Validating far-field deformation styles from the Adjara-Trialeti fold-and-thrust belt to the Greater Caucasus (Georgia) through multi-proxy thermal maturity datasets

Thermal history reconstructions can help to better characterise the geological history of areas that experienced a polyphase tectonic evolution. The integration of published stratigraphic/structural data with new and preexisting data on thermal maturity (clay mineralogy, Raman spectroscopy, vitrinite reflectance, and pyrolysis) of both surface and subsurface sedimentary successions of a wide region of Georgia including -north to south- the southern Greater Caucasus, the western Kura Basin, and the Adjara-Trialeti fold-and-thrust belt (FTB) provides cogent constraints on its late Mesozoic-Cenozoic tectono-sedimentary evolution. Overall, thermal maturity spans from the low diagenesis (60-80 degrees C) in the Upper Miocene section of the Kura Basin to anchizone-epizone (about 400 degrees C) in the central Greater Caucasus axial zone. In more detail, different maturity trends and thermal histories point to the existence of two domains formed by positive tectonic inversion: (i) the Adjara-Trialeti FTB from an Eocene rift basin and (ii) the Greater Caucasus from a Mesozoic rift basin. Multiple thermal indicators, along with stratigraphic/structural evidence, show that the Paleocene section of the Adjara-Trialeti basin fill reached the upper oil window (ca. 115 degrees C) during maximum sedimentary burial and that the whole basin was then exhumed starting from the late Middle Miocene. A positive correlation between thermal maturity and stratigraphic age points to a limited thermal effect of tectonic loading. In the southern Greater Caucasus, thermal maturity increases progressively with stratigraphic age, from ca. 100 degrees C (Upper Eocene) to 400 degrees C (Lower Jurassic), in broad agreement with the reconstructed thickness of the basin-fill succession, thus indicating that most of the thermal maturity was again induced by sedimentary burial. As to the flexural western Kura Basin, its Maikopian (Oligocene-Early Miocene) section reached the oil window (up to ca. 110 degrees C) whereas the Middle-Late Miocene one is immature. The Kakheti ridge -a highly tectonised portion of the Kura Basin- reached immature to early mature conditions.