Salt tectonics in the Sivas Basin, Turkey: Outstanding seismic analogues from outcrops
Résumé
The Sivas Basin in Central Anatolia is possibly the world's finest open-air museum of salt tectonics structures. It is an elongated Oligo-Miocene sag basin that developed in an orogenic context above the Neotethys suture zone. A mid-Oligocene quiet period during convergence of the Arabian and Eurasian plates allowed the deposition of a thick sequence of evaporites. Erosion of the Taurus Mountains shed clastic sediments northwards over the evaporitic basin. Sediments and deformation propagated from the south, forming mini-basins and associated evaporite diapirs and walls. Following this quiet period, compression resumed in the early Miocene, enhancing the formation of gypsum overhangs and allochtonous sheets. The Sivas outcrops expose classic salt tectonics geometries associated with the development of diapirs: halokinetic sedimentary sequences along diapir walls, welds and evaporite sheets or canopies, minibasins, and overturned minibasin wings (overturned edges of minibasins). These exposures are some of the finest field analogues for classical petroleum provinces controlled by salt tectonics such as the Gulf of Mexico and offshore Angola. We illustrate seismic-scale structures and, in the vicinity of the evaporite bodies, interesting analogues for drilled structures where seismic data do not provide an image.