Salt tectonics in the Sivas basin (Turkey): crossing salt walls and minibasins

Abstract

The Sivas basin (Turkey) shows pronounced salt tectonics activity involving the Oligocene evaporites. Despite the complete exposure of the structures, the tectonic evolution of the basin has been so far misunderstood because it has only been envisioned in a context of thrust tectonics. The core of the basin, a 35x25 km area, displays rounded minibasins separated by evaporitic walls, and partially covered by remobilized gypsum (either sedimentary or flowage). The minibasins are filled by Mid-Oligocene to Early Miocene clastics (fluvial silts and sandstones), marls, and lacustrine to marine limestones, the thickness of which may reach 4 kilometres. The stratal architecture along evaporite walls records the progressive subsidence of the minibasins, with strong rotation of beds, unconformities and local reworking of evaporites. Within the basin, the sediments show lateral thickness variations and spectacular angular unconformities. The observed geometries show striking similarities with the seismic data from petroleum basins suffering strong salt tectonism (gulf of Mexico, Precaspian basin, Angolan margin).