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Upper Miocene Mtkvari Ignimbrite Geoheritage, Lesser Caucasus, Georgia: A historical ritual, defensive and residential area

Avtandil Okrostsvaridze1,  Mirian Makadze2

  • Affiliations:  1Institute of Earth Sciences, Ilia State University. 0162 Tbilisi, Georgia.  2Tbilisi State University, Faculty of Exact and Natural Sciences, Tbilisi, Georgia.   

  • Presentation type: Poster

  • Presentation time: Monday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 84

  • Programme No: 7.1.10

  • Theme 7 > Session 1

Abstract

Since the Middle Miocene, Late Cenozoic subaerial volcanic activity in Eastern Anatolia and the western Lesser Caucasus began and continued until the Holocene. In Georgia, this magmatic activity formed the Samtskhe-Javakheti volcanic plateau (~4,500 km²), which is traversed by the deep canyon of the Mtkvari River in its central part.       This canyon exposes the lowermost Upper Miocene 800-1200 m thick volcanogenic formation (Goderdzi Formation), predominantly of andesitic composition (Skhirtladze, 1958).  In the lower part of the Goderdzi formation, the 80-120 m thick ignitable (Kura/Mtkvari Ignimbrites) is exposed. It originates from the Upper Miocene Keltepe-Gumbati resurgent caldera and is continuously traced along the left banks of the Kura River for ~35 km (Makadze et al., 2024).         Isotopic studies of this flow show that it contains a large mantle-derived component (εNd from +3.1; 87Sr/86Sr = 0.704316), and by the U-Pb method of zircons, it is dated to 7.5 ± 0.2 Ma. This flow crosses a regional fault followed by the Mtkvari River, along which the eastern block is submerged ~126 m below the western block (Okrostsvaridze et al., 2020). **       ** In addition to its scale, excellent exposures, and fascinating geological structure, the Mtkvari Ignimbrite is notable for containing numerous historical rock-cut buildings with ritual, defensive,  and residential functions. The synthesis of geoheritage and cultural heritage is particularly remarkable in this region. Notable among these are the monumental Vardzia fortress-city, dating back to the early medieval period, with more than 600 carved rooms, and the Vahani/Vani  monastery complex, which contains approximately 200 carved rooms.