Browsing by Author "Smirnov, Pavel"

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Gypsum in Diatomaceous Strata of the Trans-Urals Region: Morphology, Lithogeochemistry, and Genetic Link To Global Warming at the Paleocene-Eocene Boundary
(Elsevier, 2022) Smirnov, Pavel; Yesilova, Pelin Gungor; Trubin, Yaroslav; Deryagina, Oksana; Novoselov, Andrey; Batalin, Georgii; Minnebayev, Kamil
This paper reports the geochemical, structural, and textural properties of evaporite minerals (gypsum) interbed-ded with from the Early Paleogene diatomite and clastics exposed in the diatomite quarry in the Kamyshlov town quarry, Trans-Urals region (Sverdlovsk Oblast, Russia). This article is the first to reveal the occurrence of these atypical minerals in local sediments for the Trans-Urals region, dating from the Paleocene to the Early Eocene. The investigated aggregates included gypsum, anhydrite, and diatomite. Gypsum crystallization occurred rapidly in the low-density non-lithified stratum of the seafloor sediment under warm conditions. Gypsum elemental composition reflects its genesis in a low bio-productivity environment strongly influenced by the influx of highly mineralized groundwater. Terrigenous influx (coarse-grained quartz and fine clay fractions) is high. As a result, radial-fibrous stellate gypsum crystals formed in the fissures that penetrated the diatomite stratum. Geochemical indicators, such as Sr/Ba ratios, show that the salinity of the watershed was variable at the onset of evaporitic con-ditions. Chronologically, gypsum formation is dated to the beginning of the transgressive cycle (early Eocene, the end of the Paleocene-Eocene Thermal Maximum (PETM)) or to the end of post-PETM sedimentation. (c) 2022 Elsevier B.V. All rights reserved.
Insights Into Diagenetic Evolution and Paleoenvironment of Eocene Jatta Gypsum in the Kohat Basin, Pakistan
(Springer, 2025) Ullah, Hassanat; Qiu, Longwei; Kashif, Muhammad; Smirnov, Pavel; Yesilova, Pelin Gungor; Aman-e-room, Shahab; Khan, Khalid Ali
This study examines the depositional and diagenetic evolution of the Eocene Jatta Gypsum in the Kohat Basin, Pakistan, using sedimentological, petrographic, mineralogical, geochemical, isotopic, and Raman spectroscopic data. Lithofacies analysis identified selenitic, radial, discoidal, massive, laminated, and nodular gypsum, along with gypsum arenite and anhydrite nodules, reflecting deposition in restricted sabkha-lagoonal settings. Petrographic and SEM observations revealed pseudomorphic anhydrite laths, secondary calcite and celestite replacements, Fe-oxidation zones, alabastrine and granoblastic textures, and satin spar veins, documenting a complex multi-stage diagenetic history. Geochemical data indicate that high Sr and Sr/Mn ratios in selenitic and massive facies reflect pure evaporitic precipitation, whereas nodular and satin spar facies, enriched in Si-Al, Mn-Ag-Cu, and Rb, record detrital influx, microbial sulfate reduction, and hydrothermal fluid circulation. Isotopic values (delta S-3(4): 16.3-17.6 parts per thousand CDT; delta O-1(8): 19.2-22.2 parts per thousand SMOW) confirm microbial activity, strong evaporation, and episodic freshwater influx. Raman spectra provide further confirmation: sharp SO42- stretching bands (1008-1012 cm(-)(1)) indicate primary gypsum, while broadened signals and weakened hydration bands reflect dehydration to anhydrite and fluid-driven transformations. Overall, the Jatta Gypsum represents a multi-regime evaporitic system, where pure evaporitic facies formed under strongly evaporitic arid conditions, while detrital-rich facies reflect semi-arid restricted settings modified by diagenesis, microbial processes, and hydrothermal influence. These results offer new insights into the paleoenvironmental and tectonic evolution of the Kohat Basin during the late stages of the India-Eurasia collision.