Post-halite gypsum pseudomorphs with evidence of challenging climatic conditions and diagenetic replacement: a study from the southwest of Kağızman Basin (Eastern Anatolia, Türkiye)

Abstract

The study area is about the evaporitic-dominated Middle Miocene sequence situated in the southwest of the Kağızman Basin in Eastern Anatolia. The aim of this study is to investigate the formation conditions and diagenetic development of pseudomorph gypsum formed after halite. Pseudomorph gypsum formations are intriguing geological features found in terrestrial deposits. These formations are replaced by primary halite crystals during the very early phases of diagenesis, giving the appearance of halite crystals but being composed of gypsum. The development of these pseudomorphs is indicative of specific paleoenvironmental conditions. The fact that these gypsum pseudomorphs are found in shallow depths of the lake and are well-preserved, smooth-surfaced, and varying in size suggests that they were the result of intense evaporation and rapid fluctuations in the water and pH level. This evaporation likely led to a decrease in the lake level and changes in the concentration of saltwater over time. The correlation coefficient relationships and element concentration values of these gypsums show that these elements are both continental in origin and subject to microbial influence. These pseudomorph gypsum and the clastic materials (transported by fluvial activity) that were interbedded gave important insights into the hot, long-drought, and low-humidity climate of the era and adapted to the Middle Miocene global warming conditions.