Stratigraphy, mineralogy, paleodepositional environment, and diagenetic evolution of the Pülümür evaporites (Tunceli, Eastern Anatolia, Türkiye)

The gypsum member of the Balpayam Formation (GMoBF) in the Pülümür Kırmızıköprü Basin (PKB), Eastern Anatolia, records a complex evaporitic system shaped by episodic tectonism, volcanism, and fluctuating hydrological conditions. Stratigraphic logging, facies analysis, and systematic sampling from outcrops and quarries enabled a detailed assessment of the evaporite succession. Petrographic data reveal pervasive secondary gypsum textures, including porphyroblastic, alabastrine, laminated, brecciated, and satin-spar fabrics preserving relics of primary anhydrite and calcite. XRD and FIB-SEM-EDS analyses identify gypsum, anhydrite, celestine, dolomite, calcite, clay minerals, and minor siliciclastic, clarifying diagenetic pathways. Diagenesis initiated with early calcite and aragonite precipitation, followed by replacement by primary anhydrite and gypsum under elevated Mg2+/Ca2+ ratios and shallow burial. Later hydration, dehydration, and rehydration cycles produced secondary gypsum with distinctive microtextures and micro-hydration channels. The PKB reflects a dual depositional system: a shallow, low-energy, restricted lagoon dominated by massive-laminated gypsum, stromatolitic textures, and organic-rich layers, and a comparatively deeper open marine setting with laminated-banded gypsum and transported gypsum arenite-rudite facies. Chicken-wire gypsum and anhydrite nodules indicate synsedimentary to early diagenetic formation under hypersaline conditions. A schematic depositional model constrains the temporal and spatial evolution of diagenetic processes, highlighting the interaction among evaporite deposition, tectonic activity, and environmental fluctuations in the southern Neo-Tethys Ocean of Eastern Anatolia.