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

Onise V Enukidze,Victor M Alania,Sveva Corrado,Massimiliano Zattin,Thomas Gusmeo,William Cavazza

doi:10.1016/j.tecto.2020.228702

Onise V Enukidze, Victor M Alania + Show 4 more

Open Access

https://doi.org/10.1016/j.tecto.2020.228702

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Abstract

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.

Highlights

Et al, 2011; Okay et al, 1994), the timing of opening of the eastern Black Sea has been variously interpreted as coeval with the western Black Sea (e.g. Nikishin et al, 2015a, 2015b, 2003; Okay et al, 1994; Zonenshain and Le Pichon, 1986), as late Campanian-Danian (Vincent et al, 2016), Paleocene-Early Eocene (Robinson et al, 1996, 1995a, 1995b; Shillington et al, 2008; Spadini et al, 1996) or as Eocene (Kazmin et al, 2000)
The formation of the Black Sea basins has been explained in terms of geodynamic models derived from the study of modern back-arc basins, where extension is driven by slab roll- back
Stephenson and Schellart (2010) interpreted the Black Sea as an asymmetric back-arc basin bordering a subduction slab undergoing asymmetric anticlockwise slab roll-back, a model compat-ible with an earlier onset of extensional structures in the western compared to the eastern sub-basin

Summary

Introduction

Et al, 2011; Okay et al, 1994), the timing of opening of the eastern Black Sea has been variously interpreted as coeval with the western Black Sea (e.g. Nikishin et al, 2015a, 2015b, 2003; Okay et al, 1994; Zonenshain and Le Pichon, 1986), as late Campanian-Danian (Vincent et al, 2016), Paleocene-Early Eocene (Robinson et al, 1996, 1995a, 1995b; Shillington et al, 2008; Spadini et al, 1996) or as Eocene (Kazmin et al, 2000). The formation of the Black Sea basins has been explained in terms of geodynamic models derived from the study of modern back-arc basins, where extension is driven by slab roll- back.

Results

Conclusion