From Fold-and-Thrust Belts on Salt to Salt Deposition and Tectonics in a Fold-and-Thrust Belt, Sivas, Turkey

Salt is a very efficient detachment in fold-and-thrust belts. It has a very low shear resistance and produces wide fold belts with low taper, characterized by long detachment folds. These belts do not follow the classical in-sequence propagation of a Coulomb tectonic wedge developed over stronger detachments, such as the Rocky Mountains. Examples from Zagros and Tajikistan, among others, will illustrate the salt-controlled thin-skinned style, and how late basement involvement can interfere with the thin-skinned belt. In most salt related fold-and-thrust belts, like in most salt provinces, salt tectonic occurred very early in the basin evolution. In Zagros, only the lastest part of the salt story, squeezed cylindrical passive diapirs, can be observed, although halokinesis is known to have started as early as Cambrian. In the southeastern Alps, although evaporites have disappeared, paleo-diapirs, welds and megaflaps can be deciphered. The resulting fold and thrust thus build up at the expenses of preexisting salt related structures. In the recently revisited Sivas Basin in Turkey, thick evaporites structures are preserved. The basin lies above the Neotethyan suture and ophiolite nappe. Thick evaporite deposited in several episodes from Late Eocene to Miocene in a context of north-verging triangle zone. During this evolution fluvial to shallow marine sediments recorded several episodes of salts tectonics on large evaporite sheets that have a mixed origin, partly salt sheet, partly redeposition. Classical salt basins on passive margins (e.g. Gulf of Mexico, West African Margin) formed in tectonically quiet deep offshore settings and are filled with turbidites. The Sivas Basin evolved in a very different overall convergent tectonic setting and in fluvial to shallow marine sedimentary environments. However, the mini basin structures exposed in Sivas can be directly compared to seismic images from offshore basins. Structures like salt walls and sheets, welds, halokinetic sequences and mega flaps can be illustrated and compared with high quality seismic data.