GLAUBERITE-HALITE ASSOCIATION IN BOZKIR FORMATION (Pliocene, Çankırı-Çorum Basin, Central Anatolia, Turkey)

Tertiary Çankırı ? Çorum Basin is one of the biggest basin covering evaporitic formations in the Central Anatolia. During borehole drills carried out in Bozkır Formation which contain Pliocene aged evaporites in the basin, a thick rocksalt (halite, NaCl) deposit was detected that consisting of glauberite (Na2Ca(SO4)2) interlayers (sabhka) synchronous with sedimentation. Rocksalt bearing layers in Bozkır formation which was deposited in playa- lake ? sabhka environment, where seasonal changes are effective, were first defined as Tuz member in this study. Bozkır formation was divided into three zones in drillings carried out in sabhka ? playa -lake transitional environment. From bottom to top, these are ordered as claystone-less anhydrite zone, rock salt-claystone-anhydrite-glauberite zone (Tuz member) and claystone-gypsum-less anhydrite zone. Rocksalt was cut in thicknesses reaching 115 meters within Tuz member. Rocksalt (playa-lake) which is mostly bedded and white, pale/dark gray colored is conformable with sedimentation and is low dipping. The level at which glauberite deposition within Tuz member is observed the thickest was defined as glauberite-mudstone zone. Glauberite mineral which is observed as disc and rosette shaped individual forms within mudstone dominant matrix was formed as a diagenetic mineral in saline mudflat environment (sabhka). In geochemical analyses carried out (XRD, XRF, SEM) it was detected that glauberite mineral had been crystallized following anhydrite mineral within matrix that includes complex crystal forms in sabhka environment, halite mineral had grown on glauberite mineral and it was sometimes observed in the form of fracture and crack infill. The glauberite mineral deposition which does not have an economical thickness is of great importance in terms of the existence of fossil Na-sulfate deposition scientifically in Çankırı-Çorum Basin