Origin and palaeodepositional environment of evaporites in the Bala sub-basin, Central Anatolia, Türkiye

ABSTRACT

Bala is located in Central Anatolia and is a sub-basin of the Tuzgölü basin, which consists of many basins formed in response to the closure of the Neotethys ocean. The evaporites in Bala sub-basin formed under the influence of regional uplifting during the Middle Eocene period with gradual shallowing in response to the structural compressional regime. The Bala sub-basin comprises four units from bottom to top: the Lower Unit (BU1) consisting of mudstone, claystone with limestone layers; the Evaporites (BU2) containing dominant gypsum with anhydrite; mixed siliciclastic-carbonate-evaporitic deposits (BU3); and the Upper Unit (BU4) containing conglomerate-sandstone-claystone and siltstones. The evaporitic unit, which are the main subject of study consists of primary selenitic gypsum, anhydrite, locally celestite crystals and secondary gypsum formed due to the anhydritization of primary gypsum and then hydration of these anhydrites. The results obtained from mineralogical-petrographic, geochemical and isotopic (δ¹⁸O and δ³⁴S) investigations indicate that these evaporites were deposited in shallow marine to sabkha environments dominated by arid conditions. The presence of primary selenite crystals, the anhydrite with nodular, chicken-wire, and mosaic structures support precipitation occurred in a partially saline shallow water. The excessive thickness of the evaporitic accumulation, chaotic masses including gypsum breccia, salt diapirs and dome structures are attributed to tectonic processes acting during the formation of the Central Anatolian basins.

KEYWORDS:

• Bala sub-basin
• Central Anatolia
• evaporite
• shallow marine
• sabkha
• salt diapir
• tectonic

Acknowledgments

This study was financially supported by Hacettepe University (research project number: FDS-2015-5824). We thank Madinsan A.Ş. and the director of the company, Hamdi Kozacı, for allowing the use of their drill cores. Prof. Dr. S. Kulaksız was the contact for Madinsan A.Ş. and we also appreciate his aid in the field and helpful comments. Thanks to Prof. Dr. C. Harris (University of Cape Town, South Africa) for the isotope analysis and to Dr. B. Alan (General Directorate of Mineral Research and Exploration, Türkiye), Dr. A. Tuncer (Hacettepe University, Türkiye) and for his scientific supports in the micro-fossils investigation. We also thanks to Prof. Dr. A. Temel, Dr. G. Deniz Külahcı, Dr. Guilhem Hoareau and anonymous reviewers for helpful comments which improved the manuscript, and Catherine Yiğit for editing the manuscript. Finally, we are very grateful to Robert J. Stern for his editorial suggestions.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2022.2114021

Additional information

Funding

This work was supported by the Hacettepe University [FDS-2015-5824].