Speleogenesis of Gap-Gotan (Cupp-Coutunn) cave system, Köýtendag massif, Turkmenistan Proceedings : Volume II Audra, P. Cazes, G. /Robert, Xavier Barriquand, L. Dublyansky, Y. Koltai, G. Temovski, M. Polyak, V. Carbone, C. Heresanu, V. Gruat, J.P. De Waele, J. The Gap-Gotan (Cupp-Coutunn) system (Turkmenistan) is known for its mineralogical wealth, thanks to the considerable work carried out by Vladimir Maltsev in the 80s. However, following fieldwork carried out in 2024, Maltsev's speleogenetic hypotheses have been revised, in terms of stages, chronology and processes. Several phases of speleogenesis can be identified. 1) Hydrothermal mineralizing fluids, leading to Pb-Zn deposits in the vicinity, and impregnation of the host rock with sulfides, fluorite, and calcite veins. 2) The formation of large horizontal phreatic conduits at shallow depth, fed by infiltration at high altitude, with dissolution produced by flows reacting with the sulfides in the host rock. This process has been repeated in stages as the base level fell, until the present day. Nowadays similar active phreatic conduits are presumed to exist beneath the gypsum collapses. 3) Once drained, the caves are decorated with gypsum speleothems mainly formed by sulfate-rich seepage from the surface (e.g., chandeliers), and filled with fluvial sediments injected locally from canyon sinkholes. Mapping, isotopic and mineralogical analyses, and U-series and U-Pb dating of the sediments are providing preliminary evidence for this model of speleogenesis in these unique and exceptional caves. SBE Calux, A. (ed.) 2025 text https://www.documentation.ird.fr/hor/fdi:010096584 fdi:010096584 Audra P., Cazes G., Robert Xavier, Barriquand L., Dublyansky Y., Koltai G., Temovski M., Polyak V., Carbone C., Heresanu V., Gruat J.P., De Waele J.. Speleogenesis of Gap-Gotan (Cupp-Coutunn) cave system, Köýtendag massif, Turkmenistan. In : Calux A. (ed.), . Proceedings : Volume II SBE, 2025, 134-139 International Congress of Speleology ; Congresso Brasileiro de Espeleologia, 19. ; 38., Belo Horizonte (BRA), 2025/07/20-27 EN TURKMENISTAN