authors:
Irakli Gamkrelidze at Tbilisi State University
Irakli Gamkrelidze
Kakhaber Koiava at Tbilisi State University
Kakhaber Koiava
Jon Mosar at University of Fribourg
Jon Mosar
Lika Kvaliashvili
Lika Kvaliashvili
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Abstract

Main features of geological structure and a new tectonic map of Georgia
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Geophysical Research Abstracts
Vol. 20, EGU2018-5040, 2018
EGU General Assembly 2018
© Author(s) 2018. CC Attribution 4.0 license.
Main features of geological structure and a new tectonic map of Georgia
Irakli Gamkrelidze (1), Kakhaber Koiava (1), Jon Mosar (2), Lika Kvaliashvili (3), and Jérémiah Mauvilly (2)
(1) A. Janelidze Institute of Geology of Tbilisi State University, 31 Politkovskaia str., 0186 Tbilisi, Georgia, (2) University of
Fribourg, Earth Sciences, Department of Geosciences, Fribourg, Switzerland (jon.mosar@unifr.ch), (3) LTD
"GeoEngService", 5 Ambrolauri str., 0160 Tbilisi, Georgia
The territory of Georgia is a component of the Caucasian segment of the Mediterranean (Alpine-Himalayan)
collisional orogenic belt. The Greater Caucasian, Black Sea-Central Transcaucasian, Baiburt-Sevanian and Iran
Afghanian accretionary terranes (island arcs or microcontinents in geological past), separated by ophiolite sutures
of different age, are identified within the Caucasus area. Georgia covers the S part of the Greater Caucasian
terrane, the Black Sea – Central Transcaucasian terrane and the N part of the Baiburt-Sevanian terrane. In addition
we can find in many places of the Caucasus ophiolite terranes – relics of Proto-Paleo- and Neo-tetethys oceanic
basins, which have been obducted from above mentioned ophiolite sutures.
The territory of Georgia is built up of Neoproterozoic-Paleozoic metamorphic complexes (migmatites, gneisses,
granite-gneisses, metabasites, metaophiolites) of supra-subduction zones, Mesozoic-Cenozoic sedimentary,
submarine and subaerial volcanic rocks and intrusives of various ages and composition. These rocks exhibit quite
different character within the separate terranes and subterranes (tectonic zones) of Georgia. The Earth’s crust of
Georgia thus contains tectonic structures of different age, type, scale and genesis. Complex tectonic nappes can
be found, both, in the pre-Alpine crystalline basement and in the Mesozoic-Cenozoic sedimentary cover. Late
Alpine southward-directed nappes are well documented on the southern slopes of the Greater Caucasus. They
formed as a result of northward advance and underthrusting (continental collision – due to closing of rifted Greater
Caucasus basin and underplating possible initiation of subduction) of the Transcaucasian massifs beneath the
Greater Caucasian folded system, mainly during the pre-Late Pliocene time (Rodanian phase) but continuing to
develop into present time.
On the basis of the latest geological and geophysical data a new tectonic map of Georgia in scale 1: 500 000m
was drawn. The map has a complex character and contains a wide spectrum of data on structure and development
of the Earth’s crust of the Georgian territory, composition, attitude and geodynamic types of sedimentary
and magmatic rocks. In addition tectonic deformation of rocks and the history of their formation, different
tectonic structures (faults and folds), their age and kinematic nature, and the deep structure of the Earth’s crust
is shown by means of the structure contours of different geological horizons, geodynamic conditions of the
Caucasus in Mesozoic and Early Cenozoic time, character (direction and velocity) of horizontal movements
and stress conditions of the Earth’s crust in the territory of Georgia at the neotectonic, stage are pictured on the map.
... For analytical details of apatite fission-track central ages and (U-Th)/He mean ages and exact samples locations, see Tables 1 and 2. Traces of geological cross-sections of Figs. 5, 6, 7 and 8 and location of Fig. 9 are also shown. Adamia et al., 2017bAdamia et al., , 2011Gamkrelidze et al., 2018;Yılmaz et al., 2014Yılmaz et al., , 2000 tion-related magmatic arc, located immediately to the south (Adamia et al., 1992(Adamia et al., , 1981Yılmaz et al., 2014) or (ii) to the opening of the Eastern Black Sea (Nikishin et al., 2015a(Nikishin et al., , 2015b. While there is ample evidence that the western Black Sea opened in late Early Cretaceous times (e.g. ...
... being deposited in the eastern sector of the ATFTB, whereas volcaniclastic turbidites interbedded with lava sheets and pyroclastic rocks were predominant in the central and western sectors (Adamia et al., 2017b(Adamia et al., , 2011Gamkrelidze et al., 2018). Seismic data show that the ATFTB continues offshore in the Eastern Black Sea and suggest coeval extension in the Black Sea -Pontide domain and in the Adjara-Trialeti basin (Banks et al., 1997;Robinson et al., 1995bRobinson et al., , 1996Robinson et al., , 1997Shillington et al., 2008;. ...
Structural inversion of back-arc basins–The Neogene Adjara-Trialeti fold-and-thrust belt (SW Georgia) as a far-field effect of the Arabia-Eurasia collision
Article
Full-text available
  • Feb 2021
  • TECTONOPHYSICS
The 350 km-long Adjara-Trialeti fold-and-thrust belt of southwestern Georgia is the result of the structural inversion of a continental back-arc basin developed in the Paleogene on the upper (Eurasian) plate of the northward subducting northern branch of the Neotethys. Low-temperature thermochronological data [fission- track and (U-Th)/He analyses on apatite] from sedimentary and plutonic rocks provide robust constraints on the tectonic evolution of the Adjara-Trialeti orogenic belt. Fission-track central ages range from the Middle Eocene to the Middle Miocene (46–15 Ma); helium ages are clustered in the Late Miocene-Pliocene (10–3 Ma). Time-temperature paths obtained integrating thermochronologic, stratigraphic, and radiometric data show that the volcanosedimentary basin fill of the Adjara-Trialeti back-arc basin underwent progressive burial heating prior to final cooling/exhumation in the late Middle Miocene-Pliocene. These new data show that the Adjara- Trialeti back-arc basin was inverted and developed as a fold-and-thrust belt starting at 14–10 Ma, in tune with widespread Middle-to-Late Miocene shortening and exhumation across wide areas of the Middle East, from the eastern Pontides of NE Turkey to the Lesser Caucasus in northern Armenia and NW Azerbaijan, and the Talysh and Alborz ranges in northern Iran. Such a supraregional tectonism is interpreted as a far-field effect of the Arabia-Eurasia collision along the Bitlis suture ca. 400 km to the south of the study area.
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Surface and subsurface structures of the Greater Caucasus flexural basin in Georgia, reconstruction of its tectonic inversion since the Early Cretaceous
Thesis
  • Jul 2021
The Greater Caucasus Mountain Belt is a rifted basin that formed during the Middle Jurassic to the Upper Cretaceous and has been inverted during the Cenozoic (age still debated). The belt is deformed by a complex combination of thick and thin-skinned tectonic. We talk about thick-skinned tectonic when the basement is involved in the deformations, and thin-skinned deformation when the cover is deformed.The flexural basin of the Greater Caucasus developped since the Lower Cretaceous during the collision in the Lesser Caucasus between the Taurides-Anatolides-South-Armenian microcontinent and the Eurasian plate, and is still active because of the collision with the Arabian Plate to the south.The Caucasus frame present a key area for two reasons. First, the propagation of the deformations from the Lesser Caucasus to the south, and toward the north in the Greater Caucasus allow us to better constrain the tectonic evolution of this Tethysian belt’part, and to better understand the inversion tectonic mechanisms.Then, the study of the flexural basin structure, and the involved lithologies, offers the possibility to lead explorations about the oil and gaz resources systems, such as in the Eastern Azerbaijan basin.We propose new field data (cartography, structural and lithostratigraphic analysis) to constrain the shallow structures, and we combine it with seismic lines interpretations and wells data analysis to constrain the deeper structures. The study was lead following two paths: first, we have localised the deformations and their related style and geometries. Then, the identification of the pre-, syn-, and post-tectonic deposits by the identification of growth strata allowed us to propose the chronology of the deformation during the multi-stage tectonic history in different structures of the flexural basin.The first part concerns the study of the Rioni flexural basin that borders the Eastern Black Sea and is located south of the western Greater Caucasus. We highlighted a Barremian to Turonian basin beneath the Rioni flexural basin, and which continues eastward in the Georgian Block.In the second part, we present our results related to the style and the timing of the deformations in the Rioni and the Kura flexural basin during the Paleogene and the Neogene. We highlight a two-stage compression: the first stage is during the Palaeocene-Eocene, and the second since the Upper Miocene. The study of the style of deformation allows us to compare the structural evolution of two basins with regard to the structural inheritance. The Rioni flexural basin structure and the localisation of the deformation are driven by the inherited normal faults, while the Kura flexural basin structure presents only thin-skinned tectonic. Finally, the third part presents our results about the avorted rifted Adjara-Trialet basin. This basin borders to the south the flexural basin, and is affected by the Lower to Upper Cretaceous extension in its western part, south of Rioni. During the Palaeocene-Eocene a superimposed basin was formed and developed eastward, south of the western Kura basin. This extension is coeval with the compression observed in the flexural basin. We show that the structure of this basin is related to the inversion of the inherited normal faults, but is also deformed by thin-skinned tectonic because of some decollement levels in the syn- and post-rift deposits. Our results are presented in three cross-sections and reconstitutions of more than 50km and that cross the whole Trancaucasian area and constrain the structures and the timing of the deformations between the Lesser and the Greater Caucasus since the Lower Cretaceous.
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