--> Structure and kinematics of the Central Sivas Basin (Turkey): A mixed fold- and salt-and-thrust belt

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Structure and kinematics of the Central Sivas Basin (Turkey): A mixed fold- and salt-and-thrust belt


The Sivas Basin in central-eastern Anatolia, is a north-verging fold-and-thrust belt with syn-orogenic salt tectonics. It formed above the northern leading edge of the Tauride platform, the Kırşehir micro-continent, the edge of the Pontide arc and the related ophiolitic suture. We revised the entire tectonostratigraphy of the central Sivas Basin to propose a geological map at the 1/50,000 scale together with a synthetic stratigraphic chart and cross-sections.

Five regional cross-sections supported by 2D seismic data have been constructed to decipher the complex geometries and basin evolution. We define three tectonics domains from south to north: (i) to the south, a Maastrichtian to Eocene north-verging thrust wedge (FTB), (ii) in the center, an Oligo-Miocene shaped by salt tectonics detached above the thrust wedge which contains two generations of minibasins separated by a canopy, controlled by a mix of shortening and salt controlled tectonics, then (iii) a Late Miocene to Pliocene depocenter onlapping onto the Kırşehir basement.

The network of cross-sections shows along-strike varying structures and increasing shortening in the FTB from west (~15km) to east (~25km), with variable degree of decoupling from the STB due to the salt layer. We show that the mechanical behaviour of the prism is controlled by the incremental advance of the frictional FTB and by the initial geometry of the mother salt basin. Coupling with the STB is favoured in the case of a thinner salt layer, in opposition with the thick salt domain which allows intracutaneous FTB propagation below salt withdrawal minibasins.

The geometries of the Sivas Basin are unique due to the volume of salt integrated into the deformation. Salt-related structures are comparable to classical salt basins on passive margins (e.g. West Africa, Gulf of Mexico), but in a compressive context. Generally, halokinesis in salt related fold-and-thrust belts occurred early in the evolution (e.g. Zagros), while it is strongly active in the Sivas basin until final stages of the contraction. In fact, a thick syn-orogenic salt level formed a very efficient detachment which will be strongly recycled during contraction. Successively, the primary salt, then the canopy, were reincorporated in the system by mechanical and geochemical processes