The Sivas Basin, located on the Central Anatolian Plateau in Turkey, is an elongate Oligo-Miocene basin that contains numerous salt-walled minibasins. Through field analysis, including stratigraphic section logging, facies analysis and geological mapping, a detailed tectono-stratigraphic study of the Emirhan mini-basin and its 2Á6 km thick sediment fill has been undertaken. Three main palaeoenvironments are recognizedplaya-lake, braided stream and lacustrineeach corresponds to a relatively long-lived depositional episode within a system that was dominated overall by the development of a distributive fluvial system. At local scale, this affects the geometry of the succession and influences facies distributions within preserved sequences. Sequences affected by wedge geometries are characterized by localized channelized sandstone bodies in the area of maximum subsidence and these pass laterally to floodplain mudstone towards the diaper; several internal unconformities are recognized. By contrast, sequences affected by hook geometries display narrow and steep drape-fold geometries with no evidence of lateral facies change and apparent conformity in the preserved succession. The sediment fill of the Emirhan mini-basin records the remobilization of diapir-derived detritus and the presence of evaporitic bodies interbedded within the mini-basin, implying the growth of salt walls expressed at the surface as palaeo-topographic highs. The mini-basin also records the signature of a regional change in stratigraphic assemblage, passing from playa-lake facies to large-scale highly amalgamated fluvial facies that represent progradation of the fluvial system. The initiation and evolution of this mini-basin involves a variety of local and regional controls. Local factors include: (i) salt withdrawal, which influenced the rate and style of subsidence and consequently temporal and spatial variation in the stratigraphic assemblage and the stratal response related to halokinesis; and (ii) salt inflation, which influenced the topographic expression of the diapirs and consequently the occurrence of diapir-derived detritus intercalated within the otherwise clastic-dominated succession.

No abstract

The Sivas Basin, located in the Central Anatolian Plateau of Turkey, is a foreland basin that records a complex interaction between sedimentation, salt tectonics and regional shortening during the Oligo-Miocene leading to the formation of numerous mini-basins. The Oligocene sedimentary infill of the mini-basins consists of a thick continental succession, the Karay€ un Formation, comprising a vertical succession of three main sub-environments: (i) playa-lake, (ii) fluvial braided, and (iii) saline lacustrine. These sub-environments are seen as forming a large Distributive Fluvial System (DFS) modified through time as a function of sediment supply and accommodation related to regional changes in climate and tectonic regime. Within neighbouring mini-basins and despite a similar vertical stratigraphic succession, subtle variations in facies assemblages and thickness are observed in stratigraphic units of equivalent age, thus demonstrating the local control exerted by halokinesis. Stratigraphic and stratal patterns reveal in great detail the complex interaction between salt tectonics and sedimentation including different types of halokinetic structures such as hooks, wedges and halokinetic folds. The regional variations of accommodation/sediment supply led to coeval changes in the architectural patterns recorded in the mini-basins. The type of accommodation regime produces several changes in the sedimentary record: (i) a regime dominated by regional accommodation limits the impact of halokinesis, which is recorded as very small variations in stratigraphic thickness and facies distribution within and between mini-basins; (ii) a regime dominated by localized saltinduced accommodation linked to the subsidence of each individual mini-basin enhances the facies heterogeneity within the DFS, causing sharp changes in stratigraphic thickness and facies assemblages within and between mini-basins.Correspondence: Charlotte Ribes, Laboratoire des Fluides Complexes et leurs R eservoirs,