Tectono-stratigraphic evolution of salt-controlled minibasins in a fold and thrust belt, the Oligo-Miocene central Sivas Basin

Abstract

The Central Sivas Basin (Turkey) provides an outcrop example of a minibasin province developed above a salt canopy within a foreland-fold and thrust belt. Several minibasins are examined to assess the influence of regional Oligo-Miocene shortening during the development of a minibasin province. The results are based on extensive field work, including regional and detailed outcrop mapping of at least 15 minibasin margins and analysis of the structural elements at all scales. This reveals a progressive increase in shortening and a decrease in salt tectonics during evolution of the province. The initiation of minibasins is driven mostly by the salt-induced accommodation forming a polygonal network of salt structures with mainly local halokinetic sequences (i.e. hooks and wedges). The initiation of shortening is marked by an abrupt increase in sedimentation rate within the flexural foreland basin causing burial of the preexisting salt structures. Subsequently, orogenic compression encourages the rejuvenation of linear salt structures oriented at right angle to the regional shortening direction. The influence of orogenic shortening during the last steps of the minibasin province evolution is clearly shown by: (i) the squeezing of salt structures to form welds which are developed both at right angle and oblique to the regional shortening direction, (ii) the emergence of thrust faults, (iii) the tilting and rotation of minibasins about vertical axis associated with the formation of strike-slip fault zones, and (iv) the extrusion of salt sheets. The pre-shortening geometry of the salt structures pattern, polygonal network of walls and diapirs versus linear and sub-parallel walls, influence the resultant structural style of the minibasin province subjected to shortening. Preexisting linear depocenter limited by sub-parallel walls accommodate preferentially the shortening compare to the preexisting sub-circular depocenter limited by polygonal network of salt walls and diapirs.