Genesis of Sulfate Lithofacies Between Erzincan-Divriği Basin With Sedimentologic and Geochemical Evidences: an Example From the Paleogene Basins of Eastern Turkey

Abstract

This study provided insight into the origin, age, and formation conditions of the Late Oligocene sulfate lithofacies that were deposited in the SW Erzincan Basin throughout a broad region. Primary, secondary gypsum, and anhydrite make up the majority of sulfates, which are interbedded with clastic, volcanic, volcaniclastic and carbonated rocks. During the early-late diagenetic processes, primary gypsum changes into secondary gypsum along with primary anhydrite that is growing within the host-sediment. In the lithofacies, sedimentary structures created by tectonism and diagenesis are commonly found. The distribution of element concentrations shows that continental detrital input has a significant impact. Fe- and Mg-rich clays imply alkaline and hot-humid environmental conditions in the basin. The negative trend relationship of CaO with MgO refers to carbonation in the environment, while Sr, Ba, U, Mo, Ni, Cu and Zn values and Co, Ni/Co (0.98), Co/Zn (11.3), Cu/Zn (1.39) ratios and the high positive correlation of Cu with Al2O3 (r = +0.72) indicate the dominance of biologic factor, high salinity and reducing conditions in sulfates. The presence and values of Fe-Mn-rich alteration zones detected by field, mineralogical and geochemical studies within the gypsum revealed the hydrothermal solution activity in the region. 87Sr/86Sr, 18O/16O, 34S/32S and delta 13C isotope data are consistent with Late Oligocene marine sulfates and suggest occasional mixing of freshwater. In addition, the origin and age data revealed by this study; It contributed to the paleogeographic evolution of the northern branch of Neotethys (Inner Tauride Ocean), which extends along the Central and northern-central Anatolia and Eastern Anatolia basins line, which includes Paleogene evaporitic deposits in Turkey, where the study area is located. Accordingly, it is obvious that the Neotethys, which extends along the basins from west to east, is quite shallow (lagoonal and coastal sabkha, etc.) and started to close further east during the Middle-Late Miocene (Erzurum-Pasinler- Horasan, Erzurum-H & imath;n & imath;s-Tekman, I & gbreve;d & imath;r-Tuzluca lacustrine basins, etc.).