PRELIMINARY INVESTIGATION OF KARTLI BASIN STRATIGRAPHY IN GEORGIA: INSIGHT INTO THE GROWTH OF THE GREATER CAUCASUS AND THE DEMISE OF PARATETHYS

The Greater Caucasus (GC) are a young (late Miocene – Pliocene) orogen and the northernmost topographic response to the on-going NNW directed Arabia (Ab) – Eurasia (Eu) collision. Exposures of pre- and syn-tectonic foreland strata south of the GC allow for detailed investigations of the tectonic and climatic conditions that influenced this orogen during early orogenesis. The Kartli Basin (KrB) is the central pro-foreland basin between the southern margin of the GC and northern margin of the Lesser Caucasus (LC), lying between the Rioni Basin (RB) to the west and Kura Basin (KB) to the east. Compared to the RB or KB, the KrB’s exposed stratigraphy has seen relatively limited work due to a combination of poor exposure of the Miocene – Pliocene pre- and syn-collisional sediments and a focus of prior workers on the eastern KB. Both the timeframe spanned by the exposed KrB stratigraphy and its location are key because this stratigraphy should capture the early phases of the hard collision between the GC and LC that in part drove uplift of the GC, and the latter history of the dismemberment of the Eastern Paratethys Sea, a large lake that previously stretched from Western Europe to Asia and for which the KrB represented a critical gateway between larger, deeper basins. Here we address the lack of detailed stratigraphic work focused on the KrB by characterizing the mid to late Miocene – Early Pliocene pre- and syn-collisional sediments now exposed between the Georgian cities of Gori and Kaspi. We present results from a suite of composite measured stratigraphic sections covering 1.2 kilometers of section and spanning ~13 Ma of depositional history. During this period, depositional environments broadly changed from deltaic to shallow marine/tidal to entirely fluvial/terrigenous. We additionally augment the newly established stratigraphic and depositional framework with a characterization of sediment provenance from point counting and petrographic analysis, and bulk-geochemical analysis of mudstones, sandstones, and various carbonates collected throughout the measured sections. These new results allow us to evaluate the tectonic history of interactions between the GC and LC margins, the stratigraphic response of the KrB to those interactions, and the final stages of closure of the southern gateway between the Black and Caspian Seas.